Method and device for binary segmentation of a signal representing a digital image with a threshold obtained using a histogram

Claim 3

The method according to claim 1, wherein said segmentation threshold is determined by locating a first grey level above which the count of said histogram never exceeds a predetermined number.

Claim 4

The method according to claim 1, wherein said segmentation threshold is determined by locating the lowest grey level in a range of grey levels for which said histogram has a flat, non-zero height.

Claim 5

The method according to claim 1, further comprising smoothing said histogram to form a smoothed histogram curve; and wherein said segmentation threshold is determined by determining, for each of a plurality of test grey levels, a deviation measure combining a deviation of a first slope of said histogram curve from a vertical line and a deviation of a second slope of said histogram curve from a horizontal line; and locating that one of said test grey levels having the minimum for said deviation measure.

Claim 6

The method according to claim 4, wherein said deviation measure is a sum of the squares of the deviations of said first and second slopes.

Claim 7

The method according to claim 2, wherein said predetermined number is the number of target objects expected in video said image.

Claim 8

The method according to claim 1, further comprising smoothing said histogram to form a smoothed histogram curve; and wherein said segmentation threshold is determined by locating a first grey level above which the count of said histogram curve never exceeds a predetermined number.

Claim 9

The method according to claim 7, wherein said predetermined number is the number of target objects expected in said video image.

Claim 10

The method according to claim 1, further comprising smoothing said histogram to form a smoothed histogram curve; and wherein said segmentation threshold is determined by locating a lowest grey level in a highest range of grey levels in which said histogram curve has a flat, non-zero height.

Claim 11

The method according to claim 1, further comprising processing said video signal prior to thresholding thereof so as to compensate for grey level variations of the background of said video image but without degrading representation by said video signal of contours of said at least one target object.

Claim 12

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.

Claim 13

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.

Claim 14

Apparatus according to claim 11, wherein said video image is a localized portion of a larger video image and said apparatus further comprises means for deriving a video signal representative of said localized portion from a video signal which is representative of said larger video image.

Claim 15

Apparatus according to claim 11, further comprising top hat filter means coupled to said input means for equalizing said video signal for grey level variations of the background of said video image but without degrading representation by said video signal of contours of said at least one target object.

Claim 16

Video image segmentation apparatus 1, wherein said segmentation thresholding determining means comprises: 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.

Claim 17

Video image segmentation apparatus 1, wherein said segmentation thresholding determining means comprises: 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.