Method and circuit arrangement for enhancing the contrast of an image
First Claim
1. A method for enhancing the contrast of an image, the image being composed of a multiplicity of pixels each having a specific brightness value, the method comprising the steps of:
- a) determining a mean brightness valvue of the individual pixels of the image;
b) processing the brightness values of those pixels of the image that have a brightness less than or equal to the mean brightness value, in accordance with a first transformation function;
c) processing the brightness values of those pixels of the image that have a brightness greater than the mean brightness value, in accordance with a second transformation function; and
d) outputting the pixels having the brightness values processed in steps b) and c), respectively, in the form of a transformed output image;
wherein a first straight-line function having a first variable slope factor is the first transformation function and the second transformation function is a second straight-line function having a second variable slope factor, the first slope factor of the first straight-line function and the second slope factor of the second straight-line function being determined by an analysis of the transformed output image.
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Abstract
A method and apparatus for enhancing the contrast of an image, where pixels of the image having a brightness less than a mean brightness of the image are transformed in accordance with a first straight-line function, and pixels having a brightness greater than the mean brightness of the image are transformed in accordance with a second straight-line function. Variable slope factors of the two straight-line functions are determined by an analysis of the brightness distribution of the transformed output image. The pixels, thus transformed, produce the contrast-enhanced output image.
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Citations
28 Claims
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1. A method for enhancing the contrast of an image, the image being composed of a multiplicity of pixels each having a specific brightness value, the method comprising the steps of:
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a) determining a mean brightness valvue of the individual pixels of the image;
b) processing the brightness values of those pixels of the image that have a brightness less than or equal to the mean brightness value, in accordance with a first transformation function;
c) processing the brightness values of those pixels of the image that have a brightness greater than the mean brightness value, in accordance with a second transformation function; and
d) outputting the pixels having the brightness values processed in steps b) and c), respectively, in the form of a transformed output image;
wherein a first straight-line function having a first variable slope factor is the first transformation function and the second transformation function is a second straight-line function having a second variable slope factor, the first slope factor of the first straight-line function and the second slope factor of the second straight-line function being determined by an analysis of the transformed output image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A circuit arrangement for enhancing the contrast of an image, wherein the image is comprised of a plurality of individual pixels each having a specific brightness value, the circuit arrangement comprising:
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a mean value calculation unit configured to determine a mean brightness value of the individual pixels of the image;
a first transformation function calculation unit configured to determine a first transformation function that is used to process a first set of pixels of the image having a brightness less than or equal to the mean brightness value;
a second transformation function calculation unit configured to determine a second transformation function that is used to process a second set of pixels of the image having a brightness greater than the mean brightness value; and
an image processing unit configured for processing the brightness values of the first set of pixels of the image in accordance with the first transformation function and the brightness values of the second set of pixels of the image in accordance with the second transformation function and for outputting the processed pixels in the form of a transformed output image;
wherein the first and second transformation function calculation units are further configured to respectively determine a first straight-line function and a second straight-line function by analyzing the transformed output image;
the first and second straight-line functions respectively having a variable slope factor as the corresponding first and second transformation functions. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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Specification