Merging cv::Mat horizontally

Question

I want to merge a few cv::Mat, when I use mat1.push_back(mat2) it add mat2 to the end of mat1 vertically , is there a way to do this horizontally? The only other option I can think of is making every cv::Mat into a cv::RotatedRect, rotate it, creating a new Mat, merging, rotating everything in the end in the same way, but it sound pointlessly long if there is another way

Solution 1

Take a look at hconcat and vconcat.

usage:

Mat M1,M2,HM,VM;
// M1 and M2 - source matrices
// HM,VM - results matrices
 ...

 hconcat(M1,M2,HM); // horizontal concatenation
 vconcat(M1,M2,VM); // vertical   concatenation

Take care, these methods are not documented.

Solution 2

There is a very simple way of displaying two images side by side. The following function can be used which is provided by opencv.

Mat image1, image2;
hconcat(image1,image2,image1);//Syntax->
hconcat(source1,source2,destination);

This function can also be used to copy a set of columns from an image to another image.

Mat image;
Mat columns=image.colRange(20,30);
hconcat(image,columns,image);

Comments

[Ruchir]

Minor typo in the comment on line 3 (HM and VM instead of MH and MV) but doesn't affect the results :)

[beaker]

Note that these methods are now documented: hconcat and vconcat.

[Andrey Smorodov]

It mentioned in answer.

[Teh Sunn Liu]

I tried hconcat with different number of rows it crashes. Works only if number of rows are same. but works fine if number of cols are different

[Andrey Smorodov]

Yes that's correct and can't be else. You can't combine horizontally matrices with different number of rows. As you can't combine vertically matrices with different number of cols.