What percentage/ratio are used to scale Blender's background images?

Question

I'm trying to create a plane that is the exact height and width of the image instanced as a background image. What are the exact proportions that Blender uses to scale these images? For example, what are the proportions used to "Fit?" Let's say I have an image that is "275x183", what calculation is Blender using to upscale or normalize it within its basic 1920x1080 / 16:9 Aspect Ratio bounds? and vice versa, if I have an image that is "3840x2160", what calculation is Blender using to downscale or normalize within these "1920x1080" bounds?

My goal is to automate this plane making process for about 100+ cameras, by applying this ratio scaling across a multitude of unique image dimensions.

1st image is a sample image, 2nd image is my desired output, a plane that is sized based on this calculation/formula.

Thanks so much in advance :)

Answer 1

The 'Import Images as Planes' Addon already has the option to batch import multiple images, you can even set a small automatic offset between the imported planes. Also, there's an option to Fit or Fill the Camera's render area when you set the Plane Dimensions to Camera Relative.

This will create all planes exactly perpendicular to the Camera and scale all images so that the rendered images will always be 1920x1080 (or whatever resolution you define in the Output Properties), regardless of their original pixel size.