public static BitmapSource Stretch(IImageStatistics statistics, Bitmap img, System.Windows.Media.PixelFormat pf, double factor, double blackClipping)
{
using (MyStopWatch.Measure()) {
var filter = ImageUtility.GetColorRemappingFilter(statistics, factor, blackClipping, pf);
filter.ApplyInPlace(img);
var source = ImageUtility.ConvertBitmap(img, pf);
source.Freeze();
return(source);
}
}
public static ColorRemappingGeneral GetColorRemappingFilterUnlinked(
IImageStatistics redStatistics,
IImageStatistics greenStatistics,
IImageStatistics blueStatistics,
double targetHistogramMeanPct,
double shadowsClipping,
System.Windows.Media.PixelFormat pf)
{
ushort[] mapRed = GetStretchMap(redStatistics, targetHistogramMeanPct, shadowsClipping);
ushort[] mapGreen = GetStretchMap(greenStatistics, targetHistogramMeanPct, shadowsClipping);
ushort[] mapBlue = GetStretchMap(blueStatistics, targetHistogramMeanPct, shadowsClipping);
if (pf == PixelFormats.Rgb48)
{
var filter = new ColorRemappingGeneral(mapRed, mapGreen, mapBlue);
return(filter);
}
else
{
throw new NotSupportedException();
}
}
public static ColorRemappingGeneral GetColorRemappingFilter(
IImageStatistics statistics,
double targetHistogramMeanPct,
double shadowsClipping,
System.Windows.Media.PixelFormat pf)
{
ushort[] map = GetStretchMap(statistics, targetHistogramMeanPct, shadowsClipping);
if (pf == PixelFormats.Gray16)
{
var filter = new ColorRemappingGeneral(map);
return(filter);
}
else if (pf == PixelFormats.Rgb48)
{
var filter = new ColorRemappingGeneral(map, map, map);
return(filter);
}
else
{
throw new NotSupportedException();
}
}
private static ushort[] GetStretchMap(IImageStatistics statistics, double targetHistogramMedianPercent, double shadowsClipping)
{
ushort[] map = new ushort[ushort.MaxValue + 1];
var normalizedMedian = NormalizeUShort(statistics.Median);
var normalizedMAD = NormalizeUShort(statistics.MedianAbsoluteDeviation);
var scaleFactor = 1.4826; // see https://en.wikipedia.org/wiki/Median_absolute_deviation
double shadows = 0d;
double midtones = 0.5d;
double highlights = 1d;
//Assume the image is inverted or overexposed when median is higher than half of the possible value
if (normalizedMedian > 0.5)
{
shadows = 0d;
highlights = normalizedMedian - shadowsClipping * normalizedMAD * scaleFactor;
midtones = MidtonesTransferFunction(highlights - normalizedMedian, targetHistogramMedianPercent);
}
else
{
shadows = normalizedMedian + shadowsClipping * normalizedMAD * scaleFactor;
midtones = MidtonesTransferFunction(targetHistogramMedianPercent, normalizedMedian - shadows);
highlights = 1;
}
for (int i = 0; i < map.Length; i++)
{
double value = NormalizeUShort(i);
map[i] = DenormalizeUShort(MidtonesTransferFunction(midtones, 1 - highlights + value - shadows));
}
return(map);
}
