/// <summary>
/// Calculate the gradient of a given pixel.
/// </summary>
/// <param name="x">x coordinate of pixel, must be between 1..cols-1</param>
/// <param name="y">y coordinate of pixel, must be between 1..rows-1</param>
/// <returns>The gradient of the given pixel, considering x and y directions.</returns>
public byte GetPixelGradient(int x, int y)
{
int GXxy = 0; //the y portion
int GYxy = 0; //the x portion
byte Gxy = 0; //final value
if (directBitmapReader == null)
{
directBitmapReader = new DirectBitmapReader(grayBitmap.Bitmap);
}
GXxy = ((directBitmapReader.GetGrayPixel(x + 1, y + 1)) - (directBitmapReader.GetGrayPixel(x - 1, y + 1)));
GXxy = GXxy + (2 * ((directBitmapReader.GetGrayPixel(x + 1, y)) - (directBitmapReader.GetGrayPixel(x - 1, y))));
GXxy = GXxy + ((directBitmapReader.GetGrayPixel(x + 1, y - 1)) - (directBitmapReader.GetGrayPixel(x - 1, y - 1)));
GXxy = GXxy / 4;
GYxy = ((directBitmapReader.GetGrayPixel(x + 1, y + 1)) - (directBitmapReader.GetGrayPixel(x + 1, y - 1)));
GYxy = GYxy + (2 * ((directBitmapReader.GetGrayPixel(x, y + 1)) - (directBitmapReader.GetGrayPixel(x, y - 1))));
GYxy = GYxy + ((directBitmapReader.GetGrayPixel(x - 1, y + 1)) - (directBitmapReader.GetGrayPixel(x - 1, y - 1)));
GYxy = GYxy / 4;
/* This is how we did this in CS 450, it's faster than doing
* a square root, but not quite as accurate, hence the clamping.
* It does bring out more edges, but I don't know if that is
* good or not - Ryan
* Gxy = (Math.Abs(GXxy) + Math.Abs(GYxy));
* Gxy = Math.Max(0, Gxy);
* Gxy = Math.Min(imgMaxGray, Gxy);
*/
Gxy = (byte)Math.Sqrt((double)(GXxy * GXxy) + (double)(GYxy * GYxy));
return(Gxy);
}
