// See also: http://matlabtricks.com/post-5/3x3-convolution-kernels-with-online-demo#demo
public static ImageBuffer Convolution(this ImageBuffer buffer, double[,] kernel, double factor = 1, int bias = 0)
{
byte[] source = buffer.Bytes;
ImageBuffer output = buffer.Fill(Color.Black);
byte[] target = output.Bytes;
double blue, green, red;
int width = kernel.GetLength(0);
//int height = kernel.GetLength(1); // ?? wordt (nog?) niet gebruikt (20150101 FH)
int matrixOffset = (width - 1) / 2;
int calcOffset, byteOffset;
for (int offsetY = matrixOffset; offsetY < buffer.Height - matrixOffset; offsetY++)
{
for (int offsetX = matrixOffset; offsetX < buffer.Width - matrixOffset; offsetX++)
{
blue = 0;
green = 0;
red = 0;
byteOffset = offsetY * buffer.Stride + offsetX * 4;
for (int filterY = -matrixOffset; filterY <= matrixOffset; filterY++)
{
for (int filterX = -matrixOffset; filterX <= matrixOffset; filterX++)
{
calcOffset = byteOffset + (filterX * 4) + (filterY * buffer.Stride);
blue += (double)(source[calcOffset + 0]) * kernel[filterY + matrixOffset, filterX + matrixOffset];
green += (double)(source[calcOffset + 1]) * kernel[filterY + matrixOffset, filterX + matrixOffset];
red += (double)(source[calcOffset + 2]) * kernel[filterY + matrixOffset, filterX + matrixOffset];
}
}
blue = factor * blue + bias;
green = factor * green + bias;
red = factor * red + bias;
target[byteOffset + 0] = ByteConversion.Bounded(blue);
target[byteOffset + 1] = ByteConversion.Bounded(green);
target[byteOffset + 2] = ByteConversion.Bounded(red);
target[byteOffset + 3] = 255;
}
}
return(output);
}