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copied!<p>IplImage and cv::Mat are different header types for matrix/image data. They're basically compatible with each other, but IplImage is used in OpenCV's C API, while cv::Mat is used in the <strong>new</strong> C++ API.</p> <p>When you decide to use OpenCV's C API, you will mostly use IplImages. Otherwise you will mostly use cv::Mats.</p> <p>Of course, you can convert IplImages and cv::Mats to each other, e.g.</p> <pre><code>cv::Mat mat(myIplImage); </code></pre> <p>In this case, they share the same underlying data, i.e. modifications made through either header will be visible regardless of what header you're using to access the data.</p> <p>Deep-copy (not only header is "transformed"/copied, but also the underlying data) is possible with</p> <pre><code>cv::Mat mat(myIplImage, true) </code></pre> <p>Note that multiple IplImages can also point to the same underlying data, as can multiple cv::Mats.</p> <hr> <p>When working with OpenCV and similar libraries it is important to notice that cv::Mats and IplImages are only "headers" for the actual data. <strong>You could say that cv::Mats and IplImages are basically pointers plus important <em>meta information</em> like number of rows, columns, channels and the datatype used for individual cells/pixels of the matrix/image.</strong> And, like real pointers, they can reference/point to the same <em>real</em> data.</p> <p>For example, look at the definition of IplImage: <a href="http://opencv.willowgarage.com/documentation/basic_structures.html#iplimage">http://opencv.willowgarage.com/documentation/basic_structures.html#iplimage</a></p> <p>The most important member is <code>char *imageData;</code>. This pointer references the <em>actual</em> image data. However, the IplImage <em>as a whole</em> contains meta information about the image as well, like number of rows and columns.</p>

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