1. A method comprising: receiving a markup language file, and a style sheet file containing breakpoints and a set of image display rules for generating image renditions of a first image; displaying a first image rendition for the first image based on the breakpoints, the first image rendition having: the first image; and crop borders corresponding to the breakpoints; receiving an input indicating a modification to the image rendition; displaying a second image rendition that includes the modification to the first image rendition; and amending the markup language file with at least one image display rule based upon the second image rendition, the at least one image display rule conforming to the set of image display rules.