Back to results
US 4,941,038 AGranted
Method for color image processing
AssigneeThe Mead Corporation
InventorEric Walowit
Life of this patent
Estimating the term…
Abstract
A method for processing color image data converts input RGB color data to output CMY color data. An input device is calibrated to a intermediate color space, and an output device is calibrated to the intermediate color space. The input RGB color data is collected from the input device, and is converted to intermediate color space data. The intermediate color space data is converted to the output CMY color data, and is outputted to the output device. During the conversion process, the image data is processed to compensate for gamut mismatch.
Claims25
A method of converting input color data to output color data comprising the steps of:
- calibrating in a first calibration an input device to an intermediate color space;
- calibrating in a second calibration an output device to said intermediate color space;
- collecting said input color data from said input device;
- converting said input color data to intermediate color space data in accordance with said first calibration;
- outputting said color data to said output device;
- wherein said converting of said intermediate color space data to said output color data includes processing said intermediate color space data for matching an input gamut to an output gamut for said output device, and wherein said intermediate color space is a uniform color space;
- said processing includes identifying at least one unprintable device independent color output value which, when converted to a device dependent color output value, cannot be represented by said output device, and determining an adjusted device dependent color output value for representing said device independent color output value which is within said output gamut;
- said adjusted device dependent color output value being determined within said intermediate color space;
- said adjusted device dependent color value being determined as the shortest vector distance within said intermediate color space between said unprintable color output value and a color output value which is printable by said output device.
6 more elements
A method of converting input color data to output color data comprising the steps of:
- calibrating in a first calibration an input device to an intermediate color space;
- calibrating in a second calibration an output device to said intermediate color space;
- collecting said input color data from said input device;
- converting said input color data to intermediate color space data in accordance with said first calibration;
- converting said intermediate color space data to said output color data in accordance with said second calibration;
- and
- outputting said color data to said output device;
- wherein said converting of said intermediate color space data to said output color data includes processing said intermediate color space data for matching an input gamut to an output gamut for said output device, and wherein said intermediate color space is a uniform color space;
- said processing includes identifying at least one unprintable device independent color output value which, when converted to a device dependent color output value, cannot be represented by said output device, and determining an adjusted device dependent color output value for representing said device independent color output value which is within said output gamut;
- said adjusted device dependent color output value being determined within said intermediate color space;
- said adjusted device dependent color value being determined by maintaining at least one coordinate within said intermediate color space as constant, and compressing all color input values along at least a second coordinate between zero and said unprintable coordinate value until said unprintable value is within said output color gamut.
8 more elements
A method of converting input color data to output color data comprising the steps of:
- calibrating in a first calibration an input device to an intermediate color space;
- calibrating in a second calibration an output device to said intermediate color space;
- collecting said input color data from said input device;
- converting said input color data to intermediate color space data in accordance with said first calibration;
- converting said intermediate color space data to said output color data in accordance with said second calibration;
- and
- outputting said color data to said output device;
- wherein said converting of said intermediate color space data to said output color data includes processing said intermediate color space data for matching an input gamut to an output gamut for said output device, and wherein said intermediate color space is a uniform color space;
- said processing includes identifying at least one unprintable device independent color output value which, when converted to a device dependent color output value, cannot be represented by said output device, and determining an adjusted device dependent color output value for representing said device independent color output value which is within said output gamut;
- said adjusted device dependent color output value being determined within said intermediate color space;
- said adjusted device dependent color value being determined by maintaining at least one coordinate within said intermediate color space as constant, and clipping all color input values along at least a second coordinate between the outer edge of said output color gamut and said unprintable coordinate value such that said unprintable value is at said outer edge of said output color gamut.
8 more elements
A method of converting input color data to output color data, comprising the steps of:
- calibrating in a first calibration an input device to an intermediate color space, said intermediate color space defining an input gamut;
- calibrating in a second calibration an output device to said intermediate color space;
- collecting said input color data from said input device;
- converting said input color data to intermediate color space data in accordance with said first calibration;
- converting said intermediate color space data to said output color data in accordance with said second calibration;
- and
- outputting said color data to said output device;
- said first calibration comprising the steps of:
- measuring colorimetrically a plurality of color patches to obtain a set of device independent color input values corresponding to said patches;
- measuring with said input device said patches to obtain a set of device dependent color input values corresponding to said patches;
- dividing said input gamut into a plurality of subspaces;
- correlating said device independent and said device dependent color input values for said patches, by separately defining a relationship between said device independent and said device dependent color input values for each of said subspaces;
- calculating other device independent color input values from said set to correspond to input not represented by said patches;
- said calculating of said other device independent color input values being performed separately for each of said subspaces using said relationships;
- and
- creating from said device independent and said device dependent color input values an input lookup table mapping said input color data to said intermediate color space data.
13 more elements
A method of converting input color data to output color data comprising the steps of:
- calibrating in a first calibration an input device to an intermediate color space;
- calibrating in a second calibration an output device to said intermediate color space, said intermediate color space defining an output gamut;
- collecting said input color data from said input device;
- converting said input color data to intermediate color space data in accordance with said first calibration;
- converting said intermediate color space data to said output color data in accordance with said second calibration;
- and
- outputting said color data to said output device;
- said second calibration comprising the steps of:
- printing with said output device a plurality of color patches to obtain a set of device independent color output values;
- measuring colorimetrically said patches to obtain a set of device independent color output values corresponding to said patches;
- dividing said output gamut into a plurality of subspaces;
- correlating said device independent and said device dependent color output values for said patches, by separately defining a relationship between said device independent and said device dependent color output values for each of said subspaces;
- calculating other device independent color output values from said set to correspond to output not represented by said patches;
- said calculating of said other device independent color output values being performed separately for each of said subspaces using said relationships;
- and
- creating from said device independent and said device dependent color output values an output lookup table mapping said intermediate color space data to said output color data.
13 more elements
Dependencies are inferred from the claim text.