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Merged
JimBobSquarePants merged 3 commits into from
Aug 29, 2022
Merged

Identify transparency for indexed PNG correctly #2215

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0ee5e43
Set HasTransparency to true, if tRns chunk is found. Fixes #2209
brianpopow Aug 24, 2022
0e93171
Add tests for #2209
brianpopow Aug 24, 2022
e69658e
Only assign when the relevant detail is there.
JimBobSquarePants Aug 29, 2022
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11 changes: 7 additions & 4 deletions src/ImageSharp/Formats/Png/PngDecoderCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,6 @@
using System;
using System.Buffers;
using System.Buffers.Binary;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Runtime.CompilerServices;
Expand Down Expand Up @@ -380,8 +379,8 @@ public IImageInfo Identify(BufferedReadStream stream, CancellationToken cancella
/// <summary>
/// Reads the least significant bits from the byte pair with the others set to 0.
/// </summary>
/// <param name="buffer">The source buffer</param>
/// <param name="offset">THe offset</param>
/// <param name="buffer">The source buffer.</param>
/// <param name="offset">THe offset.</param>
/// <returns>The <see cref="int"/></returns>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static byte ReadByteLittleEndian(ReadOnlySpan<byte> buffer, int offset)
Expand All @@ -392,7 +391,7 @@ private static byte ReadByteLittleEndian(ReadOnlySpan<byte> buffer, int offset)
/// specified number of bits.
/// </summary>
/// <param name="source">The bytes to convert from. Cannot be empty.</param>
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <param name="bytesPerScanline">The number of bytes per scanline.</param>
/// <param name="bits">The number of bits per value.</param>
/// <param name="buffer">The new array.</param>
/// <returns>The resulting <see cref="ReadOnlySpan{Byte}"/> array.</returns>
Expand Down Expand Up @@ -973,6 +972,10 @@ private void AssignTransparentMarkers(ReadOnlySpan<byte> alpha, PngMetadata pngM
pngMetadata.HasTransparency = true;
}
}
else if (this.pngColorType == PngColorType.Palette && alpha.Length > 0)
{
pngMetadata.HasTransparency = true;
}
}

/// <summary>
Expand Down
24 changes: 24 additions & 0 deletions tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs
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Expand Up @@ -470,6 +470,30 @@ public void Issue1765<TPixel>(TestImageProvider<TPixel> provider)
Assert.Null(ex);
}

// https://github.com/SixLabors/ImageSharp/issues/2209
[Theory]
[WithFile(TestImages.Png.Issue2209IndexedWithTransparency, PixelTypes.Rgba32)]
public void Issue2209_Decode_HasTransparencyIsTrue<TPixel>(TestImageProvider<TPixel> provider)
where TPixel : unmanaged, IPixel<TPixel>
{
using Image<TPixel> image = provider.GetImage(PngDecoder);
image.DebugSave(provider);
PngMetadata metadata = image.Metadata.GetPngMetadata();
Assert.True(metadata.HasTransparency);
}

// https://github.com/SixLabors/ImageSharp/issues/2209
[Theory]
[InlineData(TestImages.Png.Issue2209IndexedWithTransparency)]
public void Issue2209_Identify_HasTransparencyIsTrue(string imagePath)
{
var testFile = TestFile.Create(imagePath);
using var stream = new MemoryStream(testFile.Bytes, false);
IImageInfo imageInfo = Image.Identify(stream);
PngMetadata metadata = imageInfo.Metadata.GetPngMetadata();
Assert.True(metadata.HasTransparency);
}

// https://github.com/SixLabors/ImageSharp/issues/410
[Theory]
[WithFile(TestImages.Png.Bad.Issue410_MalformedApplePng, PixelTypes.Rgba32)]
Expand Down
3 changes: 3 additions & 0 deletions tests/ImageSharp.Tests/TestImages.cs
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Expand Up @@ -125,6 +125,9 @@ public static class Png
// Discussion 1875: https://github.com/SixLabors/ImageSharp/discussions/1875
public const string Issue1875 = "Png/raw-profile-type-exif.png";

// Issue 2209: https://github.com/SixLabors/ImageSharp/issues/2209
public const string Issue2209IndexedWithTransparency = "Png/issues/Issue_2209.png";

public static class Bad
{
public const string MissingDataChunk = "Png/xdtn0g01.png";
Expand Down
3 changes: 3 additions & 0 deletions tests/Images/Input/Png/issues/Issue_2209.png
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