Keystone Corrector 2.5
Another direct entry in the CPP club: KEYSTONE CORRECTOR. A bit of technicality: KeystoneC (here is the App & 64-bit installer) requires MATLAB Compiler Runtime (R2021b) to run. But you don't have to worry about what to download because the installer will figure it out (even whether MCR is already installed or not!) and install the right one before installing KeystoneC. Now, let's see how it all works out!
We start at the beginning, of course:
Ok, then we Load an Image and drag the four corners of the overlaid quadrilateral to desired positions:
Now, we choose the Aspect Ratio (W/H) of the rectangle we want (& Crop Factor) and hit the "Correct Image" button:
Isn't that amazing? We can now save the selected region within the cyan boundary or the auto-cropped region within the magenta boundary or select some custom (red) boundary of our own choice or the whole image (green boundary).
Here's just the image within the cyan boundary (saved after choosing the "Selected" option):