摘要:
An image processing method for detection and removal of halftone dots includes converting a gray scale image into a binary thresholded image with halftone dots; identifying halftone regions within the binary thresholded image; and removing halftone dots from the identified halftone regions. The identifying halftone regions step is effected by classifying the binary thresholded image to produce a halftone classification map; reclassifying the halftone classification map to produce a halftone reclassification map of lines with plural halftone pixels in each line; merging the halftone pixels in each line in the halftone reclassification map to produce a halftone line map; and merging the lines of the halftone line map to produce a halftone region map.
摘要:
A technique, specifically apparatus and an accompanying method, for accurately thresholding an image based on local image properties, specifically luminance variations, and particularly such a technique that uses multi-windowing for providing enhanced immunity to image noise and lessened boundary artifacts. Specifically, a localized intensity gradient, G(i,j), is determined for a pre-defined window (300) centered about each image pixel (i, j ) . Localized minimum and maximum pixel intensity measures, L.sub.min and L.sub.max, respectively, are also determined for another, though larger, window (330) centered about pixel (i,j). Also, a localized area gradient measure, GS(i,j), is determined as a sum of individual intensity gradients for a matrix of pixel positions (370) centered about pixel position (i,j). Each image pixel (i,j) is then classified as being an object pixel, i.e., black, or a background pixel, i.e., white, based upon its area gradient, GS (i,j), and associated L.sub.min and L.sub.max measures.
摘要:
A method for performing color dropout on a digitized document, the method comprises the steps of obtaining color values from the digitized document for background and a color of interest to a user; transforming the color values of the background and the color of interest into an identical gray scale value according to a color dropout function; obtaining a gray scale value different from the identical gray scale value for the remaining portion of the image according to the color dropout function; and thresholding the gray scale values obtained from the previous steps to obtain a binary image that substantially eliminates color classification error which retains character integrity by a functional transformation that suppresses color fringe artifacts.
摘要:
A vertical black line removal system (VBLR) is adapted to remove unwanted vertical lines produced on scanned document images by dust or other particles on the imaging apparatus. The VBLR system, placed in a document scanner after the binarization equipment, creates a stored histogram table including the difference values of “1” or “0” for the first and second image data. A vertical black line search processor compares each histogram value in the histogram table with a predetermined threshold value such that when the histogram value is greater than the threshold value the histogram value and the image address indicating the location of defect are stored in memory. An image readout then creates a corrected image by comparing each original image address with the stored defect image addresses so that when there is not a match with defect image addresses the first binary image value is output, and when the addresses are equal the difference value is analyzed for a “1” or “0” to determine when the first or second image data is to be output.
摘要:
A digital image processing system applies an edge-based adaptive thresholding technique with different contrast parameters to convert an image into first and second binary images. In the digital processing system of the invention, the first and second binary images are compared and a map of the difference between the first and second binary images is generated. A vertical profile of this map is projected and local peaks in the vertical profile which correspond to a vertical pattern or artifact in the map is detected. Pixels in the first binary image are reversed based on the vertical pattern or artifact in the map. This system is effective in reducing vertical artifacts produced by scanners.
摘要:
Document contour vectorization and the use of a modified Hough transform are used in combination to detect the skew angle of a digitized form image so that image skew may then be corrected in the preprocessing of form images prior to document analysis and classification.
摘要:
A threshold free algorithm is used to extract text in a region which has been circled with any hand drawn shape of any size that consitutes a closed curve. Use of this technique allows an operator to select intensity regions in text material in a paper-based document and automate the extraction of the enclosed text in the digitized image of the document.
摘要:
Characters which touch one another in a document image are identified and separated in accordance with their contours. The objects in the image are divided into two classes comprising, respectively, those having closed inner contours and those which do not. An object in the first class having either a closed inner contour which is not centered in the object or two horizontally offset closed inner contours or more than two closed inner contours is identified as containing two touching characters and is split in accordance with the character stroke thickness observed in the document. An object in the second class whose contours intersect three spaced horizontal reference lines at more than a predetermined number of points is compared against intersection patterns characteristic of single characters. If a match is not found, the object is identified as containing touching characters.
摘要:
A method for obtaining bitonal image data from a document obtains scanned color image data from at least two color channels and identifies, in the scanned color image data, at least one region of interest (R1) containing foreground content and background content. At least one threshold data value is obtained according to an image attribute that differs between the foreground content and the background content within the region of interest (R1). The scanned color image data of the document is converted to bitonal image data according to the at least one threshold data value obtained from the region of interest (R1).
摘要:
A scanner for digitizing a document includes a digitizer for digitizing the document into a first color space; a circuit for converting the digitized data into a second color space having a luminance channel and two chrominance channels; a multiplexer having text, approximate actual color of a uniform area and a predetermined color as input for selecting either the text, approximate actual color or the predetermined color as outputs; and multiplexer control input which determines which of the outputs will be selected as actual output based on a uniform area of the document.