Remove linq usage while getting band probability row, add additional guard checks.

src/ImageSharp/Formats/WebP/IntraPredictionMode.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Formats.WebP
+{
+    internal enum IntraPredictionMode
+    {
+        /// <summary>
+        /// Predict DC using row above and column to the left.
+        /// </summary>
+        DcPrediction = 0,
+
+        /// <summary>
+        /// Propagate second differences a la "True Motion".
+        /// </summary>
+        TrueMotion = 1,
+
+        /// <summary>
+        /// Predict rows using row above.
+        /// </summary>
+        VPrediction = 2,
+
+        /// <summary>
+        /// Predict columns using column to the left.
+        /// </summary>
+        HPrediction = 3,
+    }
+}

src/ImageSharp/Formats/WebP/Readme.md

@@ -4,6 +4,7 @@ Reference implementation, specification and stuff like that:
 
 - [google webp introduction](https://developers.google.com/speed/webp)
 - [WebP Spec 1.0.3](https://chromium.googlesource.com/webm/libwebp/+/v1.0.3/doc/webp-container-spec.txt)
-- [WebP VP8 chunk Spec](http://tools.ietf.org/html/rfc6386)
+- [WebP VP8 Spec, Lossy](http://tools.ietf.org/html/rfc6386)
+- [WebP VP8L Spec, Lossless](https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification)
 - [WebP filefront](https://wiki.fileformat.com/image/webp/)
 - [WebP test data](https://github.com/webmproject/libwebp-test-data/)

src/ImageSharp/Formats/WebP/ReconstructionFilter.cs

@@ -1,12 +0,0 @@
-// Copyright (c) Six Labors and contributors.
-// Licensed under the Apache License, Version 2.0.
-
-namespace SixLabors.ImageSharp.Formats.WebP
-{
-    internal enum ReconstructionFilter
-    {
-        None,
-        Bicubic,
-        Bilinear
-    }
-}

src/ImageSharp/Formats/WebP/VP8BandProbas.cs

@@ -8,6 +8,9 @@ namespace SixLabors.ImageSharp.Formats.WebP
     /// </summary>
     internal class Vp8BandProbas
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Vp8BandProbas"/> class.
+        /// </summary>
         public Vp8BandProbas()
         {
             this.Probabilities = new Vp8ProbaArray[WebPConstants.NumCtx];
@@ -17,6 +20,9 @@ namespace SixLabors.ImageSharp.Formats.WebP
             }
         }
 
+        /// <summary>
+        /// Gets the Probabilities.
+        /// </summary>
         public Vp8ProbaArray[] Probabilities { get; }
     }
 }

src/ImageSharp/Formats/WebP/Vp8Decoder.cs

@@ -285,12 +285,12 @@ namespace SixLabors.ImageSharp.Formats.WebP
                     baseLevel = this.SegmentHeader.FilterStrength[s];
                     if (!this.SegmentHeader.Delta)
                     {
-                        baseLevel += hdr.Level;
+                        baseLevel += hdr.FilterLevel;
                     }
                 }
                 else
                 {
-                    baseLevel = hdr.Level;
+                    baseLevel = hdr.FilterLevel;
                 }
 
                 for (int i4x4 = 0; i4x4 <= 1; ++i4x4)

src/ImageSharp/Formats/WebP/Vp8FilterHeader.cs

@@ -9,6 +9,13 @@ namespace SixLabors.ImageSharp.Formats.WebP
 
         private const int NumModeLfDeltas = 4;
 
+        private int filterLevel;
+
+        private int sharpness;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Vp8FilterHeader"/> class.
+        /// </summary>
         public Vp8FilterHeader()
         {
             this.RefLfDelta = new int[NumRefLfDeltas];
@@ -20,16 +27,36 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// </summary>
         public LoopFilter LoopFilter { get; set; }
 
-        // [0..63]
+        /// <summary>
-        public int Level { get; set; }
+        /// Gets or sets the filter level. Valid values are [0..63].
+        /// </summary>
+        public int FilterLevel
+        {
+            get => this.filterLevel;
+            set
+            {
+                Guard.MustBeBetweenOrEqualTo(value, 0, 63, nameof(this.FilterLevel));
+                this.filterLevel = value;
+            }
+        }
 
-        // [0..7]
+        /// <summary>
-        public int Sharpness { get; set; }
+        /// Gets or sets the filter sharpness. Valid values are [0..7].
+        /// </summary>
+        public int Sharpness
+        {
+            get => this.sharpness;
+            set
+            {
+                Guard.MustBeBetweenOrEqualTo(value, 0, 7, nameof(this.Sharpness));
+                this.sharpness = value;
+            }
+        }
 
         public bool UseLfDelta { get; set; }
 
-        public int[] RefLfDelta { get; private set; }
+        public int[] RefLfDelta { get; }
 
-        public int[] ModeLfDelta { get; private set; }
+        public int[] ModeLfDelta { get; }
     }
 }

src/ImageSharp/Formats/WebP/Vp8FilterInfo.cs

@@ -8,6 +8,12 @@ namespace SixLabors.ImageSharp.Formats.WebP
     /// </summary>
     internal class Vp8FilterInfo : IDeepCloneable
     {
+        private byte limit;
+
+        private byte innerLevel;
+
+        private byte highEdgeVarianceThreshold;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Vp8FilterInfo"/> class.
         /// </summary>
@@ -30,12 +36,28 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <summary>
         /// Gets or sets the filter limit in [3..189], or 0 if no filtering.
         /// </summary>
-        public byte Limit { get; set; }
+        public byte Limit
+        {
+            get => this.limit;
+            set
+            {
+                Guard.MustBeBetweenOrEqualTo(value, (byte)0, (byte)189, nameof(this.Limit));
+                this.limit = value;
+            }
+        }
 
         /// <summary>
-        /// Gets or sets the inner limit in [1..63].
+        /// Gets or sets the inner limit in [1..63], or 0 if no filtering.
         /// </summary>
-        public byte InnerLevel { get; set; }
+        public byte InnerLevel
+        {
+            get => this.innerLevel;
+            set
+            {
+                Guard.MustBeBetweenOrEqualTo(value, (byte)0, (byte)63, nameof(this.InnerLevel));
+                this.innerLevel = value;
+            }
+        }
 
         /// <summary>
         /// Gets or sets a value indicating whether to do inner filtering.
@@ -45,7 +67,15 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <summary>
         /// Gets or sets the high edge variance threshold in [0..2].
         /// </summary>
-        public byte HighEdgeVarianceThreshold { get; set; }
+        public byte HighEdgeVarianceThreshold
+        {
+            get => this.highEdgeVarianceThreshold;
+            set
+            {
+                Guard.MustBeBetweenOrEqualTo(value, (byte)0, (byte)2, nameof(this.HighEdgeVarianceThreshold));
+                this.highEdgeVarianceThreshold = value;
+            }
+        }
 
         /// <inheritdoc/>
         public IDeepCloneable DeepClone() => new Vp8FilterInfo(this);

src/ImageSharp/Formats/WebP/Vp8MacroBlockData.cs

@@ -37,8 +37,26 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// </summary>
         public byte UvMode { get; set; }
 
+        /// <summary>
+        /// Gets or sets bit-wise info about the content of each sub-4x4 blocks (in decoding order).
+        /// Each of the 4x4 blocks for y/u/v is associated with a 2b code according to:
+        ///   code=0 -> no coefficient
+        ///   code=1 -> only DC
+        ///   code=2 -> first three coefficients are non-zero
+        ///   code=3 -> more than three coefficients are non-zero
+        /// This allows to call specialized transform functions.
+        /// </summary>
         public uint NonZeroY { get; set; }
 
+        /// <summary>
+        /// Gets or sets bit-wise info about the content of each sub-4x4 blocks (in decoding order).
+        /// Each of the 4x4 blocks for y/u/v is associated with a 2b code according to:
+        ///   code=0 -> no coefficient
+        ///   code=1 -> only DC
+        ///   code=2 -> first three coefficients are non-zero
+        ///   code=3 -> more than three coefficients are non-zero
+        /// This allows to call specialized transform functions.
+        /// </summary>
         public uint NonZeroUv { get; set; }
 
         public bool Skip { get; set; }

src/ImageSharp/Formats/WebP/Vp8Proba.cs

@@ -10,11 +10,14 @@ namespace SixLabors.ImageSharp.Formats.WebP
     {
         private const int MbFeatureTreeProbs = 3;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Vp8Proba"/> class.
+        /// </summary>
         public Vp8Proba()
         {
             this.Segments = new uint[MbFeatureTreeProbs];
             this.Bands = new Vp8BandProbas[WebPConstants.NumTypes, WebPConstants.NumBands];
-            this.BandsPtr = new Vp8BandProbas[WebPConstants.NumTypes, 16 + 1];
+            this.BandsPtr = new Vp8BandProbas[WebPConstants.NumTypes][];
 
             for (int i = 0; i < WebPConstants.NumTypes; i++)
             {
@@ -26,10 +29,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
 
             for (int i = 0; i < WebPConstants.NumTypes; i++)
             {
-                for (int j = 0; j < 17; j++)
+                this.BandsPtr[i] = new Vp8BandProbas[16 + 1];
-                {
-                    this.BandsPtr[i, j] = new Vp8BandProbas();
-                }
             }
         }
 
@@ -37,6 +37,6 @@ namespace SixLabors.ImageSharp.Formats.WebP
 
         public Vp8BandProbas[,] Bands { get; }
 
-        public Vp8BandProbas[,] BandsPtr { get; }
+        public Vp8BandProbas[][] BandsPtr { get; }
     }
 }

src/ImageSharp/Formats/WebP/Vp8ProbaArray.cs

@@ -8,11 +8,17 @@ namespace SixLabors.ImageSharp.Formats.WebP
     /// </summary>
     internal class Vp8ProbaArray
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Vp8ProbaArray"/> class.
+        /// </summary>
         public Vp8ProbaArray()
         {
             this.Probabilities = new byte[WebPConstants.NumProbas];
         }
 
+        /// <summary>
+        /// Gets the probabilities.
+        /// </summary>
         public byte[] Probabilities { get; }
     }
 }

src/ImageSharp/Formats/WebP/Vp8Profile.cs

@@ -1,35 +0,0 @@
-// Copyright (c) Six Labors and contributors.
-// Licensed under the Apache License, Version 2.0.
-
-namespace SixLabors.ImageSharp.Formats.WebP
-{
-    /// <summary>
-    /// The version number of the frame header enables or disables certain features in the bitstream.
-    /// +---------+-------------------------+-------------+
-    /// | Version | Reconstruction Filter   | Loop Filter |
-    /// +---------+-------------------------+-------------+
-    /// | 0       | Bicubic                 | Normal      |
-    /// |         |                         |             |
-    /// | 1       | Bilinear                | Simple      |
-    /// |         |                         |             |
-    /// | 2       | Bilinear                | None        |
-    /// |         |                         |             |
-    /// | 3       | None                    | None        |
-    /// |         |                         |             |
-    /// | Other   | Reserved for future use |             |
-    /// +---------+-------------------------+-------------+
-    /// See paragraph 9, https://tools.ietf.org/html/rfc6386.
-    /// </summary>
-    internal class Vp8Profile
-    {
-        /// <summary>
-        /// Gets or sets the reconstruction filter.
-        /// </summary>
-        public ReconstructionFilter ReconstructionFilter { get; set; }
-
-        /// <summary>
-        /// Gets or sets the loop filter.
-        /// </summary>
-        public LoopFilter LoopFilter { get; set; }
-    }
-}

src/ImageSharp/Formats/WebP/Vp8QuantMatrix.cs

@@ -26,7 +26,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
             get => this.dither;
             set
             {
-                Guard.MustBeBetweenOrEqualTo(value, 0, 255, nameof(this.dither));
+                Guard.MustBeBetweenOrEqualTo(value, 0, 255, nameof(this.Dither));
                 this.dither = value;
             }
         }

src/ImageSharp/Formats/WebP/Vp8SegmentHeader.cs

@@ -32,11 +32,11 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <summary>
         /// Gets quantization changes.
         /// </summary>
-        public byte[] Quantizer { get; private set; }
+        public byte[] Quantizer { get; }
 
         /// <summary>
         /// Gets the filter strength for segments.
         /// </summary>
-        public byte[] FilterStrength { get; private set; }
+        public byte[] FilterStrength { get; }
     }
 }

src/ImageSharp/Formats/WebP/WebPConstants.cs

@@ -110,7 +110,6 @@ namespace SixLabors.ImageSharp.Formats.WebP
             NumDistanceCodes
         };
 
-        // VP8 constants from here on:
         public const int NumMbSegments = 4;
 
         public const int MaxNumPartitions = 8;
@@ -126,12 +125,6 @@ namespace SixLabors.ImageSharp.Formats.WebP
         // this is the common stride for enc/dec
         public const int Bps = 32;
 
-        // intra prediction modes (TODO: maybe use an enum for this)
-        public const int DcPred = 0; // predict DC using row above and column to the left
-        public const int TmPred = 1; // propagate second differences a la "True Motion"
-        public const int VPred = 2; // predict rows using row above
-        public const int HPred = 3; // predict columns using column to the left
-
         /// <summary>
         /// How many extra lines are needed on the MB boundary for caching, given a filtering level.
         /// Simple filter(1):  up to 2 luma samples are read and 1 is written.

src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs

@@ -602,7 +602,6 @@ namespace SixLabors.ImageSharp.Formats.WebP
                     int repeat = (int)(this.bitReader.ReadValue(extraBits) + repeatOffset);
                     if (symbol + repeat > numSymbols)
                     {
-                        // TODO: not sure, if this should be treated as an error here
                         return;
                     }
 

src/ImageSharp/Formats/WebP/WebPLossyDecoder.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Buffers;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
@@ -207,8 +206,8 @@ namespace SixLabors.ImageSharp.Formats.WebP
             {
                 // Hardcoded 16x16 intra-mode decision tree.
                 int yMode = this.bitReader.GetBit(156) != 0 ?
-                                this.bitReader.GetBit(128) != 0 ? WebPConstants.TmPred : WebPConstants.HPred :
+                                this.bitReader.GetBit(128) != 0 ? (int)IntraPredictionMode.TrueMotion : (int)IntraPredictionMode.HPrediction :
-                                this.bitReader.GetBit(163) != 0 ? WebPConstants.VPred : WebPConstants.DcPred;
+                                this.bitReader.GetBit(163) != 0 ? (int)IntraPredictionMode.VPrediction : (int)IntraPredictionMode.DcPrediction;
                 block.Modes[0] = (byte)yMode;
                 for (int i = 0; i < left.Length; i++)
                 {
@@ -864,7 +863,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
             int dstOffset = 0;
             Vp8MacroBlockData block = dec.CurrentBlockData;
             Vp8QuantMatrix q = dec.DeQuantMatrices[block.Segment];
-            Vp8BandProbas[,] bands = dec.Probabilities.BandsPtr;
+            Vp8BandProbas[][] bands = dec.Probabilities.BandsPtr;
             Vp8BandProbas[] acProba;
             Vp8MacroBlock leftMb = dec.LeftMacroBlock;
             short[] dst = block.Coeffs;
@@ -876,14 +875,14 @@ namespace SixLabors.ImageSharp.Formats.WebP
             if (block.IsI4x4)
             {
                 first = 0;
-                acProba = GetBandsRow(bands, 3);
+                acProba = bands[3];
             }
             else
             {
                 // Parse DC
                 var dc = new short[16];
                 int ctx = (int)(mb.NoneZeroDcCoeffs + leftMb.NoneZeroDcCoeffs);
-                int nz = this.GetCoeffs(br, GetBandsRow(bands, 1), ctx, q.Y2Mat, 0, dc);
+                int nz = this.GetCoeffs(br, bands[1], ctx, q.Y2Mat, 0, dc);
                 mb.NoneZeroDcCoeffs = leftMb.NoneZeroDcCoeffs = (uint)(nz > 0 ? 1 : 0);
                 if (nz > 1)
                 {
@@ -901,7 +900,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
                 }
 
                 first = 1;
-                acProba = GetBandsRow(bands, 0);
+                acProba = bands[0];
             }
 
             byte tnz = (byte)(mb.NoneZeroAcDcCoeffs & 0x0f);
@@ -941,7 +940,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
                     for (int x = 0; x < 2; ++x)
                     {
                         int ctx = l + (tnz & 1);
-                        int nz = this.GetCoeffs(br, GetBandsRow(bands, 2), ctx, q.UvMat, 0, dst.AsSpan(dstOffset));
+                        int nz = this.GetCoeffs(br, bands[2], ctx, q.UvMat, 0, dst.AsSpan(dstOffset));
                         l = (nz > 0) ? 1 : 0;
                         tnz = (byte)((tnz >> 1) | (l << 3));
                         nzCoeffs = NzCodeBits(nzCoeffs, nz, dst[dstOffset] != 0 ? 1 : 0);
@@ -1164,11 +1163,11 @@ namespace SixLabors.ImageSharp.Formats.WebP
         {
             Vp8FilterHeader vp8FilterHeader = dec.FilterHeader;
             vp8FilterHeader.LoopFilter = this.bitReader.ReadBool() ? LoopFilter.Simple : LoopFilter.Complex;
-            vp8FilterHeader.Level = (int)this.bitReader.ReadValue(6);
+            vp8FilterHeader.FilterLevel = (int)this.bitReader.ReadValue(6);
             vp8FilterHeader.Sharpness = (int)this.bitReader.ReadValue(3);
             vp8FilterHeader.UseLfDelta = this.bitReader.ReadBool();
 
-            dec.Filter = (vp8FilterHeader.Level == 0) ? LoopFilter.None : vp8FilterHeader.LoopFilter;
+            dec.Filter = (vp8FilterHeader.FilterLevel == 0) ? LoopFilter.None : vp8FilterHeader.LoopFilter;
             if (vp8FilterHeader.UseLfDelta)
             {
                 // Update lf-delta?
@@ -1314,7 +1313,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
 
                 for (int b = 0; b < 16 + 1; ++b)
                 {
-                    proba.BandsPtr[t, b] = proba.Bands[t, WebPConstants.Bands[b]];
+                    proba.BandsPtr[t][b] = proba.Bands[t, WebPConstants.Bands[b]];
                 }
             }
 
@@ -1391,13 +1390,6 @@ namespace SixLabors.ImageSharp.Formats.WebP
             return nzCoeffs;
         }
 
-        [MethodImpl(InliningOptions.ShortMethod)]
-        private static Vp8BandProbas[] GetBandsRow(Vp8BandProbas[,] bands, int rowIdx)
-        {
-            Vp8BandProbas[] bandsRow = Enumerable.Range(0, bands.GetLength(1)).Select(x => bands[rowIdx, x]).ToArray();
-            return bandsRow;
-        }
-
         [MethodImpl(InliningOptions.ShortMethod)]
         private static int CheckMode(int mbx, int mby, int mode)
         {

tests/ImageSharp.Tests/TestImages.cs

@@ -506,10 +506,10 @@ namespace SixLabors.ImageSharp.Tests
 
                 // Invalid / corrupted images
                 // Below images have errors according to webpinfo. The error message webpinfo gives is "Truncated data detected when parsing RIFF payload."
-                public const string LossLessCorruptImage1 = "Webp/lossless_big_random_alpha.webp"; // substract_green, predictor, cross_color.
+                public const string LossLessCorruptImage1 = "WebP/lossless_big_random_alpha.webp"; // substract_green, predictor, cross_color.
-                public const string LossLessCorruptImage2 = "Webp/lossless_vec_2_7.webp"; // color_indexing, predictor.
+                public const string LossLessCorruptImage2 = "WebP/lossless_vec_2_7.webp"; // color_indexing, predictor.
-                public const string LossLessCorruptImage3 = "Webp/lossless_color_transform.webp"; // cross_color, predictor
+                public const string LossLessCorruptImage3 = "WebP/lossless_color_transform.webp"; // cross_color, predictor
-                public const string LossLessCorruptImage4 = "Webp/near_lossless_75.webp"; // predictor, cross_color.
+                public const string LossLessCorruptImage4 = "WebP/near_lossless_75.webp"; // predictor, cross_color.
             }
 
             public static class Lossy

tests/Images/Input/WebP/grid.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:5c53fb4527509058a8a4caf72e03ee8634f4704ab5369a8e5d194e62359d6ad0
-size 117

tests/Images/Input/WebP/lossless_with_iccp.webp

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:312aea5ac9557bdfa78ec95bab5c3446a97c980317f46c96a20a4b7837d0ae37
+oid sha256:3cdb75584ac3db92d78c2c1ec828cb813d280540e5f1bb262ba0b2c352900f81
-size 68355
+size 69076

tests/Images/Input/WebP/peak.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:b9b56ed5c1278664222c77f9a452b824b4f9215c819502b3f6b0e0d44270e7e7
-size 26456