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copied!<p>Firstly, if you're comfortable with C++, you should consider using <a href="http://sourceforge.net/projects/opencvlibrary/" rel="nofollow noreferrer">OpenCV 2.0</a> which does away with different data types for images and matrices (<code>IplImage*</code> and <code>CvMat*</code>) and uses one structure (<code>Mat</code>) to handle both. Apart from automatic memory management and a truckload of useful routines to handle channels, etc. and some MATLAB-esque ones as well, it's really fun to use.</p> <p>For your specific problem, you access the channels of an <code>IplImage*</code> with <code>Mat</code>, like this:</p> <pre><code> IplImage *image = cvLoadImage("lena.bmp"); Mat Lena(image); vector<Mat> Channels; split(Lena,Channels); namedWindow("LR",CV_WINDOW_AUTOSIZE); imshow("LR",Channels[0]); waitKey(); </code></pre> <p>Now you have the copies of each channel in the <code>vector</code> <code>Channels</code>. </p> <p>If you <em>don't</em> want to use <code>OpenCV2.0</code> and extract channels, note the following. OpenCV orders multi-channel images in the following manner:</p> <p><code>x(1,1,1) x(1,1,2) x(1,1,3) x(1,2,1) x(1,2,2) x(1,2,3) ...</code></p> <p>where <code>x(i,j,k) = an element in row i of column j in channel k</code></p> <p>Also, OpenCV <strong>pads</strong> it's images .. so don't forget to jump rows with <code>widthStep</code> which accounts for these padding gaps. And along the lines of what <a href="https://stackoverflow.com/questions/1568377/convert-rgb-iplimage-to-3-arrays/1568532#1568532">csl said</a>, increase your row pointer in the outer loop (using <code>widthStep</code>) and increment this pointer to access elements in a row.</p> <p><strong>NOTE:</strong></p> <p>Since you're using 2.0 now, you can bypass <code>IplImage*</code> with <code>Mat Lena = imread("Lena.bmp");</code>.</p>

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