Hi pior, I'm not entirely sure that I'm following all of what you described but for specific pixel sizes the script in the first message of this same thread can do that.

This is the part of the script that has the pixel dimensions:

.render( 4000, 2500 );

That's making an image of 4000 pixels in width and 2500 in height. Replace the 4000 and 2500 with your desired pixel sizes instead.

- Michael