In an image output device a test chart 18 including tests charts 6 of each color is used, and a tone correction table is calculated. The test charts 6 are patterned in a checkered pattern, each including continuous areas 10 in which the tones increase in steps and reference areas 11 for comparison with the continuous areas 10. The reference areas 11 are formed of white ground of paper in a highlight proof part 7, a solid pattern with a maximum density in a shadow proof part 8, and halftone dot-concentrated or line screens with a lower resolution than in the continuous areas in a middle proof part 9. Tone correction values are calculated from characteristic values of the highlight, shadow and middle parts, obtained from visual data of the test chart 18.