
Hey there
I'm trying to implement edge detection on an image using the sobel operator. I have successfully applied both kernels for x and y detection onto the image using .Convolute(), but now I'm stuck adding both images to one. The problem is, that all the pixels of
both images seem to have the value 0 for transparency (so the A in ARGB). I can display both images on their own without a Problem, but adding them gives me just a black picture. So my questions are:
 Why is the transparency set to 0 for every pixel after the convolution?
 Why can I still display the Image without it being all black?
 Why is it black when I add two Images?
For calrification, here's my code so far. I can display both wbmpY and wbmpX, but finalbmp is completely black.
public int[,] sobelY = new int[3, 3] { { 1, 2, 1 }, { 0, 0, 0 }, { 1, 2, 1 } };
public int[,] sobelX = new int[3, 3] { { 1, 0, 1 }, { 2, 0, 2 }, { 1, 0, 1 } };
public void trim(WriteableBitmap wbmp)
{
var graybmp = wbmp.Clone();
graybmp.ForEach(toGrayscale);
var wbmpY = graybmp.Clone();
var wbmpX = graybmp.Clone();
wbmpY = wbmpY.Convolute(sobelY, 1, 0);
wbmpX = wbmpX.Convolute(sobelX, 1, 0);
var finalbmp = combineSobel(wbmpX, wbmpY);
}
public WriteableBitmap combineSobel(WriteableBitmap img, WriteableBitmap img2)
{
int height = img.PixelHeight;
int width = img.PixelWidth;
WriteableBitmap result = img.Clone();
for (int x = 0; x < width; x++)
{
for (int y = 0; y < height; y++)
{
Color imgColor = img.GetPixel(x, y);
Color img2Color = img2.GetPixel(x, y);
Color newColor = Color.FromArgb(
Math.Min((byte)Math.Sqrt(Math.Pow(imgColor.A, 2) + Math.Pow(img2Color.A, 2)), (byte)255),
Math.Min((byte)Math.Sqrt(Math.Pow(imgColor.R, 2) + Math.Pow(img2Color.R, 2)), (byte)255),
Math.Min((byte)Math.Sqrt(Math.Pow(imgColor.G, 2) + Math.Pow(img2Color.G, 2)), (byte)255),
Math.Min((byte)Math.Sqrt(Math.Pow(imgColor.B, 2) + Math.Pow(img2Color.B, 2)), (byte)255)
);

