JPH04369173A - Document reader - Google Patents

Abstract

PURPOSE:To obtain a binary picture with less dirt and a high picture compression efficiency by dividing a binary picture into plural areas and setting all picture elements in the area to a white level when number of black level picture elements in the area does not reach a prescribed number so as to suppress background noise. CONSTITUTION:A binary data is inputted to a black picture element counter circuit 6 and divided into a discrimination area of a prescribed size and the count of black picture elements in the discrimination area is inputted to a 1st discrimination circuit 7, in which the count is compared with a prescribed value and when the black level picture element number is a prescribed value or below, all picture elements of the area are set to a white level and the result is inputted to a 2nd discrimination circuit 8. The circuit 8 consists of a surrounding area reference circuit 8a and an AND circuit 8b and the picture elements are discriminated to be at a white level when the circuit 8a discriminates it that the adjacent areas all satisfy the similar condition. Thus, granular noise is suppressed and a binary picture with a high picture compression rate with less dirt is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device that binarizes and stores image information having multivalued gradation information for each pixel.

0002

2. Description of the Related Art Currently, image reading devices are being made faster. The scanned images are stored, transmitted, and printed, but in any process, binarization is more advantageous in terms of cost and speed, so binarization is widely used, and is used in special fields. This trend is expected to continue. When binarizing an image, in order to binarize thin patterns without erasing them, the binarization threshold is set as close as possible to the background, but at this time, brightness unevenness caused by paper fibers is Therefore, small grainy noise appears in the binary image. This noise makes binary images difficult to view and reduces image compression efficiency, so it has been desired to develop a method for removing it.

[0003] Conventionally, methods for removing background noise from this paper include a method of uniformly thinning the pattern, and a method of referring to pixels in a predetermined range around a pixel of interest, and determining that the binary information in this predetermined range is all the same. In the case of information, a circle method was used in which the pixel of interest has the same value as the surrounding binary information.

0004

[Problem to be solved by the invention] In the conventional device,
Since the method described above was used to remove noise, the following problems occurred.

[0005] In the method of uniformly thinning the pattern, as a result of the thinning of the pattern, the printed portion that should originally be preserved disappears, and in the circle method, it is difficult to remove large-sized granular noise. In this case, it is necessary to widen the reference range, which increases the number of reference pixels, making this difficult to achieve. This limits the amount of noise that can be removed, making it difficult to effectively remove grainy noise. could not.

The present invention has been made to solve the above-mentioned problems, and effectively suppresses grainy noise caused by paper background noise while preserving the printed pattern, and allows thinner patterns to be printed on the screen. It is an object of the present invention to provide a document reading device that can obtain a binary image with little dirt and high image compression efficiency even when converted into a value.

[0007]

Means for Solving the Problems In order to solve the above problem, in the document reading device according to claim 1, the binarized data is divided into a plurality of judgment areas having a predetermined size, and the a counting circuit that counts the number of black pixels in each determination area;
When the number of black pixels in each determination area is less than or equal to a predetermined value,
The first determination circuit determines that the total number of pixels in the determination area is white, and compares each determination area that has been determined to be white with the determination results of the adjacent surrounding areas, and if all of the surrounding areas have been determined to be white, the first determination circuit 1 determination is fixed, and a second determination circuit that invalidates the first determination when any adjacent area is not determined to be white.

[0008] Furthermore, the document reading device according to claim 2 is the device according to claim 1, further comprising: executing the determination process when displaying or printing the binarized data stored in the storage device. This is a characteristic feature.

The document reading device according to claim 3 further includes a counting circuit for counting the number of black pixels within a predetermined range around each pixel; A determination circuit that determines the pixel to be white when the pixel is equal to or less than the value, compares the determination results of neighboring pixels of the pixel determined to be white, and if all the surrounding pixels are determined to be white, the determination circuit determines the pixel as white. , and a determination circuit that invalidates the determination if any pixel is not determined to be white.

0010

[Operation] The present invention focuses on the fact that most character symbols written on manuscripts are made up of relatively large chunks, whereas noise patterns are made up of relatively small chunks dispersed. Divide the area into multiple areas, count the number of black pixels in each area, and if the number of black pixels does not reach a predetermined number, all pixels in that area are treated as white. be. In this case, the above conditions hold around the character symbol pattern, and in order to prevent the character symbol pattern from being erased, the conditions in the region adjacent to the region to which the relevant pixel belongs are also checked, and if all the adjacent regions meet the above conditions, If the conditions are not met, the masking process is canceled. According to this, it becomes possible to remove relatively large particle size noise without erasing the faded printed pattern portion.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a first embodiment. Manuscript 1
The pattern written on is illuminated by a light source 2 and imaged by a lens 3 onto a one-dimensional image sensor 4 . The image sensor 4 converts the light input to each pixel into an electrical signal, and sequentially outputs the signal of each pixel to the outside. And the image sensor 4
In synchronization with the time when one row of images is output, the document is moved by one pixel in the direction of the arrow, and the reading operation is repeated again to read all patterns on the document 1. At this time, the image information output from the image sensor 4 is sequentially transferred to the binarization circuit 5.
The signal is converted into a binary signal by, for example, the pattern portion (black portion) as logic “1” and the background (white portion) as logic “0” and input to the black pixel counting circuit 6. In the black pixel counting circuit 6, based on the image signal sample clock VCLK and the scan synchronization signal LSNC output from the image sensor 4, the input binary image is divided into regions each consisting of 8 pixels in the vertical and horizontal directions, for example. do. And black pixel counting circuit 6
Count the black pixels in each of the divided areas. The result of the black pixel number counting circuit 6 is input to the first determination circuit 7 and compared with a predetermined value. The result is the second judgment circuit 8
is input. The second determination circuit is a surrounding area reference circuit 8a.
The surrounding area reference circuit 8a outputs logic "0" when all eight adjacent areas satisfy the same condition. Further, the output of the binarization circuit 5 is delayed by a delay circuit 9 until the black pixel counting circuit 6 finishes counting within a predetermined area and the result of the surrounding area reference circuit 8a is obtained, and is input to an AND circuit 8b. . Then, if the result of the surrounding area reference circuit 8d is logic "0", that is, the number of black patterns does not reach a predetermined number in a certain area, and the same is true in the surrounding area, the AND circuit 8b is closed. Prohibits outputting black patterns.

FIG. 2 shows a specific example of the black pixel counting circuit 6. A pixel clock VCLK that is output in synchronization with each pixel and a line synchronization signal LSNC that is output in synchronization with each scanning line are input from the image sensor 4. Both signals are
It is input to octal counters 101 and 104. The counters 101 and 104 repeatedly change values from 0 to 7 in sequence. The output of the counter 101 is input to the comparison circuit 102, and each time the value of the counter reaches 7, the output of the comparison circuit 102 becomes true, and the gate of the AND circuit 103 is opened to output a pixel clock once every eight clocks. Similarly, the output of the counter 104 is input to the comparison circuit 105, and each time the counter value reaches 7, the output of the comparison circuit 105 becomes true, and the gate of the AND circuit 106 is opened to apply the pixel clock once every 8 lines. Output. The image information converted into a binary signal by the binarization circuit 5 is input to the addition circuit 107. The output of the adder circuit 107 is input to the register 108, and the output thereof is input to the other terminal of the adder circuit 107. A pixel clock VCLK is input to the clock terminal of the register 108. Thereby, the number of black pixels in the binary image information is accumulated in the register 108 in synchronization with the pixel clock. The pixel clock 1/8 VCLK output from the AND circuit 103 for every eight pixels is delayed by a certain period of time in the delay circuit 110 and input to the clock terminal of the register 109. As a result, the number of black pixels accumulated every eight pixels is stored in the register 109. 1/ passed through the delay circuit 110
The 8VCLK signal is further delayed by the delay circuit 111 and input to the reset terminal of the register 108. As a result, the contents of the register 108 are transferred to the register 109, and then the value of the register 108 is set to 0 in preparation for the integration of the next eight pixels. Further, the results of counting every eight pixels in the main scanning direction are input to the adding circuit 112. Addition circuit 1
The other terminal of 12 is inputted with data from FIFO-113, which stores the total results up to the previous row, and the adder circuit 112 outputs the cumulative results including the corresponding scanning line, and the data is sent to the FIFO again. -113 is stored. Then, by the clock output from the AND circuit 106 every 8 scanning lines, the integration results for every 8 scanning lines are stored in the register 114.
is stored and output to the outside. In addition, the gate circuit 11
5 is closed every 8 scan lines by the output of the comparator circuit 105, and prohibits the output of the FIFO-113 from being returned to the adder circuit 112. Thereby, the integrated value can be initialized every 8 scanning lines.

FIG. 3 shows a specific example of the surrounding area reference circuit 8a. The output of the first determination circuit 7 is input to the shift register 201, and this output is sequentially input to the shift register 201.
2, input to 203. Shift register 201-2
Each of the registers 03 is composed of the number of stages of registers necessary to store data for one scanning line. Then, data is extracted from the first three bits of each shift register and input to a nine-input OR circuit 204. As a result, when the area around the point of interest e is all logic "0", that is, when there is no black pixel by a predetermined number in any of the nine blocks, the OR circuit 2
04 outputs logic "0" and closes the gate of the AND circuit 10 in FIG.

FIG. 4 shows a second embodiment. In Figure 4,
Components having the same configuration as those in the first embodiment are given the same reference numerals, and their explanation will be omitted. In this embodiment, the image information binarized by the binarization circuit 5 is stored in the image compression circuit 1.
1 and then stored in the storage circuit 12. Thereafter, if necessary, the image is read out from the storage circuit 12 and restored to the original image by the compressed image restoration circuit 13, and then the black pixel counting circuit 6 and the first determination circuit 7 are processed as in the embodiment according to claim 1. And by the function of the second determination circuit 8, when the number of black pixels in each block does not reach a predetermined number, that area is determined to be white,
Black pixels are removed and displayed on the display element 14. In addition,
In this embodiment, instead of the image sensor 4, the compressed image restoration circuit 13 receives the pixel synchronization signal VCLK and the scanning line synchronization signal LS.
Generates NC. According to the second embodiment, all patterns including noise are stored in the storage device 12, and if
If there are patterns similar to background noise on the document and you do not want to erase them, simply disable the judgment of this circuit and you can display or print those patterns without having to read the document again. .

Next, a third embodiment will be described. In this embodiment, the configuration of the black pixel counting circuit 6 is different from the embodiment according to claim 1, and this is shown in FIG.

In this embodiment, instead of dividing an image into a plurality of areas, the number of black pixels is counted for each pixel in a surrounding area of 9 pixels on each side. The output of the binarization circuit 5 is input to the shift register 301, and further,
The outputs are sequentially input to shift registers 302-309. The shift registers 301 to 309 each include the number of stages of registers necessary to store data for one scanning line. Then, the first 9 of each shift register
Data is extracted from the bits (p1 to p9), and the total number of black pixels in each scanning line is determined by adder circuits 310 to 317. Further, adding circuits 318 to 325 calculate the sum of the numbers of black pixels between each scanning line.

The case where the background is white and the text information is black has been described above, but even when the background is black and the text information is white, the relationship between black and white can be reversed in each embodiment. , a similar effect can be obtained.

[0019]

As described above, according to the present invention, it is possible to suppress grainy noise caused by uneven brightness caused by paper fibers while preserving the print pattern, and to create a binary image with less dirt and high image compression efficiency. image.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment according to claim 1.

FIG. 2 is a diagram showing a specific example of a black pixel counting circuit 6. FIG.

FIG. 3 is a diagram showing a specific example of a surrounding area reference circuit 8a.

FIG. 4 is a diagram showing an embodiment according to claim 2.

FIG. 5 is a diagram showing another embodiment of the pixel counting circuit 6. FIG.

[Explanation of symbols]

1 Manuscript 4 One-dimensional image sensor 5 Binarization circuit 6 Black pixel counting circuit 7 First judgment circuit 8 Second judgment circuit 12 Memory circuit 14 Display element

Claims (3)

[Claims] Claim 1: A text reading device that sequentially reads image information having multivalued shading information, binarizes and stores this image information for each pixel, and converts the binarized data into a predetermined size. a counting circuit that divides the judgment area into a plurality of judgment areas and counts the number of black pixels in each judgment area; A first determination circuit that determines white, compares each determination area that has been determined to be white with the determination results of adjacent surrounding areas, and fixes the first determination when all adjacent areas are determined to be white; a second determination circuit that invalidates the first determination when the adjacent area is not determined to be white. 2. The document reading device according to claim 1, wherein the determination process is executed when displaying or printing the binarized data stored in the storage device. 3. In a document reading device that sequentially scans image information having multivalued grayscale information, converts this pixel information into binarized information for each pixel, and stores the image information, in which each pixel is read within a predetermined range around the pixel. a counting circuit that counts the number of black pixels of the pixel; a first determination circuit that determines the pixel to be white when the number of black pixels within the predetermined range is less than or equal to a predetermined value; and a first determination circuit that determines that the pixel is white, and adjacent surroundings of the pixel that has been determined to be white. Compare the determination result of the pixel, and if all surrounding pixels are determined to be white, fix the determination,
a second determination circuit that invalidates the determination if any pixel is not determined to be white.