1. A printer comprising: a central processing unit; a memory in communication with the central processing unit; and a printer driver implemented by the central processing unit and memory, the printer driver to: notionally divide a digital image of a document to be printed into a number of square sectors, each sector comprising a plurality of pixels of the digital image; for each sector, compare luminosity of the pixels to a threshold based on this comparison, determine whether each sector is likely to show an image defect if printed at a lower image quality print mode; select a print mode such that all sectors are determined not to be likely to show an image defect; and print the document using the selected print mode.