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POEdge Detection with Lockbits C#
 

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  1. POEdge Detection with Lockbits C#
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    <p>i make a program that implements an edge detection algorithm. but, it takes a long time for the process. i've read about use lockbits and unsafe state instead of getpixel and setpixel, but i still understand how to use it.</p> <p>this is my example code :</p> <pre><code>private Bitmap SobelEdgeDetect(Bitmap original) { 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); else bb.SetPixel(i, j, Color.Transparent); } } return bb; } </code></pre> <p>i am using fastbitmap class, and i implement it like this :</p> <pre><code>private Bitmap SobelEdgeDetectTwo(Bitmap original) { int width = original.Width; int height = original.Height; Bitmap result = new Bitmap(width,height); FastBitmap b = new FastBitmap(original); FastBitmap bb = new FastBitmap(result); b.LockBitmap(); bb.LockBitmap(); 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++) { var pixel = b.GetPixel(i,j); allPixR[i, j] = pixel.Red; allPixG[i, j] = pixel.Green; allPixB[i, j] = pixel.Blue; } } 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; width - 1; i++) { for (int j = 1; j &lt; 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) { PixelData p = new PixelData(Color.Black); bb.SetPixel(i, j, p); } else { PixelData p = new PixelData(Color.Transparent); bb.SetPixel(i, j, p); } } } b.UnlockBitmap(); bb.UnlockBitmap(); return result; } </code></pre> <p>but, the image doesn't change at all. could you give an advice to me about which part of my code that was mistake?</p>
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