Backlight image determining apparatus, backlight image determining method, backlight image correction apparatus, and backlight image correction method

• US 20070237392A1
• Filed: 03/29/2007
• Published: 10/11/2007
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Ohara, Taira
• Granted Patent: US 8,014,602 B2
• Time in Patent Office: Days
• US Class Current: 382/171
• CPC Class Codes: H04N 1/4074 using histograms

Abstract

A backlight image determining apparatus includes: (A) a histogram data generation section that, based on data of pixels constituting an image to be determined, generates data of histograms for respective colors, the histograms representing a distribution of the number of pixels in respect to density values of the respective colors of those pixels; (B) an attribute information obtaining section that obtains, for each color, attribute information relating to a first small region and a second small region by partitioning regions given by the histograms for the respective colors into at least three small regions according to the magnitude of the density values, based on the data of the histograms for the respective colors generated by the histogram data generation section, selecting for each color at least one small region from the at least three small regions as the first small region, and selecting, from the at least three small regions, for each color at least one small region whose density values are larger than those of the first small region and which is not adjacent to the first small region, as the second small region; and (C) a determination section that determines whether the image to be determined is a backlight image, based on the attribute information relating to the first small region for each color and the attribute information relating to the second small region for each color, which is obtained with the attribute information obtaining section.

Claims

1. A backlight image determining apparatus comprising:

a histogram data generation section that, based on data of pixels constituting an image to be determined, generates data of histograms for respective colors, the histograms representing a distribution of the number of pixels in respect to density values of the respective colors of those pixels;

an attribute information obtaining section that obtains, for each color, attribute information relating to a first small region and a second small region by partitioning regions given by the histograms for the respective colors into at least three small regions according to the magnitude of the density values, based on the data of the histograms for the respective colors generated by the histogram data generation section, selecting for each color at least one small region from the at least three small regions as the first small region, and selecting, from the at least three small regions, for each color at least one small region whose density values are larger than those of the first small region and which is not adjacent to the first small region, as the second small region; and

a determination section that determines whether the image to be determined is a backlight image, based on the attribute information relating to the first small region for each color and the attribute information relating to the second small region for each color, which is obtained with the attribute information obtaining section.

2. A backlight image determining apparatus according to claim 1,

wherein the at least three small regions include at least two small regions that have at least one of the same pixel number and the same area, and

the first small region is the small region with the smallest density values among the at least two small regions.

3. A backlight image determining apparatus according to claim 1,

wherein the at least three small regions include at least two small regions that have at least one of the same pixel number and the same area, and

the second small region is the small region with the largest density values among the at least two small regions.

4. A backlight image determining apparatus according to claim 1,

wherein the attribute information obtaining section obtains a maximum value of the density values of the first small region or the second small region as the attribute information of the first small region or the second small region.

5. A backlight image determining apparatus according to claim 1,

wherein the determination section determines whether the image to be determined is a backlight image based on a result of a comparison between the attribute information relating to the first small region for each color and the attribute information relating to the second small region for each color.

6. A backlight image determining apparatus according to claim 5,

wherein the determination section determines whether the image to be determined is a backlight image by comparing a value that is obtained based on a value obtained for each color as the attribute information relating to the first small region for each color and a value that is obtained based on a value obtained for each color as the attribute information relating to the second small region for each color.

7. A backlight image determining apparatus according to claim 6,

wherein the determination section determines whether the image to be determined is a backlight image based on a difference between a value that is obtained based on a value obtained for each color as the attribute information relating to the first small region for each color and a value that is obtained based on a value obtained for each color as the attribute information relating to the second small region for each color.

8. A backlight image determining apparatus according to claim 7,

wherein the determination section determines whether the image to be determined is a backlight image by comparing the difference with a predetermined threshold value.

9. A backlight image determining method comprising:

generating, based on data of pixels constituting an image to be determined, data of histograms for respective colors, the histograms representing a distribution of the number of pixels in respect to density values of the respective colors of those pixels;

partitioning regions given by the histograms for the respective colors into at least three small regions according to the magnitude of the density values, based on the data of the histograms for the respective colors generated by the histogram data generation section;

selecting for each color at least one small region from the at least three small regions as a first small region, and selecting, from the at least three small regions, for each color at least one small region whose density values are larger than those of the first small region and which is not adjacent to the first small region, as a second small region;

obtaining, for each color, attribute information relating to the first small region and the second small region; and

determining whether an image to be determined is a backlight image, based on the attribute information relating to the first small region obtained for each color and the attribute information relating to the second small region obtained for each color.

10. A backlight image enhancement apparatus comprising:

a histogram data generation section that, based on data of pixels constituting an image, generates data of histograms for respective colors, the histograms representing a distribution of the number of pixels in respect to density values for the respective colors of those pixels;

an attribute information obtaining section that obtains, for each color, attribute information for a relevant small region by partitioning, based on the histogram data for the respective colors generated with the histogram data generation section, the regions given by the histograms for the respective colors into at least two small regions according to the magnitude of the density values and selecting at least one small region from the at least two small regions;

an enhancement information generation section that generates enhancement information for performing a backlight enhancement process on the image based on the attribute information for each color obtained with the attribute information obtaining section; and

a backlight enhancement processing section that performs a backlight enhancement process on the image, based on the enhancement information generated with the enhancement information generation section.

11. A backlight image enhancement apparatus according to claim 10,

wherein the at least two small regions include at least two small regions that have at least one of the same pixel number and the same area, and

the attribute information obtaining section obtains the attribute information respectively from the at least two small regions having at least one of the same pixel number and the same area.

12. A backlight image enhancement apparatus according to claim 10,

wherein the attribute information obtaining section obtains, for each color, an average value of the density values for the at least one small region as the attribute information.

13. A backlight image enhancement apparatus according to claim 12,

wherein the enhancement information generation section obtains information relating to the luminance of the at least one small region based on an average value of the density values of each color obtained with the attribute information obtaining section, and generates the enhancement information based on information relating to this luminance.

14. A backlight image enhancement apparatus according to claim 13,

wherein the enhancement information generation section obtains an average value of the luminance of the individual pixels for the at least one small region as the information relating to the luminance.

15. A backlight image enhancement apparatus according to claim 14,

wherein the enhancement information generation section generates the enhancement information based on a value obtained by adding at least one of the average values of the luminance obtained respectively for the at least one small region to the average value of the overall luminance of the image.

16. A backlight image enhancement apparatus according to claim 10,

wherein the backlight enhancement processing section converts the density values of the respective pixels constituting the image when performing the backlight enhancement process based on the enhancement information.

17. A backlight image enhancement apparatus according to claim 16,

wherein the enhancement information generation section generates, as the enhancement information, information relating to a correspondence relationship between the density values prior to conversion with the backlight enhancement processing section and the density values after conversion with the backlight enhancement processing section.

18. A method for backlight image enhancement, comprising:

generating, based on data of pixels constituting an image, data of histograms for respective colors, the histograms representing a distribution of the number of pixels in respect to density values of the respective colors of those pixels;

partitioning regions given by the histograms for the various colors into at least two small regions according to the magnitude of the density values, based on the data of the histograms for each color generated with the histogram data generation section;

obtaining, for each color, attribute information for that small region by selecting at least one small region from the at least two small regions;

generating enhancement information for performing a backlight enhancement process on the image based on the obtained attribute information for each color; and

performing a backlight enhancement process on the image, based on the generated enhancement information.