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POOpenCV template matching and transparency
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copied!<p>What's the way OpenCV handles transparency in image during template matching?</p> <p>The problem is that the template image needs to have transparent parts, because in the original image there could be anything at those places.</p> <p>I tried all of the methods, and none of them yielded positive results (e.g. position of template in original image wasn't detected correctly).</p> <p><strong>Edit:</strong> OK, I see that is necessary to provide examples.</p> <p><a href="http://img35.imageshack.us/img35/3829/imageau.png" rel="noreferrer"><strong>Original image</strong></a></p> <p><a href="http://img151.imageshack.us/img151/6174/maskz.png" rel="noreferrer"><strong>Template image</strong></a></p> <p>As you can see, it's nearly impossible to match such template to image like that. The "background" around the object could have any color (like this, or white, brown...)</p> <p><a href="http://img46.imageshack.us/img46/778/sobel2.png" rel="noreferrer"><strong>Sobel on grayscaled image & template + cvConvertScaleAbs</strong></a></p> <p><a href="http://img411.imageshack.us/img411/8463/image3cc.png" rel="noreferrer"><strong>Additional original image</strong></a></p> <p><strong>Edit 2:</strong> misha's solution works even with a bit of obstacles around (the "transparency" works). Example:</p> <p><a href="http://img220.imageshack.us/img220/1717/matchtemplatesuccesful.png" rel="noreferrer"><strong>Template match sucessful</strong></a></p> <p><strong>Edit 3 - multiple occurences:</strong></p> <p>I've made a quick and dirty solution of finding multiple occurences of a template, however when template is not found I get a "lot" of false positives. Mainly because of my implementation:</p> <ul> <li>iterate over image data</li> <li>if (imageData[y, x, 0] >= maxValue * 0.95f) then it counts [x,y] as a match (maxValue is from cvMinMaxLoc)</li> </ul> <p>It <a href="http://img94.imageshack.us/img94/1664/multipletemplatesok.png" rel="noreferrer">works</a> for images, when there's at least one positive match, however results in awful situation for images, on which there <a href="http://img441.imageshack.us/img441/9446/multipletemplatesbad.png" rel="noreferrer">isn't such template</a>.</p>

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