Device for the dynamic adjustment of a black/white discrimination threshold for the processing of images containing grey values
First Claim
1. A device for the dynamic adjustment of a black/white discrimination threshold for the processing of images which are composed of a matrix of pixels which each contain a grey value and which are arranged in rows and columns of the matrix, said device comprising:
- a. a first input (60) for receiving the grey values;
b. a threshold generator (68) which comprises;
b1. first means (72,
74) for receiving the grey values of a first sequence of first local sub-sets of pixels and for determining for each first local sub-set a local black/white threshold for presentation on a first output;
c. a discriminator (64) for presenting alternatively a black or a white signal on a second output (66) by comparison of the grey value of a pixel with the local black/white threshold applicable to the relevant pixel, characterized in that the threshold generator comprises;
b2. an edge detector which comprises a second input which is connected to said first input in order to receive the grey values of a second sequence of second local sub-sets of pixels for the detection of a local edge between darker pixels and lighter pixels, thus forming an accept signal on a third output (82), but forming a reject signal on the third output in the absence of such a local edge;
there are also being provided;
d. time control means (62) for presenting a black/white signl of a pixel, on the basis of a first local sub-set of pixels to the second output together with the accept/reject signal on the third output which has been generated on the basis of a second local sub-set of pixels associated with said first local sub-set of pixels.
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Abstract
A device for binarizing an image consisting of grey values by means of a dynamically adjusted black/white discrimination threshold comprises:
a. a generator (74) for determining a discrimination threshold each time for a first local sub-set of pixels;
b. an edge detector (90) for determining a local edge between darker and lighter pixels from a second local sub-set of pixels, associated with a first local sub-set of pixels, in order to form an accept signal, and otherwise a reject signal; and
c. a discriminator (64) for presenting, on the basis of a grey value and the relevant discrimination threshold, alternatively a black or a white signal.
43 Citations
10 Claims
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1. A device for the dynamic adjustment of a black/white discrimination threshold for the processing of images which are composed of a matrix of pixels which each contain a grey value and which are arranged in rows and columns of the matrix, said device comprising:
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a. a first input (60) for receiving the grey values; b. a threshold generator (68) which comprises; b1. first means (72,
74) for receiving the grey values of a first sequence of first local sub-sets of pixels and for determining for each first local sub-set a local black/white threshold for presentation on a first output;c. a discriminator (64) for presenting alternatively a black or a white signal on a second output (66) by comparison of the grey value of a pixel with the local black/white threshold applicable to the relevant pixel, characterized in that the threshold generator comprises; b2. an edge detector which comprises a second input which is connected to said first input in order to receive the grey values of a second sequence of second local sub-sets of pixels for the detection of a local edge between darker pixels and lighter pixels, thus forming an accept signal on a third output (82), but forming a reject signal on the third output in the absence of such a local edge; there are also being provided; d. time control means (62) for presenting a black/white signl of a pixel, on the basis of a first local sub-set of pixels to the second output together with the accept/reject signal on the third output which has been generated on the basis of a second local sub-set of pixels associated with said first local sub-set of pixels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification