//Find limits to contrast stretch an image\\ Using for default BW contrast
//IntensityProcent - intensity in % pixels saturated at low and high intensities of image
private static double[] StretchlimsCount(int[,] grayColor, double intensityProcent)
{
double[] imLH = new double[2]; //contatin a pair of gray values, which represent image low & high limits to contrast stretch an image
double[] tol = new double[2]; //tol saturates equal fractions at low and high pixel values
if (intensityProcent == 0.01)
{
tol[0] = .01; //default
tol[1] = .99; //default
}
else
{
tol[0] = intensityProcent;
tol[1] = 1 - intensityProcent;
}
if (tol[0] < tol[1]) // tol[0] - low, tol[1] - high
{
var ImHist = ContrastProcess.ImHist(grayColor); //obtain img histohram
int[] CumulativeSum = new int[256];
//CumulativeSum[0] = ImHist[0];
for (int i = 0; i < 256; i++)
{
if (i == 0)
{
CumulativeSum[i] = ImHist[i];
}
else
{
CumulativeSum[i] = ImHist[i] + CumulativeSum[i - 1];
}
}
//cumulative distribution function
var cdf = CumulativeSum.VectorToDouble().VectorDivByConst(ImHist.Sum());
var ilow = Array.IndexOf(cdf, cdf.First(x => x > tol[0])); //index first low
var ihigh = Array.IndexOf(cdf, cdf.First(x => x >= tol[1])); //index first high
if (ilow == ihigh) //this could happen if img is flat
{
//no implementation exception c(: ImLH[0, 0] = 1; ImLH[1, 0] = 256;
}
else
{
imLH[0] = ((double)ilow - 1) / 255; imLH[1] = ((double)ihigh - 1) / 255; //convert to range [0 1]
}
}
else
{
imLH[0] = 0; imLH[1] = 1;
}
return(imLH);
}
//if want use for RGB image, input Rc, Gc, Bc args. Trying for def lims such as for balckwhite image
private static double[] StretchlimsCount(int[,] grayColor, double low, double high)
{
double[] imLH = new double[2];
double[] tol = { low, high };
if (tol[0] < tol[1]) // tol[0] - low, tol[1] - high
{
var ImHist = ContrastProcess.ImHist(grayColor); //obtain img histohram
int[] CumulativeSum = new int[256];
//CumulativeSum[0] = ImHist[0];
for (int i = 0; i < 256; i++)
{
if (i == 0)
{
CumulativeSum[i] = ImHist[i];
}
else
{
CumulativeSum[i] = ImHist[i] + CumulativeSum[i - 1];
}
}
//cumulative distribution function
var cdf = CumulativeSum.VectorToDouble().VectorDivByConst(ImHist.Sum());
var ilow = Array.IndexOf(cdf, cdf.First(x => x > tol[0])); //index first low
var ihigh = Array.IndexOf(cdf, cdf.First(x => x >= tol[1])); //index first high
if (ilow == ihigh) //this could happen if img is flat
{
//no implementation exception c(: ImLH[0, 0] = 1; ImLH[1, 0] = 256;
}
else
{
imLH[0] = ((double)ilow - 1) / 255; imLH[1] = ((double)ihigh - 1) / 255;
}
}
else
{
imLH[0] = 0; imLH[1] = 1;
}
return(imLH);
}
