private CvImage DrawCannyEdges(Bitmap sobel_x, Bitmap sobel_y)
{
CvImage image = new CvImage();
int[,] edge_direction = new int[sobel_x.Width, sobel_x.Height];
int[,] edge_mag = new int[sobel_x.Width, sobel_x.Height];
int[,] non_max = new int[sobel_x.Width, sobel_x.Height];
int kernWid = GAUSSIAN_FILTER.MATRIX.GetLength(1);
int kernHei = GAUSSIAN_FILTER.MATRIX.GetLength(0);
int kernOffset = (kernWid - 1) / 2;
for (int wid_ic = kernOffset; wid_ic < sobel_x.Width - kernOffset; wid_ic++)
{
for (int hei_ic = kernOffset; hei_ic < sobel_x.Height - kernOffset; hei_ic++)
{
var pixel_y = sobel_y.GetPixel(wid_ic, hei_ic);
var pixel_x = sobel_x.GetPixel(wid_ic, hei_ic);
var mag_y = PixelMath.pixelMag(pixel_y);
var mag_x = PixelMath.pixelMag(pixel_y);
var edge_strength = mag_y + mag_x;
edge_mag[wid_ic, hei_ic] = (int)edge_strength;
non_max[wid_ic, hei_ic] = (int)edge_strength;
}
}
for (int wid_ic = kernWid; wid_ic < sobel_x.Width - kernWid; wid_ic++)
{
for (int hei_ic = kernHei; hei_ic < sobel_x.Height - kernHei; hei_ic++)
{
var pixel_y = sobel_y.GetPixel(wid_ic, hei_ic);
var pixel_x = sobel_x.GetPixel(wid_ic, hei_ic);
var mag_y = PixelMath.pixelMag(pixel_y);
var mag_x = PixelMath.pixelMag(pixel_y);
var current_mag = edge_mag[wid_ic, hei_ic];
double theta = current_mag != 0 ? Math.Atan2(mag_y, mag_x) : 90;
//CHO_ACTIVE: clean this up
//near horizontal
if ((theta > -22.5 && theta <= 22.5) ||
(theta > 157.5) ||
(theta < -157.5))
{
if ((current_mag < edge_mag[wid_ic, hei_ic + 1]) ||
(current_mag < edge_mag[wid_ic, hei_ic - 1]))
{
non_max[wid_ic, hei_ic] = 0;
}
}
// +45 degree
else if ((theta > 22.5 && theta <= 67.5) ||
(theta <= -67.5 && theta > -22.5))
{
if ((current_mag < edge_mag[wid_ic + 1, hei_ic + 1]) ||
(current_mag < edge_mag[wid_ic - 1, hei_ic - 1]))
{
non_max[wid_ic, hei_ic] = 0;
}
}
//vertical
else if ((theta > 67.5 && theta <= 112.5) ||
(theta <= -67.5 && theta > -112.5))
{
if ((current_mag < edge_mag[wid_ic + 1, hei_ic]) ||
(current_mag < edge_mag[wid_ic - 1, hei_ic]))
{
non_max[wid_ic, hei_ic] = 0;
}
}
// +135 degree
else
{
if ((current_mag < edge_mag[wid_ic + 1, hei_ic - 1]) ||
(current_mag < edge_mag[wid_ic - 1, hei_ic + 1]))
{
non_max[wid_ic, hei_ic] = 0;
}
}
edge_direction[wid_ic, hei_ic] = (int)theta;
}
}
image.bitmap = TraceCannyEdge(non_max);
return(image);
}
