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POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
 

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  1. POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
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    <p>I am trying to perform an inverse and a pseudo-inverse filtering in the frequency domain.</p> <p>However I am having trouble accessing DFT coefficients and multiplying DFT matrices afterwards, since I got complex numbers and, therefore, actually two matrices...</p> <p>Basically the inverse filtering performs </p> <p>F = G/H,</p> <p>where F is the restored image, G is the blurred image and H is the kernel that blurred the image.</p> <p>The pseudo-inverse needs to access the values in H, since if the value is near 0 it should be replaced in order to avoid problems in the restoration. For this we must change the H so that:</p> <p>H(u,v) = 1/H(u,v) if H(u,v) > threshold and = 0 otherwise</p> <p>I have a kernel1 (h_1), and the images imf (restored) and img (blurred). Here is the code:</p> <pre><code> // compute the DFTs of the kernel (DFT_B) and the blurred image (DBF_A) cvDFT( dft_A, dft_A, CV_DXT_FORWARD, complexInput1-&gt;height ); cvDFT( dft_B, dft_B, CV_DXT_FORWARD, complexInput2-&gt;height ); // the first type is the inverse fitlering if (type == 1) { printf("...performing inverse filtering\n"); // dividing the transforms cvDiv(dft_A, dft_B, dft_C, 1); } // the second type is the pseudo-inverse filtering else { printf("...prepare kernel for pseudo-inverse filtering\n"); // will try to access the real values in order to see if value is above a threshold cvSplit( dft_B, image_Re1, image_Im1, 0, 0 ); // pointers to access the data into the real and imaginary matrices uchar * dRe1 = (uchar *)image_Re1-&gt;imageData; uchar * dIm1 = (uchar *)image_Im1-&gt;imageData; int width = image_Re1-&gt;width; int height = image_Re1-&gt;height; int step = image_Re1-&gt;widthStep; image_Re2 = cvCreateImage(cvGetSize(image_Re1), IPL_DEPTH_32F, 1); image_Im2 = cvCreateImage(cvGetSize(image_Im2), IPL_DEPTH_32F, 1); // pointers to access the data into the real and imaginary matrices // it will be the resulting pseudo-inverse filter uchar * dRe2 = (uchar *)image_Re2-&gt;imageData; uchar * dIm2 = (uchar *)image_Im2-&gt;imageData; printf("...building kernel for pseudo-inverse filtering\n"); for ( i = 0; i &lt; height; i++ ) { for ( j = 0; j &lt; width; j++ ) { // generate the 1/H(i,j) value if (dRe1[i * step + j] &gt; threshold) { float realsq = dRe1[i * step + j]*dRe1[i * step + j]; float imagsq = dIm1[i * step + j]*dIm1[i * step + j]; dRe2[i * step + j] = dRe1[i * step + j] / (realsq + imagsq); dIm2[i * step + j] = -1 * (dIm1[i * step + j] / (realsq + imagsq)); } else { dRe2[i * step + j] = 0; dIm2[i * step + j] = 0; } } } printf("...merging final kernel\n"); cvMerge(image_Re2, image_Im2, 0, 0, dft_B); printf("...performing pseudo-inverse filtering\n"); cvMulSpectrums(dft_A, dft_B, dft_C, 1); } printf("...performing IDFT\n"); cvDFT(dft_C, dft_H, CV_DXT_INV_SCALE, 1); printf("...getting size\n"); cvGetSubRect(dft_H, &amp;tmp3, cvRect(0, 0, img-&gt;width, img-&gt;height)); printf("......(%d, %d) - (%d, %d)\n", tmp3.cols, tmp3.rows, restored-&gt;width, restored-&gt;height); cvSplit( &amp;tmp3, image_Re1, image_Im1, 0, 0 ); cvNamedWindow("re", 0); cvShowImage("re", image_Re2); cvWaitKey(0); printf("...copying final image\n"); // error is in the line below cvCopy(image_Re1, imf, NULL); </code></pre> <p>I have an error on the last line: --- OpenCV Error: Assertion failed (src.depth() == dst.depth() &amp;&amp; src.size() == dst.size()) in cvCopy, file /build/buildd/opencv-2.1.0/src/cxcore/cxcopy.cpp, line 466</p> <p>I know it have to do with the size or depth but I don't know how to control. Anyway, I tried to show the image_Re1 and it is empty...</p> <p>Can anyone shed some light on it?</p>
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    1. This table or related slice is empty.
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    1. USMoacir Ponti
    1. USMoacir Ponti
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    1. This table or related slice is empty.
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      1. POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
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    2. VO
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      1. POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
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      1. POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
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    1. COTry and reduce the above code to a minimal example which still exhibits the problem - you're much more likely to get an answer that way.
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      1. POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
      1. USPaul R
    2. COThanks. I'll try.
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      1. POInverse filtering on OpenCV - accessing DFT values and multiplying DFT matrices
      1. USMoacir Ponti
 

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