I have two different resolutions, the original one is 567x756 (wXh), the one which I want to display is 512x768 (wXh).

How to find out the scaling ratio for these two resolutions?

For example if the font size used in 567x756 resolution is 7 pts then whats the values I should multiply with the font size (7 pts) to display the text in 512x768 resolution.

Can anyone help me in finding the percentage difference between the two different resolutions?

These two resolutions have different

aspect ratios, so it's not a simple scale factor.

I'll assume that you meant what you wrote with wXh and that the images are taller than they are wide.

Horizontally, scaling from the first to the second is by a factor of \(\displaystyle \frac{512}{567}\approx 0.90300 = 90.3\%\).

Vertically, scaling from the first to the second is by a factor of \(\displaystyle \frac{768}{756}\approx 1.01587 = 101.587\%\).

By area, there is a scaling factor of \(\displaystyle \frac{(512)(768)}{(567)(756)}\approx 0.91733 = 91.733\%\).