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Respect alpha channel bits from image descriptor during tga decoding

pull/1157/head
Brian Popow 6 years ago
parent
7244d06a0e
commit
1fd1a62136
9 changed files with 126 additions and 37 deletions
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  1. 1
      src/ImageSharp/Formats/Tga/TgaDecoder.cs
  2. 138
      src/ImageSharp/Formats/Tga/TgaDecoderCore.cs
  3. 5
      src/ImageSharp/Formats/Tga/TgaMetadata.cs
  4. 15
      tests/ImageSharp.Tests/Formats/Tga/TgaDecoderTests.cs
  5. 4
      tests/ImageSharp.Tests/TestImages.cs
  6. BIN
      tests/Images/Input/Tga/16bit_noalphabits.tga
  7. BIN
      tests/Images/Input/Tga/16bit_rle_noalphabits.tga
  8. BIN
      tests/Images/Input/Tga/32bit_noalphabits.tga
  9. BIN
      tests/Images/Input/Tga/32bit_rle_no_alphabits.tga

1
src/ImageSharp/Formats/Tga/TgaDecoder.cs
View File

@ -1,7 +1,6 @@
// Copyright (c) Six Labors and contributors.
// Licensed under the Apache License, Version 2.0.
using System;
using System.IO;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;

138
src/ImageSharp/Formats/Tga/TgaDecoderCore.cs
View File

@ -12,6 +12,9 @@ using SixLabors.ImageSharp.PixelFormats;
namespace SixLabors.ImageSharp.Formats.Tga
{
/// <summary>
/// Performs the tga decoding operation.
/// </summary>
internal sealed class TgaDecoderCore
{
/// <summary>
@ -49,6 +52,11 @@ namespace SixLabors.ImageSharp.Formats.Tga
/// </summary>
private readonly ITgaDecoderOptions options;
/// <summary>
/// Indicates whether there is a alpha channel present.
/// </summary>
private bool hasAlpha;
/// <summary>
/// Initializes a new instance of the <see cref="TgaDecoderCore"/> class.
/// </summary>
@ -89,7 +97,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
TgaThrowHelper.ThrowNotSupportedException($"Unknown tga colormap type {this.fileHeader.ColorMapType} found");
}
if (this.fileHeader.Width == 0 || this.fileHeader.Height == 0)
if (this.fileHeader.Width is 0 || this.fileHeader.Height is 0)
{
throw new UnknownImageFormatException("Width or height cannot be 0");
}
@ -199,7 +207,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
break;
default:
TgaThrowHelper.ThrowNotSupportedException("Does not support this kind of tga files.");
TgaThrowHelper.ThrowNotSupportedException("ImageSharp does not support this kind of tga files.");
break;
}
@ -241,9 +249,13 @@ namespace SixLabors.ImageSharp.Formats.Tga
{
int colorIndex = rowSpan[x];
// Set alpha value to 1, to treat it as opaque for Bgra5551.
Bgra5551 bgra = Unsafe.As<byte, Bgra5551>(ref palette[colorIndex * colorMapPixelSizeInBytes]);
bgra.PackedValue = (ushort)(bgra.PackedValue | 0x8000);
if (!this.hasAlpha)
{
// Set alpha value to 1, to treat it as opaque for Bgra5551.
bgra.PackedValue = (ushort)(bgra.PackedValue | 0x8000);
}
color.FromBgra5551(bgra);
pixelRow[x] = color;
}
@ -291,6 +303,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
using (IMemoryOwner<byte> buffer = this.memoryAllocator.Allocate<byte>(width * height * bytesPerPixel, AllocationOptions.Clean))
{
TPixel color = default;
var alphaBits = this.tgaMetadata.AlphaChannelBits;
Span<byte> bufferSpan = buffer.GetSpan();
this.UncompressRle(width, height, bufferSpan, bytesPerPixel: 1);
@ -308,16 +321,30 @@ namespace SixLabors.ImageSharp.Formats.Tga
color.FromL8(Unsafe.As<byte, L8>(ref palette[bufferSpan[idx] * colorMapPixelSizeInBytes]));
break;
case 2:
// Set alpha value to 1, to treat it as opaque for Bgra5551.
Bgra5551 bgra = Unsafe.As<byte, Bgra5551>(ref palette[bufferSpan[idx] * colorMapPixelSizeInBytes]);
bgra.PackedValue = (ushort)(bgra.PackedValue | 0x8000);
if (!this.hasAlpha)
{
// Set alpha value to 1, to treat it as opaque for Bgra5551.
bgra.PackedValue = (ushort)(bgra.PackedValue | 0x8000);
}
color.FromBgra5551(bgra);
break;
case 3:
color.FromBgr24(Unsafe.As<byte, Bgr24>(ref palette[bufferSpan[idx] * colorMapPixelSizeInBytes]));
break;
case 4:
color.FromBgra32(Unsafe.As<byte, Bgra32>(ref palette[bufferSpan[idx] * colorMapPixelSizeInBytes]));
if (this.hasAlpha)
{
color.FromBgra32(Unsafe.As<byte, Bgra32>(ref palette[bufferSpan[idx] * colorMapPixelSizeInBytes]));
}
else
{
var alpha = alphaBits is 0 ? byte.MaxValue : bufferSpan[idx + 3];
color.FromBgra32(new Bgra32(bufferSpan[idx + 2], bufferSpan[idx + 1], bufferSpan[idx], (byte)alpha));
}
break;
}
@ -345,11 +372,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
this.currentStream.Read(row);
int newY = Invert(y, height, inverted);
Span<TPixel> pixelSpan = pixels.GetRowSpan(newY);
PixelOperations<TPixel>.Instance.FromL8Bytes(
this.configuration,
row.GetSpan(),
pixelSpan,
width);
PixelOperations<TPixel>.Instance.FromL8Bytes(this.configuration, row.GetSpan(), pixelSpan, width);
}
}
}
@ -372,19 +395,18 @@ namespace SixLabors.ImageSharp.Formats.Tga
this.currentStream.Read(row);
Span<byte> rowSpan = row.GetSpan();
// We need to set each alpha component value to fully opaque.
for (int x = 1; x < rowSpan.Length; x += 2)
if (!this.hasAlpha)
{
rowSpan[x] = (byte)(rowSpan[x] | (1 << 7));
// We need to set the alpha component value to fully opaque.
for (int x = 1; x < rowSpan.Length; x += 2)
{
rowSpan[x] = (byte)(rowSpan[x] | (1 << 7));
}
}
int newY = Invert(y, height, inverted);
Span<TPixel> pixelSpan = pixels.GetRowSpan(newY);
PixelOperations<TPixel>.Instance.FromBgra5551Bytes(
this.configuration,
rowSpan,
pixelSpan,
width);
PixelOperations<TPixel>.Instance.FromBgra5551Bytes(this.configuration, rowSpan, pixelSpan, width);
}
}
}
@ -407,11 +429,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
this.currentStream.Read(row);
int newY = Invert(y, height, inverted);
Span<TPixel> pixelSpan = pixels.GetRowSpan(newY);
PixelOperations<TPixel>.Instance.FromBgr24Bytes(
this.configuration,
row.GetSpan(),
pixelSpan,
width);
PixelOperations<TPixel>.Instance.FromBgr24Bytes(this.configuration, row.GetSpan(), pixelSpan, width);
}
}
}
@ -427,18 +445,41 @@ namespace SixLabors.ImageSharp.Formats.Tga
private void ReadBgra32<TPixel>(int width, int height, Buffer2D<TPixel> pixels, bool inverted)
where TPixel : unmanaged, IPixel<TPixel>
{
if (this.tgaMetadata.AlphaChannelBits is 8)
{
using (IManagedByteBuffer row = this.memoryAllocator.AllocatePaddedPixelRowBuffer(width, 4, 0))
{
for (int y = 0; y < height; y++)
{
this.currentStream.Read(row);
int newY = Invert(y, height, inverted);
Span<TPixel> pixelSpan = pixels.GetRowSpan(newY);
PixelOperations<TPixel>.Instance.FromBgra32Bytes(this.configuration, row.GetSpan(), pixelSpan, width);
}
}
return;
}
TPixel color = default;
var alphaBits = this.tgaMetadata.AlphaChannelBits;
using (IManagedByteBuffer row = this.memoryAllocator.AllocatePaddedPixelRowBuffer(width, 4, 0))
{
for (int y = 0; y < height; y++)
{
this.currentStream.Read(row);
int newY = Invert(y, height, inverted);
Span<TPixel> pixelSpan = pixels.GetRowSpan(newY);
PixelOperations<TPixel>.Instance.FromBgra32Bytes(
this.configuration,
row.GetSpan(),
pixelSpan,
width);
Span<TPixel> pixelRow = pixels.GetRowSpan(newY);
Span<byte> rowSpan = row.GetSpan();
for (int x = 0; x < width; x++)
{
int idx = x * 4;
var alpha = alphaBits is 0 ? byte.MaxValue : rowSpan[idx + 3];
color.FromBgra32(new Bgra32(rowSpan[idx + 2], rowSpan[idx + 1], rowSpan[idx], (byte)alpha));
pixelRow[x] = color;
}
}
}
}
@ -456,6 +497,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
where TPixel : unmanaged, IPixel<TPixel>
{
TPixel color = default;
var alphaBits = this.tgaMetadata.AlphaChannelBits;
using (IMemoryOwner<byte> buffer = this.memoryAllocator.Allocate<byte>(width * height * bytesPerPixel, AllocationOptions.Clean))
{
Span<byte> bufferSpan = buffer.GetSpan();
@ -474,15 +516,28 @@ namespace SixLabors.ImageSharp.Formats.Tga
color.FromL8(Unsafe.As<byte, L8>(ref bufferSpan[idx]));
break;
case 2:
// Set alpha value to 1, to treat it as opaque for Bgra5551.
bufferSpan[idx + 1] = (byte)(bufferSpan[idx + 1] | 128);
if (!this.hasAlpha)
{
// Set alpha value to 1, to treat it as opaque for Bgra5551.
bufferSpan[idx + 1] = (byte)(bufferSpan[idx + 1] | 128);
}
color.FromBgra5551(Unsafe.As<byte, Bgra5551>(ref bufferSpan[idx]));
break;
case 3:
color.FromBgr24(Unsafe.As<byte, Bgr24>(ref bufferSpan[idx]));
break;
case 4:
color.FromBgra32(Unsafe.As<byte, Bgra32>(ref bufferSpan[idx]));
if (this.hasAlpha)
{
color.FromBgra32(Unsafe.As<byte, Bgra32>(ref bufferSpan[idx]));
}
else
{
var alpha = alphaBits is 0 ? byte.MaxValue : bufferSpan[idx + 3];
color.FromBgra32(new Bgra32(bufferSpan[idx + 2], bufferSpan[idx + 1], bufferSpan[idx], (byte)alpha));
}
break;
}
@ -524,7 +579,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
// The high bit of a run length packet is set to 1.
int highBit = runLengthByte >> 7;
if (highBit == 1)
if (highBit is 1)
{
int runLength = runLengthByte & 127;
this.currentStream.Read(pixel, 0, bytesPerPixel);
@ -577,7 +632,18 @@ namespace SixLabors.ImageSharp.Formats.Tga
this.tgaMetadata = this.metadata.GetTgaMetadata();
this.tgaMetadata.BitsPerPixel = (TgaBitsPerPixel)this.fileHeader.PixelDepth;
// Bit at position 5 of the descriptor indicates, that the origin is top left instead of bottom right.
var alphaBits = this.fileHeader.ImageDescriptor & 0xf;
if (alphaBits != 0 && alphaBits != 1 && alphaBits != 8)
{
TgaThrowHelper.ThrowImageFormatException("Invalid alpha channel bits");
}
this.tgaMetadata.AlphaChannelBits = (byte)alphaBits;
this.hasAlpha = alphaBits > 0;
// TODO: bits 4 and 5 describe the image origin. See spec page 9. bit 4 is currently ignored.
// Theoretically the origin could also be top right and bottom right.
// Bit at position 5 of the descriptor indicates, that the origin is top left instead of bottom left.
if ((this.fileHeader.ImageDescriptor & (1 << 5)) != 0)
{
return true;

5
src/ImageSharp/Formats/Tga/TgaMetadata.cs
View File

@ -29,6 +29,11 @@ namespace SixLabors.ImageSharp.Formats.Tga
/// </summary>
public TgaBitsPerPixel BitsPerPixel { get; set; } = TgaBitsPerPixel.Pixel24;
/// <summary>
/// Gets or sets the the number of alpha bits per pixel.
/// </summary>
public byte AlphaChannelBits { get; set; } = 0;
/// <inheritdoc/>
public IDeepCloneable DeepClone() => new TgaMetadata(this);
}

15
tests/ImageSharp.Tests/Formats/Tga/TgaDecoderTests.cs
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@ -198,6 +198,21 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tga
}
}
[Theory]
[WithFile(NoAlphaBits32Bit, PixelTypes.Rgba32)]
[WithFile(NoAlphaBits16Bit, PixelTypes.Rgba32)]
[WithFile(NoAlphaBits32BitRle, PixelTypes.Rgba32)]
[WithFile(NoAlphaBits16BitRle, PixelTypes.Rgba32)]
public void TgaDecoder_CanDecode_WhenAlphaBitsNotSet<TPixel>(TestImageProvider<TPixel> provider)
where TPixel : unmanaged, IPixel<TPixel>
{
using (Image<TPixel> image = provider.GetImage(TgaDecoder))
{
image.DebugSave(provider);
TgaTestUtils.CompareWithReferenceDecoder(provider, image);
}
}
[Theory]
[WithFile(Bit16, PixelTypes.Rgba32)]
[WithFile(Bit24, PixelTypes.Rgba32)]

4
tests/ImageSharp.Tests/TestImages.cs
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@ -390,6 +390,10 @@ namespace SixLabors.ImageSharp.Tests
public const string Bit32Rle = "Tga/targa_32bit_rle.tga";
public const string Bit16Pal = "Tga/targa_16bit_pal.tga";
public const string Bit24Pal = "Tga/targa_24bit_pal.tga";
public const string NoAlphaBits16Bit = "Tga/16bit_noalphabits.tga";
public const string NoAlphaBits16BitRle = "Tga/16bit_rle_noalphabits.tga";
public const string NoAlphaBits32Bit = "Tga/32bit_noalphabits.tga";
public const string NoAlphaBits32BitRle = "Tga/32bit_rle_no_alphabits.tga";
}
}
}

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