Color correction system and method with localized color sampling

• US 4,679,067 A
• Filed: 04/09/1984
• Issued: 07/07/1987
• Est. Priority Date: 04/09/1984
• Status: Expired due to Term

• Current Assignee: Cintel SRL
• Original Assignee: Corporate Communications Consultants, Inc. (Aduddell Industries, Inc.)
• Inventors: Chayka, Stanley J., Belmares-Sarabia, Armand
• Primary Examiner(s): Shepperd, John W.
• Application Number:
  US06/598,468
• Time in Patent Office: 1,184 Days
• Field of Search: 358/22, 358/29, 358/105, 358/126, 358/183, 358/80
• US Class Current: 348/655
• CPC Class Codes: H04N 1/6011 with simulation on a subsidiary picture reproducer H04N1/622 takes precedence; matching two or more picture reproducers H04N1/6052
• CPC Class Codes: H04N 19/142 Detection of scene cut or scene change
• CPC Class Codes: H04N 19/179 the unit being a scene or a shot
• CPC Class Codes: H04N 19/87 involving scene cut or scene change detection in combination with video compression
• CPC Class Codes: H04N 5/147 Scene change detection
• CPC Class Codes: H04N 9/64 Circuits for processing colour signals H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

In a scene-by-scene color corrector, automatic color correction circuitry produces color correction signals which are stored and utilized in preparing color-corrected video tape. Preferably, the automatic correction circuit tests only a pre-selected portion of the video picture displayed on a monitor. This portion or "window" is visible on the monitor screen, and its position and size can be changed as desired. The use of the "window" permits the exclusion of portions of the picture on which the automatic circuitry is less than fully effective, or which do not have components desirable for use in automatic color correction. If a separately variable luminance signal is produced, the automatic color correction circuitry preferably uses the luminance signal as a reference, thus allowing one to maintain color balance despite changes in the luminance signal.

Claims

1. Apparatus for color-correcting video picture signals having red, green, and blue color component signals and a luminance signal, said apparatus comprising, in combination, display means for displaying on a video monitor screen a picture composed of said video picture signals, means for detecting the color characteristics of selected ones of said signals, selecting means for selecting the ones of said video picture signals for which said color characteristics are detected as those which create picture elements within a predetermined area which is less than the area of the entire picture, means for selectively moving and locating said predetermined area within said picture, said means for selectively moving and locating including means for selectively changing the size and position of sid predetermined area, and automatic color balancing means for automatically developing color balance signals for said selected picture signals, said automatic color balancing means including means for comparing each of said red, green, and blue color signals with said luminance signal, and means for adjusting each of said red, green, and blue color signals to attain a predetermined relationship with said luminance signal.

2. Apparatus as in claim 1 in which said selecting means includes means for making said predetermined area visible as a window area on said screen.

3. Apparatus as in claim 2 including means for attenuating video picture signals which create other picture elements outside of said window, whereby the picture elements within said window are highlighted relative to said other picture elements.

4. Apparatus as in claim 1 including primary signal means for supplying signals representing the primary color components of said picture signals, and in which said automatic color correction means comprises automatic color balancing means for automatically balancing the primary color signals with respect to one another.

5. Apparatus as in claim 4 in which said video picture signals include red, blue and green color signals, and a luminance signal, said color balancing means including means for comparing each of said red, blue and green signals with sid luminance signal, and means for adjusting each of said red, blue and green color signals to attain a pre-determined relationship with said luminance signal.

6. Apparatus as in claim 4 in which said video picture signals include red, blue and green color signals, including manually-operable means for producing adjustment signals for adjusting said primary color signals, said automatic color balancing means including means for adding correction signals to or subtracting correction signals from said adjustment signals, and means for adjusting said luminance signal.

7. Apparatus as in claim 1, 2 wherein said balancing means includes means for determining the hue of said video picture signals within said predetermined area, said hue determining means having means for measuring the difference between each of the red, green, and blue color component signals and the luminance signal.

8. Apparatus as in claim 1, wherein said balancing means includes means for determining the saturation of said video picture signals within said predetermined area, said saturation determining means having means for measuring the difference between each of the red, green, and blue color component signals and the luminance signal.

9. In a color correcting system for color-correcting video picture signal representative of images stored by an image recording medium, display means for displaying on a video monitor screen a picture composed of said video picture signals, primary signal means for supplying signals representing red, green, and blue color components of said picture signals, means for producing a luminance signal representing the luminance of said picture signals, automatic color balancing means for detecting said picture signals and automatically producing correction signals to color-correct said signals, said automatic color balancing means including means for comparing each of said red, green, and blue color signals with said luminance signal, and means for adjusting each of said red, green, sand blue color signals to attain a predetermined relationship with said luminance signal, storage means for storing said correction signals, locating means for producing location signals indicating the location of each of said images in said recording medium, location storage means for storing said location signals, readout means for sequentially reading said location and correction signals out of storage in snychronism with said video picture signals, and combining means for selectively combining said video picture signals with said correction signals under the control of said location signals to produce color-corrected video picture signals.

10. Apparatus as in claim 9 including selecting means for selecting picture signals which create picture elements in only a portion of said screen, and means for enabling said automatic color corrector means to sample only said selected signals for determining the values of said color correction signals.

11. Apparatus as in claim 10, in which said selecting means includes means for defining a visible window area on said screen, said selected signals comprising those which create picture elements within said window, and means for changing the size and location of said window on said screen.

12. A method of color-correnting uncorrected video color component signals, said method comprising the steps of sequentially displaying video pictures composed from said uncorrected signals, locating scene changes by providing means for developing electrical scene-location signals, selecting a limited area of the video pictures for a scene, sampling black, gray, white, and color-indicative signals only within said limited area, correcting said uncorrected signals by using automatic color balancing means to automatically produce color correction signals for the displayed pictures, said correction signals being derived from said sampled black, gray, white, and color-indicative signals, digitally storing said color correction signals, and repeating said displaying, locating, selecting, sampling, correction making, and storing steps for each other scene requiring color correction, and reading said correction signals out of storage under the control of said scene location signals and using said correction signals to modify said uncorrected video color component signals.

13. A method as in claim 12 in which said automatic color correction means includes primary signal means for supplying signals representing the primary color components of said picture signals, and in which said correction means comprises automatic color balancing means for automatically balancing the primary color signals with respect to one another.

14. A method as in claim 12 including the step of stopping said sequential display step to provide a stationary display of a picture in a scene requiring color correction.

15. A color correction system for color correcting video picture signals representative of images stored by an large recording medium, comprising

means for producing video picture signals representative of each of the image stored by the image recording medium;

display means responsive to said video picture signals for displaying pictures corresponding to each of the images stored by the image recording medium;

discrimination means for discriminating video picture signals forming one area of the picture from video picture signals forming th remainder of the picture, said one area being smaller than the area of the entire picture, said one area being selectively movable within the picture;

means for determining color characteristics of video picture signals solely within said one area, said color characteristic determining means including means for determining the white, gray, and black levels of the luminance signal, means for determining the gain, gamma, and pedestal of each of the red, green, and blue signals, and means for comparing the gain, gamma, and pedestal of each of the red, green, and blue signals with the white, gray, and black levels of the luminance signal;

color correction means for generating color correction signals based upon said color characteristics;

storage means for storing said color correction signals;

location means for producing signals representative of the location of an initial image of each of a plurality of scenes recorded on said recording medium;

means for storing said location signals in said storage means;

readout means for reading form said storage means said color correction signals and said location signals; and

combining means responsive to the location signals read from said storage means for selectively combining color correction signals read from said storage means with said video picture signals.

16. A system as in claim 15, wherein said color characteristic determining means includes means for determining the white, gray, and black levels of the luminance signal, means for determining the gain, gamma, and pedestal of each of each of the red, green, and blue signals, and means for comparing the gain, gamma, and pedestal of each of the red, green, and blue signals with the white, gray, and black levels of the luminance signal.

17. A method of color-correcting video image signals stored on a record medium, said video image signals including red, green, and blue color signals as well as a luminance signal, said method comprising the steps of:

displaying on a monitor a picture formed from said video image signals;

using movable isolation means to isolate a selected portion of said picture having a specific graphic content from the remainder of said picture;

automatically detecting the color characteristics of the signals in said selected portion, said detecting step including the step of comparing each of said red, green, and blue color signals with said luminance signal;

utilizing the detected color characteristics in automatically developing color balance signals for said picture, said utilizing step including the step of automatically adjusting each of said red, green, and blue color signals to attain a predetermined relationship with said luminance signal;

storing said color correction signals in a computer memory;

repeating the foregoing steps for other pictures on said record medium;

developing and storing in said memory image location signals to locate on the record medium the images to which the corrections are to be applied; and

combining said viedeo image signals with said correction signals under the control of said location signals to form color corrected video images.

18. A method for color correcting video picture signals including red, green, and blue color signals as well as a luminance signal, comprising the steps of:

displaying on a video monitor screen a picture composed of said video picture signals;

selecting video picutre signals within a predetermined area which is less than the area of the entire picture;

selectibely changing the size and position of said predetermined area, whereby undesirable sampling areas may be excluded;

detecting the color characteristics of video picture signals within said predetermined area;

producing a detection signal in response to the detection in said predetermined area of a color condition requriring correction; and

automatically developing color correction signals in response to said detection signal, said developing step including the steps of comparing each of said red, green, and blue color signals with said luminance signal and adjusting each of said red, green, sand blue color signals to attain a predetermined relationship with said luminance signal.

19. Apparatus for color-correcting video picture signals, said apparatus comprising, in combination, display means for displaying on a video monitor screen a picture composed of said video picture signals, means for detecting the color characteristics of selected ones of said video picture signals, selecting means for selecting the ones of said video picture signals for which said color characteristics are detected as those which create picture elements within a predetermined area which is less than the area of the entire picture, means for selectively moving and locating said predetermined area within said picture, and means for developing correction signals for said selected picture signals;

wherein said video picture signals include a luminance signal; and

wherein said detecting means includes means for determining the white, gray, and black levels of said luminance signal within said predetermined area; and

wherein said video picture signals include red, green, and blue signals; and

wherein said detecting means further includes means for determining the gain, gamma, and pedestal of each of the red, green, and blue signals and means for comparing the gain, gamma, and pedestal of each of the red, green, and blue signals with the white, gray, and black levels of said luminance signal.