EP0287995A2
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EP
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Method and apparatus for recognizing pattern of halftone image
Assignee: Hitachi Ltd
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Filing: 1988-04-18
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Granted: —
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Expires: 2008-04-18
Abstract
Abstract In a method of recognizing a pattern of a halftone image of a first invention, a halftone image to be processed is subjected to a normalization process (3), local halftone feature parameters are extracted (4, 7, 8, 9) from the normalized image at its sampling points, and the pattern is identified (5) by using the extracted feature parameters in accordance with a predetermined recognition procedure. An apparatus for recognizing a pattern of a halftone image of a second invention, comprises a memory (211) for storing a halftone image having several brightness tone levels, a normalization circuit (3, 212 - 216) for normalizing the brightness of the halftone image to be processed, an extraction circuit (4, 212 - 216) for extracting local halftone feature parameters from the obtained normalized image at specific points, and a recognition circuit (5) for identifying the pattern by using the feature parameters in accordance with a predetermined recognition procedure.
Inventors
- 👤 Tadaaki Mishima
- 👤 Morio Kanasaki
- 👤 Masao Takatoo
- 👤 Hideo Ota
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 18:54
CPC Classifications
G; G06; G06V; G06V10/00; G06V10/20; G06V30/00; G06V30/10; G06V30/18; G06V30/18086; G06V30/18095
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
57 words
A method of recognizing a pattern of a halftone image comprising the steps of: normalizing (3) a halftone image to be processed; extracting (4, 7, 8, 9) local feature parameters of said normalized halftone image at its sampling points; and identifying (5) a pattern by using said extracted feature parameters in accordance with a predetermined recognition procedure.
Claim 2
Independent Claim
57 words
A method of recognizing a pattern of a halftone image comprising the steps of: normalizing (3) a halftone image to be processed; extracting (4, 7, 8, 9) local feature parameters of said normalized halftone image at its sampling points; and identifying (5) a pattern by using said extracted feature parameters in accordance with a predetermined recognition procedure.
Claim 3
Dependent Claim
29 words
A method according to claim 1, wherein said local halftone feature parameters are obtained at specific positions of said normalized halftone image through multiplication/additon calculation by a local filter.
Claim 4
Dependent Claim
33 words
A method according to claim 1, wherein said local halftone feature parameters are the sum, average or dispersion values of densities at specific positions of said normalized halftone image within a local area.
Claim 5
Dependent Claim
57 words
A method according to claim 1, wherein said local halftone feature parameters are differences between two average densities, one average densities being brighter than a predetermined threshold value and the other average densities being darker than said threshold value, said two average densities being obtained at specific positions of said normalized halftone image within a local area.
Claim 6
Dependent Claim
35 words
A method according to claim 1, wherein said specific positions used in obtaining said local halftone feature parameters are determined by using a pattern to be recognized, said pattern being binarized prior to said determination.
Claim 7
Dependent Claim
27 words
A method according to claim 2 or 4, wherein said local halftone parameters at said specific positions are maximum values among values obtained near said specific positions.
Claim 8
Dependent Claim
38 words
A method according to claim 2, wherein the coefficients of said local filter for performing said multiplication/addition calculation are set so as to match a change in brightness of a character line of said pattern to be processed.
Claim 9
Independent Claim
95 words
An apparatus for recognizing a pattern of a halftone image comprising: a memory (211) for storing a halftone image having a change in brightness in the order of several tone levels; a normalization circuit (3, 212, 213, 214, 215, 216) for normalizing the brightness of said halftone image to be processed; an extraction circuit (4, 212, 213, 214, 215, 216) for extracting local halftone feature parameters at specific positions of said normalized halftone image; and a recognition circuit (5) for identifying a pattern by using said feature parameters in accordance with a predetermined recognition procedure.
Claim 10
Independent Claim
95 words
An apparatus for recognizing a pattern of a halftone image comprising: a memory (211) for storing a halftone image having a change in brightness in the order of several tone levels; a normalization circuit (3, 212, 213, 214, 215, 216) for normalizing the brightness of said halftone image to be processed; an extraction circuit (4, 212, 213, 214, 215, 216) for extracting local halftone feature parameters at specific positions of said normalized halftone image; and a recognition circuit (5) for identifying a pattern by using said feature parameters in accordance with a predetermined recognition procedure.
Claim 11
Dependent Claim
51 words
An apparatus according to claim 8, wherein said halftone image normalization circuit comprises a local maximum filter circuit, a local minimum filter circuit, and an inter-image calculation circuit for obtaining a difference image between an image obtained by said local maximum and minimum filter circuits and an image to be processed.
References Cited (Backward Citations)
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