An image output apparatus includes: an image forming unit that forms an image on a recording medium; a test-threshold acquiring unit that acquires a test threshold that is a pass-fail criterion for the image test for determining whether the test image data passes or fails the image test; a changing unit that changes a density detection mode of at least one of the image forming unit and the image reading apparatus on the basis of the test threshold; a density correcting unit that corrects density used in an image forming process performed by the image forming unit; and a reference-image-data acquiring unit that acquires the reference image data.