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POSobel operator & Convolution with WriteableBitmapEx
 

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  1. POSobel operator & Convolution with WriteableBitmapEx
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    <p>So I'm using WriteableBitmapEx for an app on Windows RT. 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:</p> <ul> <li>Why is the transparency set to 0 for every pixel after the convolution?</li> <li>Why can I still display the Image without it being all black?</li> <li>Why is it black when I add two Images?</li> <li>Is there a better way of combining two Images? Blit unfortunatley doesn't seem to support this kind of pixel-adding. But ForEach really is slow...</li> </ul> <p>For calrification, here's my code so far. I can display both wbmpY and wbmpX, but finalbmp is completely black.</p> <pre><code> 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 &lt; width; x++) { for (int y = 0; y &lt; 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) ); result.SetPixel(x, y, newColor); } } return result; } </code></pre>
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