/// <summary>
/// Encodes the image as webp to the specified stream.
/// </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>
/// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
public void Encode <TPixel>(Image <TPixel> image, Stream stream, CancellationToken cancellationToken)
where TPixel : unmanaged, IPixel <TPixel>
{
Guard.NotNull(image, nameof(image));
Guard.NotNull(stream, nameof(stream));
this.configuration = image.GetConfiguration();
bool lossless;
if (this.fileFormat is not null)
{
lossless = this.fileFormat == WebpFileFormatType.Lossless;
}
else
{
WebpMetadata webpMetadata = image.Metadata.GetWebpMetadata();
lossless = webpMetadata.FileFormat == WebpFileFormatType.Lossless;
}
if (lossless)
{
using var enc = new Vp8LEncoder(
this.memoryAllocator,
this.configuration,
image.Width,
image.Height,
this.quality,
this.method,
this.transparentColorMode,
this.nearLossless,
this.nearLosslessQuality);
enc.Encode(image, stream);
}
else
{
using var enc = new Vp8Encoder(
this.memoryAllocator,
this.configuration,
image.Width,
image.Height,
this.quality,
this.method,
this.entropyPasses,
this.filterStrength,
this.spatialNoiseShaping,
this.alphaCompression);
enc.Encode(image, stream);
}
}
/// <summary>
/// Encodes the alpha channel data.
/// Data is either compressed as lossless webp image or uncompressed.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
/// <param name="configuration">The global configuration.</param>
/// <param name="memoryAllocator">The memory manager.</param>
/// <param name="compress">Indicates, if the data should be compressed with the lossless webp compression.</param>
/// <param name="size">The size in bytes of the alpha data.</param>
/// <returns>The encoded alpha data.</returns>
public IMemoryOwner <byte> EncodeAlpha <TPixel>(Image <TPixel> image, Configuration configuration, MemoryAllocator memoryAllocator, bool compress, out int size)
where TPixel : unmanaged, IPixel <TPixel>
{
int width = image.Width;
int height = image.Height;
this.alphaData = ExtractAlphaChannel(image, configuration, memoryAllocator);
if (compress)
{
WebpEncodingMethod effort = WebpEncodingMethod.Default;
int quality = 8 * (int)effort;
using var lossLessEncoder = new Vp8LEncoder(
memoryAllocator,
configuration,
width,
height,
quality,
effort,
WebpTransparentColorMode.Preserve,
false,
0);
// The transparency information will be stored in the green channel of the ARGB quadruplet.
// The green channel is allowed extra transformation steps in the specification -- unlike the other channels,
// that can improve compression.
using Image <Rgba32> alphaAsImage = DispatchAlphaToGreen(image, this.alphaData.GetSpan());
size = lossLessEncoder.EncodeAlphaImageData(alphaAsImage, this.alphaData);
return(this.alphaData);
}
size = width * height;
return(this.alphaData);
}
