/// <summary>
/// Converts the 8x8 region of the image whose top-left corner is x,y to its YCbCr values.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <param name="pixels">The pixel accessor.</param>
/// <param name="x">The x-position within the image.</param>
/// <param name="y">The y-position within the image.</param>
/// <param name="yBlock">The luminance block.</param>
/// <param name="cbBlock">The red chroma block.</param>
/// <param name="crBlock">The blue chroma block.</param>
/// <param name="rgbBytes">Temporal <see cref="PixelArea{TColor}"/> provided by the caller</param>
private static void ToYCbCr <TColor>(
PixelAccessor <TColor> pixels,
int x,
int y,
Block8x8F *yBlock,
Block8x8F *cbBlock,
Block8x8F *crBlock,
PixelArea <TColor> rgbBytes)
where TColor : struct, IPackedPixel, IEquatable <TColor>
{
float *yBlockRaw = (float *)yBlock;
float *cbBlockRaw = (float *)cbBlock;
float *crBlockRaw = (float *)crBlock;
rgbBytes.Reset();
pixels.CopyRGBBytesStretchedTo(rgbBytes, y, x);
byte *data = (byte *)rgbBytes.DataPointer;
for (int j = 0; j < 8; j++)
{
int j8 = j * 8;
for (int i = 0; i < 8; i++)
{
// Convert returned bytes into the YCbCr color space. Assume RGBA
int r = data[0];
int g = data[1];
int b = data[2];
// Speed up the algorithm by removing floating point calculation
// Scale by 65536, add .5F and truncate value. We use bit shifting to divide the result
int y0 = 19595 * r; // (0.299F * 65536) + .5F
int y1 = 38470 * g; // (0.587F * 65536) + .5F
int y2 = 7471 * b; // (0.114F * 65536) + .5F
int cb0 = -11057 * r; // (-0.168736F * 65536) + .5F
int cb1 = 21710 * g; // (0.331264F * 65536) + .5F
int cb2 = 32768 * b; // (0.5F * 65536) + .5F
int cr0 = 32768 * r; // (0.5F * 65536) + .5F
int cr1 = 27439 * g; // (0.418688F * 65536) + .5F
int cr2 = 5329 * b; // (0.081312F * 65536) + .5F
float yy = (y0 + y1 + y2) >> 16;
float cb = 128 + ((cb0 - cb1 + cb2) >> 16);
float cr = 128 + ((cr0 - cr1 - cr2) >> 16);
int index = j8 + i;
yBlockRaw[index] = yy;
cbBlockRaw[index] = cb;
crBlockRaw[index] = cr;
data += 3;
}
}
}
public void CopyStretchedRGBTo_FromOrigo <TPixel>(TestImageProvider <TPixel> provider)
where TPixel : struct, IPixel <TPixel>
{
using (Image <TPixel> src = provider.GetImage())
using (Image <TPixel> dest = new Image <TPixel>(8, 8))
using (PixelArea <TPixel> area = new PixelArea <TPixel>(8, 8, ComponentOrder.Xyz))
using (PixelAccessor <TPixel> s = src.Lock())
using (PixelAccessor <TPixel> d = dest.Lock())
{
s.CopyRGBBytesStretchedTo(area, 0, 0);
d.CopyFrom(area, 0, 0);
Assert.Equal(s[0, 0], d[0, 0]);
Assert.Equal(s[7, 0], d[7, 0]);
Assert.Equal(s[0, 7], d[0, 7]);
Assert.Equal(s[7, 7], d[7, 7]);
}
}
/// <summary>
/// Converts the 8x8 region of the image whose top-left corner is x,y to its YCbCr values.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <param name="pixels">The pixel accessor.</param>
/// <param name="x">The x-position within the image.</param>
/// <param name="y">The y-position within the image.</param>
/// <param name="yBlock">The luminance block.</param>
/// <param name="cbBlock">The red chroma block.</param>
/// <param name="crBlock">The blue chroma block.</param>
/// <param name="rgbBytes">Temporal <see cref="PixelArea{TColor}"/> provided by the caller</param>
private static void ToYCbCr <TColor>(
PixelAccessor <TColor> pixels,
int x,
int y,
Block8x8F *yBlock,
Block8x8F *cbBlock,
Block8x8F *crBlock,
PixelArea <TColor> rgbBytes)
where TColor : struct, IPixel <TColor>
{
float *yBlockRaw = (float *)yBlock;
float *cbBlockRaw = (float *)cbBlock;
float *crBlockRaw = (float *)crBlock;
rgbBytes.Reset();
pixels.CopyRGBBytesStretchedTo(rgbBytes, y, x);
ref byte data0 = ref rgbBytes.Bytes[0];
public void CopyStretchedRGBTo_FromOrigo <TColor>(TestImageProvider <TColor> provider)
where TColor : struct, IPackedPixel, IEquatable <TColor>
{
using (Image <TColor> src = provider.GetImage())
using (Image <TColor> dest = provider.Factory.CreateImage(8, 8))
using (PixelArea <TColor> area = new PixelArea <TColor>(8, 8, ComponentOrder.Xyz))
using (PixelAccessor <TColor> s = src.Lock())
using (PixelAccessor <TColor> d = dest.Lock())
{
s.CopyRGBBytesStretchedTo(area, 0, 0);
d.CopyFrom(area, 0, 0);
Assert.Equal(s[0, 0], d[0, 0]);
Assert.Equal(s[7, 0], d[7, 0]);
Assert.Equal(s[0, 7], d[0, 7]);
Assert.Equal(s[7, 7], d[7, 7]);
}
}
public void CopyStretchedRGBTo_WithOffset <TColor>(TestImageProvider <TColor> provider)
where TColor : struct, IPackedPixel, IEquatable <TColor>
{
Image <TColor> src = provider.GetImage();
PixelArea <TColor> area = new PixelArea <TColor>(8, 8, ComponentOrder.Xyz);
Image <TColor> dest = provider.Factory.CreateImage(8, 8);
using (PixelAccessor <TColor> s = src.Lock())
{
using (var d = dest.Lock())
{
s.CopyRGBBytesStretchedTo(area, 7, 6);
d.CopyFrom(area, 0, 0);
Assert.Equal(s[6, 7], d[0, 0]);
Assert.Equal(s[6, 8], d[0, 1]);
Assert.Equal(s[7, 8], d[1, 1]);
Assert.Equal(s[6, 9], d[0, 2]);
Assert.Equal(s[6, 9], d[0, 3]);
Assert.Equal(s[6, 9], d[0, 7]);
Assert.Equal(s[7, 9], d[1, 2]);
Assert.Equal(s[7, 9], d[1, 3]);
Assert.Equal(s[7, 9], d[1, 7]);
Assert.Equal(s[9, 9], d[3, 2]);
Assert.Equal(s[9, 9], d[3, 3]);
Assert.Equal(s[9, 9], d[3, 7]);
Assert.Equal(s[9, 7], d[3, 0]);
Assert.Equal(s[9, 7], d[4, 0]);
Assert.Equal(s[9, 7], d[7, 0]);
Assert.Equal(s[9, 9], d[3, 2]);
Assert.Equal(s[9, 9], d[4, 2]);
Assert.Equal(s[9, 9], d[7, 2]);
Assert.Equal(s[9, 9], d[4, 3]);
Assert.Equal(s[9, 9], d[7, 7]);
}
}
}
public void CopyStretchedRGBTo_WithOffset <TPixel>(TestImageProvider <TPixel> provider)
where TPixel : struct, IPixel <TPixel>
{
using (Image <TPixel> src = provider.GetImage())
using (PixelArea <TPixel> area = new PixelArea <TPixel>(8, 8, ComponentOrder.Xyz))
using (Image <TPixel> dest = new Image <TPixel>(8, 8))
using (PixelAccessor <TPixel> s = src.Lock())
using (PixelAccessor <TPixel> d = dest.Lock())
{
s.CopyRGBBytesStretchedTo(area, 7, 6);
d.CopyFrom(area, 0, 0);
Assert.Equal(s[6, 7], d[0, 0]);
Assert.Equal(s[6, 8], d[0, 1]);
Assert.Equal(s[7, 8], d[1, 1]);
Assert.Equal(s[6, 9], d[0, 2]);
Assert.Equal(s[6, 9], d[0, 3]);
Assert.Equal(s[6, 9], d[0, 7]);
Assert.Equal(s[7, 9], d[1, 2]);
Assert.Equal(s[7, 9], d[1, 3]);
Assert.Equal(s[7, 9], d[1, 7]);
Assert.Equal(s[9, 9], d[3, 2]);
Assert.Equal(s[9, 9], d[3, 3]);
Assert.Equal(s[9, 9], d[3, 7]);
Assert.Equal(s[9, 7], d[3, 0]);
Assert.Equal(s[9, 7], d[4, 0]);
Assert.Equal(s[9, 7], d[7, 0]);
Assert.Equal(s[9, 9], d[3, 2]);
Assert.Equal(s[9, 9], d[4, 2]);
Assert.Equal(s[9, 9], d[7, 2]);
Assert.Equal(s[9, 9], d[4, 3]);
Assert.Equal(s[9, 9], d[7, 7]);
}
}