/*
* // ratio of lower:upper threshold
* private static int ratio = 3;
*
* // maximum value for the lower Threshold
* private static int max_lowThreshold = 100;
* private static double[][] Gx =
* new[] {
* new double[] { -1, 0, +1 },
* new double[] { -2, 0, +2 },
* new double[] { -1, 0, +1 }
* };
*
* private static double[][] Gy =
* new[] {
* new double[] { -1, -2, -1 },
* new double[] { +0, +0, +0 },
* new double[] { +1, +2, +1 }
* };
*/
/*
*
* GAUSSIAN_NOISE_ REDUCE
*
* apply 5x5 Gaussian convolution filter, shrinks the image by 4 pixels in each direction, using Gaussian filter found here:
*
* http://en.wikipedia.org/wiki/Canny_edge_detector
*
*/
private static IImage <double> CannyEdgeDetect(IImage <double> img_in, double highThresholdPercentage, double lowThresholdPercentage)
{
double[] g;
int[] direction;
CalcGradientSobel(img_in, out g, out direction);
IImage <double> img_scratch = ImageFactory.Generate(img_in.Width, img_in.Height);
CannyEdgeDetector.NonMaxSuppression(img_scratch, g, direction);
double high, low;
EstimateThreshold(img_scratch, highThresholdPercentage, lowThresholdPercentage, out high, out low);
return(hysteresis(high, low, img_scratch));
}
public static IImage <double> Run(IImage <double> img, CannyOptions options)
{
options = options ?? new CannyOptions();
var img256 = img.Copy();
if (options.NormalizeImage)
{
img256 = img256.Normalize256();
}
// or morph_close
var img_out = options.NoiseReduce ? CannyEdgeDetector.GaussianNoiseReduce(img256) : img256;
return(CannyEdgeDetector.CannyEdgeDetect(img_out, options.HighThresholdPercentage, options.LowThresholdPercentage));
}
private static IImage <double> hysteresis(double high, double low, IImage <double> img_in)
{
IImage <double> img_out = new Image(img_in.Width, img_in.Height);
for (int y = 0; y < img_out.Height; y++)
{
for (int x = 0; x < img_out.Width; x++)
{
if (img_in[y * img_out.Width + x] >= high)
{
CannyEdgeDetector.Trace(x, y, low, img_in, img_out);
}
}
}
return(img_out);
}
public static IImage <double> Run(IImage <double> img)
{
return(CannyEdgeDetector.Run(img, null));
}