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POcvExtractSURF don't work when useProvidedKeypoints = true
 

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  1. POcvExtractSURF don't work when useProvidedKeypoints = true
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    <p>So, I'm trying to extract some SURF keypoints, but I want to impose these key points! So, I put the last parameter to "true" which is "useProvidedKeypoints".</p> <p>Also, when I create my Keypoint, I used the default constructor (so some default values there). I only change the point "pt" and the octave that I set to 3.</p> <p>I'm using the C++ interface with SURF. But I know that the problem is right at cvExtractSURF because I copied that part of the code in mine to help me debug.</p> <p>When I call that function, with the last parameter set to true, I got this error:</p> <pre><code>OpenCV Error: Bad argument (Unknown array type) in cvarrToMat, file /home/widgg/opencv/trunk/modules/core/src/matrix.cpp, line 651 terminate called after throwing an instance of 'cv::Exception' what(): /home/widgg/opencv/trunk/modules/core/src/matrix.cpp:651: error: (-5) Unknown array type in function cvarrToMat </code></pre> <p>I really don't know what I'm doing wrong!</p> <p>EDIT:</p> <p>Here's some code. First how I create the keypoints (I left a couple of informations, like the layer_id stuff, but you get the main idea):</p> <pre><code>for (json_pt_info_vector::iterator b_beg = beg-&gt;points.begin(); b_beg != b_end; ++b_beg) { int layer_id = b_beg-&gt;layer_id; json_point_info_coord &amp;jpic = b_beg-&gt;coord; jpic.feature_id = features[layer_id].keypoints.size(); KeyPoint kp; kp.octave = 3; kp.pt.x = jpic.x; kp.pt.y = jpic.y; features[layer_id].keypoints.push_back(kp); } </code></pre> <p>Here's the call to SURF:</p> <pre><code>SURF surf(300, 3, 4); for (int i = 0; i &lt; nb_img; ++i) { debug_msg("extract_features #4.1"); cv::detail::ImageFeatures &amp;cdif = features[i]; Mat gray_image = imread(param.layer_images[i], 0); // 0 = force to gray scale! debug_msg("extract_features #4.2"); vector&lt;float&gt; descriptors; debug_msg("extract_features #4.3"); surf(gray_image, Mat(), cdif.keypoints, descriptors, true); // MUST BE TRUE TO FORCE THE PROVIDED KEYPOINTS debug_msg("extract_features #4.4"); cdif.descriptors = Mat(descriptors, true).reshape(1, (int)cdif.keypoints.size()); debug_msg("extract_features #4.5"); gray_image.release(); debug_msg("extract_features #4.6"); images[i] = imread(param.layer_images[i]); // keep the image open } </code></pre> <p>It crashes after #4.3 in the debug message!</p> <p>Hope that helps!</p> <p>EDIT 2:</p> <p>I replaced some part by cv::SurfDescriptorExtracter. I replace everything from 4.3 to 4.5 with the following line:</p> <pre><code> extractor.compute(gray_image, cdif.keypoints, cdif.descriptors); </code></pre> <p>So now, there's still a bug, but it's located somewhere else, not necessary related to this question!</p>
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    1. COWe need to see our code to help you. If you provide your own vector of cv::Keypoint, you should use (c++ api) cv::DescriptorExtractor object to compute the descriptors.
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    2. COhow do you use that cv::DescriptorExtractor ? Also, I hope the code that I put helps you a bit!
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