GetRow returns Mat, clone or original data?

asked 2014-02-16 03:24:08 -0600

MRDaniel
489 ●3 ●9 ●25

Hello,

Are these two pieces of code equivalent? SDMat and BMat are the rows of the matrices SD and B. SDMat and BMat interact, thus changing the original SD and B matrices.

Old version

for(i = 0; i < __shape.nModes()+4; i++) { for(j = 0; j < __texture.nModes(); j++) { cvGetRow(SD, &SDMat, i); cvGetRow(B, &BMat, j); cvScaleAdd(&BMat, cvScalar(-cvmGet(V,i,j)), &SDMat, &SDMat); } }

New version.

for(i = 0; i < __shape.nModes()+4; i++) { for(j = 0; j < __texture.nModes(); j++) { SDMat = SD.row(i); BMat = B.row(j); cv::scaleAdd(BMat, -V.at<double>(i,j), SDMat, SDMat); } }

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answered 2014-02-16 06:06:33 -0600

tuannhtn

1500 ●10 ●19 http://4fire.wordpress...

updated 2014-02-16 06:45:54 -0600

I think your two pieces of code are not the same: while cvGetRow(SD, &SDMat, i);cvGetRow(B, &BMat, j); statements copy row i of SD to SDMat and row j of B to BMat, the two statements SDMat = SD.row(i); BMat = B.row(j); do not. Method row(int) of the Mat class only return matrix header whose pointer data points to a specific row of original object, it does not make the copy as you want it to do (if you mean it). You can see more at http://docs.opencv.org/modules/core/doc/basic_structures.html.