static GrayscaleFloatImage nonmax(ColorFloatImage image, float sigma)
{
int offset = 2;
string mode = "even";
ColorFloatImage temp_image = img_expansion(image, mode, offset);
temp_image = gradient(image, mode);
temp_image = img_expansion(temp_image, mode, offset);
GrayscaleFloatImage gray_grad = temp_image.ToGrayscaleFloatImage();
GrayscaleFloatImage dir_img = dir(image, sigma);
GrayscaleFloatImage out_img = new GrayscaleFloatImage(image.Width, image.Height);
float max_value = 0;
for (int y = 0; y < out_img.Height; y++)
{
for (int x = 0; x < out_img.Width; x++)
{
float M = gray_grad[x + offset, y + offset];
if (M > max_value)
{
max_value = M;
}
switch (dir_img[x, y])
{
case 0: // o
//break;
case 64: // ->
if (M < gray_grad[x + offset + 1, y + offset] ||
M < gray_grad[x + offset - 1, y + offset])
{
out_img[x, y] = 0;
}
else
{
out_img[x, y] = M;
}
break;
case 128: // ^
if (M < gray_grad[x + offset, y + offset + 1] ||
M < gray_grad[x + offset, y + offset - 1])
{
out_img[x, y] = 0;
}
else
{
out_img[x, y] = M;
}
break;
case 192: // /
if (M < gray_grad[x + offset + 1, y + offset + 1] ||
M < gray_grad[x + offset - 1, y + offset - 1])
{
out_img[x, y] = 0;
}
else
{
out_img[x, y] = M;
}
break;
case 255: // \
if (M < gray_grad[x + offset - 1, y + offset + 1] ||
M < gray_grad[x + offset + 1, y + offset - 1])
{
out_img[x, y] = 0;
}
else
{
out_img[x, y] = M;
}
break;
}
}
}
float mult = 255 / max_value;
for (int y = 0; y < out_img.Height; y++)
{
for (int x = 0; x < out_img.Width; x++)
{
out_img[x, y] *= mult;
}
}
return(out_img);
}
static GrayscaleFloatImage dir(ColorFloatImage image, float sigma)
{
string mode = "even";
int rad = (int)Math.Round(3 * sigma);
ColorFloatImage temp_img = img_expansion(image, mode, rad);
/*
* for (int y = 1; y < temp_image_x.Height + 1; y++)
* for (int x = 1; x < temp_image_x.Width + 1; x++)
* temp_image_x[x - 1, y - 1] = temp_image[x + 1, y] + (-1) * temp_image[x, y];
* for (int y = 1; y < temp_image_y.Height + 1; y++)
* for (int x = 1; x < temp_image_y.Width + 1; x++)
* temp_image_y[x - 1, y - 1] = temp_image[x, y + 1] + (-1) * temp_image[x, y];
*/
GrayscaleFloatImage temp_image = temp_img.ToGrayscaleFloatImage();
GrayscaleFloatImage out_img = new GrayscaleFloatImage(image.Width, image.Height);
float[,] Gx = g_kernel_deriv(sigma, "x");
float[,] Gy = g_kernel_deriv(sigma, "y");
for (int y = rad; y < image.Height + rad; y++)
{
for (int x = rad; x < image.Width + rad; x++)
{
float val_x = 0, val_y = 0;
int m = 0;
for (int j = y - rad; j < y + rad + 1; j++, m++)
{
int n = 0;
for (int k = x - rad; k < x + rad + 1; k++, n++)
{
val_x = val_x + Gx[n, m] * temp_image[k, j];
val_y = val_y + Gy[n, m] * temp_image[k, j];
}
}
if (val_x == 0 && val_y != 0)
{
out_img[x - rad, y - rad] = 64;
continue;
}
double theta = Math.Atan2(val_y - rad, val_x - rad) * (180 / Math.PI);
if (theta <= 22.5 && theta > -22.5 || theta <= -157.5 && theta > 157.5)
{
out_img[x - rad, y - rad] = 64; // ->
}
else if (theta <= 67.5 && theta > 22.5 || theta >= -157.5 && theta < -112.5)
{
out_img[x - rad, y - rad] = 192; // /
}
else if (theta > 67.5 && theta <= 112.5 || theta >= -112.5 && theta < -67.5)
{
out_img[x - rad, y - rad] = 128; // ^
}
else if (theta > 112.5 && theta <= 157.5 || theta >= -67.5 && theta < -22.5)
{
out_img[x - rad, y - rad] = 255; // \
}
}
}
return(out_img);
}