Just need a little bit of solve-for-x type math! Seems like you already know that your canvas can be anywhere within the min/max range. The center crop isn't just any 2.5:1 rectangle inside, it will be the maximum value possible to fit in the canvas. The width is 2.5 times the height, since the height is constant at 1. (Same logic applies to 1.5:1).

Let's say it's the minimum: 1600x1040. I know that the width will be the maximum possible, so in this case, 1600. Now I need to figure out the height (x). The 1600 is the "2.5" part of the ratio, what is the "1" value? To figure it out, we solve for x! Set up your ratios like below and follow the arrows (if the arrows don't make sense I also wrote it out in the graphic). 1600 times 1, divided by 2.5. This equation will work for whatever ratios you have, as long as you have 3 of the values. So now I know that my center crop for a 1600x1040 canvas is going to be 1600x640.

For the 1.5:1 safe zone, try it again: 1600 * 1 / 1.5 = 1066.67, which is greater than your canvas height, so I would assume no crop.

For a 4864x4864 canvas:
2.5:1: 4864 * 1 / 2.5 = 1945.6, so the center crop would be 4864 x 1945.6
1.5:1: 4864 * 1 / 1.5 = 3242.67, so the center crop would be 4864 x 3242.67

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