Perl module performing math used to constrain image sizes
Image::Math::Constrain is a Perl module that implements all of the math behind
implementing image size constraints. It allows one to restrict the dimensions
of an image by checking to see if the image is larger than the desired final
dimensions, and if so, provide a way to scale the image down proportionally so
it fits within the constraints. It can set constraints based on width, height,
or both, and is guaranteed to return dimensions that are proportional to the
original -- that is, they will have the same aspect ratio. It also returns the
necessary scaling factor, so you can pass it to a module to do the work.