diff --git a/src/ImageSharp/Formats/Jpeg/Components/Decoder/YCbCrToRgbTables.cs b/src/ImageSharp/Formats/Jpeg/Components/Decoder/YCbCrToRgbTables.cs
new file mode 100644
index 0000000000..27324b5f68
--- /dev/null
+++ b/src/ImageSharp/Formats/Jpeg/Components/Decoder/YCbCrToRgbTables.cs
@@ -0,0 +1,109 @@
+//
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+//
+
+namespace ImageSharp.Formats.Jpg
+{
+ using System.Runtime.CompilerServices;
+ using ImageSharp.PixelFormats;
+
+ ///
+ /// Provides 8-bit lookup tables for converting from YCbCr to Rgb colorspace.
+ /// Methods to build the tables are based on libjpeg implementation.
+ ///
+ internal unsafe struct YCbCrToRgbTables
+ {
+ ///
+ /// The red red-chrominance table
+ ///
+ public fixed int CrRTable[256];
+
+ ///
+ /// The blue blue-chrominance table
+ ///
+ public fixed int CbBTable[256];
+
+ ///
+ /// The green red-chrominance table
+ ///
+ public fixed int CrGTable[256];
+
+ ///
+ /// The green blue-chrominance table
+ ///
+ public fixed int CbGTable[256];
+
+ // Speediest right-shift on some machines and gives us enough accuracy at 4 decimal places.
+ private const int ScaleBits = 16;
+
+ private const int Half = 1 << (ScaleBits - 1);
+
+ ///
+ /// Initializes the YCbCr tables
+ ///
+ /// The intialized
+ public static YCbCrToRgbTables Create()
+ {
+ YCbCrToRgbTables tables = default(YCbCrToRgbTables);
+
+ for (int i = 0, x = -128; i <= 255; i++, x++)
+ {
+ // i is the actual input pixel value, in the range 0..255
+ // The Cb or Cr value we are thinking of is x = i - 128
+ // Cr=>R value is nearest int to 1.402 * x
+ tables.CrRTable[i] = RightShift((Fix(1.402F) * x) + Half);
+
+ // Cb=>B value is nearest int to 1.772 * x
+ tables.CbBTable[i] = RightShift((Fix(1.772F) * x) + Half);
+
+ // Cr=>G value is scaled-up -0.714136286
+ tables.CrGTable[i] = (-Fix(0.714136286F)) * x;
+
+ // Cb => G value is scaled - up - 0.344136286 * x
+ // We also add in Half so that need not do it in inner loop
+ tables.CbGTable[i] = ((-Fix(0.344136286F)) * x) + Half;
+ }
+
+ return tables;
+ }
+
+ ///
+ /// Optimized method to pack bytes to the image from the YCbCr color space.
+ ///
+ /// The pixel format.
+ /// The packed pixel.
+ /// The reference to the tables instance.
+ /// The y luminance component.
+ /// The cb chroma component.
+ /// The cr chroma component.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public static void Pack(ref TPixel packed, YCbCrToRgbTables* tables, byte y, byte cb, byte cr)
+ where TPixel : struct, IPixel
+ {
+ // float r = MathF.Round(y + (1.402F * cr), MidpointRounding.AwayFromZero);
+ byte r = (byte)(y + tables->CrRTable[cr]).Clamp(0, 255);
+
+ // float g = MathF.Round(y - (0.344136F * cb) - (0.714136F * cr), MidpointRounding.AwayFromZero);
+ // The values for the G calculation are left scaled up, since we must add them together before rounding.
+ byte g = (byte)(y + RightShift(tables->CbGTable[cb] + tables->CrGTable[cr])).Clamp(0, 255);
+
+ // float b = MathF.Round(y + (1.772F * cb), MidpointRounding.AwayFromZero);
+ byte b = (byte)(y + tables->CbBTable[cb]).Clamp(0, 255);
+
+ packed.PackFromBytes(r, g, b, byte.MaxValue);
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static int Fix(float x)
+ {
+ return (int)((x * (1L << ScaleBits)) + 0.5F);
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static int RightShift(int x)
+ {
+ return x >> ScaleBits;
+ }
+ }
+}
\ No newline at end of file
diff --git a/src/ImageSharp/Formats/Jpeg/Components/Encoder/RgbToYCbCrTables.cs b/src/ImageSharp/Formats/Jpeg/Components/Encoder/RgbToYCbCrTables.cs
new file mode 100644
index 0000000000..94173d3e43
--- /dev/null
+++ b/src/ImageSharp/Formats/Jpeg/Components/Encoder/RgbToYCbCrTables.cs
@@ -0,0 +1,131 @@
+//
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+//
+
+namespace ImageSharp.Formats.Jpg
+{
+ using System.Runtime.CompilerServices;
+
+ ///
+ /// Provides 8-bit lookup tables for converting from Rgb to YCbCr colorspace.
+ /// Methods to build the tables are based on libjpeg implementation.
+ ///
+ internal unsafe struct RgbToYCbCrTables
+ {
+ ///
+ /// The red luminance table
+ ///
+ public fixed int YRTable[256];
+
+ ///
+ /// The green luminance table
+ ///
+ public fixed int YGTable[256];
+
+ ///
+ /// The blue luminance table
+ ///
+ public fixed int YBTable[256];
+
+ ///
+ /// The red blue-chrominance table
+ ///
+ public fixed int CbRTable[256];
+
+ ///
+ /// The green blue-chrominance table
+ ///
+ public fixed int CbGTable[256];
+
+ ///
+ /// The blue blue-chrominance table
+ /// B=>Cb and R=>Cr are the same
+ ///
+ public fixed int CbBTable[256];
+
+ ///
+ /// The green red-chrominance table
+ ///
+ public fixed int CrGTable[256];
+
+ ///
+ /// The blue red-chrominance table
+ ///
+ public fixed int CrBTable[256];
+
+ // Speediest right-shift on some machines and gives us enough accuracy at 4 decimal places.
+ private const int ScaleBits = 16;
+
+ private const int CBCrOffset = 128 << ScaleBits;
+
+ private const int Half = 1 << (ScaleBits - 1);
+
+ ///
+ /// Initializes the YCbCr tables
+ ///
+ /// The intialized
+ public static RgbToYCbCrTables Create()
+ {
+ RgbToYCbCrTables tables = default(RgbToYCbCrTables);
+
+ for (int i = 0; i <= 255; i++)
+ {
+ // The values for the calculations are left scaled up since we must add them together before rounding.
+ tables.YRTable[i] = Fix(0.299F) * i;
+ tables.YGTable[i] = Fix(0.587F) * i;
+ tables.YBTable[i] = (Fix(0.114F) * i) + Half;
+ tables.CbRTable[i] = (-Fix(0.168735892F)) * i;
+ tables.CbGTable[i] = (-Fix(0.331264108F)) * i;
+
+ // We use a rounding fudge - factor of 0.5 - epsilon for Cb and Cr.
+ // This ensures that the maximum output will round to 255
+ // not 256, and thus that we don't have to range-limit.
+ //
+ // B=>Cb and R=>Cr tables are the same
+ tables.CbBTable[i] = (Fix(0.5F) * i) + CBCrOffset + Half - 1;
+
+ tables.CrGTable[i] = (-Fix(0.418687589F)) * i;
+ tables.CrBTable[i] = (-Fix(0.081312411F)) * i;
+ }
+
+ return tables;
+ }
+
+ ///
+ /// Optimized method to allocates the correct y, cb, and cr values to the DCT blocks from the given r, g, b values.
+ ///
+ /// The The luminance block.
+ /// The red chroma block.
+ /// The blue chroma block.
+ /// The reference to the tables instance.
+ /// The current index.
+ /// The red value.
+ /// The green value.
+ /// The blue value.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public static void Allocate(ref float* yBlockRaw, ref float* cbBlockRaw, ref float* crBlockRaw, ref RgbToYCbCrTables* tables, int index, int r, int g, int b)
+ {
+ // float y = (0.299F * r) + (0.587F * g) + (0.114F * b);
+ yBlockRaw[index] = (tables->YRTable[r] + tables->YGTable[g] + tables->YBTable[b]) >> ScaleBits;
+
+ // float cb = 128F + ((-0.168736F * r) - (0.331264F * g) + (0.5F * b));
+ cbBlockRaw[index] = (tables->CbRTable[r] + tables->CbGTable[g] + tables->CbBTable[b]) >> ScaleBits;
+
+ // float b = MathF.Round(y + (1.772F * cb), MidpointRounding.AwayFromZero);
+ crBlockRaw[index] = (tables->CbBTable[r] + tables->CrGTable[g] + tables->CrBTable[b]) >> ScaleBits;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static int Fix(float x)
+ {
+ return (int)((x * (1L << ScaleBits)) + 0.5F);
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static int RightShift(int x)
+ {
+ return x >> ScaleBits;
+ }
+ }
+}
\ No newline at end of file
diff --git a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
index 186c1e5282..9df21a3b72 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
@@ -38,6 +38,11 @@ namespace ImageSharp.Formats
public InputProcessor InputProcessor;
#pragma warning restore SA401
+ ///
+ /// Lookup tables for converting YCbCr to Rgb
+ ///
+ private static YCbCrToRgbTables yCbCrToRgbTables = YCbCrToRgbTables.Create();
+
///
/// The decoder options.
///
@@ -251,35 +256,6 @@ namespace ImageSharp.Formats
}
}
- ///
- /// Optimized method to pack bytes to the image from the YCbCr color space.
- /// This is faster than implicit casting as it avoids double packing.
- ///
- /// The pixel format.
- /// The packed pixel.
- /// The y luminance component.
- /// The cb chroma component.
- /// The cr chroma component.
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- private static void PackYcbCr(ref TPixel packed, byte y, byte cb, byte cr)
- where TPixel : struct, IPixel
- {
- int ccb = cb - 128;
- int ccr = cr - 128;
-
- // Speed up the algorithm by removing floating point calculation
- // Scale by 65536, add .5F and truncate value. We use bit shifting to divide the result
- int r0 = 91881 * ccr; // (1.402F * 65536) + .5F
- int g0 = 22554 * ccb; // (0.34414F * 65536) + .5F
- int g1 = 46802 * ccr; // (0.71414F * 65536) + .5F
- int b0 = 116130 * ccb; // (1.772F * 65536) + .5F
-
- byte r = (byte)(y + (r0 >> 16)).Clamp(0, 255);
- byte g = (byte)(y - (g0 >> 16) - (g1 >> 16)).Clamp(0, 255);
- byte b = (byte)(y + (b0 >> 16)).Clamp(0, 255);
- packed.PackFromBytes(r, g, b, 255);
- }
-
///
/// Read metadata from stream and read the blocks in the scans into .
///
@@ -705,26 +681,34 @@ namespace ImageSharp.Formats
using (PixelAccessor pixels = image.Lock())
{
Parallel.For(
- 0,
- image.Height,
- image.Configuration.ParallelOptions,
- y =>
- {
- // TODO: Simplify + optimize + share duplicate code across converter methods
- int yo = this.ycbcrImage.GetRowYOffset(y);
- int co = this.ycbcrImage.GetRowCOffset(y);
-
- for (int x = 0; x < image.Width; x++)
- {
- byte yy = this.ycbcrImage.YChannel.Pixels[yo + x];
- byte cb = this.ycbcrImage.CbChannel.Pixels[co + (x / scale)];
- byte cr = this.ycbcrImage.CrChannel.Pixels[co + (x / scale)];
-
- TPixel packed = default(TPixel);
- PackYcbCr(ref packed, yy, cb, cr);
- pixels[x, y] = packed;
- }
- });
+ 0,
+ image.Height,
+ image.Configuration.ParallelOptions,
+ y =>
+ {
+ // TODO. This Parallel loop doesn't give us the boost it should.
+ ref byte ycRef = ref this.ycbcrImage.YChannel.Pixels[0];
+ ref byte cbRef = ref this.ycbcrImage.CbChannel.Pixels[0];
+ ref byte crRef = ref this.ycbcrImage.CrChannel.Pixels[0];
+ fixed (YCbCrToRgbTables* tables = &yCbCrToRgbTables)
+ {
+ // TODO: Simplify + optimize + share duplicate code across converter methods
+ int yo = this.ycbcrImage.GetRowYOffset(y);
+ int co = this.ycbcrImage.GetRowCOffset(y);
+
+ for (int x = 0; x < image.Width; x++)
+ {
+ int cOff = co + (x / scale);
+ byte yy = Unsafe.Add(ref ycRef, yo + x);
+ byte cb = Unsafe.Add(ref cbRef, cOff);
+ byte cr = Unsafe.Add(ref crRef, cOff);
+
+ TPixel packed = default(TPixel);
+ YCbCrToRgbTables.Pack(ref packed, tables, yy, cb, cr);
+ pixels[x, y] = packed;
+ }
+ }
+ });
}
this.AssignResolution(image);
diff --git a/src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs b/src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs
index eb083c35d9..0ce59c6dec 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs
@@ -5,11 +5,9 @@
namespace ImageSharp.Formats
{
- using System;
using System.Buffers;
using System.IO;
using System.Runtime.CompilerServices;
-
using ImageSharp.Formats.Jpg;
using ImageSharp.Formats.Jpg.Components;
using ImageSharp.PixelFormats;
@@ -103,6 +101,11 @@ namespace ImageSharp.Formats
}
};
+ ///
+ /// Lookup tables for converting Rgb to YCbCr
+ ///
+ private static RgbToYCbCrTables rgbToYCbCrTables = RgbToYCbCrTables.Create();
+
///
/// A scratch buffer to reduce allocations.
///
@@ -285,6 +288,7 @@ namespace ImageSharp.Formats
///
/// The pixel format.
/// The pixel accessor.
+ /// The reference to the tables instance.
/// The x-position within the image.
/// The y-position within the image.
/// The luminance block.
@@ -293,6 +297,7 @@ namespace ImageSharp.Formats
/// Temporal provided by the caller
private static void ToYCbCr(
PixelAccessor pixels,
+ RgbToYCbCrTables* tables,
int x,
int y,
Block8x8F* yBlock,
@@ -321,29 +326,9 @@ namespace ImageSharp.Formats
int g = Unsafe.Add(ref data0, dataIdx + 1);
int b = Unsafe.Add(ref data0, dataIdx + 2);
- // Speed up the algorithm by removing floating point calculation
- // Scale by 65536, add .5F and truncate value. We use bit shifting to divide the result
- int y0 = 19595 * r; // (0.299F * 65536) + .5F
- int y1 = 38470 * g; // (0.587F * 65536) + .5F
- int y2 = 7471 * b; // (0.114F * 65536) + .5F
-
- int cb0 = -11057 * r; // (-0.168736F * 65536) + .5F
- int cb1 = 21710 * g; // (0.331264F * 65536) + .5F
- int cb2 = 32768 * b; // (0.5F * 65536) + .5F
-
- int cr0 = 32768 * r; // (0.5F * 65536) + .5F
- int cr1 = 27439 * g; // (0.418688F * 65536) + .5F
- int cr2 = 5329 * b; // (0.081312F * 65536) + .5F
-
- float yy = (y0 + y1 + y2) >> 16;
- float cb = 128 + ((cb0 - cb1 + cb2) >> 16);
- float cr = 128 + ((cr0 - cr1 - cr2) >> 16);
-
int index = j8 + i;
- yBlockRaw[index] = yy;
- cbBlockRaw[index] = cb;
- crBlockRaw[index] = cr;
+ RgbToYCbCrTables.Allocate(ref yBlockRaw, ref cbBlockRaw, ref crBlockRaw, ref tables, index, r, g, b);
dataIdx += 3;
}
@@ -464,38 +449,41 @@ namespace ImageSharp.Formats
// ReSharper disable once InconsistentNaming
int prevDCY = 0, prevDCCb = 0, prevDCCr = 0;
- using (PixelArea rgbBytes = new PixelArea(8, 8, ComponentOrder.Xyz))
+ fixed (RgbToYCbCrTables* tables = &rgbToYCbCrTables)
{
- for (int y = 0; y < pixels.Height; y += 8)
+ using (PixelArea rgbBytes = new PixelArea(8, 8, ComponentOrder.Xyz))
{
- for (int x = 0; x < pixels.Width; x += 8)
+ for (int y = 0; y < pixels.Height; y += 8)
{
- ToYCbCr(pixels, x, y, &b, &cb, &cr, rgbBytes);
-
- prevDCY = this.WriteBlock(
- QuantIndex.Luminance,
- prevDCY,
- &b,
- &temp1,
- &temp2,
- &onStackLuminanceQuantTable,
- unzig.Data);
- prevDCCb = this.WriteBlock(
- QuantIndex.Chrominance,
- prevDCCb,
- &cb,
- &temp1,
- &temp2,
- &onStackChrominanceQuantTable,
- unzig.Data);
- prevDCCr = this.WriteBlock(
- QuantIndex.Chrominance,
- prevDCCr,
- &cr,
- &temp1,
- &temp2,
- &onStackChrominanceQuantTable,
- unzig.Data);
+ for (int x = 0; x < pixels.Width; x += 8)
+ {
+ ToYCbCr(pixels, tables, x, y, &b, &cb, &cr, rgbBytes);
+
+ prevDCY = this.WriteBlock(
+ QuantIndex.Luminance,
+ prevDCY,
+ &b,
+ &temp1,
+ &temp2,
+ &onStackLuminanceQuantTable,
+ unzig.Data);
+ prevDCCb = this.WriteBlock(
+ QuantIndex.Chrominance,
+ prevDCCb,
+ &cb,
+ &temp1,
+ &temp2,
+ &onStackChrominanceQuantTable,
+ unzig.Data);
+ prevDCCr = this.WriteBlock(
+ QuantIndex.Chrominance,
+ prevDCCr,
+ &cr,
+ &temp1,
+ &temp2,
+ &onStackChrominanceQuantTable,
+ unzig.Data);
+ }
}
}
}
@@ -837,49 +825,51 @@ namespace ImageSharp.Formats
// ReSharper disable once InconsistentNaming
int prevDCY = 0, prevDCCb = 0, prevDCCr = 0;
-
- using (PixelArea rgbBytes = new PixelArea(8, 8, ComponentOrder.Xyz))
+ fixed (RgbToYCbCrTables* tables = &rgbToYCbCrTables)
{
- for (int y = 0; y < pixels.Height; y += 16)
+ using (PixelArea rgbBytes = new PixelArea(8, 8, ComponentOrder.Xyz))
{
- for (int x = 0; x < pixels.Width; x += 16)
+ for (int y = 0; y < pixels.Height; y += 16)
{
- for (int i = 0; i < 4; i++)
+ for (int x = 0; x < pixels.Width; x += 16)
{
- int xOff = (i & 1) * 8;
- int yOff = (i & 2) * 4;
-
- ToYCbCr(pixels, x + xOff, y + yOff, &b, cbPtr + i, crPtr + i, rgbBytes);
+ for (int i = 0; i < 4; i++)
+ {
+ int xOff = (i & 1) * 8;
+ int yOff = (i & 2) * 4;
+
+ ToYCbCr(pixels, tables, x + xOff, y + yOff, &b, cbPtr + i, crPtr + i, rgbBytes);
+
+ prevDCY = this.WriteBlock(
+ QuantIndex.Luminance,
+ prevDCY,
+ &b,
+ &temp1,
+ &temp2,
+ &onStackLuminanceQuantTable,
+ unzig.Data);
+ }
+
+ Block8x8F.Scale16X16To8X8(&b, cbPtr);
+ prevDCCb = this.WriteBlock(
+ QuantIndex.Chrominance,
+ prevDCCb,
+ &b,
+ &temp1,
+ &temp2,
+ &onStackChrominanceQuantTable,
+ unzig.Data);
- prevDCY = this.WriteBlock(
- QuantIndex.Luminance,
- prevDCY,
+ Block8x8F.Scale16X16To8X8(&b, crPtr);
+ prevDCCr = this.WriteBlock(
+ QuantIndex.Chrominance,
+ prevDCCr,
&b,
&temp1,
&temp2,
- &onStackLuminanceQuantTable,
+ &onStackChrominanceQuantTable,
unzig.Data);
}
-
- Block8x8F.Scale16X16To8X8(&b, cbPtr);
- prevDCCb = this.WriteBlock(
- QuantIndex.Chrominance,
- prevDCCb,
- &b,
- &temp1,
- &temp2,
- &onStackChrominanceQuantTable,
- unzig.Data);
-
- Block8x8F.Scale16X16To8X8(&b, crPtr);
- prevDCCr = this.WriteBlock(
- QuantIndex.Chrominance,
- prevDCCr,
- &b,
- &temp1,
- &temp2,
- &onStackChrominanceQuantTable,
- unzig.Data);
}
}
}
diff --git a/tests/ImageSharp.Tests/Colors/RgbaVectorTransformTests.cs b/tests/ImageSharp.Tests/Colors/RgbaVectorTransformTests.cs
index bcbc27c7c4..24850954a8 100644
--- a/tests/ImageSharp.Tests/Colors/RgbaVectorTransformTests.cs
+++ b/tests/ImageSharp.Tests/Colors/RgbaVectorTransformTests.cs
@@ -36,13 +36,13 @@ namespace ImageSharp.Tests.Colors
[Fact]
public void Multiply()
{
- Assert.Equal(RgbaVector.Multiply(Backdrop, RgbaVector.Black).ToVector4(), Rgba32.Black.ToVector4(), FloatComparer);
+ Assert.Equal(RgbaVector.Multiply(Backdrop, RgbaVector.Black).ToVector4(), RgbaVector.Black.ToVector4(), FloatComparer);
Assert.Equal(RgbaVector.Multiply(Backdrop, RgbaVector.White).ToVector4(), Backdrop.ToVector4(), FloatComparer);
RgbaVector multiply = RgbaVector.Multiply(Backdrop, Source);
Assert.Equal(multiply.ToVector4(), new RgbaVector(0, 41, 0).ToVector4(), FloatComparer);
}
-
+
[Fact]
public void Screen()
{