1. A computer-implemented method comprising: obtaining a single image file having, as part of the image file, a bitmap portion and a multi-frame portion concatenated to the bitmap portion, the multi-frame portion configured to contain multiple versions of an image having different resolutions as respective frames of the multi-frame portion and the bitmap portion enabling applications that are not configured to detect the multi-frame portion to output a bitmap image encoded in the bitmap portion without awareness of the multi-frame portion; determining when the multi-frame portion encodes one or more images; and when the multi-frame portion encodes one or more images: selecting one of the images encoded in the multi-frame portion; and outputting the selected image.