Brightness adjustment of images using digital scene analysis
First Claim
1. A system for processing a digital image signal representing an image, said image containing both luminance data and chrominance data, to map the luminance data to a tonal reproduction capability of a destination application, said system comprising:
- means for acquiring the image signal and separating the luminance data from the image signal;
an input buffer for storing said luminance data;
means for reading and partitioning said luminance data from said input buffer into a plurality of image blocks of predetermined size;
means for determining an average luminance block value for each said image block;
means for selectively combining preselected ones of said image blocks of said luminance data into sectors;
means for determining a difference between a maximum said average luminance block value and a minimum said average luminance block value of each sector, and comparing said difference with a predetermined threshold value;
means for identifying an active sector as one where said difference exceeds said predetermined threshold value;
means for determining an average luminance sector value for each active sector as an average of the maximum and minimum average luminance block values of each sector;
means for weighting and counting a number of active sectors corresponding to each said average luminance sector value;
means for generating a histogram of said number of active sectors versus said average luminance sector values;
means for selecting a tonal reproduction range corresponding to the tonal reproduction capability of the destination application; and
means for mapping said average luminance sector values into said tonal reproduction range of said destination application and generating a digital output signal corresponding to said mapping.
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Accused Products
Abstract
A system and method for processing a digital image signal which represents an image can be made to optimally map luminance values versus a tonal reproduction capability of a destination application. Specifically, the system includes a device for partitioning the image into blocks, then combining certain blocks into sectors. An average luminance block value is determined for each block and a difference is determined between the maximum and minimum average luminance block values for each sector. If the difference exceeds a predetermined threshold value, then the sector is labeled as an active sector and an average luminance sector value is obtained from maximum and minimum average luminance block values. All weighted counts of active sectors of the image are plotted versus the average luminance sector values in a histogram, then the histogram is shifted via some predetermined criterion so that the average luminance sector values of interest will fall within a destination window corresponding to the tonal reproduction capability of a destination application.
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Citations
16 Claims
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1. A system for processing a digital image signal representing an image, said image containing both luminance data and chrominance data, to map the luminance data to a tonal reproduction capability of a destination application, said system comprising:
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means for acquiring the image signal and separating the luminance data from the image signal; an input buffer for storing said luminance data; means for reading and partitioning said luminance data from said input buffer into a plurality of image blocks of predetermined size; means for determining an average luminance block value for each said image block; means for selectively combining preselected ones of said image blocks of said luminance data into sectors; means for determining a difference between a maximum said average luminance block value and a minimum said average luminance block value of each sector, and comparing said difference with a predetermined threshold value; means for identifying an active sector as one where said difference exceeds said predetermined threshold value; means for determining an average luminance sector value for each active sector as an average of the maximum and minimum average luminance block values of each sector; means for weighting and counting a number of active sectors corresponding to each said average luminance sector value; means for generating a histogram of said number of active sectors versus said average luminance sector values; means for selecting a tonal reproduction range corresponding to the tonal reproduction capability of the destination application; and means for mapping said average luminance sector values into said tonal reproduction range of said destination application and generating a digital output signal corresponding to said mapping. - View Dependent Claims (2, 5, 6, 7, 11)
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3. An image processing method for processing a digital image signal representing an image, said image containing both luminance data and chrominance data, to optimally map the luminance data to a tonal reproduction capability of a destination application, said method comprising the steps of:
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acquiring the image signal and separating the luminance data from the image signal; storing said luminance data in an input buffer; reading and partitioning said luminance data from said input buffer into a plurality of image blocks of predetermined size; determining an average luminance block value for each said image block; combining preselected ones of said image blocks of said luminance data into sectors; determining a difference between a maximum said average luminance block value and a minimum said average luminance block value of each sector, and comparing said difference with a predetermined threshold value; identifying an active sector as one where said difference exceeds said predetermined threshold value; determining an average luminance sector value for each active sector as an average of the maximum and minimum average luminance block values of each sector; weighting and counting a number of active sectors corresponding to each said average luminance sector value; generating a histogram of said number of active sectors versus said average luminance sector values; selecting a tonal reproduction range corresponding to the tonal reproduction capability of the destination application; and mapping said average luminance sector values into said tonal reproduction range of said destination application and generating a digital output signal corresponding to said mapping. - View Dependent Claims (4, 8, 9, 10, 12)
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13. A method for processing a digital input image and exporting the processed image to a downstream application having a given tonal reproduction range, said method comprising the steps of:
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partitioning the input image into sectors of predetermined size; determining for each said sector a luminance activity defined as a difference in luminance between at least two pixels within each said sector; generating an average luminance value for each said sector having said luminance activity greater than a predetermined threshold value; generating a count of sectors having each said average luminance value; mapping said average luminance values, having counts falling within a predetermined selection criterion, into the tonal reproduction range; and exporting the processed image to the downstream application in response to said mapped luminance values. - View Dependent Claims (14)
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15. A system for processing a digital input image and exporting the processed image to a destination application having a given tonal reproduction range, said system comprising:
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means for partitioning the input image into sectors of predetermined size; means for determining for each said sector a luminance activity defined as a difference in luminance between at least two pixels within each said sector; means for generating an average luminance value for each said sector having said luminance activity greater than a predetermined threshold value; means for generating a count of sectors having each said average luminance value; means for mapping said average luminance values, having counts falling within a predetermined selection criterion, into the tonal reproduction range; and means for exporting the processed image on the destination application in response to said mapped luminance values. - View Dependent Claims (16)
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Specification