Luminance and saturation linear correction.
The filter operates in HSL color space and provides with the facility of luminance and saturation linear correction - mapping specified channels' input ranges to specified output ranges.
The filter accepts 24 and 32 bpp color images for processing.
Sample usage:
// create filter HSLLinear filter = new HSLLinear( ); // configure the filter filter.InLuminance = new DoubleRange( 0, 0.85 ); filter.OutSaturation = new DoubleRange( 0.25, 1 ); // apply the filter filter.ApplyInPlace( image ); Initial image:
Result image:
/// <summary>
///
/// </summary>
/// <param name="f"></param>
/// <param name="contrast">-1..1 float to adjust contrast. </param>
/// <param name="brightness">-1..1 float to adjust luminance (brightness). 0 does nothing</param>
/// <param name="saturation">-1..1 float to adjust saturation. 0 does nothing </param>
/// <param name="truncate">If false, adjusting brightness and luminance will adjust contrast also. True causes white/black washout instead.</param>
protected void AdjustContrastBrightnessSaturation(HSLLinear f, float contrast, float brightness, float saturation, bool truncate)
{
brightness = Math.Max(-1.0f, Math.Min(1.0f, brightness));
saturation = Math.Max(-1.0f, Math.Min(1.0f, saturation));
contrast = Math.Max(-1.0f, Math.Min(1.0f, contrast));
// create luminance filter
if (brightness > 0) {
f.InLuminance = new Range(0.0f, 1.0f - (truncate ? brightness : 0)); //TODO - isn't it better not to truncate, but compress?
f.OutLuminance = new Range(brightness, 1.0f);
} else {
f.InLuminance = new Range((truncate ? -brightness : 0), 1.0f);
f.OutLuminance = new Range(0.0f, 1.0f + brightness);
}
// create saturation filter
if (saturation > 0) {
f.InSaturation = new Range(0.0f, 1.0f - (truncate ? saturation : 0)); //Ditto?
f.OutSaturation = new Range(saturation, 1.0f);
} else {
f.InSaturation = new Range((truncate ? -saturation : 0), 1.0f);
f.OutSaturation = new Range(0.0f, 1.0f + saturation);
}
if (contrast > 0) {
float adjustment = contrast * (f.InLuminance.Max - f.InLuminance.Min) / 2;
f.InLuminance = new Range(f.InLuminance.Min + adjustment, f.InLuminance.Max - adjustment);
} else if (contrast < 0) {
float adjustment = -contrast * (f.OutLuminance.Max - f.OutLuminance.Min) / 2;
f.OutLuminance = new Range(f.OutLuminance.Min + adjustment, f.OutLuminance.Max - adjustment);
}
}
public ContrastCorrection(double factor)
{
this.baseFilter = new HSLLinear();
this.formatTranslations = new Dictionary <PixelFormat, PixelFormat>();
this.Factor = factor;
this.formatTranslations[PixelFormat.Format24bppRgb] = PixelFormat.Format24bppRgb;
this.formatTranslations[PixelFormat.Format32bppRgb] = PixelFormat.Format32bppRgb;
this.formatTranslations[PixelFormat.Format32bppArgb] = PixelFormat.Format32bppArgb;
}
public BrightnessCorrection(double adjustValue)
{
this.baseFilter = new HSLLinear();
this.formatTranslations = new Dictionary <PixelFormat, PixelFormat>();
this.AdjustValue = adjustValue;
this.formatTranslations[PixelFormat.Format24bppRgb] = PixelFormat.Format24bppRgb;
this.formatTranslations[PixelFormat.Format32bppRgb] = PixelFormat.Format32bppRgb;
this.formatTranslations[PixelFormat.Format32bppArgb] = PixelFormat.Format32bppArgb;
}
protected void ApplyFiltersTo(ref Bitmap b, ImageState s)
{
//TODO: if the image is unrotated, use a rectangle to limit the effect to the desired area
string str = null;
int i = 0;
//If radiusunits is specified, use that code path.
double units = s.settings.Get<double>("a.radiusunits",1000);
i = GetRadius(s, "blur", "a.blur", units);
if (i > 0) new GaussianBlur(1.4, i).ApplyInPlace(b);
i = GetRadius(s, "sharpen", "a.sharpen", units);
if (i > 0) new GaussianSharpen(1.4, Math.Min(11,i)).ApplyInPlace(b);
i = GetRadius(s, "a.oilpainting", null, units);
if (i > 0) new OilPainting(i).ApplyInPlace(b);
if ("true".Equals(s.settings["a.removenoise"], StringComparison.OrdinalIgnoreCase)) {
new ConservativeSmoothing(3).ApplyInPlace(b);
} else {
i = GetRadius(s, "a.removenoise", null, units);
if (i > 0) new ConservativeSmoothing(i).ApplyInPlace(b);
}
//Sobel only supports 8bpp grayscale images.
//true/false
if ("true".Equals(s.settings["a.sobel"], StringComparison.OrdinalIgnoreCase)){
Bitmap old = b;
try{
b = Grayscale.CommonAlgorithms.Y.Apply(b);
}finally{
if (old != s.sourceBitmap) old.Dispose();
}
new SobelEdgeDetector().ApplyInPlace(b);
str = s.settings["a.threshold"]; //radius
if (!string.IsNullOrEmpty(str) && int.TryParse(str, NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out i) && i > 0)
new Threshold(i).ApplyInPlace(b);
}
//Canny Edge Detector only supports 8bpp grayscale images.
//true/false
if ("true".Equals(s.settings["a.canny"], StringComparison.OrdinalIgnoreCase)) {
Bitmap old = b;
try {
b = Grayscale.CommonAlgorithms.Y.Apply(b);
} finally {
if (old != s.sourceBitmap) old.Dispose();
}
new CannyEdgeDetector().ApplyInPlace(b);
}
//true/false - duplicate with SimpleFilters?
if ("true".Equals(s.settings["a.sepia"], StringComparison.OrdinalIgnoreCase))
new Sepia().ApplyInPlace(b);
//true/false
if ("true".Equals(s.settings["a.equalize"], StringComparison.OrdinalIgnoreCase))
new HistogramEqualization().ApplyInPlace(b);
///White balance adjustment
var whiteAlg = s.settings.Get<HistogramThresholdAlgorithm>("a.balancewhite");
var whiteVal = s.settings.Get<double>("a.balancethreshold");
if (whiteAlg != null || whiteVal != null) {
var bal = new AutoWhiteBalance(whiteAlg ?? HistogramThresholdAlgorithm.Area);
if (whiteVal != null) bal.LowThreshold = bal.HighThreshold = whiteVal.Value / 100;
bal.ApplyInPlace(b);
}
str = s.settings["a.posterize"]; //number of colors to merge
if (!string.IsNullOrEmpty(str) && int.TryParse(str, NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out i) && i > 0) {
SimplePosterization sp = new SimplePosterization();
if (i < 1) i = 1;
if (i > 255) i = 255;
sp.PosterizationInterval =(byte)i;
sp.ApplyInPlace(b);
}
//Pixellate doesn't support 32-bit images, only 24-bit
//str = s.settings["a.pixelate"]; //number of colors to merge
//if (!string.IsNullOrEmpty(str) && int.TryParse(str, out i)){
// if (i < 2) i = 2;
// if (i > 32) i = 32;
// new Pixellate(i).ApplyInPlace(s.destBitmap);
//}
float contrast = s.settings.Get<float>("a.contrast", 0);
float brightness = s.settings.Get<float>("a.brightness", 0);
float saturation = s.settings.Get<float>("a.saturation", 0);
if (contrast != 0 || brightness != 0 || saturation != 0){
HSLLinear adjust = new HSLLinear();
AdjustContrastBrightnessSaturation(adjust, contrast, brightness, saturation, "true".Equals(s.settings["a.truncate"]));
adjust.ApplyInPlace(b);
}
//TODO - add grayscale?
//For adding fax-like thresholding, use BradleyLocalThresholding
//For trimming solid-color whitespace, use Shrink
}
