Apple hasn’t made printers in years, but it’s at least working on diagnostic targets for evaluating printer performance per a patent (number 20120092701) at the U.S. Patent & Trademark Office.

Per the patent, print performance is evaluated by printing a diagnostic image comprising color patches. Colorant usage in the printed image is measured by, for instance, scanning each patch. Measured color values are then compared to target color values. Based on the comparison, groups of patches whose color values vary significantly from expectations are identified.

Variant groups are then analyzed to identify, in addition to color quality control problems, spatial problems that affect only a localized area of a printed page. Such spatial problems may include, for example, problems with contrast or streaks. A heat map illustrating the differences may be generated to help an operator visualize the spatial problem. A template for the diagnostic image may be selected from a plurality of randomly generated diagnostic targets based on total colorant usage for at least one colorant in each column of color patches. Certain patches may be predefined across for each candidate target.

Nancy Wang and Karl Lang are the inventors.