Rapid Resizer can open common pictures files (PNG, JPG, GIF), PDF, and most SVGs. If used in Safari, it accepts TIFFs. It can also read .RRP files from the original Rapid Resizer though without any coloring.

If you have a picture in a document file, try to save/export it from the document into a picture file. 

Rapid Resizer can export PDF, PNG picture, and SVG vector files. For resizing, it outputs PDF. Unsized designs can be exported as PNG or SVG.