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Fix run-length encode compression implementation mistake in tga encoder #2172

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merged 2 commits into from
Jul 30, 2022
Merged

Fix run-length encode compression implementation mistake in tga encoder #2172

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4b28eb6
Fix rle compression mistake in tga encoder.
l1nxy Jul 13, 2022
ab7f384
Merge branch 'main' into fix-tga-rle-encoder
brianpopow Jul 29, 2022
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43 changes: 20 additions & 23 deletions src/ImageSharp/Formats/Tga/TgaEncoderCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@
using System.IO;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using SixLabors.ImageSharp.Advanced;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.Metadata;
Expand Down Expand Up @@ -73,7 +72,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream, CancellationToken
this.configuration = image.GetConfiguration();
ImageMetadata metadata = image.Metadata;
TgaMetadata tgaMetadata = metadata.GetTgaMetadata();
this.bitsPerPixel = this.bitsPerPixel ?? tgaMetadata.BitsPerPixel;
this.bitsPerPixel ??= tgaMetadata.BitsPerPixel;

TgaImageType imageType = this.compression is TgaCompression.RunLength ? TgaImageType.RleTrueColor : TgaImageType.TrueColor;
if (this.bitsPerPixel == TgaBitsPerPixel.Pixel8)
Expand Down Expand Up @@ -160,6 +159,8 @@ private void WriteImage<TPixel>(Stream stream, ImageFrame<TPixel> image)
case TgaBitsPerPixel.Pixel32:
this.Write32Bit(stream, pixels);
break;
default:
break;
}
}

Expand Down Expand Up @@ -213,6 +214,8 @@ private void WriteRunLengthEncodedImage<TPixel>(Stream stream, ImageFrame<TPixel
stream.WriteByte(color.R);
stream.WriteByte(color.A);
break;
default:
break;
}

encodedPixels += equalPixelCount + 1;
Expand All @@ -225,35 +228,29 @@ private void WriteRunLengthEncodedImage<TPixel>(Stream stream, ImageFrame<TPixel
/// <typeparam name="TPixel">The pixel type.</typeparam>
/// <param name="pixels">The pixels of the image.</param>
/// <param name="xStart">X coordinate to start searching for the same pixels.</param>
/// <param name="yStart">Y coordinate to start searching for the same pixels.</param>
/// <param name="yPos">Y coordinate to searching for the same pixels in only one scan line.</param>
/// <returns>The number of equal pixels.</returns>
private byte FindEqualPixels<TPixel>(Buffer2D<TPixel> pixels, int xStart, int yStart)
private byte FindEqualPixels<TPixel>(Buffer2D<TPixel> pixels, int xStart, int yPos)
where TPixel : unmanaged, IPixel<TPixel>
{
byte equalPixelCount = 0;
bool firstRow = true;
TPixel startPixel = pixels[xStart, yStart];
for (int y = yStart; y < pixels.Height; y++)
TPixel startPixel = pixels[xStart, yPos];
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Instead of using the indexer, you could use DangerousGetRowSpan, which should be faster. Like this:

Span<TPixel> pixelRow = pixels.DangerousGetRowSpan(yPos).Slice(xStart);

for (int x = xStart + 1; x < pixels.Width; x++)
{
for (int x = firstRow ? xStart + 1 : 0; x < pixels.Width; x++)
TPixel nextPixel = pixels[x, yPos];
if (startPixel.Equals(nextPixel))
{
equalPixelCount++;
}
else
{
TPixel nextPixel = pixels[x, y];
if (startPixel.Equals(nextPixel))
{
equalPixelCount++;
}
else
{
return equalPixelCount;
}

if (equalPixelCount >= 127)
{
return equalPixelCount;
}
return equalPixelCount;
}

firstRow = false;
if (equalPixelCount >= 127)
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{
return equalPixelCount;
}
}

return equalPixelCount;
Expand Down