Automatic image cropping
First Claim
Patent Images
1. A method for automatically cropping an image, comprising:
- scaling down said image to a grid having four sides;
dividing said grid into a plurality of non-overlapping blocks;
calculating a mean intensity level for each of said blocks;
calculating a variance of an intensity level for each of said blocks;
creating a variance profile for said blocks;
calculating a threshold variance based on said variance profile;
selecting said blocks having said variance higher than said threshold variance as regions of interest;
cropping said regions of interest to a bounding rectangle;
calculating a profile of edge strengths for said blocks;
calculating a threshold edge strength from said profile; and
selecting said blocks having an edge strength higher than said threshold edge strength and not selected as regions of interest.
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Abstract
The present invention describes a method for automatic cropping of images containing regions where intensity levels are uniform and other regions where intensity levels vary considerably. An image to be automatically cropped is scaled down to a grid and divided into non-overlapping blocks. The mean and variance of intensity levels are calculated for each block. Based on the distribution of variances in the blocks, a threshold is selected for the variance. All blocks with a variance higher than this threshold variance are selected as regions of interest. The regions of interest are then cropped to a bounding rectangle.
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Citations
21 Claims
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1. A method for automatically cropping an image, comprising:
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scaling down said image to a grid having four sides; dividing said grid into a plurality of non-overlapping blocks; calculating a mean intensity level for each of said blocks; calculating a variance of an intensity level for each of said blocks; creating a variance profile for said blocks; calculating a threshold variance based on said variance profile; selecting said blocks having said variance higher than said threshold variance as regions of interest; cropping said regions of interest to a bounding rectangle; calculating a profile of edge strengths for said blocks; calculating a threshold edge strength from said profile; and selecting said blocks having an edge strength higher than said threshold edge strength and not selected as regions of interest. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for automatically cropping an image, comprising:
- means for scaling down said image to a grid having four sides;
means for dividing said grid into a plurality of non-overlapping blocks; means for calculating a mean intensity level for each said blocks; means for calculating a variance of an intensity level for each of said blocks; means for creating a variance profile for said blocks; means for calculating a threshold variance based on said variance profile; means for selecting said blocks having said variance higher than said threshold variance as regions of interest; means for cropping said regions of interest to a bounding rectangle; means for calculating a profile of edge strengths for said blocks; means for calculating a threshold edge strength from said profile; and means for selecting said blocks having an edge strength higher than said threshold edge strength and not selected as regions of interest. - View Dependent Claims (19, 20, 21)
- means for scaling down said image to a grid having four sides;
Specification