How to fit desired region into smaller shape?

Hello to everyone,

Given: I have two images: I the first image I have 2 red triangles fitted into black square outline. Red triangles are my regions of interest.

_Image 1._

However on the second I have the same black square outline, but scaled down and without 2 red triangles (which I want to see).

_Image 2._

Want: So what I want is to fit 2 red triangles from Image 1 into scaled down Image 2.

What would be the best way of doing it?

Currently done:

What I have in mind:

1. Segmentation based one color thresholding.

2. Measure the region of interest by using region prop function.

3. Estimate geometric transformation that aligns two images.

imregtform(To_corr_im1, Original_im, 'affine', optimizer_im1, metric_im1);

4. I'm not quite sure what to do next, should I use output after affine transformation and segment it again in order to fit 2 red triangles?

Please fire out any algorithms or papers, which may handle my issue.

Thank you for any suggestions.

[Hamoon]

why don't you just scale down the first image?

[Ivan Shorokhov]

But I don't know the scaling factor, and shapes are not exactly the same, second shape is slightly wider (ratio wise).