IMAGE PROCESSING DEVICE CAPABLE OF SUPRESSING OVER-CORRECTION IN RETINEX PROCESS
First Claim
1. An image processing device comprising:
- a reflectance-component calculating portion that calculates a reflectance component based both on a pixel value of a subject pixel in an original image and on an average luminance of peripheral pixels around the subject pixel, the reflectance component being indicative of brightness of the subject pixel relative to the peripheral pixels; and
a first pixel-value generating portion that generates a pixel value of an output image when the reflectance component indicates that the subject pixel is darker than the peripheral pixels, the first pixel-value generating portion comprising;
a first lower-range generating portion that generates the pixel value of the output image based on a first nonlinear function in a first lower range where the pixel value of the subject pixel is lower than a first predetermine value; and
a first upper-range generating portion that generates the pixel value of the output image based on a first monotonically increasing function in a first upper range where the pixel value of the subject pixel is greater than or equal to the first predetermine value, the pixel value of the output image increasing toward a first maximum output luminance value as the pixel value of the subject pixel increases, the first maximum output luminance value being greater than a luminance value obtained by correcting a maximum pixel value of the original image based on the first nonlinear function, the first maximum output luminance value being proximate to the maximum pixel value of the original image.
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Abstract
A first lower-range generating portion generates a pixel value of an output image based on a first nonlinear function in a first lower range where a pixel value of a subject pixel is lower than a predetermine value. The first upper-range generating portion generates the pixel value of the output image based on a first monotonically increasing function in a first upper range where the pixel value of the subject pixel is greater than or equal to the predetermine value. The pixel value of the output image increases toward a first maximum output luminance value as the pixel value of the subject pixel increases. The first maximum output luminance value is greater than a luminance value obtained by correcting a maximum pixel value of the original image based on the first nonlinear function. The first maximum output luminance value is proximate to the maximum pixel value of the original image.
16 Citations
25 Claims
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1. An image processing device comprising:
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a reflectance-component calculating portion that calculates a reflectance component based both on a pixel value of a subject pixel in an original image and on an average luminance of peripheral pixels around the subject pixel, the reflectance component being indicative of brightness of the subject pixel relative to the peripheral pixels; and a first pixel-value generating portion that generates a pixel value of an output image when the reflectance component indicates that the subject pixel is darker than the peripheral pixels, the first pixel-value generating portion comprising; a first lower-range generating portion that generates the pixel value of the output image based on a first nonlinear function in a first lower range where the pixel value of the subject pixel is lower than a first predetermine value; and a first upper-range generating portion that generates the pixel value of the output image based on a first monotonically increasing function in a first upper range where the pixel value of the subject pixel is greater than or equal to the first predetermine value, the pixel value of the output image increasing toward a first maximum output luminance value as the pixel value of the subject pixel increases, the first maximum output luminance value being greater than a luminance value obtained by correcting a maximum pixel value of the original image based on the first nonlinear function, the first maximum output luminance value being proximate to the maximum pixel value of the original image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A storage medium storing a set of program instructions executable on an image processing device, the set of program instructions comprising:
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(a) calculating a reflectance component based both on a pixel value of a subject pixel in an original image and on an average luminance of peripheral pixels around the subject pixel, the reflectance component being indicative of brightness of the subject pixel relative to the peripheral pixels; and (b) generating a pixel value of an output image when the reflectance component indicates that the subject pixel is darker than the peripheral pixels, the instructions (b) comprising; (c) generating the pixel value of the output image based on a first nonlinear function in a first lower range where the pixel value of the subject pixel is lower than a first predetermine value; and (d) generating the pixel value of the output image based on a first monotonically increasing function in a first upper range where the pixel value of the subject pixel is greater than or equal to the first predetermine value, the pixel value of the output image increasing toward a first maximum output luminance value as the pixel value of the subject pixel increases, the first maximum output luminance value being greater than a luminance value obtained by correcting a maximum pixel value of the original image based on the first nonlinear function, the first maximum output luminance value being proximate to the maximum pixel value of the original image. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification