public void RGBToYCbCrPerformanceTest()
{
byte[] rgba = GetRgba(1);
const int runs = 20;
const int iterations = 100;
var slowPerf = new PerformanceMonitor("TheoreticallySlower", runs);
var fastPerf = new PerformanceMonitor("TheoreticallyFaster", runs);
for (int run = 0; run < runs; run++)
{
slowPerf.Start();
for (int i = 0; i < iterations; i++)
{
for (int p = 0; p < rgba.Length; p++)
{
byte b = rgba[p++];
byte g = rgba[p++];
byte r = rgba[p++];
YCbCr.fromRGBSlow(ref r, ref g, ref b);
}
}
slowPerf.Stop();
fastPerf.Start();
for (int i = 0; i < iterations; i++)
{
for (int p = 0; p < rgba.Length; p++)
{
byte b = rgba[p++];
byte g = rgba[p++];
byte r = rgba[p++];
YCbCr.fromRGB(ref r, ref g, ref b);
}
}
fastPerf.Stop();
}
#if !DEBUG
// This is only true when running with the optimized JIT.
Assert.IsTrue(fastPerf.AverageCompletionTimeInMs < slowPerf.AverageCompletionTimeInMs,
"The fast conversion method took {0:0.00} ms, while the slow took {1:0.00}", fastPerf.AverageCompletionTimeInMs, slowPerf.AverageCompletionTimeInMs);
#endif
}
public void RGBToYCbCrTest()
{
const int maxVariance = 1;
byte[] rgba = GetRgba(1);
for (int i = 0; i < rgba.Length; i++)
{
byte b2 = rgba[i];
byte b1 = rgba[i++];
byte g2 = rgba[i];
byte g1 = rgba[i++];
byte r2 = rgba[i];
byte r1 = rgba[i++];
YCbCr.fromRGBSlow(ref r1, ref g1, ref b1);
YCbCr.fromRGB(ref r2, ref g2, ref b2);
Assert.IsTrue(Math.Abs(r1 - r2) <= maxVariance);
Assert.IsTrue(Math.Abs(g1 - g2) <= maxVariance);
Assert.IsTrue(Math.Abs(b1 - b2) <= maxVariance);
}
}
private void LoadSubsampledRaster(byte[] rgbaBuffer)
{
int rgbaPos = 0;
for (short y = 0; y < height; y++)
{
int yy = y / vSampleFactor[yIndex];
int cby = y / vSampleFactor[cbIndex];
int cry = y / vSampleFactor[crIndex];
int yx = 0, cbx = 0, crx = 0;
for (short x = 0; x < width; x++)
{
// Convert to YCbCr colorspace.
// The order of bytes is (oddly enough) BGRA
byte b = rgbaBuffer[rgbaPos++];
byte g = rgbaBuffer[rgbaPos++];
byte r = rgbaBuffer[rgbaPos++];
YCbCr.fromRGB(ref r, ref g, ref b);
// Only include the byte in question in the raster if it matches the appropriate sampling factor.
if (IncludeInSample(yIndex, x, y))
{
rasterBuffer[yIndex][yx++][yy] = r;
}
if (IncludeInSample(cbIndex, x, y))
{
rasterBuffer[cbIndex][cbx++][cby] = g;
}
if (IncludeInSample(crIndex, x, y))
{
rasterBuffer[crIndex][crx++][cry] = b;
}
// For YCbCr, we ignore the Alpha byte of the RGBA byte structure, so advance beyond it.
rgbaPos++;
}
}
}
