Overlap two 2D array images by coordinate mapping

I'm doing pixel-by-pixel analysis. I have one parametric image, img1, and one parametric ROI matrix image (contains only values within the ROI and is zero elsewhere), img2, with resolutions 256x256 that I'm trying to overlap What I've got at my disposal are:

• The two image arrays, img1 and img2, that have the same FoV extent, but are shifted and covers different areas.
• Real world reference points (in mm) for both images, which are refpoint1=(-88.5,-98.6) and refpoint2=(-86.1,-96.7), respectively for img1 and img2. The reference points are located in the top left pixel (1,1) in their respective images.
• Pixel spacing for both images, which is 1.42 pixel/mm.

I want to shift img2 to overlap on img1 by coordinate mapping.

Attempt

    temp = zeros(size(img1));
    s = size(img2);
    x = abs(refpoint1(1) - refpoint2(1)) * pixspacing;
    y = abs(refpoint1(2) - refpoint2(2)) * pixspacing;
    temp(x:x+s(1)-1, y:y+s(2)-1) = img2;

Close solution

    x = (refpoint1(1) - refpoint2(1)) * pixspacing;
    y = (refpoint1(2) - refpoint2(2)) * pixspacing;
    img2 = imtranslate(img2, [x, y], 'FillValues', 0, 'OutputView', 'full');

The problem now is that the ROI images are aligned and do overlap with each other, but I can't perform the operation img1 .* img2 since img2 is of different resolution than img1. How can I crop img2 and keep it aligned?

Answer 1

[Image Analyst]

See https://blogs.mathworks.com/steve/2006/03/28/image-overlays/

and

http://www.mathworks.com/matlabcentral/answers/104889-how-to-overlay-a-foreground-image-over-a-background-image

You may have to use imtranslate() or imregister() if they're not aligned in the way you want.