# US 8,542,918 B2 · Image color enhancement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,918 B2 - Document ID: US8542918B2 - Status: Granted - Kind: B2 - Application number: 12/892,918 - Filed: 2010-09-28 - Published: 2012-03-29 - Granted: 2013-09-24 - Earliest claimed: 2010-09-28 - Assignees: Apple Inc. - Applicants: Andrew Bryant; Adriana Dumitras - Inventors: Andrew Bryant; Adriana Dumitras - Web page: https://patentgrep.com/patent/US8542918B2 ## CPC - H04N 9/77: Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase (circuits for matrixing H04N9/67) - G06T 5/92: based on global image properties - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract Some embodiments of the invention provide a non-linear image-enhancement method to enhance an image that includes a number of picture elements. The non-linear enhancement method adjusts the brightness value of each pixel in the image and adjusts at least one chromatic value of each pixel in the image based on the adjustment to the brightness value of that pixel. ## Claims ### Claim 1 A method of enhancing color values of an image comprising a plurality of pixels, wherein each pixel comprises an achromatic color component value and a chromatic color component value, the method comprising: applying a continuous, monotonically increasing, non-linear function to each pixel's achromatic color component value; and for each pixel, adjusting the pixel's chromatic color component value based on a relative change of the pixel's achromatic color component value that resulted from the application of the function. ### Claim 2 (depends on 1) The method of claim 1, wherein the function is a sigmoidal function. ### Claim 3 (depends on 1) The method of claim 1, wherein said achromatic color component value is a brightness value. ### Claim 4 (depends on 1) The method of claim 1, wherein said achromatic color component value is a luminance value. ### Claim 5 (depends on 1) The method of claim 1, wherein adjusting the pixel's chromatic color component value comprises multiplying the chromatic value by a factor that depends on the adjustment to the pixel's achromatic color component value. ### Claim 6 (depends on 1) The method of claim 1 further comprising receiving a contrast adjustment value, wherein said function depends on said contrast adjustment value. ### Claim 7 (depends on 6) The method of claim 6, wherein the non-linear function is a sigmoidal function with a slope that is at least partly based on said contrast adjustment value. ### Claim 8 (depends on 7) The method of claim 7, wherein a central portion of the sigmoidal function is steeper for larger contrast adjustment values than for smaller contrast adjustment values. ### Claim 9 A computer readable medium storing a media editing computer program which when executed on at least one processor adjusts achromatic and chromatic values of an image, the computer program comprising sets of instructions for: applying a continuous, monotonically increasing, non-linear function to each pixel's achromatic color component value; and for each pixel, adjusting the pixel's chromatic color component value based on a relative change of the pixel's achromatic color component value that resulted from the application of the function. ### Claim 10 (depends on 9) The computer readable medium of claim 9, wherein the computer program further comprises a set of instructions for: providing a graphical user interface (GUI) control for receiving a contrast adjustment value; and adjusting said function based on said contrast adjustment value. ### Claim 11 (depends on 10) The computer readable medium of claim 10, wherein the function is a sigmoidal function with a slope that is at least partly based on said contrast adjustment value. ### Claim 12 (depends on 11) The computer readable medium of claim 11, wherein a central portion of the sigmoidal function is steeper for larger contrast adjustment values than for smaller contrast adjustment values. ### Claim 13 (depends on 11) The computer readable medium of claim 11, wherein the set of instructions for adjusting said function comprises a set of instructions for rescaling the function in relation to said contrast adjustment. ### Claim 14 (depends on 9) The computer readable medium of claim 9, wherein the function is a sigmoidal function. ### Claim 15 (depends on 9) The computer readable medium of claim 9, wherein said achromatic color component value is a brightness value. ### Claim 16 (depends on 9) The computer readable medium of claim 9, wherein said achromatic color component value is a luminance value. ### Claim 17 (depends on 9) The computer readable medium of claim 9, wherein the set of instructions for adjusting the pixel's chromatic color component value comprises a set of instructions for multiplying the chromatic value by a factor that depends on the adjustment to the pixel's achromatic color component value. ### Claim 18 A system comprising a processor, a memory, and an electronic display device that displays a graphical user interface (GUI) for enhancing color values of an image comprising a plurality of pixels, wherein each pixel comprises an achromatic color component value and a chromatic color component value, the GUI comprising: a display area for displaying said image; a control for receiving a command to enhance said color values, wherein upon receiving said command, said computer system uses the processor to (i) adjust a non-linear function for converting a set of original achromatic color component values into a set of adjusted achromatic color component values; (ii) apply said adjusted non-linear function to the pixels; (iii) adjust the pixel's chromatic color component value based on a relative change of the pixel's achromatic color component value that resulted from the application of the function. ### Claim 19 (depends on 18) The system of claim 18, wherein the non-linear function is a sigmoidal function with a slope that is at least partly based on said contrast adjustment value. ### Claim 20 (depends on 19) The system of claim 19, wherein a central portion of the sigmoidal function is steeper for larger contrast adjustment values than for smaller contrast adjustment values. ### Claim 21 (depends on 19) The system of claim 19, wherein said image is stored in said memory of the computer system in a color coordinate system that the achromatic color component value and two chromatic color component values.