How to mask a float mat in opencv

Question

I have a mat A of type CV_32F and a mask M with binary value 0 and 255. For example,

A = [0.1 0.2; 0.3 0.4]  
M = [1   0  ; 0   0  ]

I want to get the result of A&B = [0.1, 0;0 0] While bitwise operation does not work on float mat. And I tried to convert the mask to CV_32F and then mask like the following, also not work.

M.convertTo(M, CV_32F);
A.copyTo(A, M);

So how to do it ?

Why do you need to convert the mask to `CV_32F`? – herohuyongtao Apr 03 '15 at 15:22 — herohuyongtao, Apr 03 '15 at 15:22
convert or not, neither works – Frazer Apr 04 '15 at 03:01 — Frazer, Apr 04 '15 at 03:01
Please provide your code and explain how doesn't it work. – herohuyongtao Apr 04 '15 at 05:17 — herohuyongtao, Apr 04 '15 at 05:17

herohuyongtao · Accepted Answer · 2015-04-07T02:50:44.723

3

Your code doesn't work because, as the doc of Mat::copyTo says, the function does not handle the case of a partial overlap between the source and the destination matrices, while the source and the destination matrices are the same in your case.

You should save the result elsewhere, like

cv::Mat dst;
A.copyTo(dst, M);  // dst is what you want

edited Apr 07 '15 at 02:50

answered Apr 07 '15 at 02:20

herohuyongtao

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This works, thanks. I was trying to use bitwise_and without success. Can you add that option? – Pedro77 Jun 03 '22 at 21:39

score 0 · Answer 2 · edited May 28 '18 at 06:26

0

I think this might help:

//to create mask
cv :: Mat floatMask
cv::threshold( someimage , floatMask , 0 , 1 , cv ::THRESH_BINARY );
floatMask.convertTo( floatMask , cv :: CV_32F);

// now to mask image 
floatImageToBeMasked = floatImageToBeMasked.mul ( floatMask ) ;

edited May 28 '18 at 06:26

cela

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answered May 28 '18 at 06:06

Gagesh Madaan

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How to mask a float mat in opencv

2 Answers2