Methods and apparatus for calibrating a color display
Improved methods are provided for calibrating color on a color display coupled to a computer, which are useful for obtaining calibrated data in a virtual proof network for enabling different color devices to render consistent color. Methods involve user interactions with screens on the display to set color display parameters. An apparatus is also provided for calibrating a sensor which may be used for measuring color of a display in one or more of these methods.
1. A color reproduction system comprising:
a computer system having a link to at least one video display device; and
memory storing data and programs, wherein said data comprise:
a plurality of screens comprising graphical elements for display on said display device, wherein said screens provide an interface enabling user interaction with one or more of said programs; and
information for transforming colors from device-independent coordinates to values employed in rendering to said display device, wherein at least part of said information is stored in a file and said information comprises at least a desired tone reproduction and color coordinates characterizing a desired neutral balance for said display device, stored values representing the tone reproduction and neutral balance initially associated with said display device, values representing neutral balance and tone reproduction for said display device modified in accordance with user visual judgments, and a chromatic adaptation transform enabling conversion of input color coordinates to output color coordinates representative of different viewing conditions, wherein at least said chromatic adaptation transform is accessible through a header of said file; and
wherein said programs comprise:
one or more programs for displaying said screens on said display device and recording modifications to neutral balance and tone reproduction curves based upon visual judgments of displayed screens by said user;
one or more programs that use said visual judgments to set at least the brightness of said display device and to derive correction functions based upon said modifications; and
one or more programs that modify said information for transforming in accordance with said correction functions and direct rendering of colors on said display device with improved matching to desired values.
2. The system according to claim 1 further comprising a program to store one or more of modified tone reproduction curves or correction functions for modifying tone reproduction in said file to be accessible through said header.
3. The system according to claim 2 further comprising said video display device and a graphics section interfacing said video display device to said computer system.
4. The system according to claim 3 wherein said graphics section corrects rendering upon said video display device in accordance with user modifications to tone reproduction.
5. The system according to claim 4 wherein said graphical elements comprise at least slide bars enabling user adjustment of at least the color channels of said video display, an image comprising gradations of at least lightness, and an image comprising stripes enabling threshold discriminations by a user.
6. The system according to claim 1 wherein said graphical elements comprise at least slide bars enabling user adjustment of at least the color channels of said video display, an image comprising gradations of at least lightness, and an image comprising stripes enabling threshold discriminations by a user.
7. The system according to claim 6 wherein said interface enabling user interaction with one or more programs further provides user access to tutorial assistance in the use of displayed screens that enable a user to calibrate said video display in accordance with visual judgments.
8. The system according to claim 6 further comprising a program that alerts the user to the effects of ambient illumination.
9. A non-transitory computer-readable medium for calibrating a color video display comprising:
data comprising a plurality of screens, said screens comprising graphical elements for display on said video display to enable a user to calibrate said video display in accordance with visual judgments, by said user, of displayed screens, wherein said screens provide an interface enabling user interaction with one or more programs executable by a computer system linked to said video display, said data further comprising information for transforming colors from device-independent coordinates to values employed in rendering to said video display, wherein at least part of said information is stored in a file having a header, and said information comprises at least a desired tone reproduction and color coordinates characterizing a desired gray balance for said video display, stored values representing the initial tone reproduction and gray balance of said video display, values representing modifications to tone reproduction curves and gray balance for said video display, and a chromatic adaptation transform enabling conversion of input color coordinates to output color coordinates representative of different viewing conditions; and
software comprising programs that display said screens on said video display; record modifications to gray balance and tone reproduction curves based upon visual judgments of displayed screens by said user; employ visual judgments to set at least the brightness of said video display revise said information for transforming in accordance with said modifications; and direct rendering of colors on said display device with improved matching to desired values.
10. The non-transitory computer-readable medium according to claim 9 wherein said software further comprises a program to store one or more of modified tone reproduction curves or correction functions for modifying said initial tone reproduction curves in said file to be accessible through said header.
11. The non-transitory computer-readable medium according to claim 10 wherein said software further comprises a device driver to operate a graphics section of said computer system.
12. The non-transitory computer-readable medium according to claim 11 wherein corrected tone reproduction curves are stored in said graphics section to affect rendering upon said video display device.
13. The non-transitory, computer-readable medium according to claim 9 wherein said software further comprises a program to set contrast of said video display.
14. The non-transitory computer-readable medium according to claim 9 wherein said graphical elements comprise at least slide bars enabling user adjustment of at least the color channels of said video display, an image comprising gradations of at least lightness, and an image comprising stripes used to enable threshold discriminations by a user.
15. The non-transitory, computer-readable medium according to claim 14 wherein said gradations comprise an orderly step wedge of lightness values.
16. The non-transitory, computer-readable medium according to claim 14 further comprising a program that alerts the user to the effects of ambient illumination.
17. The non-transitory, computer-readable medium according to claim 14 wherein said interface enabling user interaction with one or more programs further provides user access to tutorial assistance in the use of said screens that enable a user to calibrate said video display in accordance with visual judgments.
18. The non-transitory, computer-readable medium according to claim 14 wherein said software further comprises a program to set contrast of said video display.