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Minor optimizations to Wu

pull/705/head
James Jackson-South 8 years ago
parent
eaab4f0728
commit
bd36a3fb57
1 changed files with 32 additions and 20 deletions
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  1. 52
      src/ImageSharp/Processing/Processors/Quantization/WuFrameQuantizer{TPixel}.cs

52
src/ImageSharp/Processing/Processors/Quantization/WuFrameQuantizer{TPixel}.cs
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@ -37,7 +37,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
where TPixel : struct, IPixel<TPixel>
{
// TODO: The WuFrameQuantizer<TPixel> code is rising several questions:
// - Do we really need to ALWAYS allocate the whole table of size TableLength? (~ 2471625 * sizeof(long) * 5 bytes )
// - Do we really need to ALWAYS allocate the whole table of size TableLength? (~ 2471625 * sizeof(long) * 5 bytes ) JS. I'm afraid so.
// - Isn't an AOS ("array of structures") layout more efficient & more readable than SOA ("structure of arrays") for this particular use case?
// (T, R, G, B, A, M2) could be grouped together!
// - It's a frequently used class, we need tests! (So we can optimize safely.) There are tests in the original!!! We should just adopt them!
@ -49,7 +49,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
private const int IndexBits = 5;
/// <summary>
/// The index alpha bits.
/// The index alpha bits. Keep separate for now to allow easy adjustment.
/// </summary>
private const int IndexAlphaBits = 5;
@ -64,7 +64,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
private const int IndexAlphaCount = (1 << IndexAlphaBits) + 1;
/// <summary>
/// The table length.
/// The table length. Now 1185921.
/// </summary>
private const int TableLength = IndexCount * IndexCount * IndexCount * IndexAlphaCount;
@ -179,18 +179,24 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
if (this.palette is null)
{
this.palette = new TPixel[this.colors];
Span<long> vwtSpan = this.vwt.GetSpan();
Span<long> vmrSpan = this.vmr.GetSpan();
Span<long> vmgSpan = this.vmg.GetSpan();
Span<long> vmbSpan = this.vmb.GetSpan();
Span<long> vmaSpan = this.vma.GetSpan();
for (int k = 0; k < this.colors; k++)
{
this.Mark(ref this.colorCube[k], (byte)k);
float weight = Volume(ref this.colorCube[k], this.vwt.GetSpan());
float weight = Volume(ref this.colorCube[k], vwtSpan);
if (MathF.Abs(weight) > Constants.Epsilon)
{
float r = Volume(ref this.colorCube[k], this.vmr.GetSpan());
float g = Volume(ref this.colorCube[k], this.vmg.GetSpan());
float b = Volume(ref this.colorCube[k], this.vmb.GetSpan());
float a = Volume(ref this.colorCube[k], this.vma.GetSpan());
float r = Volume(ref this.colorCube[k], vmrSpan);
float g = Volume(ref this.colorCube[k], vmgSpan);
float b = Volume(ref this.colorCube[k], vmbSpan);
float a = Volume(ref this.colorCube[k], vmaSpan);
ref TPixel color = ref this.palette[k];
color.PackFromScaledVector4(new Vector4(r, g, b, a) / weight / 255F);
@ -427,8 +433,6 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
/// <param name="height">The height in pixels of the image.</param>
private void Build3DHistogram(ImageFrame<TPixel> source, int width, int height)
{
// Build up the 3-D color histogram
// Loop through each row
Span<long> vwtSpan = this.vwt.GetSpan();
Span<long> vmrSpan = this.vmr.GetSpan();
Span<long> vmgSpan = this.vmg.GetSpan();
@ -436,6 +440,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
Span<long> vmaSpan = this.vma.GetSpan();
Span<float> m2Span = this.m2.GetSpan();
// Build up the 3-D color histogram
// Loop through each row
for (int y = 0; y < height; y++)
{
Span<TPixel> row = source.GetPixelRowSpan(y);
@ -632,22 +638,28 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
/// <returns>The <see cref="float"/>.</returns>
private float Maximize(ref Box cube, int direction, int first, int last, out int cut, float wholeR, float wholeG, float wholeB, float wholeA, float wholeW)
{
long baseR = Bottom(ref cube, direction, this.vmr.GetSpan());
long baseG = Bottom(ref cube, direction, this.vmg.GetSpan());
long baseB = Bottom(ref cube, direction, this.vmb.GetSpan());
long baseA = Bottom(ref cube, direction, this.vma.GetSpan());
long baseW = Bottom(ref cube, direction, this.vwt.GetSpan());
Span<long> vwtSpan = this.vwt.GetSpan();
Span<long> vmrSpan = this.vmr.GetSpan();
Span<long> vmgSpan = this.vmg.GetSpan();
Span<long> vmbSpan = this.vmb.GetSpan();
Span<long> vmaSpan = this.vma.GetSpan();
long baseR = Bottom(ref cube, direction, vmrSpan);
long baseG = Bottom(ref cube, direction, vmgSpan);
long baseB = Bottom(ref cube, direction, vmbSpan);
long baseA = Bottom(ref cube, direction, vmaSpan);
long baseW = Bottom(ref cube, direction, vwtSpan);
float max = 0F;
cut = -1;
for (int i = first; i < last; i++)
{
float halfR = baseR + Top(ref cube, direction, i, this.vmr.GetSpan());
float halfG = baseG + Top(ref cube, direction, i, this.vmg.GetSpan());
float halfB = baseB + Top(ref cube, direction, i, this.vmb.GetSpan());
float halfA = baseA + Top(ref cube, direction, i, this.vma.GetSpan());
float halfW = baseW + Top(ref cube, direction, i, this.vwt.GetSpan());
float halfR = baseR + Top(ref cube, direction, i, vmrSpan);
float halfG = baseG + Top(ref cube, direction, i, vmgSpan);
float halfB = baseB + Top(ref cube, direction, i, vmbSpan);
float halfA = baseA + Top(ref cube, direction, i, vmaSpan);
float halfW = baseW + Top(ref cube, direction, i, vwtSpan);
if (MathF.Abs(halfW) < Constants.Epsilon)
{

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