US4501016A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for the dynamic adjustment of a black/white discrimination threshold for the processing of images containing grey values
Assignee: US Philips Corp
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Filing: 1982-11-22
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Granted: 1985-02-19
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Expires: 2002-11-22
Abstract
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.
Inventors
- 👤 Eric H. J. Persoon
- 👤 Ratnayake M. S. S. Abeysekera
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:09
CPC Classifications
G; G06; G06V; G06V10/00; G06V10/20; G06V10/28; G06V10/36
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
279 words
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.
Claim 2
Independent Claim
279 words
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.
Claim 3
Dependent Claim
33 words
A device as claimed in claim 1, characterized in that the locally determined threshold value is formed as a mean value of the maximum and minimum grey values within the first local sub-set.
Claim 4
Dependent Claim
45 words
A device as claimed in claim 1, characterized in that the edge detector determines an edge under the control of a difference between a minimum grey value in a first sub-set and a maximum grey value in a second sub-set within said second local sub-set.
Claim 5
Dependent Claim
26 words
A device as claimed in claim 2, characterized in that a first local sub-set of pixels each time coincides with a second local sub-set of pixels.
Claim 6
Dependent Claim
95 words
A device as claimed in claim 1, characterized in that after the first input and before further processing means there is arranged a resolution enhancer (86) for forming, for each pixel received, a larger number of m×n secondary pixels of an m×n submatrix which is situated in the area of the pixel received, the secondary grey values of the secondary pixels being formed by means of m×n interpolation operations on the grey value of the pixel received and on the grey values of a third local sub-set of pixels which directly adjoin the pixel received.
Claim 7
Independent Claim
50 words
A device as claimed in any one of claims 1 to 4, characterized in that to the input of the threshold detector there is connected a low-pass filter (70) for receiving the grey values of a sequence of third local sub-sets of pixels and for performing an averaging operation thereon.
Claim 8
Dependent Claim
61 words
A device as claimed in claim 2, characterized in that said first means and the edge detector are constructed as a tree structure consisting of two-input arithmetic elements, each time two outputs of arithmetic elements of higher level in the tree structure being connected to the relevant inputs of a single arithmetic element of a lower level in the tree structure.
Claim 9
Dependent Claim
28 words
A device as claimed in claim 7, characterized in that the tree structure determines the highest as well as the lowest grey value of the relevant local sub-set.
Claim 10
Dependent Claim
104 words
A device as claimed in claim 1, characterized in that the threshold generator also comprises: a memory (22) which comprises a third input which is connected to the first output and to a fourth output in order to buffer a local black/white threshold, and a difference-determining device (46) which comprises a fourth and a fifth input for comparing the local black/white thresholds on the first and the fourth output and, when a predetermined difference between said local black/white thresholds is exceeded, for supplying the memory with a storage control signal in order to store a new local black/white threshold for presentation to said discriminator.
Claim 11
Dependent Claim
51 words
A device as claimed in claim 9, characterized in that when said difference is not zero but does not exceed a second predetermined difference, the difference-determining device supplies an increment/decrement signal in order to increment/decrement the stored local black/white threshold in the same direction as the variation of the grey values.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-19 | 1988-08-20 | 1989-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-19 | 1992-08-20 | 1993-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-19 | 1996-08-20 | 1997-02-19 | $7700.00 | Window Closed / Lapsed |