1. A method comprising: receiving a page request for a requested document, the requested document specifying a plurality of first images as being presentable within the requested document; generating a modified document by modifying the requested document in response to the receiving of the page request, the modified document specifying a second image, the second image to be generated based on the plurality of first images; generating the second image from the plurality of first images, the generating of the second image being performed using a processor of a machine; and providing the modified document and access to the second image in response to the received page request for the requested document.