Need to compare images with different pixel counts

I need to compare two images, one a idealized image of a laser aberration and the other, the actual observed aberration. Unfortunately, the two images (though equally sized) have different pixel counts. The idealized image is 512 by 512, the actual is 279 by 369. If I can get similar pixel counts, I can easily write something to compare them. Obviously I can't increase the pixel count of the observed image, but can I somehow change the pixel count of the idealized to match it?

[Walter Roberson]

Please expand on what you mean when you say that the two images are "equally sized", but have different pixel counts ?

Answer 1

[David Young]

If you have the Image Processing Toolbox, use imresize.