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POFastest Sobel Edge Detection C#
 

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  1. POFastest Sobel Edge Detection C#
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    <p>I want to make a program that implements sobel edge detection. This is my code :</p> <pre><code>private Bitmap SobelEdgeDetect(Bitmap ori) { Bitmap b = original; Bitmap bb = original; int width = b.Width; int height = b.Height; int[,] gx = new int[,] { { -1, 0, 1 }, { -2, 0, 2 }, { -1, 0, 1 } }; int[,] gy = new int[,] { { 1, 2, 1 }, { 0, 0, 0 }, { -1, -2, -1 } }; int[,] allPixR = new int[width, height]; int[,] allPixG = new int[width, height]; int[,] allPixB = new int[width, height]; int limit = 128 * 128; for (int i = 0; i &lt; width; i++) { for (int j = 0; j &lt; height; j++) { allPixR[i, j] = b.GetPixel(i, j).R; allPixG[i, j] = b.GetPixel(i, j).G; allPixB[i, j] = b.GetPixel(i, j).B; } } int new_rx = 0, new_ry = 0; int new_gx = 0, new_gy = 0; int new_bx = 0, new_by = 0; int rc, gc, bc; for (int i = 1; i &lt; b.Width - 1; i++) { for (int j = 1; j &lt; b.Height - 1; j++) { new_rx = 0; new_ry = 0; new_gx = 0; new_gy = 0; new_bx = 0; new_by = 0; rc = 0; gc = 0; bc = 0; for (int wi = -1; wi &lt; 2; wi++) { for (int hw = -1; hw &lt; 2; hw++) { rc = allPixR[i + hw, j + wi]; new_rx += gx[wi + 1, hw + 1] * rc; new_ry += gy[wi + 1, hw + 1] * rc; gc = allPixG[i + hw, j + wi]; new_gx += gx[wi + 1, hw + 1] * gc; new_gy += gy[wi + 1, hw + 1] * gc; bc = allPixB[i + hw, j + wi]; new_bx += gx[wi + 1, hw + 1] * bc; new_by += gy[wi + 1, hw + 1] * bc; } } if (new_rx * new_rx + new_ry * new_ry &gt; limit || new_gx * new_gx + new_gy * new_gy &gt; limit || new_bx * new_bx + new_by * new_by &gt; limit) bb.SetPixel(i, j, Color.Black); //bb.SetPixel (i, j, Color.FromArgb(allPixR[i,j],allPixG[i,j],allPixB[i,j])); else bb.SetPixel(i, j, Color.Transparent); } } return bb; } </code></pre> <p>i want to using lockbits so my program can run faster, but i actually still not understand how to use it. could anyone give some explanation or example code?</p>
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    1. COYour original code had the Sobel algorithm but was slow because of `GetPixel` and `SetPixel`. Now your code should use `LockBits` on *both* bitmaps (input and output) and access the pixels by `(x,y)` as I demonstrated in my answer. You're very close now - don't give up.
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      1. USRoger Rowland
    2. COcould you tell me, which one of the part of my code should exchange to lockbits? i feel very depression. thx
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