/// <inheritdoc/>
public virtual QuantizedFrame <TPixel> QuantizeFrame(ImageFrame <TPixel> image)
{
Guard.NotNull(image, nameof(image));
// Get the size of the source image
int height = image.Height;
int width = image.Width;
// Call the FirstPass function if not a single pass algorithm.
// For something like an Octree quantizer, this will run through
// all image pixels, build a data structure, and create a palette.
if (!this.singlePass)
{
this.FirstPass(image, width, height);
}
// Collect the palette. Required before the second pass runs.
TPixel[] palette = this.GetPalette();
this.paletteVector = new Vector4[palette.Length];
PixelOperations <TPixel> .Instance.ToVector4(image.Configuration, (ReadOnlySpan <TPixel>) palette, (Span <Vector4>) this.paletteVector, PixelConversionModifiers.Scale);
var quantizedFrame = new QuantizedFrame <TPixel>(image.MemoryAllocator, width, height, palette);
if (this.Dither)
{
// We clone the image as we don't want to alter the original via dithering.
using (ImageFrame <TPixel> clone = image.Clone())
{
this.SecondPass(clone, quantizedFrame.GetPixelSpan(), palette, width, height);
}
}
else
{
this.SecondPass(image, quantizedFrame.GetPixelSpan(), palette, width, height);
}
return(quantizedFrame);
}
/// <inheritdoc />
protected override void OnFrameApply(ImageFrame <TPixel> source, Rectangle sourceRectangle, Configuration configuration)
{
using (IFrameQuantizer <TPixel> executor = this.quantizer.CreateFrameQuantizer <TPixel>(configuration))
using (QuantizedFrame <TPixel> quantized = executor.QuantizeFrame(source))
{
int paletteCount = quantized.Palette.Length - 1;
// Not parallel to remove "quantized" closure allocation.
// We can operate directly on the source here as we've already read it to get the
// quantized result
for (int y = 0; y < source.Height; y++)
{
Span <TPixel> row = source.GetPixelRowSpan(y);
ReadOnlySpan <byte> quantizedPixelSpan = quantized.GetPixelSpan();
int yy = y * source.Width;
for (int x = 0; x < source.Width; x++)
{
int i = x + yy;
row[x] = quantized.Palette[Math.Min(paletteCount, quantizedPixelSpan[i])];
}
}
}
}
