An image forming apparatus includes an image forming device, a heater, and a control circuit. The control circuit is configured to generate first energization data based on at least part of first raster image data representing a first image to be formed on a first page, and then compress the first raster image data into first compressed image data. The control circuit is also configured to generate second energization data based on at least part of second raster image data representing a second image to be formed on a second page, and then compress the second raster image data into second compressed image data. The control circuit is configured to further determine whether rotation of the second image by a predetermined degree will lower power consumption based on a comparison of the first energization data to the second energization data.