public static void OtsuBinarizedImage(GrayImage image, Otsu otsu, bool isWhiteOnBlack)
{
if (isWhiteOnBlack)
{
Parallel.For(0, image.Pixels.Length, (i) =>
{
image.Pixels[i] = image.Pixels[i] > otsu.Threshold ? image.Pixels[i] : MIN_BINARY;
});
}
else
{
Parallel.For(0, image.Pixels.Length, (i) =>
{
image.Pixels[i] = image.Pixels[i] > otsu.Threshold ? MIN_BINARY : (byte)(MAX_BINARY - image.Pixels[i]);
});
}
}
public static void ModifiedBinarizedImage(GrayImage image, Otsu otsu)
{
double delta = 0.3 * otsu.Sigma;
double lowThreshold = otsu.Threshold - delta;
double highThreshold = otsu.Threshold + delta;
int width = image.Width;
int height = image.Height;
byte[] pixels = new byte[image.Pixels.Length];
for (int i = 0; i < image.Width; i++)
{
if (image.Pixels[i] < otsu.Threshold)
{
pixels[i] = MIN_BINARY;
}
else
{
pixels[i] = MAX_BINARY;
}
}
for (int i = width * (height - 1); i < pixels.Length; i++)
{
if (image.Pixels[i] < otsu.Threshold)
{
pixels[i] = MIN_BINARY;
}
else
{
pixels[i] = MAX_BINARY;
}
}
for (int index = width; index < image.Pixels.Length - width; index++)
{
if (image.Pixels[index] < otsu.Threshold)
{
pixels[index] = MIN_BINARY;
}
else
{
pixels[index] = MAX_BINARY;
}
for (int j = 1; j < width - 1; j++)
{
index++;
if (image.Pixels[index] < lowThreshold)
{
pixels[index] = MIN_BINARY;
}
else if (image.Pixels[index] >= highThreshold)
{
pixels[index] = MAX_BINARY;
}
else
{
if ((image.Pixels[index - width] > 0 && image.Pixels[index] >= image.Pixels[index - width]) ||
(image.Pixels[index + width] > 0 && image.Pixels[index] >= image.Pixels[index + width]) ||
(image.Pixels[index - 1] > 0 && image.Pixels[index] >= image.Pixels[index - 1]) ||
(image.Pixels[index + 1] > 0 && image.Pixels[index] >= image.Pixels[index + 1])
)
{
pixels[index] = MAX_BINARY;
}
else
{
pixels[index] = MIN_BINARY;
}
}
}
index++;
if (image.Pixels[index] < otsu.Threshold)
{
pixels[index] = MIN_BINARY;
}
else
{
pixels[index] = MAX_BINARY;
}
}
image.Pixels = pixels;
}
public static Otsu GetOtsuBinarizedParams(GrayImage image)
{
var imgHist = GetImageHistogram(image);
double maxSigma = 0;
int threshold = 0;
float sumWhite = 0;
float sumBlack = 0;
float mulWhite = 0;
float mulBlack = 0;
int i;
for (i = 1; i < imgHist.Length - 1; i++)
{
if (imgHist[i] == 0)
{
continue;
}
for (int j = 0; j <= i; j++)
{
int histLevel = imgHist[j];
sumWhite = sumWhite + imgHist[j];
mulWhite = mulWhite + (j + 1) * histLevel;
}
for (int j = i + 1; j < imgHist.Length; j++)
{
int histLevel = imgHist[j];
sumBlack = sumBlack + histLevel;
mulBlack = mulBlack + (j + 1) * histLevel;
}
if (sumBlack == 0)
{
break;
}
double sigma = FindOtsuSigma(image.Pixels.Length, sumWhite, mulWhite, sumBlack, mulBlack);
if (sigma > maxSigma)
{
maxSigma = sigma;
threshold = i;
}
break;
}
i++;
for (; i < imgHist.Length - 1; i++)
{
if (imgHist[i] == 0)
{
continue;
}
int histLevel = imgHist[i];
int mulHistLevel = (i + 1) * histLevel;
sumWhite = sumWhite + histLevel;
mulWhite = mulWhite + mulHistLevel;
sumBlack = sumBlack - histLevel;
mulBlack = mulBlack - mulHistLevel;
if (sumBlack == 0)
{
break;
}
double sigma = FindOtsuSigma(image.Pixels.Length, sumWhite, mulWhite, sumBlack, mulBlack);
if (sigma > maxSigma)
{
maxSigma = sigma;
threshold = i;
}
}
Otsu param = new Otsu()
{
Threshold = threshold, Sigma = Math.Sqrt(maxSigma)
};
return(param);
}
