public static Sobel Sobel(float[,] input, int min = 1, int max = 2)
{
var width = input.GetLength(0);
var height = input.GetLength(1);
var result = new Sobel(width, height);
Parallel.For(1, width - 1, x =>
{
for (var y = 1; y < height - 1; y++)
{
var gx =
input[x + 1, y - 1] * min +
input[x + 1, y] * max +
input[x + 1, y + 1] * min -
input[x - 1, y - 1] * min -
input[x - 1, y] * max -
input[x - 1, y + 1] * min;
var gy =
input[x - 1, y + 1] * min +
input[x, y + 1] * max +
input[x + 1, y + 1] * min -
input[x - 1, y - 1] * min -
input[x, y - 1] * max -
input[x + 1, y - 1] * min;
result.Magnitude[x, y] = Math.Abs(gx) + Math.Abs(gy);
result.Horizontal[x, y] = gx;
result.Vertical[x, y] = gy;
}
});
return(result);
}
public static float[,] Canny(Sobel sobel, int min, int max)
{
var width = sobel.Orientation.GetLength(0);
var height = sobel.Orientation.GetLength(1);
var result = new float[width, height];
Parallel.For(1, width - 1, x =>
{
for (var y = 0; y < height - 1; y++)
{
result[x, y] = sobel.Magnitude[x, y];
}
});
// Non maximum supression
for (var x = 1; x < width - 1; x++)
{
for (var y = 1; y < height - 1; y++)
{
var gx = sobel.Horizontal[x, y];
var gy = sobel.Vertical[x, y];
var magnitude = sobel.Magnitude[x, y];
var orientation = Math.Atan2(gy, gx) * 180f / Math.PI;
//if (orientation >= 0 && orientation <= 45 ||
// orientation < -135 && orientation >= -180)
//{
// var yBot = new[]
// {
// sobel.Magnitude[x, y + 1], sobel.Magnitude[x + 1, y + 1]
// };
// var yTop = new[]
// {
// sobel.Magnitude[x, y - 1], sobel.Magnitude[x - 1, y - 1]
// };
// var xEst = Math.Abs(gy / magnitude);
// if (magnitude >= (yBot[1] - yBot[0]) * xEst + yBot[0] &&
// magnitude >= (yTop[1] - yTop[0]) * xEst + yTop[0])
// {
// result[x, y] = magnitude;
// }
// else
// {
// result[x, y] = 0;
// }
// continue;
//}
//if (orientation > 45 && orientation <= 90 ||
// orientation < -90 && orientation >= -135)
//{
// var yBot = new[]
// {
// sobel.Magnitude[x + 1, y], sobel.Magnitude[x + 1, y + 1]
// };
// var yTop = new[]
// {
// sobel.Magnitude[x - 1, y], sobel.Magnitude[x - 1, y - 1]
// };
// var xEst = Math.Abs(gy / magnitude);
// if (magnitude >= (yBot[1] - yBot[0]) * xEst + yBot[0] &&
// magnitude >= (yTop[1] - yTop[0]) * xEst + yTop[0])
// {
// result[x, y] = magnitude;
// }
// else
// {
// result[x, y] = 0;
// }
// continue;
//}
//if (orientation > 90 && orientation <= 135 ||
// orientation < -45 && orientation >= -90)
//{
// var yBot = new[]
// {
// sobel.Magnitude[x + 1, y], sobel.Magnitude[x + 1, y - 1]
// };
// var yTop = new[]
// {
// sobel.Magnitude[x - 1, y], sobel.Magnitude[x - 1, y + 1]
// };
// var xEst = Math.Abs(gy / magnitude);
// if (magnitude >= (yBot[1] - yBot[0]) * xEst + yBot[0] &&
// magnitude >= (yTop[1] - yTop[0]) * xEst + yTop[0])
// {
// result[x, y] = magnitude;
// }
// else
// {
// result[x, y] = 0;
// }
// continue;
//}
//if (orientation > 135 && orientation <= 180 ||
// orientation < 0 && orientation >= -45)
//{
// var yBot = new[]
// {
// sobel.Magnitude[x, y - 1], sobel.Magnitude[x + 1, y - 1]
// };
// var yTop = new[]
// {
// sobel.Magnitude[x, y + 1], sobel.Magnitude[x - 1, y + 1]
// };
// var xEst = Math.Abs(gy / magnitude);
// if (magnitude >= (yBot[1] - yBot[0]) * xEst + yBot[0] &&
// magnitude >= (yTop[1] - yTop[0]) * xEst + yTop[0])
// {
// result[x, y] = magnitude;
// }
// else
// {
// result[x, y] = 0;
// }
//}
// E-W
if (orientation <= 22.5 && orientation >= -22.5 ||
orientation >= 157.5 || orientation <= -157.5)
{
if (magnitude < sobel.Magnitude[x - 1, y] ||
magnitude < sobel.Magnitude[x + 1, y])
{
result[x, y] = 0;
}
}
// N-S
if (orientation >= 67.5 && orientation <= 112.5 ||
orientation >= -112.5 && orientation <= -67.5)
{
if (magnitude < sobel.Magnitude[x, y - 1] ||
magnitude < sobel.Magnitude[x, y + 1])
{
result[x, y] = 0;
}
continue;
}
// SE-NW
if (orientation <= -112.5 && orientation >= -157.5 ||
orientation >= 22.5 && orientation <= 67.5)
{
if (magnitude < sobel.Magnitude[x - 1, y - 1] ||
magnitude < sobel.Magnitude[x + 1, y + 1])
{
result[x, y] = 0;
}
continue;
}
if (orientation <= 157.5 && orientation >= 112.5 ||
orientation >= -67.5 && orientation <= -22.5)
{
if (magnitude < sobel.Magnitude[x + 1, y - 1] ||
magnitude < sobel.Magnitude[x - 1, y + 1])
{
result[x, y] = 0;
}
continue;
}
}
}
;
return(result);// Hysteresis(result, min, max);
}
