Is it possible to resize images using resolution (dpi)?

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Hello,

I have some images which do not have the same width and height resolution (eg: width 200 dpi height 400 dpi). For some reasons I need to resize the image to have a square resolution by keeping one of the existing one that means the image should be either 200x200 dpi or 400x400 dpi in this case. I tried using the resize function the following way:

resize( inputImgMat, outImgMat, Size(0,0), 1, 0.5, INTER_LANCZOS4 )

but the resolution is reduced to be 96 dpi. Note that I tried all possible algorithms and each time the same result.

Is that possible using the resize function? is there any other function I can use?

Thanks.