two different size image coregistration

Hi, I have two image 64*64, and 320*320. The actual center of the image is different. I know the actual center of the two images and the size of the two images. For example, for the 64*64 image, the center is at(3.256,10.589),size is 300*300, for the 320*320 image the center is at(2.3,5.9), size is 300*300. They are images with different resolution, so the matrix size is different. My problem is to choose a ROI on the 320*320 image, I wanna get the related roi data in the 64*64 image. Thanks.

[Walter Roberson]

I do not understand how a 64 by 64 matrix is "size is 300*300" ? Do you mean that the 64 x 64 pixels cover 300 x 300 "units" of data and for the 320 x 320 pixels cover the same 300 x 300 "units" of data? The 320 covers the same "space" as the 64 bit is 5 times finer resolution?

When you give the centers like that, is that in pixel coordinates or in the 300x300 data coordinates?

[Image Analyst]

Don't make us work "blind" - just attach the images with the green and brown frame icon.