/// <summary>
/// Creates the quantized frame.
/// </summary>
/// <typeparam name="TPixel">The type of the pixel.</typeparam>
/// <param name="options">The options.</param>
/// <param name="image">The image.</param>
public static IndexedImageFrame <TPixel> CreateQuantizedFrame <TPixel>(
PngEncoderOptions options,
Image <TPixel> image)
where TPixel : unmanaged, IPixel <TPixel>
{
if (options.ColorType != PngColorType.Palette)
{
return(null);
}
// Use the metadata to determine what quantization depth to use if no quantizer has been set.
if (options.Quantizer is null)
{
byte bits = (byte)options.BitDepth;
var maxColors = ImageMaths.GetColorCountForBitDepth(bits);
options.Quantizer = new WuQuantizer(new QuantizerOptions {
MaxColors = maxColors
});
}
// Create quantized frame returning the palette and set the bit depth.
using (IQuantizer <TPixel> frameQuantizer = options.Quantizer.CreatePixelSpecificQuantizer <TPixel>(image.GetConfiguration()))
{
ImageFrame <TPixel> frame = image.Frames.RootFrame;
return(frameQuantizer.BuildPaletteAndQuantizeFrame(frame, frame.Bounds()));
}
}
/// <summary>
/// Creates the quantized frame.
/// </summary>
/// <typeparam name="TPixel">The type of the pixel.</typeparam>
/// <param name="options">The options.</param>
/// <param name="image">The image.</param>
public static IndexedImageFrame <TPixel> CreateQuantizedFrame <TPixel>(
PngEncoderOptions options,
Image <TPixel> image)
where TPixel : unmanaged, IPixel <TPixel>
{
if (options.ColorType != PngColorType.Palette)
{
return(null);
}
byte bits = (byte)options.BitDepth;
if (Array.IndexOf(PngConstants.ColorTypes[options.ColorType.Value], bits) == -1)
{
throw new NotSupportedException("Bit depth is not supported or not valid.");
}
// Use the metadata to determine what quantization depth to use if no quantizer has been set.
if (options.Quantizer is null)
{
var maxColors = ImageMaths.GetColorCountForBitDepth(bits);
options.Quantizer = new WuQuantizer(new QuantizerOptions {
MaxColors = maxColors
});
}
// Create quantized frame returning the palette and set the bit depth.
using (IFrameQuantizer <TPixel> frameQuantizer = options.Quantizer.CreateFrameQuantizer <TPixel>(image.GetConfiguration()))
{
ImageFrame <TPixel> frame = image.Frames.RootFrame;
return(frameQuantizer.QuantizeFrame(frame, frame.Bounds()));
}
}
/// <summary>
/// Reads the <see cref="BmpFileHeader"/> and <see cref="BmpInfoHeader"/> from the stream and sets the corresponding fields.
/// </summary>
/// <returns>Bytes per color palette entry. Usually 4 bytes, but in case of Windows 2.x bitmaps or OS/2 1.x bitmaps
/// the bytes per color palette entry's can be 3 bytes instead of 4.</returns>
private int ReadImageHeaders(Stream stream, out bool inverted, out byte[] palette)
{
this.stream = stream;
this.ReadFileHeader();
this.ReadInfoHeader();
// see http://www.drdobbs.com/architecture-and-design/the-bmp-file-format-part-1/184409517
// If the height is negative, then this is a Windows bitmap whose origin
// is the upper-left corner and not the lower-left. The inverted flag
// indicates a lower-left origin.Our code will be outputting an
// upper-left origin pixel array.
inverted = false;
if (this.infoHeader.Height < 0)
{
inverted = true;
this.infoHeader.Height = -this.infoHeader.Height;
}
int colorMapSize = -1;
int bytesPerColorMapEntry = 4;
if (this.infoHeader.ClrUsed == 0)
{
if (this.infoHeader.BitsPerPixel == 1 ||
this.infoHeader.BitsPerPixel == 4 ||
this.infoHeader.BitsPerPixel == 8)
{
int colorMapSizeBytes = this.fileHeader.Offset - BmpFileHeader.Size - this.infoHeader.HeaderSize;
int colorCountForBitDepth = ImageMaths.GetColorCountForBitDepth(this.infoHeader.BitsPerPixel);
bytesPerColorMapEntry = colorMapSizeBytes / colorCountForBitDepth;
colorMapSize = colorMapSizeBytes;
}
}
else
{
colorMapSize = this.infoHeader.ClrUsed * bytesPerColorMapEntry;
}
palette = null;
if (colorMapSize > 0)
{
// 256 * 4
if (colorMapSize > 1024)
{
throw new ImageFormatException($"Invalid bmp colormap size '{colorMapSize}'");
}
palette = new byte[colorMapSize];
this.stream.Read(palette, 0, colorMapSize);
}
this.infoHeader.VerifyDimensions();
return(bytesPerColorMapEntry);
}
/// <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="ImageFrame{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;
// Always take the encoder options over the metadata values.
ImageMetaData metaData = image.MetaData;
PngMetaData pngMetaData = metaData.GetFormatMetaData(PngFormat.Instance);
this.gamma = this.gamma ?? pngMetaData.Gamma;
this.writeGamma = this.gamma > 0;
this.pngColorType = this.pngColorType ?? pngMetaData.ColorType;
this.pngBitDepth = this.pngBitDepth ?? pngMetaData.BitDepth;
this.use16Bit = this.pngBitDepth.Equals(PngBitDepth.Bit16);
stream.Write(PngConstants.HeaderBytes, 0, PngConstants.HeaderBytes.Length);
QuantizedFrame <TPixel> quantized = null;
ReadOnlySpan <byte> quantizedPixelsSpan = default;
if (this.pngColorType == PngColorType.Palette)
{
byte bits;
// Use the metadata to determine what quantization depth to use if no quantizer has been set.
if (this.quantizer == null)
{
bits = (byte)Math.Min(8u, (short)this.pngBitDepth);
int colorSize = ImageMaths.GetColorCountForBitDepth(bits);
this.quantizer = new WuQuantizer(colorSize);
}
// Create quantized frame returning the palette and set the bit depth.
quantized = this.quantizer.CreateFrameQuantizer <TPixel>().QuantizeFrame(image.Frames.RootFrame);
quantizedPixelsSpan = quantized.GetPixelSpan();
bits = (byte)ImageMaths.GetBitsNeededForColorDepth(quantized.Palette.Length).Clamp(1, 8);
// Png only supports in four pixel depths: 1, 2, 4, and 8 bits when using the PLTE chunk
if (bits == 3)
{
bits = 4;
}
else if (bits >= 5 && bits <= 7)
{
bits = 8;
}
this.bitDepth = bits;
}
else
{
this.bitDepth = (byte)(this.use16Bit ? 16 : 8);
}
this.bytesPerPixel = this.CalculateBytesPerPixel();
var header = new PngHeader(
width: image.Width,
height: image.Height,
bitDepth: this.bitDepth,
colorType: this.pngColorType.Value,
compressionMethod: 0, // None
filterMethod: 0,
interlaceMethod: 0); // TODO: Can't write interlaced yet.
this.WriteHeaderChunk(stream, header);
// Collect the indexed pixel data
if (quantized != null)
{
this.WritePaletteChunk(stream, header, quantized);
}
this.WritePhysicalChunk(stream, metaData);
this.WriteGammaChunk(stream);
this.WriteExifChunk(stream, metaData);
this.WriteDataChunks(image.Frames.RootFrame, quantizedPixelsSpan, stream);
this.WriteEndChunk(stream);
stream.Flush();
quantized?.Dispose();
}
/// <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="ImageFrame{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.configuration = image.GetConfiguration();
this.width = image.Width;
this.height = image.Height;
// Always take the encoder options over the metadata values.
ImageMetaData metaData = image.MetaData;
PngMetaData pngMetaData = metaData.GetFormatMetaData(PngFormat.Instance);
this.gamma = this.gamma ?? pngMetaData.Gamma;
this.writeGamma = this.gamma > 0;
this.pngColorType = this.pngColorType ?? pngMetaData.ColorType;
this.pngBitDepth = this.pngBitDepth ?? pngMetaData.BitDepth;
this.use16Bit = this.pngBitDepth.Equals(PngBitDepth.Bit16);
// Ensure we are not allowing impossible combinations.
if (!ColorTypes.ContainsKey(this.pngColorType.Value))
{
throw new NotSupportedException("Color type is not supported or not valid.");
}
stream.Write(PngConstants.HeaderBytes, 0, PngConstants.HeaderBytes.Length);
QuantizedFrame <TPixel> quantized = null;
if (this.pngColorType == PngColorType.Palette)
{
byte bits = (byte)this.pngBitDepth;
if (!ColorTypes[this.pngColorType.Value].Contains(bits))
{
throw new NotSupportedException("Bit depth is not supported or not valid.");
}
// Use the metadata to determine what quantization depth to use if no quantizer has been set.
if (this.quantizer == null)
{
this.quantizer = new WuQuantizer(ImageMaths.GetColorCountForBitDepth(bits));
}
// Create quantized frame returning the palette and set the bit depth.
quantized = this.quantizer.CreateFrameQuantizer <TPixel>(image.GetConfiguration())
.QuantizeFrame(image.Frames.RootFrame);
byte quantizedBits = (byte)ImageMaths.GetBitsNeededForColorDepth(quantized.Palette.Length).Clamp(1, 8);
bits = Math.Max(bits, quantizedBits);
// Png only supports in four pixel depths: 1, 2, 4, and 8 bits when using the PLTE chunk
// We check again for the bit depth as the bit depth of the color palette from a given quantizer might not
// be within the acceptable range.
if (bits == 3)
{
bits = 4;
}
else if (bits >= 5 && bits <= 7)
{
bits = 8;
}
this.bitDepth = bits;
}
else
{
this.bitDepth = (byte)this.pngBitDepth;
if (!ColorTypes[this.pngColorType.Value].Contains(this.bitDepth))
{
throw new NotSupportedException("Bit depth is not supported or not valid.");
}
}
this.bytesPerPixel = this.CalculateBytesPerPixel();
var header = new PngHeader(
width: image.Width,
height: image.Height,
bitDepth: this.bitDepth,
colorType: this.pngColorType.Value,
compressionMethod: 0, // None
filterMethod: 0,
interlaceMethod: 0); // TODO: Can't write interlaced yet.
this.WriteHeaderChunk(stream, header);
// Collect the indexed pixel data
if (quantized != null)
{
this.WritePaletteChunk(stream, quantized);
}
this.WritePhysicalChunk(stream, metaData);
this.WriteGammaChunk(stream);
this.WriteExifChunk(stream, metaData);
this.WriteDataChunks(image.Frames.RootFrame, quantized, stream);
this.WriteEndChunk(stream);
stream.Flush();
quantized?.Dispose();
}