private static void HysteresisConnect(PNM image, int index, int width, int height, byte lowValue, byte highValue)
{
int x = index % width;
int y = index / height;
for (int x0 = x - 1; x0 < x + 1; x0++)
{
for (int y0 = y - 1; y0 < y + 1; y0++)
{
int currentIndex = (width * y0) + x0;
if (!IsPixelOnEdge(currentIndex, width, height))
{
byte l;
image.GetPixel(currentIndex, out l, out l, out l);
if (l != 255)
{
if (l >= lowValue)
{
image.SetPixel(currentIndex, 255, 255, 255);
HysteresisConnect(image, currentIndex, width, height, lowValue, highValue);
}
}
}
}
}
}
public static PNM ApplyDistanceTransform(this PNM image)
{
PNM binaryImage = image.ApplyCannyDetector();
int pixelCount = 0;
double[][] distanceMap = ToInitialDistanceMap(binaryImage, ref pixelCount);
CalculateDistances(distanceMap, pixelCount);
PNM distancedImage = new PNM(image.Width, image.Height);
for(int i=0; i < image.Width * image.Height; i++)
{
byte distance = Filter.Coerce(distanceMap[i % image.Width][i / image.Width]);
distancedImage.SetPixel(i, distance, distance, distance);
}
return distancedImage;
}
public static PNM ApplyDistanceTransform(this PNM image)
{
PNM binaryImage = image.ApplyCannyDetector();
int pixelCount = 0;
double[][] distanceMap = ToInitialDistanceMap(binaryImage, ref pixelCount);
CalculateDistances(distanceMap, pixelCount);
PNM distancedImage = new PNM(image.Width, image.Height);
for (int i = 0; i < image.Width * image.Height; i++)
{
byte distance = Filter.Coerce(distanceMap[i % image.Width][i / image.Width]);
distancedImage.SetPixel(i, distance, distance, distance);
}
return(distancedImage);
}
private static PNM ApplyHysteresis(byte[] suppressed, int width, int height, double low, double high)
{
PNM image = new PNM(width, height);
byte lowValue = (byte)(low * 255);
byte highValue = (byte)(high * 255);
for (int i = 0; i < suppressed.Length; i++)
{
if (suppressed[i] >= highValue)
{
image.SetPixel(i, 255, 255, 255);
HysteresisConnect(image, i, width, height, lowValue, highValue);
}
}
return(image);
}
public static PNM ApplyZeroCrossingDetector(this PNM image)
{
// preprare
PNM workImage = PNM.Copy(image);
Filter.Pad(workImage, 4);
// apply loG
Tuple <float[], float[], float[]> LoGRaster = Filter.ApplyConvolutionUnbound(workImage, LoG, 9);
PNM returnImage = new PNM(image.Width, image.Height);
// Apply zero crossing except last row and last column
Parallel.For(0, image.Height - 1, i =>
{
for (int j = 0; j < image.Width - 1; j++)
{
byte r = 0;
byte g = 0;
byte b = 0;
// current index position
int position = i * image.Width + j;
float currentR = LoGRaster.Item1[position];
float neighbourR = LoGRaster.Item1[position + image.Width + 1];
float currentG = LoGRaster.Item2[position];
float neighbourG = LoGRaster.Item2[position + image.Width + 1];
float currentB = LoGRaster.Item3[position];
float neighbourB = LoGRaster.Item3[position + image.Width + 1];
if ((currentR * neighbourR) < 0 && (Math.Abs(currentR) < Math.Abs(neighbourR)))
{
r = 255;
}
if ((currentG * neighbourG) < 0 && (Math.Abs(currentG) < Math.Abs(neighbourG)))
{
g = 255;
}
if ((currentB * neighbourB) < 0 && (Math.Abs(currentB) < Math.Abs(neighbourB)))
{
b = 255;
}
returnImage.SetPixel(position, r, g, b);
}
});
return(returnImage);
}
public static PNM ApplyZeroCrossingDetector(this PNM image)
{
// preprare
PNM workImage = PNM.Copy(image);
Filter.Pad(workImage, 4);
// apply loG
Tuple<float[], float[], float[]> LoGRaster = Filter.ApplyConvolutionUnbound(workImage, LoG, 9);
PNM returnImage = new PNM(image.Width, image.Height);
// Apply zero crossing except last row and last column
Parallel.For(0, image.Height - 1, i =>
{
for (int j = 0; j < image.Width - 1; j++)
{
byte r = 0;
byte g = 0;
byte b = 0;
// current index position
int position = i * image.Width + j;
float currentR = LoGRaster.Item1[position];
float neighbourR = LoGRaster.Item1[position + image.Width + 1];
float currentG = LoGRaster.Item2[position];
float neighbourG = LoGRaster.Item2[position + image.Width + 1];
float currentB = LoGRaster.Item3[position];
float neighbourB = LoGRaster.Item3[position + image.Width + 1];
if ((currentR * neighbourR) < 0 && (Math.Abs(currentR) < Math.Abs(neighbourR)))
r = 255;
if ((currentG * neighbourG) < 0 && (Math.Abs(currentG) < Math.Abs(neighbourG)))
g = 255;
if ((currentB * neighbourB) < 0 && (Math.Abs(currentB) < Math.Abs(neighbourB)))
b = 255;
returnImage.SetPixel(position, r, g, b);
}
});
return returnImage;
}
private static void HysteresisConnect(PNM image, int index, int width, int height, byte lowValue, byte highValue)
{
int x = index % width;
int y = index / height;
for (int x0 = x - 1; x0 < x + 1; x0++)
{
for (int y0 = y - 1; y0 < y + 1; y0++)
{
int currentIndex = (width * y0) + x0;
if (!IsPixelOnEdge(currentIndex, width, height))
{
byte l;
image.GetPixel(currentIndex, out l, out l, out l);
if (l != 255)
{
if (l >= lowValue)
{
image.SetPixel(currentIndex, 255, 255, 255);
HysteresisConnect(image, currentIndex, width, height, lowValue, highValue);
}
}
}
}
}
}
private static PNM ApplyHysteresis(byte[] suppressed, int width, int height, double low, double high)
{
PNM image = new PNM(width, height);
byte lowValue = (byte)(low*255);
byte highValue = (byte)(high*255);
for (int i = 0; i < suppressed.Length; i++)
{
if (suppressed[i] >= highValue)
{
image.SetPixel(i, 255, 255, 255);
HysteresisConnect(image, i, width, height, lowValue, highValue);
}
}
return image;
}
