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Help Needed with OpenCV reg: Modifying the map

asked 2016-04-04 11:06:34 -0500

asa gravatar image

updated 2016-04-04 11:08:38 -0500


I am working with OpenCV image registration library "reg" under "opencv-contrib". I am using the MapAffine class to estimate affine motion. I need to modify the shift vector element (multiply it by a constant factor). I can get the linear transformation matrix and shift vector using getLinTr() and getShift(). Before doing the warping (using inverseWarp() ) I want to multiply the shift vector by a constant. This is what I have done so far: (Following this tutorial (

Ptr<Map> mapPtr;
MapperGradAffine mapper;
MapperPyramid mapPyr(mapper);
Ptr<Map> mapPtr;
mapPyr.calculate(image1, image2,  mapPtr);
MapAffine* mapAff = dynamic_cast<MapAffine*>(mapPtr.get());

Then doing the warping:

mapAff->inversewarp(image2, destination);

Now I want to modify the shift vector prior to doing the above step. I have tried to modify the shift part using opencv Mat obejcts:

cv::Mat lin_tr = Mat(mapAff->getLintr); //getting the linear part
cv::Mat shift = Mat(mapAff->getShift()); //getting the translation
cv::Mat* aff_mat;
cv::hconcat(lin_tr, 2 * shift, *aff_mat);

Now the affine matrix is in a Mat object. My question is how can I recast it to MapAffine so that I can use the inversewarp() function. Or is there another way to modify the mapAffine reference directly?

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answered 2016-04-06 12:10:05 -0500

asa gravatar image

I was able to solve the issue like this:


MapAffine* mapAff = dynamic_cast<MapAffine>(mapPtr.get);

I create a MapAffine object using the parameterised constructor where I multiply the shift component by the integer factor:

MapAffine mapAff2 = cv::reg::MapAffine(ampAff->getLinTr(), alpha * mapAff->getShift());
// alpha is the integer factor

Then I call inversewarp() using mapAff2:

mapAff2.inversewarp(source, destination);

If there's a more efficient way of doing it please let me know


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there is an efficient way of doing it. Use the scale() function

mapAff->scale(alpha)`//multiplies the shift vector by a factor`

somehow I missed this simple function!

asa gravatar imageasa ( 2016-04-07 17:07:41 -0500 )edit

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Asked: 2016-04-04 11:06:34 -0500

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Last updated: Apr 06 '16