Method and device for binary segmentation of a signal representing a digital image with a threshold obtained using a histogram
First Claim
1. A method of binary segmentation of a video image which includes at least one target object and at least one noise element against a common background;
- said image being represented by a video signal corresponding to grey levels of respective pixels therein, a target object having pixel grey levels which differ from the pixel grey levels of the background and of noise elements;
said method comprising the steps of;
(a) thresholding the video signal at respective grey threshold levels so as to derive for each threshold level a digital signal representing a binary segmented image corresponding to that threshold level;
(b) determining from each of the digital signals, by labelling, a count of the number of objects in the corresponding binary segmented image, and storing the respective counts applicable to the respective binary segmented images;
(c) forming a histogram of the stored counts as a function of the respective threshold levels;
(d) automatically determining from said histogram a segmentation threshold applicable to said video image for distinguishing target objects from background and noise elements therein; and
(e) applying said segmentation threshold to said video signal to derive a binary segmented video signal representing a binary segmented form of said video image in which target objects are distinguished from background and noise elements therein.
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Abstract
Method and device for binary segmentation of a digital image with a threshold obtained using a histogram to obtain a binary segmented digital image. The digital image is thresholded a number of grey levels, and the number of objects which appear when the digital image is thresholded at each of the grey levels is counted. A histogram of the number of objects per grey level is constructed, and a segmentation threshold is determined automatically on the basis of the histogram. The digital image is then thresholded at the segmentation threshold to obtain the binary segmented digital image.
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Citations
14 Claims
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1. A method of binary segmentation of a video image which includes at least one target object and at least one noise element against a common background;
- said image being represented by a video signal corresponding to grey levels of respective pixels therein, a target object having pixel grey levels which differ from the pixel grey levels of the background and of noise elements;
said method comprising the steps of;(a) thresholding the video signal at respective grey threshold levels so as to derive for each threshold level a digital signal representing a binary segmented image corresponding to that threshold level; (b) determining from each of the digital signals, by labelling, a count of the number of objects in the corresponding binary segmented image, and storing the respective counts applicable to the respective binary segmented images; (c) forming a histogram of the stored counts as a function of the respective threshold levels; (d) automatically determining from said histogram a segmentation threshold applicable to said video image for distinguishing target objects from background and noise elements therein; and (e) applying said segmentation threshold to said video signal to derive a binary segmented video signal representing a binary segmented form of said video image in which target objects are distinguished from background and noise elements therein. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- said image being represented by a video signal corresponding to grey levels of respective pixels therein, a target object having pixel grey levels which differ from the pixel grey levels of the background and of noise elements;
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11. Apparatus for binary segmentation of a video image which includes at least one target object and at least one noise element against a common background;
- said image being represented by a video signal corresponding to grey levels of respective pixels therein, a target object having pixel grey levels which differ from the pixel grey levels of the background and of noise elements;
said apparatus comprising;input means for receiving the video signal; thresholding means coupled to said input means for subjecting the video signal to thresholding at respective grey threshold levels so as to derive for each threshold level a digital signal representing a binary segmented image corresponding to such threshold level; processing means coupled to said thresholding means for determining from each digital signal, by labelling, a count of the number of objects in the corresponding binary segmented image; accumulating means coupled to said processing means for storing the respective counts applicable to the respective binary segmented images; segmentation threshold determining means coupled to said accumulating means for automatically determining a segmentation threshold on the basis of said stored counts; and means coupled to said segmentation threshold determining means and to said input means for thresholding said video signal in accordance with said segmentation threshold, to thereby derive a binary segmented video signal representing a binary segmented form of said video image wherein target objects are distinguished from background and noise elements therein. - View Dependent Claims (12, 13)
- said image being represented by a video signal corresponding to grey levels of respective pixels therein, a target object having pixel grey levels which differ from the pixel grey levels of the background and of noise elements;
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14. Video image segmentation apparatus 1, wherein said segmentation thresholding determining means comprises:
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means for creating a representation of a smooth histogram curve of said objects as a function of said respective grey levels; and means for determining a grey level at which a first slope of said histogram curve approaches infinity and a second slope of said histogram curve approaches zero.
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Specification