EP0824246A2
Expired / Lapsed
EP
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Automatic image cropping
Assignee: Xerox Corp
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Filing: 1997-07-25
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Granted: —
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Expires: 2017-07-25
Abstract
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 an intensity level 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. <IMAGE> <IMAGE> <IMAGE> <IMAGE>
Inventors
- 👤 James E. Bollman
- 👤 Ramana L. Rao
- 👤 Dennis L. Venable
- 👤 Reiner Eschbach
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 10:39
CPC Classifications
G; G06; G06T; G06T7/00; G06T7/70
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
90 words
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, and cropping said regions of interest to a bounding rectangle.
Claim 2
Dependent Claim
46 words
The automatic image cropping method of claim 1, wherein said mean intensity level,
µ, is calculated by the formula wherein g i is the intensity level of the ith pixel in the block, and N is a height and a width of each block
in pixels.
Claim 3
Dependent Claim
17 words
The automatic image cropping method of claim 2, wherein said variance, σ, is
calculated by the formula
Claim 4
Dependent Claim
33 words
The automatic image cropping method of claim 1, wherein said threshold variance is
calculated as a point on a variance profile curve furthest from a line joining a minimum and a maximum
variance.
Claim 5
Dependent Claim
18 words
The automatic image cropping method of claim 4, wherein said threshold variance is
adjusted by a selectivity factor.
Claim 6
Dependent Claim
26 words
The automatic image cropping method of any one of claims 1 to 5, further comprising
marking unselected blocks inside selected regions for further post-processing image operations.
Claim 7
Dependent Claim
28 words
The automatic image cropping method of claim 1, further comprising removing details
corresponding to noise in the background of the cropped image to provide a better bounding rectangle.
Claim 8
Dependent Claim
53 words
The automatic image cropping method of any one of claims 1 to 7, further comprising: 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.
Claim 9
Independent Claim
106 words
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 of 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, and means for cropping said regions of interest to a bounding rectangle.
Claim 10
Dependent Claim
23 words
The apparatus of claim 9, further comprising an input means for acquiring said image
and an output means for storing said autocropped image.
References Cited (Backward Citations)
No citation records indexed.
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