Package graphicx provides a useful keyword viewport which allows to show just a part of an image. However, one needs to put there the actual coordinates of the viewport window. Sometimes it is useful to have relative coordinates as fractions of natural size. For example, one may want to print a large image on a spread, putting a half on a verso page, and another half on the next recto page. For this one would need a viewport occupying exactly one half of the file's bounding box, whatever the actual width of the image may be.

This package adds a new keyword rviewport to the graphicx package specifiying Relative Viewport for graphics inclusion: a window defined by the given fractions of the natural width and height of the image.