Object extraction in images
First Claim
1. A method for extracting an object from an image, comprising:
- forming an image containing an object, said method further comprising;
a. disposing a pair of transverse axes on said object;
b. choosing a pixel on one of said axes, said pixel being denominated the reference pixel;
c. choosing a neighboring pixel, said neighboring pixel being located away from said reference pixel in a direction transverse to said one of said axes;
d. determining the dropoff in brightness between said neighboring pixel and said reference pixel;
e. replacing said reference pixel by said neighboring pixel;
f. repeating steps c through e a preselected number of times;
g. selecting a preselected number L, and selecting the L largest of said dropoffs; and
h. using said largest of said dropoffs to determine a threshold for extracting said object.
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Abstract
A method and apparatus for extracting an object from an image, in which one locates a pixel within the image (the "central" pixel), and then sequentially compares the brightness of neighboring pixels, proceeding outward from the central pixel. In so doing, one determines the largest dropoffs in brightness between neighboring pixels, and uses these to determine a brightness threshold for extracting pixels belonging to the object. In a preferred embodiment, one determines the threshold by comparing the largest dropoffs, identifies overlapping regions of brightness level common to all the dropoffs, and sets the threshold at the midpoint of the common overlapping region.
29 Citations
13 Claims
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1. A method for extracting an object from an image, comprising:
forming an image containing an object, said method further comprising; a. disposing a pair of transverse axes on said object; b. choosing a pixel on one of said axes, said pixel being denominated the reference pixel; c. choosing a neighboring pixel, said neighboring pixel being located away from said reference pixel in a direction transverse to said one of said axes; d. determining the dropoff in brightness between said neighboring pixel and said reference pixel; e. replacing said reference pixel by said neighboring pixel; f. repeating steps c through e a preselected number of times; g. selecting a preselected number L, and selecting the L largest of said dropoffs; and h. using said largest of said dropoffs to determine a threshold for extracting said object. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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2. An apparatus for extracting an object from an image, said image containing an object, comprising:
an imager for forming said image, and a processor, said processor being adapted for; disposing of a pair of transverse axes on said object; choosing a pixel on one of said axes, said pixel being denominated the reference pixel; choosing a neighboring pixel, said neighboring pixel being located away from said reference pixel in a direction transverse to said one of said axes; determining the dropoff in brightness between said neighboring pixel and said reference pixel; replacing said reference pixel by said neighboring pixel; repeating said choosing a pixel, choosing a neighboring pixel, determining said dropoff, and said replacing said reference pixel, said repeating being done a preselected number of times; said apparatus further comprising; means for selecting a preselected number L, and selecting the L largest of said dropoffs; and means for using said largest of said dropoffs to determine a threshold for extracting said object.
Specification