/// <summary>
/// A Webp lossless image can go through four different types of transformation before being entropy encoded.
/// This will reverse the transformations, if any are present.
/// </summary>
/// <param name="decoder">The decoder holding the transformation infos.</param>
/// <param name="pixelData">The pixel data to apply the transformation.</param>
/// <param name="memoryAllocator">The memory allocator is needed to allocate memory during the predictor transform.</param>
public static void ApplyInverseTransforms(Vp8LDecoder decoder, Span <uint> pixelData, MemoryAllocator memoryAllocator)
{
List <Vp8LTransform> transforms = decoder.Transforms;
for (int i = transforms.Count - 1; i >= 0; i--)
{
Vp8LTransform transform = transforms[i];
Vp8LTransformType transformType = transform.TransformType;
switch (transformType)
{
case Vp8LTransformType.PredictorTransform:
using (IMemoryOwner <uint> output = memoryAllocator.Allocate <uint>(pixelData.Length, AllocationOptions.Clean))
{
LosslessUtils.PredictorInverseTransform(transform, pixelData, output.GetSpan());
}
break;
case Vp8LTransformType.SubtractGreen:
LosslessUtils.AddGreenToBlueAndRed(pixelData);
break;
case Vp8LTransformType.CrossColorTransform:
LosslessUtils.ColorSpaceInverseTransform(transform, pixelData);
break;
case Vp8LTransformType.ColorIndexingTransform:
LosslessUtils.ColorIndexInverseTransform(transform, pixelData);
break;
}
}
}
public Vp8LTransform(Vp8LTransformType transformType, int xSize, int ySize)
{
this.TransformType = transformType;
this.XSize = xSize;
this.YSize = ySize;
}
