I have 40 .BMP bitmapped images of baseball stadiums. Some are zoomed in more than others. They all need to be on the same scale so that when you flip through the images they are overlayed to the same size and location.
Each stadium has different dimensions, and so I supply the distance from home plate to left field for each, along with a separate image of the scales of each stadium. For example, a stadium with a 363 ft left-field wall will be larger than a stadium with a 330 ft left-field wall to the correct proportions.
You can add white space to the top/bottom/left/right so that when the images are overlayed stadiums are all the same size.