/// <summary>
/// Writes the palette chunk to the stream.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="stream">The <see cref="Stream"/> containing image data.</param>
/// <param name="header">The <see cref="PngHeader"/>.</param>
/// <param name="image">The image to encode.</param>
/// <returns>The <see cref="QuantizedImage{TPixel}"/></returns>
private QuantizedImage <TPixel> WritePaletteChunk <TPixel>(Stream stream, PngHeader header, ImageBase <TPixel> image)
where TPixel : struct, IPixel <TPixel>
{
if (this.quality > 256)
{
return(null);
}
if (this.quantizer == null)
{
this.quantizer = new WuQuantizer <TPixel>();
}
// Quantize the image returning a palette. This boxing is icky.
QuantizedImage <TPixel> quantized = ((IQuantizer <TPixel>) this.quantizer).Quantize(image, this.quality);
// Grab the palette and write it to the stream.
TPixel[] palette = quantized.Palette;
byte pixelCount = palette.Length.ToByte();
// Get max colors for bit depth.
int colorTableLength = (int)Math.Pow(2, header.BitDepth) * 3;
byte[] colorTable = ArrayPool <byte> .Shared.Rent(colorTableLength);
byte[] alphaTable = ArrayPool <byte> .Shared.Rent(pixelCount);
byte[] bytes = ArrayPool <byte> .Shared.Rent(4);
bool anyAlpha = false;
try
{
for (byte i = 0; i < pixelCount; i++)
{
if (quantized.Pixels.Contains(i))
{
int offset = i * 3;
palette[i].ToXyzwBytes(bytes, 0);
byte alpha = bytes[3];
colorTable[offset] = bytes[0];
colorTable[offset + 1] = bytes[1];
colorTable[offset + 2] = bytes[2];
if (alpha > this.options.Threshold)
{
alpha = 255;
}
anyAlpha = anyAlpha || alpha < 255;
alphaTable[i] = alpha;
}
}
this.WriteChunk(stream, PngChunkTypes.Palette, colorTable, 0, colorTableLength);
// Write the transparency data
if (anyAlpha)
{
this.WriteChunk(stream, PngChunkTypes.PaletteAlpha, alphaTable, 0, pixelCount);
}
}
finally
{
ArrayPool <byte> .Shared.Return(colorTable);
ArrayPool <byte> .Shared.Return(alphaTable);
ArrayPool <byte> .Shared.Return(bytes);
}
return(quantized);
}
/// <summary>
/// Encodes the image to the specified stream from the <see cref="Image{TPixel}"/>.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="image">The <see cref="ImageBase{TPixel}"/> to encode from.</param>
/// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
public void Encode <TPixel>(Image <TPixel> image, Stream stream)
where TPixel : struct, IPixel <TPixel>
{
Guard.NotNull(image, nameof(image));
Guard.NotNull(stream, nameof(stream));
this.width = image.Width;
this.height = image.Height;
// Write the png header.
this.chunkDataBuffer[0] = 0x89; // Set the high bit.
this.chunkDataBuffer[1] = 0x50; // P
this.chunkDataBuffer[2] = 0x4E; // N
this.chunkDataBuffer[3] = 0x47; // G
this.chunkDataBuffer[4] = 0x0D; // Line ending CRLF
this.chunkDataBuffer[5] = 0x0A; // Line ending CRLF
this.chunkDataBuffer[6] = 0x1A; // EOF
this.chunkDataBuffer[7] = 0x0A; // LF
stream.Write(this.chunkDataBuffer, 0, 8);
// Ensure that quality can be set but has a fallback.
this.quality = this.options.Quality > 0 ? this.options.Quality : image.MetaData.Quality;
this.quality = this.quality > 0 ? this.quality.Clamp(1, int.MaxValue) : int.MaxValue;
this.pngColorType = this.options.PngColorType;
this.quantizer = this.options.Quantizer;
// Set correct color type if the color count is 256 or less.
if (this.quality <= 256)
{
this.pngColorType = PngColorType.Palette;
}
if (this.pngColorType == PngColorType.Palette && this.quality > 256)
{
this.quality = 256;
}
// Set correct bit depth.
this.bitDepth = this.quality <= 256
? (byte)ImageMaths.GetBitsNeededForColorDepth(this.quality).Clamp(1, 8)
: (byte)8;
// Png only supports in four pixel depths: 1, 2, 4, and 8 bits when using the PLTE chunk
if (this.bitDepth == 3)
{
this.bitDepth = 4;
}
else if (this.bitDepth >= 5 || this.bitDepth <= 7)
{
this.bitDepth = 8;
}
this.bytesPerPixel = this.CalculateBytesPerPixel();
PngHeader header = new PngHeader
{
Width = image.Width,
Height = image.Height,
ColorType = this.pngColorType,
BitDepth = this.bitDepth,
FilterMethod = 0, // None
CompressionMethod = 0,
InterlaceMethod = 0
};
this.WriteHeaderChunk(stream, header);
// Collect the indexed pixel data
if (this.pngColorType == PngColorType.Palette)
{
this.CollectIndexedBytes(image, stream, header);
}
this.WritePhysicalChunk(stream, image);
this.WriteGammaChunk(stream);
using (PixelAccessor <TPixel> pixels = image.Lock())
{
this.WriteDataChunks(pixels, stream);
}
this.WriteEndChunk(stream);
stream.Flush();
}
/// <summary>
/// Collects the indexed pixel data.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="image">The image to encode.</param>
/// <param name="stream">The <see cref="Stream"/> containing image data.</param>
/// <param name="header">The <see cref="PngHeader"/>.</param>
private void CollectIndexedBytes <TPixel>(ImageBase <TPixel> image, Stream stream, PngHeader header)
where TPixel : struct, IPixel <TPixel>
{
// Quantize the image and get the pixels.
QuantizedImage <TPixel> quantized = this.WritePaletteChunk(stream, header, image);
this.palettePixelData = quantized.Pixels;
}
/// <summary>
/// Writes the palette chunk to the stream.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <typeparam name="TPacked">The packed format. <example>uint, long, float.</example></typeparam>
/// <param name="stream">The <see cref="Stream"/> containing image data.</param>
/// <param name="header">The <see cref="PngHeader"/>.</param>
/// <param name="image">The image to encode.</param>
/// <returns>The <see cref="QuantizedImage{TColor, TPacked}"/></returns>
private QuantizedImage <TColor, TPacked> WritePaletteChunk <TColor, TPacked>(Stream stream, PngHeader header, ImageBase <TColor, TPacked> image)
where TColor : struct, IPackedPixel <TPacked>
where TPacked : struct
{
if (this.Quality > 256)
{
return(null);
}
if (this.Quantizer == null)
{
this.Quantizer = new WuQuantizer <TColor, TPacked>();
}
// Quantize the image returning a palette. This boxing is icky.
QuantizedImage <TColor, TPacked> quantized = ((IQuantizer <TColor, TPacked>) this.Quantizer).Quantize(image, this.Quality);
// Grab the palette and write it to the stream.
TColor[] palette = quantized.Palette;
int pixelCount = palette.Length;
List <byte> transparentPixels = new List <byte>();
// Get max colors for bit depth.
int colorTableLength = (int)Math.Pow(2, header.BitDepth) * 3;
byte[] colorTable = ArrayPool <byte> .Shared.Rent(colorTableLength);
byte[] bytes = ArrayPool <byte> .Shared.Rent(4);
try
{
for (int i = 0; i < pixelCount; i++)
{
int offset = i * 3;
palette[i].ToBytes(bytes, 0, ComponentOrder.XYZW);
int alpha = bytes[3];
colorTable[offset] = bytes[0];
colorTable[offset + 1] = bytes[1];
colorTable[offset + 2] = bytes[2];
if (alpha <= this.Threshold)
{
transparentPixels.Add((byte)offset);
}
}
this.WriteChunk(stream, PngChunkTypes.Palette, colorTable, 0, colorTableLength);
}
finally
{
ArrayPool <byte> .Shared.Return(colorTable);
ArrayPool <byte> .Shared.Return(bytes);
}
// Write the transparency data
if (transparentPixels.Any())
{
this.WriteChunk(stream, PngChunkTypes.PaletteAlpha, transparentPixels.ToArray());
}
return(quantized);
}
/// <summary>
/// Writes the palette chunk to the stream.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <param name="stream">The <see cref="Stream"/> containing image data.</param>
/// <param name="header">The <see cref="PngHeader"/>.</param>
/// <param name="image">The image to encode.</param>
/// <returns>The <see cref="QuantizedImage{TColor}"/></returns>
private QuantizedImage <TColor> WritePaletteChunk <TColor>(Stream stream, PngHeader header, ImageBase <TColor> image)
where TColor : struct, IPixel <TColor>
{
if (this.quality > 256)
{
return(null);
}
if (this.quantizer == null)
{
this.quantizer = new OctreeQuantizer <TColor>();
}
// Quantize the image returning a palette. This boxing is icky.
QuantizedImage <TColor> quantized = ((IQuantizer <TColor>) this.quantizer).Quantize(image, this.quality);
// Grab the palette and write it to the stream.
TColor[] palette = quantized.Palette;
int pixelCount = palette.Length;
List <byte> transparentPixels = new List <byte>();
// Get max colors for bit depth.
int colorTableLength = (int)Math.Pow(2, header.BitDepth) * 3;
byte[] colorTable = ArrayPool <byte> .Shared.Rent(colorTableLength);
byte[] bytes = ArrayPool <byte> .Shared.Rent(4);
try
{
for (int i = 0; i < pixelCount; i++)
{
int offset = i * 3;
palette[i].ToXyzwBytes(bytes, 0);
int alpha = bytes[3];
colorTable[offset] = bytes[0];
colorTable[offset + 1] = bytes[1];
colorTable[offset + 2] = bytes[2];
if (alpha < 255 && alpha <= this.options.Threshold)
{
// Ensure the index is actually being used in our array.
// I'd like to find a faster way of doing this.
if (quantized.Pixels.Contains((byte)i))
{
transparentPixels.Add((byte)i);
}
}
}
this.WriteChunk(stream, PngChunkTypes.Palette, colorTable, 0, colorTableLength);
}
finally
{
ArrayPool <byte> .Shared.Return(colorTable);
ArrayPool <byte> .Shared.Return(bytes);
}
// Write the transparency data
if (transparentPixels.Any())
{
this.WriteChunk(stream, PngChunkTypes.PaletteAlpha, transparentPixels.ToArray());
}
return(quantized);
}
/// <summary>
/// Writes the palette chunk to the stream.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <typeparam name="TPacked">The packed format. <example>uint, long, float.</example></typeparam>
/// <param name="stream">The <see cref="Stream"/> containing image data.</param>
/// <param name="header">The <see cref="PngHeader"/>.</param>
/// <param name="image">The image to encode.</param>
/// <returns>The <see cref="QuantizedImage{TColor, TPacked}"/></returns>
private QuantizedImage <TColor, TPacked> WritePaletteChunk <TColor, TPacked>(Stream stream, PngHeader header, ImageBase <TColor, TPacked> image)
where TColor : struct, IPackedPixel <TPacked>
where TPacked : struct
{
if (this.Quality > 256)
{
return(null);
}
if (this.Quantizer == null)
{
this.Quantizer = new WuQuantizer <TColor, TPacked>();
}
// Quantize the image returning a palette. This boxing is icky.
QuantizedImage <TColor, TPacked> quantized = ((IQuantizer <TColor, TPacked>) this.Quantizer).Quantize(image, this.Quality);
// Grab the palette and write it to the stream.
TColor[] palette = quantized.Palette;
int pixelCount = palette.Length;
List <byte> transparentPixels = new List <byte>();
// Get max colors for bit depth.
int colorTableLength = (int)Math.Pow(2, header.BitDepth) * 3;
byte[] colorTable = new byte[colorTableLength];
// TODO: Optimize this.
Parallel.For(
0,
pixelCount,
Bootstrapper.Instance.ParallelOptions,
i =>
{
int offset = i * 3;
Color color = new Color(palette[i].ToVector4());
int alpha = color.A;
// Premultiply the color. This helps prevent banding.
if (alpha < 255 && alpha > this.Threshold)
{
color = Color.Multiply(color, new Color(alpha, alpha, alpha, 255));
}
colorTable[offset] = color.R;
colorTable[offset + 1] = color.G;
colorTable[offset + 2] = color.B;
if (alpha <= this.Threshold)
{
transparentPixels.Add((byte)offset);
}
});
this.WriteChunk(stream, PngChunkTypes.Palette, colorTable);
// Write the transparency data
if (transparentPixels.Any())
{
this.WriteChunk(stream, PngChunkTypes.PaletteAlpha, transparentPixels.ToArray());
}
return(quantized);
}
/// <summary>
/// Collects the indexed pixel data.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <typeparam name="TPacked">The packed format. <example>uint, long, float.</example></typeparam>
/// <param name="image">The image to encode.</param>
/// <param name="stream">The <see cref="Stream"/> containing image data.</param>
/// <param name="header">The <see cref="PngHeader"/>.</param>
private void CollectIndexedBytes <TColor, TPacked>(ImageBase <TColor, TPacked> image, Stream stream, PngHeader header)
where TColor : struct, IPackedPixel <TPacked>
where TPacked : struct
{
// Quatize the image and get the pixels
QuantizedImage <TColor, TPacked> quantized = this.WritePaletteChunk(stream, header, image);
this.pixelData = quantized.Pixels;
}
/// <summary>
/// Encodes the image to the specified stream from the <see cref="ImageBase{TColor, TPacked}"/>.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <typeparam name="TPacked">The packed format. <example>uint, long, float.</example></typeparam>
/// <param name="image">The <see cref="ImageBase{TColor, TPacked}"/> to encode from.</param>
/// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
public void Encode <TColor, TPacked>(ImageBase <TColor, TPacked> image, Stream stream)
where TColor : struct, IPackedPixel <TPacked>
where TPacked : struct
{
Guard.NotNull(image, nameof(image));
Guard.NotNull(stream, nameof(stream));
this.width = image.Width;
this.height = image.Height;
// Write the png header.
stream.Write(
new byte[]
{
0x89, // Set the high bit.
0x50, // P
0x4E, // N
0x47, // G
0x0D, // Line ending CRLF
0x0A, // Line ending CRLF
0x1A, // EOF
0x0A // LF
},
0,
8);
// Ensure that quality can be set but has a fallback.
int quality = this.Quality > 0 ? this.Quality : image.Quality;
this.Quality = quality > 0 ? quality.Clamp(1, int.MaxValue) : int.MaxValue;
// Set correct color type if the color count is 256 or less.
if (this.Quality <= 256)
{
this.PngColorType = PngColorType.Palette;
}
// Set correct bit depth.
this.bitDepth = this.Quality <= 256
? (byte)ImageMaths.GetBitsNeededForColorDepth(this.Quality).Clamp(1, 8)
: (byte)8;
// Png only supports in four pixel depths: 1, 2, 4, and 8 bits when using the PLTE chunk
if (this.bitDepth == 3)
{
this.bitDepth = 4;
}
else if (this.bitDepth >= 5 || this.bitDepth <= 7)
{
this.bitDepth = 8;
}
this.bytesPerPixel = this.CalculateBytesPerPixel();
PngHeader header = new PngHeader
{
Width = image.Width,
Height = image.Height,
ColorType = (byte)this.PngColorType,
BitDepth = this.bitDepth,
FilterMethod = 0, // None
CompressionMethod = 0,
InterlaceMethod = 0
};
this.WriteHeaderChunk(stream, header);
// Collect the pixel data
if (this.PngColorType == PngColorType.Palette)
{
this.CollectIndexedBytes(image, stream, header);
}
else if (this.PngColorType == PngColorType.Grayscale || this.PngColorType == PngColorType.GrayscaleWithAlpha)
{
this.CollectGrayscaleBytes(image);
}
else
{
this.CollectColorBytes(image);
}
this.WritePhysicalChunk(stream, image);
this.WriteGammaChunk(stream);
this.WriteDataChunks(stream);
this.WriteEndChunk(stream);
stream.Flush();
}
