diff --git a/src/ImageSharp/Formats/Bmp/BmpBitsPerPixel.cs b/src/ImageSharp/Formats/Bmp/BmpBitsPerPixel.cs
index 6fdf8d634..87f3b7e31 100644
--- a/src/ImageSharp/Formats/Bmp/BmpBitsPerPixel.cs
+++ b/src/ImageSharp/Formats/Bmp/BmpBitsPerPixel.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.
namespace SixLabors.ImageSharp.Formats.Bmp
@@ -8,6 +8,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp
///
public enum BmpBitsPerPixel : short
{
+ ///
+ /// 4 bits per pixel.
+ ///
+ Pixel4 = 4,
+
///
/// 8 bits per pixel. Each pixel consists of 1 byte.
///
@@ -28,4 +33,4 @@ namespace SixLabors.ImageSharp.Formats.Bmp
///
Pixel32 = 32
}
-}
\ No newline at end of file
+}
diff --git a/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs b/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
index 7819b1ebd..7733b718a 100644
--- a/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
+++ b/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
@@ -51,6 +51,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp
///
private const int ColorPaletteSize8Bit = 1024;
+ ///
+ /// The color palette for an 4 bit image will have 16 entry's with 4 bytes for each entry.
+ ///
+ private const int ColorPaletteSize4Bit = 64;
+
///
/// Used for allocating memory during processing operations.
///
@@ -107,7 +112,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
this.configuration = image.GetConfiguration();
ImageMetadata metadata = image.Metadata;
BmpMetadata bmpMetadata = metadata.GetBmpMetadata();
- this.bitsPerPixel = this.bitsPerPixel ?? bmpMetadata.BitsPerPixel;
+ this.bitsPerPixel ??= bmpMetadata.BitsPerPixel;
short bpp = (short)this.bitsPerPixel;
int bytesPerLine = 4 * (((image.Width * bpp) + 31) / 32);
@@ -166,7 +171,15 @@ namespace SixLabors.ImageSharp.Formats.Bmp
infoHeader.Compression = BmpCompression.BitFields;
}
- int colorPaletteSize = this.bitsPerPixel == BmpBitsPerPixel.Pixel8 ? ColorPaletteSize8Bit : 0;
+ int colorPaletteSize = 0;
+ if (this.bitsPerPixel == BmpBitsPerPixel.Pixel8)
+ {
+ colorPaletteSize = ColorPaletteSize8Bit;
+ }
+ else if (this.bitsPerPixel == BmpBitsPerPixel.Pixel4)
+ {
+ colorPaletteSize = ColorPaletteSize4Bit;
+ }
var fileHeader = new BmpFileHeader(
type: BmpConstants.TypeMarkers.Bitmap,
@@ -224,6 +237,10 @@ namespace SixLabors.ImageSharp.Formats.Bmp
case BmpBitsPerPixel.Pixel8:
this.Write8Bit(stream, image);
break;
+
+ case BmpBitsPerPixel.Pixel4:
+ this.Write4BitColor(stream, image);
+ break;
}
}
@@ -344,16 +361,8 @@ namespace SixLabors.ImageSharp.Formats.Bmp
using IQuantizer frameQuantizer = this.quantizer.CreatePixelSpecificQuantizer(this.configuration);
using IndexedImageFrame quantized = frameQuantizer.BuildPaletteAndQuantizeFrame(image, image.Bounds());
- ReadOnlySpan quantizedColors = quantized.Palette.Span;
- var quantizedColorBytes = quantizedColors.Length * 4;
- PixelOperations.Instance.ToBgra32(this.configuration, quantizedColors, MemoryMarshal.Cast(colorPalette.Slice(0, quantizedColorBytes)));
- Span colorPaletteAsUInt = MemoryMarshal.Cast(colorPalette);
- for (int i = 0; i < colorPaletteAsUInt.Length; i++)
- {
- colorPaletteAsUInt[i] = colorPaletteAsUInt[i] & 0x00FFFFFF; // Padding byte, always 0.
- }
-
- stream.Write(colorPalette);
+ ReadOnlySpan quantizedColorPalette = quantized.Palette.Span;
+ this.WriteColorPalette(stream, quantizedColorPalette, colorPalette);
for (int y = image.Height - 1; y >= 0; y--)
{
@@ -404,5 +413,70 @@ namespace SixLabors.ImageSharp.Formats.Bmp
}
}
}
+
+ ///
+ /// Writes an 4 Bit color image with a color palette. The color palette has 16 entry's with 4 bytes for each entry.
+ ///
+ /// The type of the pixel.
+ /// The to write to.
+ /// The containing pixel data.
+ private void Write4BitColor(Stream stream, ImageFrame image)
+ where TPixel : unmanaged, IPixel
+ {
+ using IQuantizer frameQuantizer = this.quantizer.CreatePixelSpecificQuantizer(this.configuration, new QuantizerOptions()
+ {
+ MaxColors = 16
+ });
+ using IndexedImageFrame quantized = frameQuantizer.BuildPaletteAndQuantizeFrame(image, image.Bounds());
+ using IMemoryOwner colorPaletteBuffer = this.memoryAllocator.AllocateManagedByteBuffer(ColorPaletteSize4Bit, AllocationOptions.Clean);
+
+ Span colorPalette = colorPaletteBuffer.GetSpan();
+ ReadOnlySpan quantizedColorPalette = quantized.Palette.Span;
+ this.WriteColorPalette(stream, quantizedColorPalette, colorPalette);
+
+ ReadOnlySpan pixelRowSpan = quantized.GetPixelRowSpan(0);
+ int rowPadding = pixelRowSpan.Length % 2 != 0 ? this.padding - 1 : this.padding;
+ for (int y = image.Height - 1; y >= 0; y--)
+ {
+ pixelRowSpan = quantized.GetPixelRowSpan(y);
+
+ int endIdx = pixelRowSpan.Length % 2 == 0 ? pixelRowSpan.Length : pixelRowSpan.Length - 1;
+ for (int i = 0; i < endIdx; i += 2)
+ {
+ stream.WriteByte((byte)((pixelRowSpan[i] << 4) | pixelRowSpan[i + 1]));
+ }
+
+ if (pixelRowSpan.Length % 2 != 0)
+ {
+ stream.WriteByte((byte)((pixelRowSpan[pixelRowSpan.Length - 1] << 4) | 0));
+ }
+
+ for (int i = 0; i < rowPadding; i++)
+ {
+ stream.WriteByte(0);
+ }
+ }
+ }
+
+ ///
+ /// Writes the color palette to the stream. The color palette has 4 bytes for each entry.
+ ///
+ /// The type of the pixel.
+ /// The to write to.
+ /// The color palette from the quantized image.
+ /// A temporary byte span to write the color palette to.
+ private void WriteColorPalette(Stream stream, ReadOnlySpan quantizedColorPalette, Span colorPalette)
+ where TPixel : unmanaged, IPixel
+ {
+ int quantizedColorBytes = quantizedColorPalette.Length * 4;
+ PixelOperations.Instance.ToBgra32(this.configuration, quantizedColorPalette, MemoryMarshal.Cast(colorPalette.Slice(0, quantizedColorBytes)));
+ Span colorPaletteAsUInt = MemoryMarshal.Cast(colorPalette);
+ for (int i = 0; i < colorPaletteAsUInt.Length; i++)
+ {
+ colorPaletteAsUInt[i] = colorPaletteAsUInt[i] & 0x00FFFFFF; // Padding byte, always 0.
+ }
+
+ stream.Write(colorPalette);
+ }
}
}
diff --git a/tests/ImageSharp.Tests/Formats/Bmp/BmpEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Bmp/BmpEncoderTests.cs
index fa63642bd..35853413e 100644
--- a/tests/ImageSharp.Tests/Formats/Bmp/BmpEncoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Bmp/BmpEncoderTests.cs
@@ -13,7 +13,6 @@ using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
using Xunit;
-using Xunit.Abstractions;
using static SixLabors.ImageSharp.Tests.TestImages.Bmp;
@@ -41,14 +40,11 @@ namespace SixLabors.ImageSharp.Tests.Formats.Bmp
public static readonly TheoryData BmpBitsPerPixelFiles =
new TheoryData
{
+ { Rgb16, BmpBitsPerPixel.Pixel16 },
{ Car, BmpBitsPerPixel.Pixel24 },
{ Bit32Rgb, BmpBitsPerPixel.Pixel32 }
};
- public BmpEncoderTests(ITestOutputHelper output) => this.Output = output;
-
- private ITestOutputHelper Output { get; }
-
[Theory]
[MemberData(nameof(RatioFiles))]
public void Encode_PreserveRatio(string imagePath, int xResolution, int yResolution, PixelResolutionUnit resolutionUnit)
@@ -175,6 +171,16 @@ namespace SixLabors.ImageSharp.Tests.Formats.Bmp
bitsPerPixel,
supportTransparency: false);
+ [Theory]
+ [WithFile(Bit4, PixelTypes.Rgba32, BmpBitsPerPixel.Pixel4)]
+ public void Encode_4Bit_WithV3Header_Works(TestImageProvider provider, BmpBitsPerPixel bitsPerPixel)
+ where TPixel : unmanaged, IPixel => TestBmpEncoderCore(provider, bitsPerPixel, supportTransparency: false);
+
+ [Theory]
+ [WithFile(Bit4, PixelTypes.Rgba32, BmpBitsPerPixel.Pixel4)]
+ public void Encode_4Bit_WithV4Header_Works(TestImageProvider provider, BmpBitsPerPixel bitsPerPixel)
+ where TPixel : unmanaged, IPixel => TestBmpEncoderCore(provider, bitsPerPixel, supportTransparency: true);
+
[Theory]
[WithFile(Bit8Gs, PixelTypes.L8, BmpBitsPerPixel.Pixel8)]
public void Encode_8BitGray_WithV4Header_Works(TestImageProvider provider, BmpBitsPerPixel bitsPerPixel)