Image processing apparatus and control method thereof detecting from a histogram a gradation level whose frequency is a peak value
First Claim
1. An image processing apparatus, comprising:
- a histogram creation unit configured to create a histogram from an input image;
a detection unit configured to detect from the histogram, as a gradation level of interest, a gradation level whose frequency is a peak value, wherein a variation width of frequencies in a predetermined range including the gradation level of interest is smaller than a predetermined width;
a gradation correction parameter generation unit configured to generate a gradation correction parameter having an input-output gradation conversion characteristic that improves a gradation characteristic in a predetermined gradation range including the gradation level of interest compared to other gradation ranges on the bases of the detected result by the detection unit; and
a correction unit configured to correct the gradation of the image using the gradation correction parameter generated by the gradation correction parameter generation unit, whereinthe detection unit determines whether the variation width of frequencies in the predetermined range is smaller than the predetermined width or not based on (1) a frequency of a gradation level that is a target for which it is to be determined whether the gradation level is a gradation level of interest or not, and (2) a value obtained by multiplying a total of frequencies of a respective n number of gradation levels, where n is an integer of 1 or greater, at lower and higher sides of the gradation level that is the target, excluding the gradation level that is the target, by a predetermined value.
1 Assignment
0 Petitions
Accused Products
Abstract
An image processing apparatus includes a histogram creation unit that creates a histogram from an input image, a detection unit that detects a gradation level of interest from the histogram, a gradation correction parameter generation unit that generates a gradation correction parameter to improve a gradation characteristic in a gradation range around the gradation level of interest, and a correction unit that corrects the gradation of the image using the gradation correction parameter. The detection unit detects, as the gradation level of interest, a gradation level whose frequency is a peak value equal to or more than a predetermined threshold, and which has variation width of frequencies in a predetermined range including this gradation level to be smaller than a predetermined width in the histogram.
30 Citations
26 Claims
-
1. An image processing apparatus, comprising:
-
a histogram creation unit configured to create a histogram from an input image; a detection unit configured to detect from the histogram, as a gradation level of interest, a gradation level whose frequency is a peak value, wherein a variation width of frequencies in a predetermined range including the gradation level of interest is smaller than a predetermined width; a gradation correction parameter generation unit configured to generate a gradation correction parameter having an input-output gradation conversion characteristic that improves a gradation characteristic in a predetermined gradation range including the gradation level of interest compared to other gradation ranges on the bases of the detected result by the detection unit; and a correction unit configured to correct the gradation of the image using the gradation correction parameter generated by the gradation correction parameter generation unit, wherein the detection unit determines whether the variation width of frequencies in the predetermined range is smaller than the predetermined width or not based on (1) a frequency of a gradation level that is a target for which it is to be determined whether the gradation level is a gradation level of interest or not, and (2) a value obtained by multiplying a total of frequencies of a respective n number of gradation levels, where n is an integer of 1 or greater, at lower and higher sides of the gradation level that is the target, excluding the gradation level that is the target, by a predetermined value. - View Dependent Claims (2, 3, 4, 5, 11, 12, 13)
-
-
6. A controlling method of an image processing apparatus, comprising:
-
a histogram creation step of creating a histogram from an input image; a detection step of detecting from the histogram, as a gradation level of interest, a gradation level whose frequency is a peak value, wherein a variation width of frequencies in a predetermined range including the gradation level of interest is smaller than a predetermined width; a gradation correction parameter generation step of generating a gradation correction parameter having an input-output gradation conversion characteristic that improves a gradation characteristic in a predetermined gradation range including the gradation level of interest compared to other gradation ranges on the bases of the detected result by the detection step; and a correction step of correcting the gradation of the image using the gradation correction parameter generated by the gradation correction parameter generation step, wherein the detection step determines whether the variation width of frequencies in the predetermined range is smaller than the predetermined width or not based on (1) a frequency of a gradation level that is a target for which it is to be determined whether the gradation level is a gradation level of interest or not, and (2) a value obtained by multiplying a total of frequencies of a respective n number of gradation levels, where n is an integer of 1 or greater, at lower and higher sides of the gradation level that is the target, excluding the gradation level that is the target, by a predetermined value. - View Dependent Claims (7, 8, 9, 10, 14, 15, 16)
-
-
17. An image processing apparatus, comprising:
-
a histogram creation unit configured to divide an input image into a plurality of areas, and create a histogram for each area; a detection unit configured to detect from the histogram of each of the areas, as a gradation level of interest, a gradation level whose frequency is a peak value, wherein a variation width of frequencies in a predetermined range including the gradation level of interest is smaller than a predetermined width; a gradation correction parameter generation unit configured to generate, for each of the areas, a gradation correction parameter having an input-output gradation conversion characteristic that improves a gradation characteristic in a predetermined gradation range including the gradation level of interest of the each area compared to other gradation ranges on the bases of the detected result by the detection unit; and a correction unit configured to correct the gradation of the image by, for each pixel, using a gradation correction parameter generated for a first area to which the pixel belongs, a gradation correction parameter generated for a second area adjacent to the first area, and weights based on a positional relationship between the pixel and the first area and a positional relationship between the pixel and the second area. - View Dependent Claims (18, 19, 20, 21)
-
-
22. A controlling method of an image processing apparatus, comprising:
-
a histogram creation step of dividing an input image into a plurality of areas, and creating a histogram for each area; a detection step of detecting from the histogram of each of the areas, as a gradation level of interest, a gradation level whose frequency is a peak value, wherein a variation width of frequencies in a predetermined range including the gradation level of interest is smaller than a predetermined width; a gradation correction parameter generation step of generating, for each of the areas, a gradation correction parameter having an input-output gradation conversion characteristic that improves a gradation characteristic in a predetermined gradation range including the gradation level of interest of the each area compared to other gradation ranges on the bases of the detected result by the detection step; and a correction step of correcting the gradation of the image by, for each pixel, using a gradation correction parameter generated for a first area to which the pixel belongs, a gradation correction parameter generated for a second area adjacent to the first area, and weights based on a positional relationship between the pixel and the first area and a positional relationship between the pixel and the second area. - View Dependent Claims (23, 24, 25, 26)
-
Specification