Color correction device and color correction method

• US 20060120598A1
• Filed: 11/14/2003
• Published: 06/08/2006
• Est. Priority Date: 11/14/2003
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Matoba, Narihiro, Takahashi, Mariko
• Granted Patent: US 7,599,551 B2
• Time in Patent Office: Days
• US Class Current: 382/167
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 5/009 Global, i.e. based on properties of the image as a whole applied in cameras using an electronic image sensor H04N23/80, H04N23/70
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

A color correction apparatus is provided including a color correction means 1 for making a color correction to an input image signal 101, and a color gamut compression means 2 for performing color gamut compression on the color-corrected input image signal based on color reproduction characteristics data 103 describing color reproduction characteristics so that the color-corrected image data outputted from the color correction means 1 has a chromaticity range which is contained in a color reproduction region which is based on the color reproduction characteristics.

Claims

1. A color correction apparatus comprising:

a color correction means for making a color correction to an input image signal; and

a color gamut compression means for performing color gamut compression on the color-corrected input image signal based on data describing color reproduction characteristics so that the color-corrected image data outputted from said color correction means has a chromaticity range which is contained in a color reproduction region which is based on said color reproduction characteristics.

2. The color correction apparatus according to claim 1, characterized in that said color correction means is provided with a color reproduction correction means for converting a chromaticity range of the input image signal based on the data describing the color reproduction characteristics.

3. The color correction apparatus according to claim 1, characterized in that said color correction means is provided with a hue conversion means for converting a hue of the input image signal based on data describing the hue to be converted and an amount of adjustment.

4. The color correction apparatus according to claim 1, characterized in that said color gamut compression means performs the color gamut compression on the color-corrected input image signal based on data describing color reproduction characteristics of a color image display apparatus.

5. The color correction apparatus according to claim 1, characterized in that said color gamut compression means determines a hue of the image data converted by said color correction means, acquires both a chromaticity range indicating said color reproduction characteristics corresponding to a hue of the input image signal, and a chromaticity range indicating said color reproduction characteristics corresponding to the hue of the image data converted by said color correction means based on the data describing the color reproduction characteristics, determines a convergence point from both a color reproduction region defined by the chromaticity range indicating said color reproduction characteristics corresponding to the hue of said input image signal, and a color reproduction region defined by the chromaticity range indicating said color reproduction characteristics corresponding to the hue of the image data converted by said color correction means, and performs the color gamut compression on the color-corrected image data outputted from said color correction means in a direction of said convergence point.

6. The color correction apparatus according to claim 5, characterized in that said color gamut compression means acquires the chromaticity range indicating the color reproduction characteristics corresponding to the hue of the input image signal and the chromaticity range indicating the color reproduction characteristics corresponding to the hue of the image data converted by said color correction means, when the color reproduction region defined by the chromaticity range indicating the color reproduction characteristics corresponding to the hue of said input image signal and the color reproduction region defined by the chromaticity range indicating the color reproduction characteristics corresponding to the hue of said converted image data are expressed in a color space, determines a point of intersection where the color reproduction region for the hue of said input image signal and the color reproduction region for the hue of said converted image data intersect in a plane showing value and saturation, determines a convergence point having a value equal to that of said point of intersection and being on a value axis showing said color space, and compresses the color reproduction region for the hue of said input image signal toward said convergence point.

7. The color correction apparatus according to claim 5, characterized in that said color gamut compression means acquires the chromaticity range indicating the color reproduction characteristics corresponding to the hue of the input image signal and the chromaticity range indicating the color reproduction characteristics corresponding to the hue of the image data converted by said color correction means, when the color reproduction region defined by the chromaticity range indicating the color reproduction characteristics corresponding to the hue of said input image signal and the color reproduction region defined by the chromaticity range indicating the color reproduction characteristics corresponding to the hue of said converted image data are expressed in a color space, determines a point of intersection where the color reproduction region for the hue of said input image signal and the color reproduction region for the hue of said converted image data intersect in a plane showing value and saturation, defines an arbitrary point on a straight line connecting said point of intersection with the chromaticity range indicating the color reproduction characteristics of the hue indicated by said converted image data, determines a convergence point having a value equal to that of said arbitrary point and being on a value axis showing said color space, and compresses the color reproduction region for the hue of said input image signal toward said convergence point.

8. The color correction apparatus according to claim 1, characterized in that said color gamut compression means acquires a chromaticity range indicating first color reproduction characteristics of a hue of the input image signal based on data indicating the first color reproduction characteristics and describing color reproduction characteristics of a color image display apparatus, acquires a chromaticity range indicating second color reproduction characteristics data of a hue indicated by the image data converted by said color correction means based on data indicating the second color reproduction characteristics and describing color reproduction characteristics of an original image showing a color tone of a visually-identified image, acquires a convergence point from both a color reproduction region defined by the chromaticity range indicating the first color reproduction characteristics of the hue of said input image signal, and a color reproduction region defined by the chromaticity range indicating the second color reproduction characteristics data of the hue indicated by said corrected image data, and compresses the color reproduction region defined by the chromaticity range indicating the first color reproduction characteristics of the hue of said input image signal toward the convergence point.

9. The color correction apparatus according to claim 1, characterized in that said color correction means acquires color adjustment data describing both a hue to be value-converted and an amount of adjustment for value, and has a value conversion means for convert a value indicated by the input image signal based on said color adjustment data, and said color gamut compression means acquires a chromaticity range indicating color reproduction characteristics of a hue of the input image signal based on the data describing the color reproduction characteristics, acquires a value-converted chromaticity range with reference to a look-up table in which a hue value-converted by said value conversion means is described, acquires a convergence point from both a color reproduction region defined by the chromaticity range indicating the color reproduction characteristics of the hue of said input image signal and a color reproduction region defined by said value-converted chromaticity range, and compresses the color reproduction region defined by the chromaticity range indicating the color reproduction characteristics of the hue of said input image signal toward the convergence point.

10. The color correction apparatus according to claim 9, characterized in that said value conversion means determines both a value of a hue selected by a user and a value of a hue in a vicinity of the selected hue using a value look-up table in which a value-converted value is described.

11. The color correction apparatus according to claim 9, characterized in that said color correction means is provided with a chromaticity range conversion means for transforming a value axis indicating a color space, and said color gamut compression means acquires a convergence point on the value axis which is converted by said chromaticity range conversion means from both the color reproduction region defined by the chromaticity range indicating the color reproduction characteristics of the hue of the input image signal expressed in said color space and the color reproduction region defined by the value-converted chromaticity range.

12. A color correction apparatus comprising:

a saturation conversion means for converting a saturation of an input image signal based on both color adjustment data describing both a hue to be saturation-converted and an amount of adjustment, and color reproduction characteristics data describing color reproduction characteristics of a color image display apparatus.

13. A color correction method comprising:

a step of converting a hue indicated by image data using a hue conversion means;

a step of converting a value indicated by the image data acquired from said hue conversion means using a value conversion means;

a step of converting a saturation indicated by the image data acquired from said value conversion means based on color reproduction characteristics data describing color reproduction characteristics of a color image display apparatus using a saturation conversion means; and

a step of carrying out color gamut compression so that the image data acquired from said saturation conversion means has a chromaticity range which is contained in a color reproduction region which is based on said color reproduction characteristics using a color gamut compression means.