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POMy function is copying a PGM image file to PPM in a different way
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2013-11-04T17:07:42.880
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I have a very simple function that saves a PPM image: <pre><code>void WriteCImage(CImage *cimg, char *filename) { FILE *fp; int i,n; fp = fopen(filename,"w"); fprintf(fp,"P6\n"); fprintf(fp,"%d %d\n",cimg->C[0]->ncols,cimg->C[0]->nrows); fprintf(fp,"255\n"); n = cimg->C[0]->ncols*cimg->C[0]->nrows; for (i=0; i < n; i++) { fputc(cimg->C[0]->val[i],fp); fputc(cimg->C[1]->val[i],fp); fputc(cimg->C[2]->val[i],fp); } fclose(fp); } </code></pre> as you can see, this function receives a matrix (in CImage format) and writes the image data in the ASCII file. It seems correct, but every time I copy a grayscale image to a PPM image I have problems. Look at the code: <pre><code>//that's a PGM grayscale image gt = ReadImage(argv[1]); //creating an RGB image with same dimensions of the PGM image nwcimg = CreateCImage(gt->nrows,gt->ncols); n=gt->nrows*gt->ncols; //iterate through the PGM image for(index=0;index<n;index++) { // just a copy of the grayscale image value to all 3 layeres //of the PPM (RGB) image nwcimg->C[0]->val[index]=gt->val[index]; nwcimg->C[1]->val[index]=gt->val[index]; nwcimg->C[2]->val[index]=gt->val[index]; } WriteCImage(nwcimg,"gt-copied.ppm"); DestroyCImage(&nwcimg); DestroyImage(&gt); </code></pre> what problem i have? well, the code seems correct and simple. But when the cimage matrix/vector is written as a file, i can see that the two pictures are not the same. Seems like the pixels of the PGM image are 'shifted' or 'mirrored' in the copied image. You can see the <a href="http://www.ic.unicamp.br/~anselmoferreira/images/gt.pgm" rel="nofollow">Image File</a> and <a href="http://www.ic.unicamp.br/~anselmoferreira/images/gt-copy.ppm" rel="nofollow">The RGB copy</a> 
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<c><image><ppm><pgm>
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My function is copying a PGM image file to PPM in a different way
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