From 12ec82b25f50612c6dbae6569a59fbbf92c86e6f Mon Sep 17 00:00:00 2001 From: woutware <35376607+woutware@users.noreply.github.com> Date: Sat, 28 Apr 2018 11:57:34 +0200 Subject: [PATCH] Processed review comments and did similar refactoring to the PNG decoding. --- .../Formats/Png/Filters/AverageFilter.cs | 53 +++++-------------- .../Formats/Png/Filters/PaethFilter.cs | 38 +++---------- .../Formats/Png/Filters/SubFilter.cs | 47 +++++----------- .../Formats/Png/Filters/UpFilter.cs | 15 +----- 4 files changed, 36 insertions(+), 117 deletions(-) diff --git a/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs b/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs index e832b2d7f..ffcf9b0f3 100644 --- a/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs +++ b/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs @@ -29,21 +29,19 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters ref byte prevBaseRef = ref MemoryMarshal.GetReference(previousScanline); // Average(x) + floor((Raw(x-bpp)+Prior(x))/2) - for (int x = 1; x < scanline.Length; x++) + int x = 1; + for (; x <= bytesPerPixel /* Note the <= because x starts at 1 */; ++x) { + ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); + byte above = Unsafe.Add(ref prevBaseRef, x); + scan = (byte)(scan + (above >> 1)); + } + + for (; x < scanline.Length; ++x) { - if (x - bytesPerPixel < 1) - { - ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); - byte above = Unsafe.Add(ref prevBaseRef, x); - scan = (byte)((scan + (above >> 1)) % 256); - } - else - { - ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); - byte left = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); - byte above = Unsafe.Add(ref prevBaseRef, x); - scan = (byte)((scan + Average(left, above)) % 256); - } + ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); + byte left = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); + byte above = Unsafe.Add(ref prevBaseRef, x); + scan = (byte)(scan + Average(left, above)); } } @@ -69,30 +67,8 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters // Average(x) = Raw(x) - floor((Raw(x-bpp)+Prior(x))/2) resultBaseRef = 3; -#if OLD_AND_SLOW - for (int x = 0; x < scanline.Length; x++) - { - if (x - bytesPerPixel < 0) - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - byte above = Unsafe.Add(ref prevBaseRef, x); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)((scan - (above >> 1)) % 256); - sum += res < 128 ? res : 256 - res; - } - else - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - byte left = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); - byte above = Unsafe.Add(ref prevBaseRef, x); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)((scan - Average(left, above)) % 256); - sum += res < 128 ? res : 256 - res; - } - } -#else int x = 0; - for (; x < bytesPerPixel;) { + for (; x < bytesPerPixel; /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); byte above = Unsafe.Add(ref prevBaseRef, x); ++x; @@ -101,7 +77,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } - for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft) { + for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); byte left = Unsafe.Add(ref scanBaseRef, xLeft); byte above = Unsafe.Add(ref prevBaseRef, x); @@ -110,7 +86,6 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters res = (byte)(scan - Average(left, above)); sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } -#endif sum -= 3; } diff --git a/src/ImageSharp/Formats/Png/Filters/PaethFilter.cs b/src/ImageSharp/Formats/Png/Filters/PaethFilter.cs index 652269e27..0d3df079c 100644 --- a/src/ImageSharp/Formats/Png/Filters/PaethFilter.cs +++ b/src/ImageSharp/Formats/Png/Filters/PaethFilter.cs @@ -30,15 +30,16 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters ref byte prevBaseRef = ref MemoryMarshal.GetReference(previousScanline); // Paeth(x) + PaethPredictor(Raw(x-bpp), Prior(x), Prior(x-bpp)) - int offset = bytesPerPixel + 1; - for (int x = 1; x < offset; x++) + int offset = bytesPerPixel + 1; // Add one bcause x starts at one. + int x = 1; + for (; x < offset; x++) { ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); byte above = Unsafe.Add(ref prevBaseRef, x); scan = (byte)(scan + above); } - for (int x = offset; x < scanline.Length; x++) + for (; x < scanline.Length; x++) { ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); byte left = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); @@ -70,39 +71,17 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters // Paeth(x) = Raw(x) - PaethPredictor(Raw(x-bpp), Prior(x), Prior(x - bpp)) resultBaseRef = 4; -#if OLD_AND_SLOW - for (int x = 0; x < scanline.Length; x++) - { - if (x - bytesPerPixel < 0) - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - byte above = Unsafe.Add(ref prevBaseRef, x); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)((scan - PaethPredicator(0, above, 0)) % 256); - sum += res < 128 ? res : 256 - res; - } - else - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - byte left = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); - byte above = Unsafe.Add(ref prevBaseRef, x); - byte upperLeft = Unsafe.Add(ref prevBaseRef, x - bytesPerPixel); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)((scan - PaethPredicator(left, above, upperLeft)) % 256); - sum += res < 128 ? res : 256 - res; - } - } -#else int x = 0; - for (; x < bytesPerPixel; ++x) { + for (; x < bytesPerPixel; /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); byte above = Unsafe.Add(ref prevBaseRef, x); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); + ++x; + ref byte res = ref Unsafe.Add(ref resultBaseRef, x); res = (byte)(scan - PaethPredictor(0, above, 0)); sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } - for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft) { + for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); byte left = Unsafe.Add(ref scanBaseRef, xLeft); byte above = Unsafe.Add(ref prevBaseRef, x); @@ -112,7 +91,6 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters res = (byte)(scan - PaethPredictor(left, above, upperLeft)); sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } -#endif sum -= 4; } diff --git a/src/ImageSharp/Formats/Png/Filters/SubFilter.cs b/src/ImageSharp/Formats/Png/Filters/SubFilter.cs index f389cb2cd..cfb7781be 100644 --- a/src/ImageSharp/Formats/Png/Filters/SubFilter.cs +++ b/src/ImageSharp/Formats/Png/Filters/SubFilter.cs @@ -25,19 +25,17 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters ref byte scanBaseRef = ref MemoryMarshal.GetReference(scanline); // Sub(x) + Raw(x-bpp) - for (int x = 1; x < scanline.Length; x++) + int x = 1; + for (; x <= bytesPerPixel /* Note the <= because x starts at 1 */; ++x) { - if (x - bytesPerPixel < 1) - { - ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); - scan = (byte)(scan % 256); - } - else - { - ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); - byte prev = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); - scan = (byte)((scan + prev) % 256); - } + ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); + } + + for (; x < scanline.Length; ++x) + { + ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); + byte prev = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); + scan = (byte)(scan + prev); } } @@ -60,28 +58,8 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters // Sub(x) = Raw(x) - Raw(x-bpp) resultBaseRef = 1; -#if OLD_AND_SLOW - for (int x = 0; x < scanline.Length; x++) - { - if (x - bytesPerPixel < 0) - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)(scan % 256); - sum += res < 128 ? res : 256 - res; - } - else - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - byte prev = Unsafe.Add(ref scanBaseRef, x - bytesPerPixel); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)((scan - prev) % 256); - sum += res < 128 ? res : 256 - res; - } - } -#else int x = 0; - for (; x < bytesPerPixel;) { + for (; x < bytesPerPixel; /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); ++x; ref byte res = ref Unsafe.Add(ref resultBaseRef, x); @@ -89,7 +67,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } - for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft) { + for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); byte prev = Unsafe.Add(ref scanBaseRef, xLeft); ++x; @@ -97,7 +75,6 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters res = (byte)(scan - prev); sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } -#endif sum -= 1; } diff --git a/src/ImageSharp/Formats/Png/Filters/UpFilter.cs b/src/ImageSharp/Formats/Png/Filters/UpFilter.cs index 45ece23ef..c6a297e33 100644 --- a/src/ImageSharp/Formats/Png/Filters/UpFilter.cs +++ b/src/ImageSharp/Formats/Png/Filters/UpFilter.cs @@ -32,7 +32,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters { ref byte scan = ref Unsafe.Add(ref scanBaseRef, x); byte above = Unsafe.Add(ref prevBaseRef, x); - scan = (byte)((scan + above) % 256); + scan = (byte)(scan + above); } } @@ -57,17 +57,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters // Up(x) = Raw(x) - Prior(x) resultBaseRef = 2; -#if OLD_AND_SLOW - for (int x = 0; x < scanline.Length; x++) - { - byte scan = Unsafe.Add(ref scanBaseRef, x); - byte above = Unsafe.Add(ref prevBaseRef, x); - ref byte res = ref Unsafe.Add(ref resultBaseRef, x + 1); - res = (byte)((scan - above) % 256); - sum += res < 128 ? res : 256 - res; - } -#else - for (int x = 0; x < scanline.Length;) { + for (int x = 0; x < scanline.Length; /* Note: ++x happens in the body to avoid one add operation */) { byte scan = Unsafe.Add(ref scanBaseRef, x); byte above = Unsafe.Add(ref prevBaseRef, x); ++x; @@ -75,7 +65,6 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters res = (byte)(scan - above); sum += ImageMaths.FastAbs(unchecked((sbyte)res)); } -#endif sum -= 2; }