Merge branch 'refs/heads/pr/25'

# Conflicts:
#	src/ImageSharp/Formats/Jpg/JpegEncoderCore.cs

src/ImageSharp/Formats/Jpg/Components/Bits.cs

@@ -5,27 +5,92 @@
 
 namespace ImageSharp.Formats
 {
+    using System.Runtime.CompilerServices;
+
     /// <summary>
     /// Holds the unprocessed bits that have been taken from the byte-stream.
     /// The n least significant bits of a form the unread bits, to be read in MSB to
     /// LSB order.
     /// </summary>
-    internal class Bits
+    internal struct Bits
     {
         /// <summary>
         /// Gets or sets the accumulator.
         /// </summary>
-        public uint Accumulator { get; set; }
+        public uint Accumulator;
 
         /// <summary>
         /// Gets or sets the mask.
         /// <![CDATA[mask==1<<(unreadbits-1) when unreadbits>0, with mask==0 when unreadbits==0.]]>
         /// </summary>
-        public uint Mask { get; set; }
+        public uint Mask;
 
         /// <summary>
         /// Gets or sets the  number of unread bits in the accumulator.
         /// </summary>
-        public int UnreadBits { get; set; }
+        public int UnreadBits;
+
+        /// <summary>
+        /// Reads bytes from the byte buffer to ensure that bits.UnreadBits is at
+        /// least n. For best performance (avoiding function calls inside hot loops),
+        /// the caller is the one responsible for first checking that bits.UnreadBits &lt; n.
+        /// </summary>
+        /// <param name="n">The number of bits to ensure.</param>
+        /// <param name="decoder"></param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal JpegDecoderCore.ErrorCodes EnsureNBits(int n, JpegDecoderCore decoder)
+        {
+            while (true)
+            {
+                JpegDecoderCore.ErrorCodes errorCode;
+
+                byte c = decoder.bytes.ReadByteStuffedByte(decoder.inputStream, out errorCode);
+
+                if (errorCode != JpegDecoderCore.ErrorCodes.NoError)
+                {
+                    return errorCode;
+                }
+
+                this.Accumulator = (this.Accumulator << 8) | c;
+                this.UnreadBits += 8;
+                if (this.Mask == 0)
+                {
+                    this.Mask = 1 << 7;
+                }
+                else
+                {
+                    this.Mask <<= 8;
+                }
+
+                if (this.UnreadBits >= n)
+                {
+                    return JpegDecoderCore.ErrorCodes.NoError;
+                }
+            }
+        }
+
+        internal int ReceiveExtend(byte t, JpegDecoderCore decoder)
+        {
+            if (this.UnreadBits < t)
+            {
+                var errorCode = this.EnsureNBits(t, decoder);
+                if (errorCode != JpegDecoderCore.ErrorCodes.NoError)
+                {
+                    throw new JpegDecoderCore.MissingFF00Exception();
+                }
+            }
+
+            this.UnreadBits -= t;
+            this.Mask >>= t;
+            int s = 1 << t;
+            int x = (int)((this.Accumulator >> this.UnreadBits) & (s - 1));
+
+            if (x < (s >> 1))
+            {
+                x += ((-1) << t) + 1;
+            }
+
+            return x;
+        }
     }
 }

src/ImageSharp/Formats/Jpg/Components/Block.cs

@@ -2,14 +2,19 @@
 // Copyright (c) James Jackson-South and contributors.
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
-
 namespace ImageSharp.Formats
 {
+    using System;
+    using System.Buffers;
+    using System.Runtime.CompilerServices;
+
     /// <summary>
     /// Represents an 8x8 block of coefficients to transform and encode.
     /// </summary>
-    internal class Block
+    internal struct Block : IDisposable
     {
+        private static readonly ArrayPool<int> ArrayPool = ArrayPool<int>.Create(BlockSize, 50);
+
         /// <summary>
         /// Gets the size of the block.
         /// </summary>
@@ -18,16 +23,137 @@ namespace ImageSharp.Formats
         /// <summary>
         /// The array of block data.
         /// </summary>
-        private readonly int[] data;
+        public int[] Data;
+
+        public void Init()
+        {
+            // this.Data = new int[BlockSize];
+            this.Data = ArrayPool.Rent(BlockSize);
+        }
+
+        public static Block Create()
+        {
+            var block = new Block();
+            block.Init();
+            return block;
+        }
+
+        public static Block[] CreateArray(int size)
+        {
+            Block[] result = new Block[size];
+            for (int i = 0; i < result.Length; i++)
+            {
+                result[i].Init();
+            }
+
+            return result;
+        }
+
+        public bool IsInitialized => this.Data != null;
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="Block"/> class.
+        /// Gets the pixel data at the given block index.
         /// </summary>
-        public Block()
+        /// <param name="index">The index of the data to return.</param>
+        /// <returns>
+        /// The <see cref="int"/>.
+        /// </returns>
+        public int this[int index]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return this.Data[index];
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            set
+            {
+                this.Data[index] = value;
+            }
+        }
+
+        // TODO: Refactor Block.Dispose() callers to always use 'using' or 'finally' statement!
+        public void Dispose()
+        {
+            if (this.Data != null)
+            {
+                ArrayPool.Return(this.Data, true);
+                this.Data = null;
+            }
+        }
+
+        public static void DisposeAll(Block[] blocks)
         {
-            this.data = new int[BlockSize];
+            for (int i = 0; i < blocks.Length; i++)
+            {
+                blocks[i].Dispose();
+            }
         }
 
+        public void Clear()
+        {
+            for (int i = 0; i < this.Data.Length; i++)
+            {
+                this.Data[i] = 0;
+            }
+        }
+
+        public Block Clone()
+        {
+            Block clone = Create();
+            Array.Copy(this.Data, clone.Data, BlockSize);
+            return clone;
+        }
+    }
+
+    /// <summary>
+    /// TODO: Should be removed, when JpegEncoderCore is refactored to use Block8x8F
+    /// Temporal class to make refactoring easier.
+    /// 1. Refactor Block -> BlockF
+    /// 2. Test
+    /// 3. Refactor BlockF -> Block8x8F
+    /// </summary>
+    internal struct BlockF : IDisposable
+    {
+        private static readonly ArrayPool<float> ArrayPool = ArrayPool<float>.Create(BlockSize, 50);
+
+        /// <summary>
+        /// Size of the block.
+        /// </summary>
+        public const int BlockSize = 64;
+
+        /// <summary>
+        /// The array of block data.
+        /// </summary>
+        public float[] Data;
+
+        public void Init()
+        {
+            // this.Data = new int[BlockSize];
+            this.Data = ArrayPool.Rent(BlockSize);
+        }
+
+        public static BlockF Create()
+        {
+            var block = new BlockF();
+            block.Init();
+            return block;
+        }
+
+        public static BlockF[] CreateArray(int size)
+        {
+            BlockF[] result = new BlockF[size];
+            for (int i = 0; i < result.Length; i++)
+            {
+                result[i].Init();
+            }
+
+            return result;
+        }
+
+        public bool IsInitialized => this.Data != null;
+
         /// <summary>
         /// Gets the pixel data at the given block index.
         /// </summary>
@@ -35,10 +161,52 @@ namespace ImageSharp.Formats
         /// <returns>
         /// The <see cref="int"/>.
         /// </returns>
-        public int this[int index]
+        public float this[int index]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return this.Data[index];
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            set
+            {
+                this.Data[index] = value;
+            }
+        }
+
+        // TODO: Refactor Block.Dispose() callers to always use 'using' or 'finally' statement!
+        public void Dispose()
+        {
+            if (this.Data != null)
+            {
+                ArrayPool.Return(this.Data, true);
+                this.Data = null;
+            }
+        }
+
+        public static void DisposeAll(BlockF[] blocks)
+        {
+            for (int i = 0; i < blocks.Length; i++)
+            {
+                blocks[i].Dispose();
+            }
+        }
+
+        public void Clear()
+        {
+            for (int i = 0; i < this.Data.Length; i++)
+            {
+                this.Data[i] = 0;
+            }
+        }
+
+        public BlockF Clone()
         {
-            get { return this.data[index]; }
+            BlockF clone = Create();
-            set { this.data[index] = value; }
+            Array.Copy(this.Data, clone.Data, BlockSize);
+            return clone;
         }
     }
-}
+}

src/ImageSharp/Formats/Jpg/Components/Block8x8F.Generated.cs

@@ -0,0 +1,52 @@
+// <auto-generated />
+
+using System;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+
+
+namespace ImageSharp.Formats
+{
+	internal partial struct Block8x8F
+    {
+        private static readonly Vector4 CMin4 = new Vector4(-128f);
+        private static readonly Vector4 CMax4 = new Vector4(127f);
+        private static readonly Vector4 COff4 = new Vector4(128f);
+
+		/// <summary>
+        /// Transpose the block into d
+        /// </summary>
+        /// <param name="d">Destination</param>
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void TransposeInto(ref Block8x8F d)
+        {
+            d.V0L.X = V0L.X; d.V1L.X = V0L.Y; d.V2L.X = V0L.Z; d.V3L.X = V0L.W; d.V4L.X = V0R.X; d.V5L.X = V0R.Y; d.V6L.X = V0R.Z; d.V7L.X = V0R.W; 
+            d.V0L.Y = V1L.X; d.V1L.Y = V1L.Y; d.V2L.Y = V1L.Z; d.V3L.Y = V1L.W; d.V4L.Y = V1R.X; d.V5L.Y = V1R.Y; d.V6L.Y = V1R.Z; d.V7L.Y = V1R.W; 
+            d.V0L.Z = V2L.X; d.V1L.Z = V2L.Y; d.V2L.Z = V2L.Z; d.V3L.Z = V2L.W; d.V4L.Z = V2R.X; d.V5L.Z = V2R.Y; d.V6L.Z = V2R.Z; d.V7L.Z = V2R.W; 
+            d.V0L.W = V3L.X; d.V1L.W = V3L.Y; d.V2L.W = V3L.Z; d.V3L.W = V3L.W; d.V4L.W = V3R.X; d.V5L.W = V3R.Y; d.V6L.W = V3R.Z; d.V7L.W = V3R.W; 
+            d.V0R.X = V4L.X; d.V1R.X = V4L.Y; d.V2R.X = V4L.Z; d.V3R.X = V4L.W; d.V4R.X = V4R.X; d.V5R.X = V4R.Y; d.V6R.X = V4R.Z; d.V7R.X = V4R.W; 
+            d.V0R.Y = V5L.X; d.V1R.Y = V5L.Y; d.V2R.Y = V5L.Z; d.V3R.Y = V5L.W; d.V4R.Y = V5R.X; d.V5R.Y = V5R.Y; d.V6R.Y = V5R.Z; d.V7R.Y = V5R.W; 
+            d.V0R.Z = V6L.X; d.V1R.Z = V6L.Y; d.V2R.Z = V6L.Z; d.V3R.Z = V6L.W; d.V4R.Z = V6R.X; d.V5R.Z = V6R.Y; d.V6R.Z = V6R.Z; d.V7R.Z = V6R.W; 
+            d.V0R.W = V7L.X; d.V1R.W = V7L.Y; d.V2R.W = V7L.Z; d.V3R.W = V7L.W; d.V4R.W = V7R.X; d.V5R.W = V7R.Y; d.V6R.W = V7R.Z; d.V7R.W = V7R.W; 
+        }
+
+		/// <summary>
+        /// Level shift by +128, clip to [0, 255]
+        /// </summary>
+        /// <param name="d">Destination</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void TransformByteConvetibleColorValuesInto(ref Block8x8F d)
+        {
+            d.V0L = Vector4.Max(Vector4.Min(V0L, CMax4), CMin4) + COff4;d.V0R = Vector4.Max(Vector4.Min(V0R, CMax4), CMin4) + COff4;
+            d.V1L = Vector4.Max(Vector4.Min(V1L, CMax4), CMin4) + COff4;d.V1R = Vector4.Max(Vector4.Min(V1R, CMax4), CMin4) + COff4;
+            d.V2L = Vector4.Max(Vector4.Min(V2L, CMax4), CMin4) + COff4;d.V2R = Vector4.Max(Vector4.Min(V2R, CMax4), CMin4) + COff4;
+            d.V3L = Vector4.Max(Vector4.Min(V3L, CMax4), CMin4) + COff4;d.V3R = Vector4.Max(Vector4.Min(V3R, CMax4), CMin4) + COff4;
+            d.V4L = Vector4.Max(Vector4.Min(V4L, CMax4), CMin4) + COff4;d.V4R = Vector4.Max(Vector4.Min(V4R, CMax4), CMin4) + COff4;
+            d.V5L = Vector4.Max(Vector4.Min(V5L, CMax4), CMin4) + COff4;d.V5R = Vector4.Max(Vector4.Min(V5R, CMax4), CMin4) + COff4;
+            d.V6L = Vector4.Max(Vector4.Min(V6L, CMax4), CMin4) + COff4;d.V6R = Vector4.Max(Vector4.Min(V6R, CMax4), CMin4) + COff4;
+            d.V7L = Vector4.Max(Vector4.Min(V7L, CMax4), CMin4) + COff4;d.V7R = Vector4.Max(Vector4.Min(V7R, CMax4), CMin4) + COff4;
+        }
+
+
+	}
+}

src/ImageSharp/Formats/Jpg/Components/Block8x8F.Generated.tt

@@ -0,0 +1,80 @@
+<#@ template debug="false" hostspecific="false" language="C#" #>
+<#@ assembly name="System.Core" #>
+<#@ import namespace="System.Linq" #>
+<#@ import namespace="System.Text" #>
+<#@ import namespace="System.Collections.Generic" #>
+<#@ output extension=".cs" #>
+// <auto-generated />
+
+using System;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+
+<#
+char[] coordz = {'X', 'Y', 'Z', 'W'};
+#>
+
+namespace ImageSharp.Formats
+{
+	internal partial struct Block8x8F
+    {
+        private static readonly Vector4 CMin4 = new Vector4(-128f);
+        private static readonly Vector4 CMax4 = new Vector4(127f);
+        private static readonly Vector4 COff4 = new Vector4(128f);
+
+		/// <summary>
+        /// Transpose the block into d
+        /// </summary>
+        /// <param name="d">Destination</param>
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void TransposeInto(ref Block8x8F d)
+        {
+            <#
+			PushIndent("            "); 
+
+            for (int i = 0; i < 8; i++)
+            {
+                char destCoord = coordz[i % 4];
+                char destSide = (i / 4) % 2 == 0 ? 'L' : 'R';
+
+                for (int j = 0; j < 8; j++)
+                {
+                    char srcCoord = coordz[j % 4];
+                    char srcSide = (j / 4) % 2 == 0 ? 'L' : 'R';
+                    
+                    string expression = $"d.V{j}{destSide}.{destCoord} = V{i}{srcSide}.{srcCoord}; ";
+					Write(expression);
+                }
+				WriteLine("");
+            }
+			PopIndent();
+			#>
+        }
+
+		/// <summary>
+        /// Level shift by +128, clip to [0, 255]
+        /// </summary>
+        /// <param name="d">Destination</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void TransformByteConvetibleColorValuesInto(ref Block8x8F d)
+        {
+            <#
+
+			PushIndent("            "); 
+
+            for (int i = 0; i < 8; i++)
+            {
+                for (int j = 0; j < 2; j++)
+                {
+					char side = j == 0 ? 'L' : 'R';
+					Write($"d.V{i}{side} = Vector4.Max(Vector4.Min(V{i}{side}, CMax4), CMin4) + COff4;");
+                }
+				WriteLine("");
+            }
+			PopIndent();
+			#>
+        }
+
+
+	}
+}

src/ImageSharp/Formats/Jpg/Components/Block8x8F.cs

@@ -0,0 +1,405 @@
+// <copyright file="Block8x8F.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+// ReSharper disable InconsistentNaming
+namespace ImageSharp.Formats
+{
+    using System;
+    using System.Numerics;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.InteropServices;
+
+    /// <summary>
+    /// DCT code Ported from https://github.com/norishigefukushima/dct_simd
+    /// </summary>
+    internal partial struct Block8x8F
+    {
+        public Vector4 V0L;
+        public Vector4 V0R;
+
+        public Vector4 V1L;
+        public Vector4 V1R;
+
+        public Vector4 V2L;
+        public Vector4 V2R;
+
+        public Vector4 V3L;
+        public Vector4 V3R;
+
+        public Vector4 V4L;
+        public Vector4 V4R;
+
+        public Vector4 V5L;
+        public Vector4 V5R;
+
+        public Vector4 V6L;
+        public Vector4 V6R;
+
+        public Vector4 V7L;
+        public Vector4 V7R;
+
+        public const int VectorCount = 16;
+        public const int ScalarCount = VectorCount*4;
+
+        /// <summary>
+        /// Load raw 32bit floating point data from source
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe void LoadFrom(MutableSpan<float> source)
+        {
+            fixed (void* ptr = &this.V0L)
+            {
+                Marshal.Copy(source.Data, source.Offset, (IntPtr)ptr, ScalarCount);
+            }
+        }
+
+        /// <summary>
+        /// Load raw 32bit floating point data from source
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe void LoadFrom(Block8x8F* blockPtr, MutableSpan<float> source)
+        {
+            Marshal.Copy(source.Data, source.Offset, (IntPtr)blockPtr, ScalarCount);
+        }
+
+        /// <summary>
+        /// Load raw 32bit floating point data from source
+        /// </summary>
+        internal unsafe void LoadFrom(MutableSpan<int> source)
+        {
+            fixed (Vector4* ptr = &this.V0L)
+            {
+                float* fp = (float*)ptr;
+                for (int i = 0; i < ScalarCount; i++)
+                {
+                    fp[i] = source[i];
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copy raw 32bit floating point data to dest
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe void CopyTo(MutableSpan<float> dest)
+        {
+            fixed (void* ptr = &this.V0L)
+            {
+                Marshal.Copy((IntPtr)ptr, dest.Data, dest.Offset, ScalarCount);
+            }
+        }
+
+        /// <summary>
+        /// Copy raw 32bit floating point data to dest
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe void CopyTo(float[] dest)
+        {
+            fixed (void* ptr = &this.V0L)
+            {
+                Marshal.Copy((IntPtr)ptr, dest, 0, ScalarCount);
+            }
+        }
+
+        /// <summary>
+        /// Copy raw 32bit floating point data to dest
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe void CopyTo(Block8x8F* blockPtr, MutableSpan<float> dest)
+        {
+            Marshal.Copy((IntPtr)blockPtr, dest.Data, dest.Offset, ScalarCount);
+        }
+
+        /// <summary>
+        /// Copy raw 32bit floating point data to dest
+        /// </summary>
+        internal unsafe void CopyTo(MutableSpan<int> dest)
+        {
+            fixed (Vector4* ptr = &this.V0L)
+            {
+                float* fp = (float*)ptr;
+                for (int i = 0; i < ScalarCount; i++)
+                {
+                    dest[i] = (int)fp[i];
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void MultiplyAllInplace(Vector4 s)
+        {
+            this.V0L *= s;
+            this.V0R *= s;
+            this.V1L *= s;
+            this.V1R *= s;
+            this.V2L *= s;
+            this.V2R *= s;
+            this.V3L *= s;
+            this.V3R *= s;
+            this.V4L *= s;
+            this.V4R *= s;
+            this.V5L *= s;
+            this.V5R *= s;
+            this.V6L *= s;
+            this.V6R *= s;
+            this.V7L *= s;
+            this.V7R *= s;
+        }
+
+        /// <summary>
+        /// Apply floating point IDCT transformation into dest, using a temporary block 'temp' provided by the caller (optimization)
+        /// </summary>
+        /// <param name="dest">Destination</param>
+        /// <param name="temp">Temporary block provided by the caller</param>
+        public void TransformIDCTInto(ref Block8x8F dest, ref Block8x8F temp)
+        {
+            this.TransposeInto(ref temp);
+            temp.IDCT8x4_LeftPart(ref dest);
+            temp.IDCT8x4_RightPart(ref dest);
+
+            dest.TransposeInto(ref temp);
+
+            temp.IDCT8x4_LeftPart(ref dest);
+            temp.IDCT8x4_RightPart(ref dest);
+
+            dest.MultiplyAllInplace(c_0_125);
+        }
+
+        private static readonly Vector4 c_1_175876 = new Vector4(1.175876f);
+        private static readonly Vector4 c_1_961571 = new Vector4(-1.961571f);
+        private static readonly Vector4 c_0_390181 = new Vector4(-0.390181f);
+        private static readonly Vector4 c_0_899976 = new Vector4(-0.899976f);
+        private static readonly Vector4 c_2_562915 = new Vector4(-2.562915f);
+        private static readonly Vector4 c_0_298631 = new Vector4(0.298631f);
+        private static readonly Vector4 c_2_053120 = new Vector4(2.053120f);
+        private static readonly Vector4 c_3_072711 = new Vector4(3.072711f);
+        private static readonly Vector4 c_1_501321 = new Vector4(1.501321f);
+        private static readonly Vector4 c_0_541196 = new Vector4(0.541196f);
+        private static readonly Vector4 c_1_847759 = new Vector4(-1.847759f);
+        private static readonly Vector4 c_0_765367 = new Vector4(0.765367f);
+
+        private static readonly Vector4 c_0_125 = new Vector4(0.1250f);
+
+        /// <summary>
+        /// Do IDCT internal operations on the left part of the block. Original source:
+        /// https://github.com/norishigefukushima/dct_simd/blob/master/dct/dct8x8_simd.cpp#L261
+        /// </summary>
+        /// <param name="d">Destination block</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void IDCT8x4_LeftPart(ref Block8x8F d)
+        {
+            Vector4 my1 = this.V1L;
+            Vector4 my7 = this.V7L;
+            Vector4 mz0 = my1 + my7;
+
+            Vector4 my3 = this.V3L;
+            Vector4 mz2 = my3 + my7;
+            Vector4 my5 = this.V5L;
+            Vector4 mz1 = my3 + my5;
+            Vector4 mz3 = my1 + my5;
+
+            Vector4 mz4 = ((mz0 + mz1) * c_1_175876);
+
+            mz2 = (mz2 * c_1_961571) + mz4;
+            mz3 = (mz3 * c_0_390181) + mz4;
+            mz0 = mz0 * c_0_899976;
+            mz1 = mz1 * c_2_562915;
+
+            Vector4 mb3 = (my7 * c_0_298631) + mz0 + mz2;
+            Vector4 mb2 = (my5 * c_2_053120) + mz1 + mz3;
+            Vector4 mb1 = (my3 * c_3_072711) + mz1 + mz2;
+            Vector4 mb0 = (my1 * c_1_501321) + mz0 + mz3;
+
+            Vector4 my2 = this.V2L;
+            Vector4 my6 = this.V6L;
+            mz4 = (my2 + my6) * c_0_541196;
+            Vector4 my0 = this.V0L;
+            Vector4 my4 = this.V4L;
+            mz0 = my0 + my4;
+            mz1 = my0 - my4;
+
+            mz2 = mz4 + (my6 * c_1_847759);
+            mz3 = mz4 + (my2 * c_0_765367);
+
+            my0 = mz0 + mz3;
+            my3 = mz0 - mz3;
+            my1 = mz1 + mz2;
+            my2 = mz1 - mz2;
+
+            d.V0L = my0 + mb0;
+            d.V7L = my0 - mb0;
+            d.V1L = my1 + mb1;
+            d.V6L = my1 - mb1;
+            d.V2L = my2 + mb2;
+            d.V5L = my2 - mb2;
+            d.V3L = my3 + mb3;
+            d.V4L = my3 - mb3;
+        }
+
+        /// <summary>
+        /// Do IDCT internal operations on the right part of the block.
+        /// Original source:
+        /// https://github.com/norishigefukushima/dct_simd/blob/master/dct/dct8x8_simd.cpp#L261
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void IDCT8x4_RightPart(ref Block8x8F d)
+        {
+            Vector4 my1 = this.V1R;
+            Vector4 my7 = this.V7R;
+            Vector4 mz0 = my1 + my7;
+
+            Vector4 my3 = this.V3R;
+            Vector4 mz2 = my3 + my7;
+            Vector4 my5 = this.V5R;
+            Vector4 mz1 = my3 + my5;
+            Vector4 mz3 = my1 + my5;
+
+            Vector4 mz4 = (mz0 + mz1) * c_1_175876;
+
+            mz2 = (mz2 * c_1_961571) + mz4;
+            mz3 = (mz3 * c_0_390181) + mz4;
+            mz0 = mz0 * c_0_899976;
+            mz1 = mz1 * c_2_562915;
+
+            Vector4 mb3 = (my7 * c_0_298631) + mz0 + mz2;
+            Vector4 mb2 = (my5 * c_2_053120) + mz1 + mz3;
+            Vector4 mb1 = (my3 * c_3_072711) + mz1 + mz2;
+            Vector4 mb0 = (my1 * c_1_501321) + mz0 + mz3;
+
+            Vector4 my2 = this.V2R;
+            Vector4 my6 = this.V6R;
+            mz4 = (my2 + my6) * c_0_541196;
+            Vector4 my0 = this.V0R;
+            Vector4 my4 = this.V4R;
+            mz0 = my0 + my4;
+            mz1 = my0 - my4;
+
+            mz2 = mz4 + (my6 * c_1_847759);
+            mz3 = mz4 + (my2 * c_0_765367);
+
+            my0 = mz0 + mz3;
+            my3 = mz0 - mz3;
+            my1 = mz1 + mz2;
+            my2 = mz1 - mz2;
+
+            d.V0R = my0 + mb0;
+            d.V7R = my0 - mb0;
+            d.V1R = my1 + mb1;
+            d.V6R = my1 - mb1;
+            d.V2R = my2 + mb2;
+            d.V5R = my2 - mb2;
+            d.V3R = my3 + mb3;
+            d.V4R = my3 - mb3;
+        }
+
+        public unsafe float this[int idx]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                fixed (Block8x8F* p = &this)
+                {
+                    float* fp = (float*)p;
+                    return fp[idx];
+                }
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            set
+            {
+                fixed (Block8x8F* p = &this)
+                {
+                    float* fp = (float*)p;
+                    fp[idx] = value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Pointer-based "Indexer" (getter part)
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe float GetScalarAt(Block8x8F* blockPtr, int idx)
+        {
+            float* fp = (float*)blockPtr;
+            return fp[idx];
+        }
+
+        /// <summary>
+        /// Pointer-based "Indexer" (setter part)
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe void SetScalarAt(Block8x8F* blockPtr, int idx, float value)
+        {
+            float* fp = (float*)blockPtr;
+            fp[idx] = value;
+        }
+
+        /// <summary>
+        /// Fill the block with defaults (zeroes)
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void Clear()
+        {
+            // The cheapest way to do this in C#:
+            this = new Block8x8F();
+        }
+
+        /// <summary>
+        /// TODO: Should be removed when BlockF goes away
+        /// </summary>
+        /// <param name="legacyBlock"></param>
+        internal void LoadFrom(ref BlockF legacyBlock)
+        {
+            this.LoadFrom(legacyBlock.Data);
+        }
+
+        /// <summary>
+        /// TODO: Should be removed when BlockF goes away
+        /// </summary>
+        /// <param name="legacyBlock"></param>
+        internal void CopyTo(ref BlockF legacyBlock)
+        {
+            this.CopyTo(legacyBlock.Data);
+        }
+
+        /// <summary>
+        /// Level shift by +128, clip to [0, 255], and write to buffer.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal unsafe void CopyColorsTo(MutableSpan<byte> buffer, int stride, Block8x8F* temp)
+        {
+            this.TransformByteConvetibleColorValuesInto(ref *temp);
+
+            float* src = (float*)temp;
+            for (int i = 0; i < 8; i++)
+            {
+                buffer[0] = (byte)src[0];
+                buffer[1] = (byte)src[1];
+                buffer[2] = (byte)src[2];
+                buffer[3] = (byte)src[3];
+                buffer[4] = (byte)src[4];
+                buffer[5] = (byte)src[5];
+                buffer[6] = (byte)src[6];
+                buffer[7] = (byte)src[7];
+                buffer.AddOffset(stride);
+                src += 8;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe void UnZig(Block8x8F* block, Block8x8F* qt, int* unzigPtr)
+        {
+            float* b = (float*)block;
+            float* qtp = (float*)qt;
+            for (int zig = 0; zig < BlockF.BlockSize; zig++)
+            {
+                float* unzigPos = b + unzigPtr[zig];
+                float val = *unzigPos;
+                val *= qtp[zig];
+                *unzigPos = val;
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Jpg/Components/Bytes.cs

@@ -2,25 +2,28 @@
 // Copyright (c) James Jackson-South and contributors.
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
-
 namespace ImageSharp.Formats
 {
+    using System;
+    using System.Buffers;
+    using System.IO;
+    using System.Runtime.CompilerServices;
+
     /// <summary>
     /// Bytes is a byte buffer, similar to a stream, except that it
     /// has to be able to unread more than 1 byte, due to byte stuffing.
     /// Byte stuffing is specified in section F.1.2.3.
     /// </summary>
-    internal class Bytes
+    internal struct Bytes : IDisposable
     {
+        private static readonly ArrayPool<byte> ArrayPool = ArrayPool<byte>.Create(4096, 50);
+
         /// <summary>
-        /// Initializes a new instance of the <see cref="Bytes"/> class.
+        /// Creates a new instance of the <see cref="Bytes"/>, and initializes it's buffer.
         /// </summary>
-        public Bytes()
+        public static Bytes Create()
         {
-            this.Buffer = new byte[4096];
+            return new Bytes { Buffer = ArrayPool.Rent(4096) };
-            this.I = 0;
-            this.J = 0;
-            this.UnreadableBytes = 0;
         }
 
         /// <summary>
@@ -28,16 +31,128 @@ namespace ImageSharp.Formats
         /// buffer[i:j] are the buffered bytes read from the underlying
         /// stream that haven't yet been passed further on.
         /// </summary>
-        public byte[] Buffer { get; set; }
+        public byte[] Buffer;
 
-        public int I { get; set; }
+        public int I;
 
-        public int J { get; set; }
+        public int J;
 
         /// <summary>
         /// Gets or sets the unreadable bytes. The number of bytes to back up i after
         /// overshooting. It can be 0, 1 or 2.
         /// </summary>
-        public int UnreadableBytes { get; set; }
+        public int UnreadableBytes;
+
+        public void Dispose()
+        {
+            if (this.Buffer != null) ArrayPool.Return(this.Buffer);
+            this.Buffer = null;
+        }
+
+        /// <summary>
+        /// ReadByteStuffedByte is like ReadByte but is for byte-stuffed Huffman data.
+        /// </summary>
+        /// <returns>The <see cref="byte"/></returns>
+        internal byte ReadByteStuffedByte(Stream inputStream, out JpegDecoderCore.ErrorCodes errorCode)
+        {
+            byte x;
+
+            errorCode = JpegDecoderCore.ErrorCodes.NoError;
+
+            // Take the fast path if bytes.buf contains at least two bytes.
+            if (this.I + 2 <= this.J)
+            {
+                x = this.Buffer[this.I];
+                this.I++;
+                this.UnreadableBytes = 1;
+                if (x != JpegConstants.Markers.XFF)
+                {
+                    return x;
+                }
+
+                if (this.Buffer[this.I] != 0x00)
+                {
+                    errorCode = JpegDecoderCore.ErrorCodes.MissingFF00;
+                    return 0;
+
+                    // throw new MissingFF00Exception();
+                }
+
+                this.I++;
+                this.UnreadableBytes = 2;
+                return JpegConstants.Markers.XFF;
+            }
+
+            this.UnreadableBytes = 0;
+
+            x = this.ReadByte(inputStream);
+            this.UnreadableBytes = 1;
+            if (x != JpegConstants.Markers.XFF)
+            {
+                return x;
+            }
+
+            x = this.ReadByte(inputStream);
+            this.UnreadableBytes = 2;
+            if (x != 0x00)
+            {
+                errorCode = JpegDecoderCore.ErrorCodes.MissingFF00;
+                return 0;
+
+                // throw new MissingFF00Exception();
+            }
+
+            return JpegConstants.Markers.XFF;
+        }
+
+        /// <summary>
+        /// Returns the next byte, whether buffered or not buffered. It does not care about byte stuffing.
+        /// </summary>
+        /// <returns>The <see cref="byte"/></returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal byte ReadByte(Stream inputStream)
+        {
+            while (this.I == this.J)
+            {
+                this.Fill(inputStream);
+            }
+
+            byte x = this.Buffer[this.I];
+            this.I++;
+            this.UnreadableBytes = 0;
+            return x;
+        }
+
+        /// <summary>
+        /// Fills up the bytes buffer from the underlying stream.
+        /// It should only be called when there are no unread bytes in bytes.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void Fill(Stream inputStream)
+        {
+            if (this.I != this.J)
+            {
+                throw new ImageFormatException("Fill called when unread bytes exist.");
+            }
+
+            // Move the last 2 bytes to the start of the buffer, in case we need
+            // to call UnreadByteStuffedByte.
+            if (this.J > 2)
+            {
+                this.Buffer[0] = this.Buffer[this.J - 2];
+                this.Buffer[1] = this.Buffer[this.J - 1];
+                this.I = 2;
+                this.J = 2;
+            }
+
+            // Fill in the rest of the buffer.
+            int n = inputStream.Read(this.Buffer, this.J, this.Buffer.Length - this.J);
+            if (n == 0)
+            {
+                throw new JpegDecoderCore.EOFException();
+            }
+
+            this.J += n;
+        }
     }
-}
+}

src/ImageSharp/Formats/Jpg/Components/Component.cs

@@ -8,26 +8,26 @@ namespace ImageSharp.Formats
     /// <summary>
     /// Represents a single color component
     /// </summary>
-    internal class Component
+    internal struct Component
     {
         /// <summary>
         /// Gets or sets the horizontal sampling factor.
         /// </summary>
-        public int HorizontalFactor { get; set; }
+        public int HorizontalFactor;
 
         /// <summary>
         /// Gets or sets the vertical sampling factor.
         /// </summary>
-        public int VerticalFactor { get; set; }
+        public int VerticalFactor;
 
         /// <summary>
         /// Gets or sets the identifier
         /// </summary>
-        public byte Identifier { get; set; }
+        public byte Identifier;
 
         /// <summary>
         /// Gets or sets the quantization table destination selector.
         /// </summary>
-        public byte Selector { get; set; }
+        public byte Selector;
     }
 }

src/ImageSharp/Formats/Jpg/Components/FDCT.cs

@@ -45,7 +45,7 @@ namespace ImageSharp.Formats
         /// Performs a forward DCT on an 8x8 block of coefficients, including a level shift.
         /// </summary>
         /// <param name="block">The block of coefficients.</param>
-        public static void Transform(Block block)
+        public static void Transform(ref Block block)
         {
             // Pass 1: process rows.
             for (int y = 0; y < 8; y++)

src/ImageSharp/Formats/Jpg/Components/Huffman.cs

@@ -2,34 +2,36 @@
 // Copyright (c) James Jackson-South and contributors.
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
-
 namespace ImageSharp.Formats
 {
+    using System;
+    using System.Buffers;
+
     /// <summary>
     /// Represents a Huffman tree
     /// </summary>
-    internal class Huffman
+    internal struct Huffman : IDisposable
     {
-        /// <summary>
+        private static ArrayPool<ushort> UshortBuffer = ArrayPool<ushort>.Create(1 << JpegDecoderCore.LutSize, 50);
-        /// Initializes a new instance of the <see cref="Huffman"/> class.
+
-        /// </summary>
+        private static ArrayPool<byte> ByteBuffer = ArrayPool<byte>.Create(JpegDecoderCore.MaxNCodes, 50);
-        /// <param name="lutSize">The log-2 size of the Huffman decoder's look-up table.</param>
+
-        /// <param name="maxNCodes">The maximum (inclusive) number of codes in a Huffman tree.</param>
+        private static readonly ArrayPool<int> IntBuffer = ArrayPool<int>.Create(JpegDecoderCore.MaxCodeLength, 50);
-        /// <param name="maxCodeLength">The maximum (inclusive) number of bits in a Huffman code.</param>
+
-        public Huffman(int lutSize, int maxNCodes, int maxCodeLength)
+        public void Init(int lutSize, int maxNCodes, int maxCodeLength)
         {
-            this.Lut = new ushort[1 << lutSize];
+            this.Lut = UshortBuffer.Rent(1 << lutSize);
-            this.Values = new byte[maxNCodes];
+            this.Values = ByteBuffer.Rent(maxNCodes);
-            this.MinCodes = new int[maxCodeLength];
+            this.MinCodes = IntBuffer.Rent(maxCodeLength);
-            this.MaxCodes = new int[maxCodeLength];
+            this.MaxCodes = IntBuffer.Rent(maxCodeLength);            
-            this.Indices = new int[maxCodeLength];
+            this.Indices = IntBuffer.Rent(maxCodeLength);
-            this.Length = 0;
+            
         }
 
         /// <summary>
         /// Gets or sets the number of codes in the tree.
         /// </summary>
-        public int Length { get; set; }
+        public int Length;
 
         /// <summary>
         /// Gets the look-up table for the next LutSize bits in the bit-stream.
@@ -37,28 +39,37 @@ namespace ImageSharp.Formats
         /// are 1 plus the code length, or 0 if the value is too large to fit in
         /// lutSize bits.
         /// </summary>
-        public ushort[] Lut { get; }
+        public ushort[] Lut;
 
         /// <summary>
         /// Gets the the decoded values, sorted by their encoding.
         /// </summary>
-        public byte[] Values { get; }
+        public byte[] Values;
 
         /// <summary>
         /// Gets the array of minimum codes.
         /// MinCodes[i] is the minimum code of length i, or -1 if there are no codes of that length.
         /// </summary>
-        public int[] MinCodes { get; }
+        public int[] MinCodes;
 
         /// <summary>
         /// Gets the array of maximum codes.
         /// MaxCodes[i] is the maximum code of length i, or -1 if there are no codes of that length.
         /// </summary>
-        public int[] MaxCodes { get; }
+        public int[] MaxCodes;
 
         /// <summary>
         /// Gets the array of indices. Indices[i] is the index into Values of MinCodes[i].
         /// </summary>
-        public int[] Indices { get; }
+        public int[] Indices;
+
+        public void Dispose()
+        {
+            UshortBuffer.Return(this.Lut, true);
+            ByteBuffer.Return(this.Values, true);
+            IntBuffer.Return(this.MinCodes, true);
+            IntBuffer.Return(this.MaxCodes, true);
+            IntBuffer.Return(this.Indices, true);
+        }
     }
 }

src/ImageSharp/Formats/Jpg/Components/IDCT.cs

@@ -39,7 +39,7 @@ namespace ImageSharp.Formats
         /// ASSP, Vol. ASSP- 32, pp. 803-816, Aug. 1984.
         /// </summary>
         /// <param name="src">The source block of coefficients</param>
-        public static void Transform(Block src)
+        public static void Transform(ref Block src)
         {
             // Horizontal 1-D IDCT.
             for (int y = 0; y < 8; y++)
@@ -165,5 +165,6 @@ namespace ImageSharp.Formats
                 src[56 + x] = (y7 - y1) >> 14;
             }
         }
+
     }
 }

src/ImageSharp/Formats/Jpg/Components/MutableSpan.cs

@@ -0,0 +1,108 @@
+// <copyright file="MutableSpan.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp.Formats
+{
+    using System.Numerics;
+    using System.Runtime.CompilerServices;
+
+    /// <summary>
+    /// Like corefxlab Span, but with an AddOffset() method for efficiency.
+    /// TODO: When Span will be official, consider replacing this class!
+    /// </summary>
+    /// <see>
+    ///     <cref>https://github.com/dotnet/corefxlab/blob/master/src/System.Slices/System/Span.cs</cref>
+    /// </see>
+    /// <typeparam name="T"></typeparam>
+    internal struct MutableSpan<T>
+    {
+        public T[] Data;
+
+        public int Offset;
+
+        public int TotalCount => this.Data.Length - this.Offset;
+
+        public MutableSpan(int size, int offset = 0)
+        {
+            this.Data = new T[size];
+            this.Offset = offset;
+        }
+
+        public MutableSpan(T[] data, int offset = 0)
+        {
+            this.Data = data;
+            this.Offset = offset;
+        }
+
+        public T this[int idx]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return this.Data[idx + this.Offset];
+            }
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            set
+            {
+                this.Data[idx + this.Offset] = value;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public MutableSpan<T> Slice(int offset)
+        {
+            return new MutableSpan<T>(this.Data, this.Offset + offset);
+        }
+
+        public static implicit operator MutableSpan<T>(T[] data) => new MutableSpan<T>(data, 0);
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void AddOffset(int offset)
+        {
+            this.Offset += offset;
+        }
+    }
+
+    internal static class MutableSpanExtensions
+    {
+        public static MutableSpan<T> Slice<T>(this T[] array, int offset) => new MutableSpan<T>(array, offset);
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void SaveTo(this MutableSpan<float> data, ref Vector4 v)
+        {
+            v.X = data[0];
+            v.Y = data[1];
+            v.Z = data[2];
+            v.W = data[3];
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void SaveTo(this MutableSpan<int> data, ref Vector4 v)
+        {
+            v.X = data[0];
+            v.Y = data[1];
+            v.Z = data[2];
+            v.W = data[3];
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void LoadFrom(this MutableSpan<float> data, ref Vector4 v)
+        {
+            data[0] = v.X;
+            data[1] = v.Y;
+            data[2] = v.Z;
+            data[3] = v.W;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void LoadFrom(this MutableSpan<int> data, ref Vector4 v)
+        {
+            data[0] = (int)v.X;
+            data[1] = (int)v.Y;
+            data[2] = (int)v.Z;
+            data[3] = (int)v.W;
+        }
+    }
+}

src/ImageSharp/Formats/Jpg/JpegDecoder.cs

@@ -83,8 +83,10 @@ namespace ImageSharp.Formats
             Guard.NotNull(image, "image");
             Guard.NotNull(stream, "stream");
 
-            JpegDecoderCore decoder = new JpegDecoderCore();
+            using (JpegDecoderCore decoder = new JpegDecoderCore())
-            decoder.Decode(image, stream, false);
+            {
+                decoder.Decode(image, stream, false);
+            }
         }
 
         /// <summary>

src/ImageSharp/Formats/Jpg/JpegEncoderCore.cs

@@ -246,6 +246,7 @@ namespace ImageSharp.Formats
             /// <summary>
             /// The AC luminance huffman table index
             /// </summary>
+
             LuminanceAC = 1,
             // ReSharper restore UnusedMember.Local
 
@@ -487,9 +488,9 @@ namespace ImageSharp.Formats
         /// <param name="index">The quantization table index.</param>
         /// <param name="prevDC">The previous DC value.</param>
         /// <returns>The <see cref="int"/></returns>
-        private int WriteBlock(Block block, QuantIndex index, int prevDC)
+        private int WriteBlock(ref Block block, QuantIndex index, int prevDC)
         {
-            FDCT.Transform(block);
+            FDCT.Transform(ref block);
 
             // Emit the DC delta.
             int dc = Round(block[0], 8 * this.quant[(int)index][0]);
@@ -540,7 +541,7 @@ namespace ImageSharp.Formats
         /// <param name="cbBlock">The red chroma block.</param>
         /// <param name="crBlock">The blue chroma block.</param>
         // ReSharper disable StyleCop.SA1305
-        private void ToYCbCr<TColor, TPacked>(PixelAccessor<TColor, TPacked> pixels, int x, int y, Block yBlock, Block cbBlock, Block crBlock)
+        private void ToYCbCr<TColor, TPacked>(PixelAccessor<TColor, TPacked> pixels, int x, int y, ref Block yBlock, ref Block cbBlock, ref Block crBlock)
             // ReSharper restore StyleCop.SA1305
             where TColor : struct, IPackedPixel<TPacked>
             where TPacked : struct
@@ -577,7 +578,7 @@ namespace ImageSharp.Formats
         /// </summary>
         /// <param name="destination">The destination block array</param>
         /// <param name="source">The source block array.</param>
-        private void Scale16X16To8X8(Block destination, Block[] source)
+        private void Scale16X16To8X8(ref Block destination, Block[] source)
         {
             for (int i = 0; i < 4; i++)
             {
@@ -847,10 +848,10 @@ namespace ImageSharp.Formats
             where TColor : struct, IPackedPixel<TPacked>
             where TPacked : struct
         {
-            Block b = new Block();
+            Block b = Block.Create();
-            Block cb = new Block();
+            Block cb = Block.Create();
-            Block cr = new Block();
+            Block cr = Block.Create();
-           
+
             // ReSharper disable once InconsistentNaming
             int prevDCY = 0, prevDCCb = 0, prevDCCr = 0;
 
@@ -858,12 +859,16 @@ namespace ImageSharp.Formats
             {
                 for (int x = 0; x < pixels.Width; x += 8)
                 {
-                    this.ToYCbCr(pixels, x, y, b, cb, cr);
+                    this.ToYCbCr(pixels, x, y, ref b, ref cb, ref cr);
-                    prevDCY = this.WriteBlock(b, QuantIndex.Luminance, prevDCY);
+                    prevDCY = this.WriteBlock(ref b, QuantIndex.Luminance, prevDCY);
-                    prevDCCb = this.WriteBlock(cb, QuantIndex.Chrominance, prevDCCb);
+                    prevDCCb = this.WriteBlock(ref cb, QuantIndex.Chrominance, prevDCCb);
-                    prevDCCr = this.WriteBlock(cr, QuantIndex.Chrominance, prevDCCr);
+                    prevDCCr = this.WriteBlock(ref cr, QuantIndex.Chrominance, prevDCCr);
                 }
             }
+
+            b.Dispose();
+            cb.Dispose();
+            cr.Dispose();
         }
 
         /// <summary>
@@ -877,23 +882,13 @@ namespace ImageSharp.Formats
             where TColor : struct, IPackedPixel<TPacked>
             where TPacked : struct
         {
-            Block b = new Block();
+            Block b = Block.Create();
-            Block[] cb = new Block[4];
+            Block[] cb = Block.CreateArray(4);
-            Block[] cr = new Block[4];
+            Block[] cr = Block.CreateArray(4);
-           
+
             // ReSharper disable once InconsistentNaming
             int prevDCY = 0, prevDCCb = 0, prevDCCr = 0;
 
-            for (int i = 0; i < 4; i++)
-            {
-                cb[i] = new Block();
-            }
-
-            for (int i = 0; i < 4; i++)
-            {
-                cr[i] = new Block();
-            }
-
             for (int y = 0; y < pixels.Height; y += 16)
             {
                 for (int x = 0; x < pixels.Width; x += 16)
@@ -903,16 +898,20 @@ namespace ImageSharp.Formats
                         int xOff = (i & 1) * 8;
                         int yOff = (i & 2) * 4;
 
-                        this.ToYCbCr(pixels, x + xOff, y + yOff, b, cb[i], cr[i]);
+                        this.ToYCbCr(pixels, x + xOff, y + yOff, ref b, ref cb[i], ref cr[i]);
-                        prevDCY = this.WriteBlock(b, QuantIndex.Luminance, prevDCY);
+                        prevDCY = this.WriteBlock(ref b, QuantIndex.Luminance, prevDCY);
                     }
 
-                    this.Scale16X16To8X8(b, cb);
+                    this.Scale16X16To8X8(ref b, cb);
-                    prevDCCb = this.WriteBlock(b, QuantIndex.Chrominance, prevDCCb);
+                    prevDCCb = this.WriteBlock(ref b, QuantIndex.Chrominance, prevDCCb);
-                    this.Scale16X16To8X8(b, cr);
+                    this.Scale16X16To8X8(ref b, cr);
-                    prevDCCr = this.WriteBlock(b, QuantIndex.Chrominance, prevDCCr);
+                    prevDCCr = this.WriteBlock(ref b, QuantIndex.Chrominance, prevDCCr);
                 }
             }
+
+            b.Dispose();
+            Block.DisposeAll(cb);
+            Block.DisposeAll(cr);
         }
 
         /// <summary>

tests/ImageSharp.Tests/Formats/Bmp/BitmapTests.cs

@@ -3,6 +3,8 @@
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
 
+using ImageSharp.Formats;
+
 namespace ImageSharp.Tests
 {
     using System.IO;

tests/ImageSharp.Tests/Formats/Jpg/Block8x8FTests.cs

@@ -0,0 +1,367 @@
+// Uncomment this to turn unit tests into benchmarks:
+//#define BENCHMARKING
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using ImageSharp.Formats;
+using Xunit;
+using Xunit.Abstractions;
+// ReSharper disable InconsistentNaming
+
+namespace ImageSharp.Tests.Formats.Jpg
+{
+    public class Block8x8FTests : UtilityTestClassBase
+    {
+#if BENCHMARKING
+        public const int Times = 1000000;
+#else
+        public const int Times = 1;
+#endif
+
+        public Block8x8FTests(ITestOutputHelper output) : base(output)
+        {
+        }
+
+        [Fact]
+        public void Indexer()
+        {
+            float sum = 0;
+            this.Measure(Times, () =>
+            {
+                Block8x8F block = new Block8x8F();
+
+                for (int i = 0; i < Block8x8F.ScalarCount; i++)
+                {
+                    block[i] = i;
+                }
+                sum = 0;
+                for (int i = 0; i < Block8x8F.ScalarCount; i++)
+                {
+                    sum += block[i];
+                }
+                });
+            Assert.Equal(sum, 64f * 63f * 0.5f);
+        }
+
+        [Fact]
+        public unsafe void Indexer_GetScalarAt_SetScalarAt()
+        {
+            float sum = 0;
+            Measure(Times, () =>
+            {
+                Block8x8F block = new Block8x8F();
+
+                for (int i = 0; i < Block8x8F.ScalarCount; i++)
+                {
+                    Block8x8F.SetScalarAt(&block, i, i);
+                }
+                sum = 0;
+                for (int i = 0; i < Block8x8F.ScalarCount; i++)
+                {
+                    sum += Block8x8F.GetScalarAt(&block, i);
+                }
+            });
+            Assert.Equal(sum, 64f*63f*0.5f);
+        }
+
+        [Fact]
+        public void Indexer_ReferenceBenchmarkWithArray()
+        {
+            float sum = 0;
+
+
+            Measure(Times, () =>
+            {
+                //Block8x8F block = new Block8x8F();
+                float[] block = new float[64];
+                for (int i = 0; i < Block8x8F.ScalarCount; i++)
+                {
+                    block[i] = i;
+                }
+                sum = 0;
+                for (int i = 0; i < Block8x8F.ScalarCount; i++)
+                {
+                    sum += block[i];
+                }
+            });
+            Assert.Equal(sum, 64f*63f*0.5f);
+        }
+
+        [Fact]
+        public void Load_Store_FloatArray()
+        {
+            float[] data = new float[Block8x8F.ScalarCount];
+            float[] mirror = new float[Block8x8F.ScalarCount];
+
+            for (int i = 0; i < Block8x8F.ScalarCount; i++)
+            {
+                data[i] = i;
+            }
+            Measure(Times, () =>
+            {
+                Block8x8F b = new Block8x8F();
+                b.LoadFrom(data);
+                b.CopyTo(mirror);
+            });
+
+            Assert.Equal(data, mirror);
+            //PrintLinearData((MutableSpan<float>)mirror);
+        }
+
+        [Fact]
+        public unsafe void Load_Store_FloatArray_Ptr()
+        {
+            float[] data = new float[Block8x8F.ScalarCount];
+            float[] mirror = new float[Block8x8F.ScalarCount];
+
+            for (int i = 0; i < Block8x8F.ScalarCount; i++)
+            {
+                data[i] = i;
+            }
+            Measure(Times, () =>
+            {
+                Block8x8F b = new Block8x8F();
+                Block8x8F.LoadFrom(&b, data);
+                Block8x8F.CopyTo(&b, mirror);
+            });
+
+            Assert.Equal(data, mirror);
+            //PrintLinearData((MutableSpan<float>)mirror);
+        }
+
+        [Fact]
+        public void Load_Store_IntArray()
+        {
+            int[] data = new int[Block8x8F.ScalarCount];
+            int[] mirror = new int[Block8x8F.ScalarCount];
+
+            for (int i = 0; i < Block8x8F.ScalarCount; i++)
+            {
+                data[i] = i;
+            }
+            Measure(Times, () =>
+            {
+                Block8x8F v = new Block8x8F();
+                v.LoadFrom(data);
+                v.CopyTo(mirror);
+            });
+
+            
+            Assert.Equal(data, mirror);
+            //PrintLinearData((MutableSpan<int>)mirror);
+        }
+        
+        
+        [Fact]
+        public void TransposeInto()
+        {
+            float[] expected = Create8x8FloatData();
+            ReferenceImplementations.Transpose8x8(expected);
+
+            Block8x8F source = new Block8x8F();
+            source.LoadFrom(Create8x8FloatData());
+
+            Block8x8F dest = new Block8x8F();
+            source.TransposeInto(ref dest);
+
+            float[] actual = new float[64];
+            dest.CopyTo(actual);
+
+            Assert.Equal(expected, actual);
+        }
+        
+
+
+        private class BufferHolder
+        {
+            public Block8x8F Buffer;
+        }
+
+        [Fact]
+        public void TranposeInto_Benchmark()
+        {
+            BufferHolder source = new BufferHolder();
+            source.Buffer.LoadFrom(Create8x8FloatData());
+            BufferHolder dest = new BufferHolder();
+
+            Output.WriteLine($"TranposeInto_PinningImpl_Benchmark X {Times} ...");
+            Stopwatch sw = Stopwatch.StartNew();
+
+            for (int i = 0; i < Times; i++)
+            {
+                source.Buffer.TransposeInto(ref dest.Buffer);
+            }
+
+            sw.Stop();
+            Output.WriteLine($"TranposeInto_PinningImpl_Benchmark finished in {sw.ElapsedMilliseconds} ms");
+
+        }
+        
+        [Fact]
+        public void iDCT2D8x4_LeftPart()
+        {
+            float[] sourceArray = Create8x8FloatData();
+            float[] expectedDestArray = new float[64];
+
+            ReferenceImplementations.iDCT2D8x4_32f(sourceArray, expectedDestArray);
+
+            Block8x8F source = new Block8x8F();
+            source.LoadFrom(sourceArray);
+
+            Block8x8F dest = new Block8x8F();
+
+            source.IDCT8x4_LeftPart(ref dest);
+
+            float[] actualDestArray = new float[64];
+            dest.CopyTo(actualDestArray);
+
+            Print8x8Data(expectedDestArray);
+            Output.WriteLine("**************");
+            Print8x8Data(actualDestArray);
+
+            Assert.Equal(expectedDestArray, actualDestArray);
+        }
+
+        [Fact]
+        public void iDCT2D8x4_RightPart()
+        {
+            MutableSpan<float> sourceArray = Create8x8FloatData();
+            MutableSpan<float> expectedDestArray = new float[64];
+
+            ReferenceImplementations.iDCT2D8x4_32f(sourceArray.Slice(4), expectedDestArray.Slice(4));
+
+            Block8x8F source = new Block8x8F();
+            source.LoadFrom(sourceArray);
+
+            Block8x8F dest = new Block8x8F();
+
+            source.IDCT8x4_RightPart(ref dest);
+
+            float[] actualDestArray = new float[64];
+            dest.CopyTo(actualDestArray);
+
+            Print8x8Data(expectedDestArray);
+            Output.WriteLine("**************");
+            Print8x8Data(actualDestArray);
+
+            Assert.Equal(expectedDestArray.Data, actualDestArray);
+        }
+
+        private struct ApproximateFloatComparer : IEqualityComparer<float>
+        {
+            private const float Eps = 0.0001f;
+
+            public bool Equals(float x, float y)
+            {
+                float d = x - y;
+
+                return d > -Eps && d < Eps;
+            }
+
+            public int GetHashCode(float obj)
+            {
+                throw new InvalidOperationException();
+            }
+        }
+
+        [Fact]
+        public void IDCTInto()
+        {
+            float[] sourceArray = Create8x8FloatData();
+            float[] expectedDestArray = new float[64];
+            float[] tempArray = new float[64];
+
+            ReferenceImplementations.iDCT2D_llm(sourceArray, expectedDestArray, tempArray);
+
+            //ReferenceImplementations.iDCT8x8_llm_sse(sourceArray, expectedDestArray, tempArray);
+
+            Block8x8F source = new Block8x8F();
+            source.LoadFrom(sourceArray);
+
+            Block8x8F dest = new Block8x8F();
+            Block8x8F tempBuffer = new Block8x8F();
+
+            source.TransformIDCTInto(ref dest, ref tempBuffer);
+
+            float[] actualDestArray = new float[64];
+            dest.CopyTo(actualDestArray);
+
+            Print8x8Data(expectedDestArray);
+            Output.WriteLine("**************");
+            Print8x8Data(actualDestArray);
+            Assert.Equal(expectedDestArray, actualDestArray, new ApproximateFloatComparer());
+            Assert.Equal(expectedDestArray, actualDestArray, new ApproximateFloatComparer());
+        }
+
+
+        [Fact]
+        public unsafe void CopyColorsTo()
+        {
+            var data = Create8x8FloatData();
+            Block8x8F block = new Block8x8F();
+            block.LoadFrom(data);
+            block.MultiplyAllInplace(new Vector4(5, 5, 5, 5));
+
+            int stride = 256;
+            int height = 42;
+            int offset = height*10 + 20;
+
+            byte[] colorsExpected = new byte[stride*height];
+            byte[] colorsActual = new byte[stride*height];
+
+            Block8x8F temp = new Block8x8F();
+            
+            ReferenceImplementations.CopyColorsTo(ref block, new MutableSpan<byte>(colorsExpected, offset), stride);
+
+            block.CopyColorsTo(new MutableSpan<byte>(colorsActual, offset), stride, &temp);
+
+            //Output.WriteLine("******* EXPECTED: *********");
+            //PrintLinearData(colorsExpected);
+            //Output.WriteLine("******** ACTUAL: **********");
+
+            Assert.Equal(colorsExpected, colorsActual);
+        }
+        
+        private static float[] Create8x8ColorCropTestData()
+        {
+            float[] result = new float[64];
+            for (int i = 0; i < 8; i++)
+            {
+                for (int j = 0; j < 8; j++)
+                {
+                    result[i * 8 + j] = -300 + i * 100 + j * 10;
+                }
+            }
+            return result;
+        }
+
+        [Fact]
+        public void TransformByteConvetibleColorValuesInto()
+        {
+            Block8x8F block = new Block8x8F();
+            var input = Create8x8ColorCropTestData();
+            block.LoadFrom(input);
+            Output.WriteLine("Input:");
+            PrintLinearData(input);
+            
+
+            Block8x8F dest = new Block8x8F();
+            block.TransformByteConvetibleColorValuesInto(ref dest);
+
+            float[] array = new float[64];
+            dest.CopyTo(array);
+            Output.WriteLine("Result:");
+            PrintLinearData(array);
+            foreach (float val in array)
+            {
+                Assert.InRange(val, 0, 255);
+            }
+        }
+
+    }
+}

tests/ImageSharp.Tests/Formats/Jpg/JpegTests.cs

@@ -0,0 +1,85 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using ImageSharp.Formats;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace ImageSharp.Tests.Formats.Jpg
+{
+    public class JpegTests
+    {
+        
+        public const string TestOutputDirectory = "TestOutput/Jpeg";
+
+        private ITestOutputHelper Output { get; }
+
+        public JpegTests(ITestOutputHelper output)
+        {
+            Output = output;
+        }
+
+        protected string CreateTestOutputFile(string fileName)
+        {
+            if (!Directory.Exists(TestOutputDirectory))
+            {
+                Directory.CreateDirectory(TestOutputDirectory);
+            }
+
+            //string id = Guid.NewGuid().ToString().Substring(0, 4);
+
+            string ext = Path.GetExtension(fileName);
+            fileName = Path.GetFileNameWithoutExtension(fileName);
+
+            return $"{TestOutputDirectory}/{fileName}{ext}";
+        }
+
+        protected Stream CreateOutputStream(string fileName)
+        {
+            fileName = CreateTestOutputFile(fileName);
+            Output?.WriteLine("Opened for write: "+fileName);
+            return File.OpenWrite(fileName);
+        }
+
+        public static IEnumerable<object[]> AllJpegFiles
+            => TestImages.Jpeg.All.Select(fn => new object[] {fn});
+
+        [Theory]
+        [MemberData(nameof(AllJpegFiles))]
+        public void OpenJpeg_SaveBmp(string jpegPath)
+        {
+            string bmpFileName = Path.GetFileNameWithoutExtension(jpegPath) + ".bmp";
+
+            using (var inputStream = File.OpenRead(jpegPath))
+            {
+                var image = new Image(inputStream);
+                
+                using (var outputStream = CreateOutputStream(bmpFileName))
+                {
+                    image.Save(outputStream, new BmpFormat());
+                }
+            }
+        }
+
+        public static IEnumerable<object[]> AllBmpFiles
+            => TestImages.Bmp.All.Select(fn => new object[] {fn});
+
+        [Theory]
+        [MemberData(nameof(AllBmpFiles))]
+        public void OpenBmp_SaveJpeg(string bmpPath)
+        {
+            string jpegPath = Path.GetFileNameWithoutExtension(bmpPath) + ".jpeg";
+
+            using (var inputStream = File.OpenRead(bmpPath))
+            {
+                var image = new Image(inputStream);
+
+                using (var outputStream = CreateOutputStream(jpegPath))
+                {
+                    image.Save(outputStream, new JpegFormat());
+                }
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/Formats/Jpg/ReferenceImplementations.cs

@@ -0,0 +1,335 @@
+// ReSharper disable InconsistentNaming
+
+namespace ImageSharp.Tests.Formats.Jpg
+{
+    using System.Numerics;
+    using System.Runtime.CompilerServices;
+
+    using ImageSharp.Formats;
+
+    /// <summary>
+    /// This class contains simplified (unefficient) reference implementations to produce verification data for unit tests
+    /// DCT code Ported from https://github.com/norishigefukushima/dct_simd
+    /// </summary>
+    internal static class ReferenceImplementations
+    {
+        /// <summary>
+        /// Transpose 8x8 block stored linearly in a span (inplace)
+        /// </summary>
+        /// <param name="data"></param>
+        internal static void Transpose8x8(MutableSpan<float> data)
+        {
+            for (int i = 1; i < 8; i++)
+            {
+                int i8 = i * 8;
+                for (int j = 0; j < i; j++)
+                {
+                    float tmp = data[i8 + j];
+                    data[i8 + j] = data[j * 8 + i];
+                    data[j * 8 + i] = tmp;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Transpose 8x8 block stored linearly in a span
+        /// </summary>
+        internal static void Transpose8x8(MutableSpan<float> src, MutableSpan<float> dest)
+        {
+            for (int i = 0; i < 8; i++)
+            {
+                int i8 = i * 8;
+                for (int j = 0; j < 8; j++)
+                {
+                    dest[j * 8 + i] = src[i8 + j];
+                }
+            }
+        }
+
+        /// <summary>
+        /// https://github.com/norishigefukushima/dct_simd/blob/master/dct/dct8x8_simd.cpp#L200
+        /// </summary>
+        /// <param name="y"></param>
+        /// <param name="x"></param>
+        private static void iDCT1Dllm_32f(MutableSpan<float> y, MutableSpan<float> x)
+        {
+            float a0, a1, a2, a3, b0, b1, b2, b3;
+            float z0, z1, z2, z3, z4;
+
+            float r0 = 1.414214f;
+            float r1 = 1.387040f;
+            float r2 = 1.306563f;
+            float r3 = 1.175876f;
+            float r4 = 1.000000f;
+            float r5 = 0.785695f;
+            float r6 = 0.541196f;
+            float r7 = 0.275899f;
+
+            z0 = y[1] + y[7];
+            z1 = y[3] + y[5];
+            z2 = y[3] + y[7];
+            z3 = y[1] + y[5];
+            z4 = (z0 + z1) * r3;
+
+            z0 = z0 * (-r3 + r7);
+            z1 = z1 * (-r3 - r1);
+            z2 = z2 * (-r3 - r5) + z4;
+            z3 = z3 * (-r3 + r5) + z4;
+
+            b3 = y[7] * (-r1 + r3 + r5 - r7) + z0 + z2;
+            b2 = y[5] * (r1 + r3 - r5 + r7) + z1 + z3;
+            b1 = y[3] * (r1 + r3 + r5 - r7) + z1 + z2;
+            b0 = y[1] * (r1 + r3 - r5 - r7) + z0 + z3;
+
+            z4 = (y[2] + y[6]) * r6;
+            z0 = y[0] + y[4];
+            z1 = y[0] - y[4];
+            z2 = z4 - y[6] * (r2 + r6);
+            z3 = z4 + y[2] * (r2 - r6);
+            a0 = z0 + z3;
+            a3 = z0 - z3;
+            a1 = z1 + z2;
+            a2 = z1 - z2;
+
+            x[0] = a0 + b0;
+            x[7] = a0 - b0;
+            x[1] = a1 + b1;
+            x[6] = a1 - b1;
+            x[2] = a2 + b2;
+            x[5] = a2 - b2;
+            x[3] = a3 + b3;
+            x[4] = a3 - b3;
+        }
+
+        /// <summary>
+        /// Original: https://github.com/norishigefukushima/dct_simd/blob/master/dct/dct8x8_simd.cpp#L239
+        /// Applyies IDCT transformation on "s" copying transformed values to "d", using temporal block "temp"
+        /// </summary>
+        /// <param name="s"></param>
+        /// <param name="d"></param>
+        /// <param name="temp"></param>
+        internal static void iDCT2D_llm(MutableSpan<float> s, MutableSpan<float> d, MutableSpan<float> temp)
+        {
+            int j;
+
+            for (j = 0; j < 8; j++)
+            {
+                iDCT1Dllm_32f(s.Slice(j * 8), temp.Slice(j * 8));
+            }
+
+            Transpose8x8(temp, d);
+
+            for (j = 0; j < 8; j++)
+            {
+                iDCT1Dllm_32f(d.Slice(j * 8), temp.Slice(j * 8));
+            }
+
+            Transpose8x8(temp, d);
+
+            for (j = 0; j < 64; j++)
+            {
+                d[j] *= 0.125f;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector4 _mm_load_ps(MutableSpan<float> src, int offset)
+        {
+            src = src.Slice(offset);
+            return new Vector4(src[0], src[1], src[2], src[3]);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void _mm_store_ps(MutableSpan<float> dest, int offset, Vector4 src)
+        {
+            dest = dest.Slice(offset);
+            dest[0] = src.X;
+            dest[1] = src.Y;
+            dest[2] = src.Z;
+            dest[3] = src.W;
+        }
+
+        private static readonly Vector4 _1_175876 = new Vector4(1.175876f);
+
+        private static readonly Vector4 _1_961571 = new Vector4(-1.961571f);
+
+        private static readonly Vector4 _0_390181 = new Vector4(-0.390181f);
+
+        private static readonly Vector4 _0_899976 = new Vector4(-0.899976f);
+
+        private static readonly Vector4 _2_562915 = new Vector4(-2.562915f);
+
+        private static readonly Vector4 _0_298631 = new Vector4(0.298631f);
+
+        private static readonly Vector4 _2_053120 = new Vector4(2.053120f);
+
+        private static readonly Vector4 _3_072711 = new Vector4(3.072711f);
+
+        private static readonly Vector4 _1_501321 = new Vector4(1.501321f);
+
+        private static readonly Vector4 _0_541196 = new Vector4(0.541196f);
+
+        private static readonly Vector4 _1_847759 = new Vector4(-1.847759f);
+
+        private static readonly Vector4 _0_765367 = new Vector4(0.765367f);
+
+        /// <summary>
+        /// Original:
+        /// https://github.com/norishigefukushima/dct_simd/blob/master/dct/dct8x8_simd.cpp#L261
+        /// Does a part of the IDCT job on the given parts of the blocks
+        /// </summary>
+        /// <param name="y"></param>
+        /// <param name="x"></param>
+        internal static void iDCT2D8x4_32f(MutableSpan<float> y, MutableSpan<float> x)
+        {
+            /*
+	        float a0,a1,a2,a3,b0,b1,b2,b3; float z0,z1,z2,z3,z4; float r[8]; int i;
+	        for(i = 0;i < 8;i++){ r[i] = (float)(cos((double)i / 16.0 * M_PI) * M_SQRT2); }
+	        */
+            /*
+	        0: 1.414214
+	        1: 1.387040
+	        2: 1.306563
+	        3: 
+	        4: 1.000000
+	        5: 0.785695
+	        6: 
+	        7: 0.275899
+	        */
+
+            Vector4 my1 = _mm_load_ps(y, 8);
+            Vector4 my7 = _mm_load_ps(y, 56);
+            Vector4 mz0 = my1 + my7;
+
+            Vector4 my3 = _mm_load_ps(y, 24);
+            Vector4 mz2 = my3 + my7;
+            Vector4 my5 = _mm_load_ps(y, 40);
+            Vector4 mz1 = my3 + my5;
+            Vector4 mz3 = my1 + my5;
+
+            Vector4 mz4 = ((mz0 + mz1) * _1_175876);
+            //z0 = y[1] + y[7]; z1 = y[3] + y[5]; z2 = y[3] + y[7]; z3 = y[1] + y[5];
+            //z4 = (z0 + z1) * r[3];
+
+            mz2 = mz2 * _1_961571 + mz4;
+            mz3 = mz3 * _0_390181 + mz4;
+            mz0 = mz0 * _0_899976;
+            mz1 = mz1 * _2_562915;
+
+            /*
+            -0.899976
+            -2.562915
+            -1.961571
+            -0.390181
+            z0 = z0 * (-r[3] + r[7]);
+            z1 = z1 * (-r[3] - r[1]);
+            z2 = z2 * (-r[3] - r[5]) + z4;
+            z3 = z3 * (-r[3] + r[5]) + z4;*/
+
+            Vector4 mb3 = my7 * _0_298631 + mz0 + mz2;
+            Vector4 mb2 = my5 * _2_053120 + mz1 + mz3;
+            Vector4 mb1 = my3 * _3_072711 + mz1 + mz2;
+            Vector4 mb0 = my1 * _1_501321 + mz0 + mz3;
+
+            /*
+            0.298631
+            2.053120
+            3.072711
+            1.501321
+            b3 = y[7] * (-r[1] + r[3] + r[5] - r[7]) + z0 + z2;
+            b2 = y[5] * ( r[1] + r[3] - r[5] + r[7]) + z1 + z3;
+            b1 = y[3] * ( r[1] + r[3] + r[5] - r[7]) + z1 + z2;
+            b0 = y[1] * ( r[1] + r[3] - r[5] - r[7]) + z0 + z3;
+            */
+
+            Vector4 my2 = _mm_load_ps(y, 16);
+            Vector4 my6 = _mm_load_ps(y, 48);
+            mz4 = (my2 + my6) * _0_541196;
+            Vector4 my0 = _mm_load_ps(y, 0);
+            Vector4 my4 = _mm_load_ps(y, 32);
+            mz0 = my0 + my4;
+            mz1 = my0 - my4;
+
+            mz2 = mz4 + my6 * _1_847759;
+            mz3 = mz4 + my2 * _0_765367;
+
+            my0 = mz0 + mz3;
+            my3 = mz0 - mz3;
+            my1 = mz1 + mz2;
+            my2 = mz1 - mz2;
+            /*
+	        1.847759
+	        0.765367
+	        z4 = (y[2] + y[6]) * r[6];
+	        z0 = y[0] + y[4]; z1 = y[0] - y[4];
+	        z2 = z4 - y[6] * (r[2] + r[6]);
+	        z3 = z4 + y[2] * (r[2] - r[6]);
+	        a0 = z0 + z3; a3 = z0 - z3;
+	        a1 = z1 + z2; a2 = z1 - z2;
+	        */
+
+            _mm_store_ps(x, 0, my0 + mb0);
+
+            _mm_store_ps(x, 56, my0 - mb0);
+
+            _mm_store_ps(x, 8, my1 + mb1);
+
+            _mm_store_ps(x, 48, my1 - mb1);
+
+            _mm_store_ps(x, 16, my2 + mb2);
+
+            _mm_store_ps(x, 40, my2 - mb2);
+
+            _mm_store_ps(x, 24, my3 + mb3);
+
+            _mm_store_ps(x, 32, my3 - mb3);
+            /*
+            x[0] = a0 + b0; x[7] = a0 - b0;
+            x[1] = a1 + b1; x[6] = a1 - b1;
+            x[2] = a2 + b2; x[5] = a2 - b2;
+            x[3] = a3 + b3; x[4] = a3 - b3;
+            for(i = 0;i < 8;i++){ x[i] *= 0.353554f; }
+            */
+        }
+
+        /// <summary>
+        /// Copies color values from block to the destination image buffer.
+        /// </summary>
+        /// <param name="block"></param>
+        /// <param name="buffer"></param>
+        /// <param name="stride"></param>
+        internal static unsafe void CopyColorsTo(ref Block8x8F block, MutableSpan<byte> buffer, int stride)
+        {
+            fixed (Block8x8F* p = &block)
+            {
+                float* b = (float*)p;
+
+                for (int y = 0; y < 8; y++)
+                {
+                    int y8 = y * 8;
+                    int yStride = y * stride;
+
+                    for (int x = 0; x < 8; x++)
+                    {
+                        float c = b[y8 + x];
+
+                        if (c < -128)
+                        {
+                            c = 0;
+                        }
+                        else if (c > 127)
+                        {
+                            c = 255;
+                        }
+                        else
+                        {
+                            c += 128;
+                        }
+
+                        buffer[yStride + x] = (byte)c;
+                    }
+                }
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/Formats/Jpg/UtilityTestClassBase.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Text;
+using ImageSharp.Formats;
+using Xunit.Abstractions;
+
+namespace ImageSharp.Tests.Formats.Jpg
+{
+    public class UtilityTestClassBase
+    {
+        public UtilityTestClassBase(ITestOutputHelper output)
+        {
+            Output = output;
+        }
+
+        protected ITestOutputHelper Output { get; }
+
+        // ReSharper disable once InconsistentNaming
+        public static float[] Create8x8FloatData()
+        {
+            float[] result = new float[64];
+            for (int i = 0; i < 8; i++)
+            {
+                for (int j = 0; j < 8; j++)
+                {
+                    result[i * 8 + j] = i * 10 + j;
+                }
+            }
+            return result;
+        }
+
+      
+
+
+        // ReSharper disable once InconsistentNaming
+        public static int[] Create8x8IntData()
+        {
+            int[] result = new int[64];
+            for (int i = 0; i < 8; i++)
+            {
+                for (int j = 0; j < 8; j++)
+                {
+                    result[i * 8 + j] = i * 10 + j;
+                }
+            }
+            return result;
+        }
+
+        internal void Print8x8Data<T>(MutableSpan<T> data) => Print8x8Data(data.Data);
+
+        internal void Print8x8Data<T>(T[] data)
+        {
+            StringBuilder bld = new StringBuilder();
+            for (int i = 0; i < 8; i++)
+            {
+                for (int j = 0; j < 8; j++)
+                {
+                    bld.Append($"{data[i * 8 + j],3} ");
+                }
+                bld.AppendLine();
+            }
+
+            Output.WriteLine(bld.ToString());
+        }
+
+        internal void PrintLinearData<T>(T[] data) => PrintLinearData(new MutableSpan<T>(data), data.Length);
+
+        internal void PrintLinearData<T>(MutableSpan<T> data, int count = -1)
+        {
+            if (count < 0) count = data.TotalCount;
+
+            StringBuilder bld = new StringBuilder();
+            for (int i = 0; i < count; i++)
+            {
+                bld.Append($"{data[i],3} ");
+            }
+            Output.WriteLine(bld.ToString());
+        }
+
+        protected void Measure(int times, Action action, [CallerMemberName] string operationName = null)
+        {
+            Output.WriteLine($"{operationName} X {times} ...");
+            Stopwatch sw = Stopwatch.StartNew();
+
+            for (int i = 0; i < times; i++)
+            {
+                action();
+            }
+
+            sw.Stop();
+            Output.WriteLine($"{operationName} finished in {sw.ElapsedMilliseconds} ms");
+        }
+    }
+}

tests/ImageSharp.Tests/Formats/Png/PngTests.cs

@@ -3,6 +3,8 @@
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
 
+using ImageSharp.Formats;
+
 namespace ImageSharp.Tests
 {
     using System.IO;

tests/ImageSharp.Tests/TestImages.cs

@@ -38,13 +38,18 @@ namespace ImageSharp.Tests
         {
             private static readonly string folder = "TestImages/Formats/Jpg/";
             public static string Cmyk => folder + "cmyk.jpg";
-            public static string Exif => folder + "exif.jpeg";
+            public static string Exif => folder + "exif.jpg";
             public static string Floorplan => folder + "Floorplan.jpeg";
             public static string Calliphora => folder + "Calliphora.jpg";
             public static string Turtle => folder + "turtle.jpg";
             public static string Fb => folder + "fb.jpg";
             public static string Progress => folder + "progress.jpg";
             public static string GammaDalaiLamaGray => folder + "gamma_dalai_lama_gray.jpg";
+
+
+            public static readonly string[] All = {
+                Cmyk, Exif, Floorplan, Calliphora, Turtle, Fb, Progress, GammaDalaiLamaGray
+            };
         }
 
         public static class Bmp
@@ -56,6 +61,10 @@ namespace ImageSharp.Tests
             public static string F => folder + "F.bmp";
 
             public static string NegHeight => folder + "neg_height.bmp";
+
+            public static readonly string[] All = {
+                Car, F, NegHeight
+            };
         }
 
         public static class Gif