JPS62104273A - Picture information processor - Google Patents

Abstract

PURPOSE:To decompose a mixed picture comprising a multi-value component and a binary value component such as photograph and character into a dither and a binary value and to output them simultaneously without complicating a device by applying a dither processing to an input picture data and correcting/ restoring the bit missing of the character component of an original picture especially. CONSTITUTION:A picture reader 9 reads an original picture, a dither conversion means 2 applies dither conversion to an input picture data and stores the dither picture data after conversion in a buffer memory 6. Then one picture element piece of a character being original a binary picture receives remarkably the damage to the picture of the character component. Then an operator designates a character picture or its area mixed in a gradation picture from a keyboard 11 while observing the image of a dither picture data displayed on a picture display device 10 to apply bit correction processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image information processing device, and more particularly to an image information processing device that satisfactorily reproduces binary image information related to characters and the like from dither-converted image information.

[Prior Art] Generally, when dither conversion processing is applied to image data in which a halftone image such as a photograph and a binary image such as text are mixed, the outline of the binary image portion tends to become blurred. Particularly, bits in the outline are missing, making characters etc. blurry and difficult to see.

Conventionally, blurring of binary images has been suppressed by applying edge enhancement processing to the image before dither conversion, by devising the dither matrix itself, or by switching between multiple dither matrices.

Therefore, these methods have the disadvantage of requiring complicated processing when reading images.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned drawbacks of the prior art, and its purpose is to provide a simple structure for converting dither-converted image information into characters, etc. An object of the present invention is to provide an image information processing device that satisfactorily reproduces binary image information related to.

[Means for solving the problem] As a means for solving this problem, for example, the image information processing apparatus 1 of the embodiment shown in FIG. a comparison means 5 for comparing the matrix elements of a predetermined area extracted in 1 with a predetermined threshold value T)Ih or THI generated by the threshold value generation means 4; A determining means 7 for determining whether all image bits after dither conversion corresponding to matrix elements of a lower or higher level have been dither-converted to a level of 1 or to a level of 0; and a determination by the determining means 7. A data replacement means 8 is provided for replacing all image bits corresponding to the predetermined area read from the buffer memory 6 with levels of 1 or 0 according to the output.

[Operation] In the configuration shown in FIG. 1, the block extracting means 3 extracts the first 2×2 sub-blocks SB from the dither matrix.
Extract I 1. Further, the block extracting means 3 sequentially scans each element of the sub-block 5Bi1 of the dither matrix, and the comparing means 5 sends a logic signal to the discriminating means 7 when a dither element with a level lower than a predetermined threshold THh (for example, level 30) is detected. Send information on 1. Further, the determining means 7 checks whether the corresponding dither image bit read from the buffer memory 6 has been converted to a logical 1 (black level) when the output of the comparing means 5 is logical 1. In this way, the comparing means 5 compares all the dither elements in the sub-block SBi with a predetermined threshold value T)Ih=30,
When the determining means 7 satisfies the condition that all the corresponding dither image bits read from the buffer memory 6 have been converted to logical 1 (black level) when the output of the comparing means 5 is logical 1, the replacing means 8 All of the dithered image bits corresponding to the sub-block are replaced with logic 1 (black level).

Note that the same applies to the replacement to the white level, and the details will be shown in the description of the embodiment described later.

[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an image information processing apparatus according to an embodiment. In the figure, reference numeral 1 denotes an image information processing device, and the block includes a microprocessor (CPU) that includes a ROM that stores the bit correction processing procedure shown in FIG. 2, for example, and a RAM that stores various information necessary for controlling the device. ) are shown in blocks. Regarding these, 2 is a dither conversion means for dithering input image data, 3 is a block extraction means for sequentially extracting matrix elements in a predetermined area from the dither matrix possessed by the dither conversion means 2, and 4 is a predetermined threshold value T)Ih. or T) threshold generation means for generating II; 5 is a comparison means for comparing the content of the matrix element extracted by the block extraction means 3 with a predetermined threshold; 6 is a buffer memory that holds the dithered image data after dither conversion; 7 is a According to the output of the comparison result of the comparison means 5, all image bits after dither conversion corresponding to matrix elements with a level lower or higher than the predetermined threshold T)Ih or THI are dithered to a level of 1 or to a level of 0. Determination means 8 for determining whether conversion has been performed is data replacement means for replacing all image bits corresponding to the predetermined area read from buffer memory 6 with levels of 1 or 0 in accordance with the determination output of determination means 7. Note that the determining means 7 also determines the boundary conditions regarding the dithered image data. In addition, numeral 9 is an image reading device that reads image data manually, 10 is an image output device that prints or displays dithered image data, and 11 is a keyboard that specifies areas such as character images mixed in the halftone image.

In this configuration, the image reading device 9 first reads the original image. Then, the dither conversion means 2 dither converts the human image data and stores the converted dither image data in the buffer memory 6.

FIG. 3(a) is a diagram showing an example of input image data of one pixel piece of a character expressed at density levels 2 and 50, and FIG. 3(b)
) consists of 8x8 bit area, 65 from 0 to 64.
FIG. 5(a) is a diagram showing an example of a dither matrix having different slice levels. FIG. 5(a) shows dithered image data obtained by converting the input image data of FIG. The figure shown in FIG. 5(b) is a diagram showing the case where the dithered image data of FIG. 5(a) is corrected according to the present invention. That is, one pixel piece of a character, which was originally a binary image, becomes as shown in FIG. 5(a) by being subjected to well-known dither conversion.

Here, it is clearly shown that white bits are mixed in what should be original black areas according to the arrangement of the dither matrix, and black bits are mixed in places that should be original white areas. Therefore, if dithered image data is sent to the image output device 10 as it is, the image of the character portion will be significantly damaged. Therefore, we decided to perform 1'1) correction of the dithered image data as described below.

For example, by viewing the image of the dithered image data displayed on the image display device 1o, the operator can specify the character image or its area mixed in the gradation image using the keyboard 11. The image information processing device 1 performs the bit correction process described below regarding the specified character image or area.

FIG. 2 is a flowchart showing the bit correction process of the embodiment, FIGS. 4(a) and (c) are diagrams showing 2×2 sub-blocks SB of dithered image data before correction, and FIG. 4(b)
, (d) are diagrams showing 2×2 sub-blocks SB of dithered image data after modification.

In FIG. 2, in step S1 of the bit correction process read from the ROM, the block extracting means 3 extracts the first 2×2 sub-block SB11 from the dither matrix. In step S2, the block extracting means 3 sequentially scans each element of the sub-block SB11 of the dither matrix, and the comparing means 5 detects a predetermined threshold value T! -1h
When a dither element of a lower level (for example, level 30) is detected, information of logic 1 is sent to the discrimination means 7, and the discrimination means 7 receives the corresponding dither element read from the buffer memory 6 when the output of the comparison means 5 is logic 1. Image bit is logical 1 (
check whether the image has been converted to black level). In this way, the comparing means 5 compares all the dither elements in the sub-block SBI i with the predetermined threshold value THh=30, and the determining means 7 determines the correspondence read from the buffer memory 6 when the output of the comparing means 5 is logic 1. When the condition that all the dither image bits are converted to logic 1 (black level) is satisfied, the determination in step S2 is satisfied (Y). Subblock 5844 in FIG. 4(C) clearly illustrates this situation. Here, the dither elements whose level is lower than the predetermined threshold value THh = 30 are only "5" and "21". Moreover, as shown in sub-block 5B44 in FIG. 5(a), all dither image bits corresponding to dither elements 5'' and 21' are logical 1 (black level). Therefore, the flow proceeds to step S3, where the sub-block SB
The entire dithered image bit corresponding to 44 is replaced with a logical 1 (black level). This state is shown in FIG. 4(d).

Further, if the determination in step S2 is not satisfied (N), step S3 is skipped.

In step S4, the block extracting means 3 once again sequentially scans each element of the same sub-block SBz 1, and the comparing means 5 selects a predetermined threshold Tot (for example, level 20
) When a dither element of a higher level is detected, information of logic 1 is sent to the discriminating means 7, and when the output of the comparing means 5 is logic 1, the corresponding dither image bit read from the buffer memory 6 is logic 1. Check whether it has been converted to 0 (white level). In this way, the comparison means 5 sets the predetermined threshold value TH for all dither elements in the sub-block 5B11.
A comparison is made with I=20, and the determining means 7 is compared with the comparing means 5.
If the condition that all the corresponding dither image bits read from the buffer memory 6 are converted to logic 0 (white level) when the output is logic 1 is satisfied, step S
4 is satisfied (Y). Sub-block SBz 1 in FIG. 4(a) clearly shows this state. Here, the dither element whose level is higher than the predetermined threshold TH1=20 is “3”.
2" and "48° only. Moreover, as shown in sub-block 5Bx1 in FIG. 5(a), the dither element "
The dithered image bits corresponding to 32'' and 48'' are all logic O (white level). Therefore, the flow is step S5
Then, the entire dither image bits corresponding to the sub-block set are replaced with logic 0 (white level). This state is shown in FIG. 4(b). Further, if the determination in step S4 is not satisfied (N), step S5 is skipped.

Note that after the process of step S3 is performed, the process of step S5 is not performed.

Next, in step S6, it is determined whether or not it is a boundary pattern. If the determinations in step S2 and step s4 are negative (N), this is for other cases, and for example, it can be determined that the line is a boundary line between a white area and a black area of a character. Therefore, in order to further improve the accuracy of character restoration, the following boundary portion restoration is performed. In step S6, FIGS. 6(a) to (d)
) A pattern matching process is performed to apply one of the boundary sub-block groups shown in FIG.

For example, the determining means 7 compares the left and right two bits of each sub-block of the dithered image data, and if the left side is black and the right side is white, the pattern shown in FIG. 6(a) is selected as the boundary butter, and If the left side is white and the right side is black, select the pattern shown in FIG. 6(b). Furthermore, in other cases, the upper and lower 2 bits are compared, and if the upper side is black and the lower side is white, the pattern shown in Figure 6 (C) is selected as the boundary pattern, and if the upper side is white and the lower side is black, the pattern shown in Figure 6 (C) is selected as the boundary pattern. Select the pattern shown in figure (d). When the matching of any of the above patterns is satisfied, the flow proceeds to step S7, and the sub-block of the dithered image data is replaced with the selected boundary pattern data.

Note that there are also boundary patterns other than those shown in FIGS. 6(a) to 6(d). For example, the boundary pattern has a shape as shown in FIG. 7(a). It is not desirable to immediately judge such a pattern to be a boundary pattern. Step S2, Step S
4. All the determinations in step S6 are negative (N),
This is also because such a block may be left in a black area or a white area. In such a case, the determining means 7 examines the surroundings of the sub-block of the dithered image data. For example, in the case of FIG. 7(a), the sub-blocks above and below the sub-block SB+n are white, the left sub-block SBI is white, and the right sub-block S
Since Br is black, the discriminating means 7 selects the sixth color in step S6.
Select the boundary pattern shown in Figure (b). In step S7, boundary subblocks are restored. Figure 7(b) is shown in Figure 7(b).
a) An example of restoring a boundary subblock is shown.

Next, in step S8, it is determined whether or not processing has been completed for all subblocks of one pixel. If not completed, the address of the subblock is updated to the next subblock in step S9, and the process returns to step S1. If the process ends, the process exits once to perform preprocessing for the next pixel.

Further, the dithered image data of one pixel corrected and restored as described above is shown in FIG. 5(b).

In the example described above, the 8x8 dither block and the 2x2 sub-block were mainly taken up, but similar processing is possible for blocks of other sizes.

[Effects of the Invention] As described above, according to the present invention, after performing dither processing on human image data, by correcting and restoring bit loss particularly in the character portion of the original image, it is possible to perform dither processing without complicating the device. It is now possible to decompose a mixed image of multi-value parts and binary parts, such as photographs and text, into dither and binary parts and output them simultaneously.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of an image information processing device according to an embodiment. FIG. 2 is a flowchart showing bit correction processing according to an embodiment. FIG. 3(a) shows an example of input image data of one pixel piece of a character. Figure 3(b) is a diagram showing an example of an 8x8 dither matrix, Figures 4(a) and (c) are diagrams showing a 2x2 sub-block SB of dithered image data before correction, respectively. Figure 4(b),
(d) is a diagram showing the 2×2 sub-blocks SB of the dithered image data after each correction, and FIG. 5(a) is a diagram showing the input image data of FIG. 3(a) into the dither matrix of FIG. FIG. 5(b) is a diagram showing dithered image data after the dithered image data of FIG. 5(a) has been corrected according to the present invention; FIG. 6(a) -(d) are diagrams showing typical patterns of boundary sub-blocks, and FIGS. 7(a) and 7(b) are diagrams showing examples of boundary sub-blocks before and after modification. In the figure, 1... Image information processing device, 2... Dither conversion means, 3... Block extraction means, 4... Threshold generation means, 5... Comparison means, 6... Buffer memory, 7.
. . . Discrimination means, 8 . . . Data replacement means, 9 . . . Image reading device, 10 . . . Image output device, 11 . Figure 3 40 (C) (d) (G) (G) Figure 5 (b) Figure 6 (1)) (C) (d) Figure 7 (O) (b)

Claims (1)

[Claims] a comparison means for sequentially comparing elements in a predetermined area of the dither matrix with a predetermined threshold; and according to the output of the comparison means, all image bits after dither conversion corresponding to matrix elements having a level lower or higher than the predetermined threshold are 1. determination means for determining whether the dither conversion has been performed to a level of 1 or a level of 0;
An image information processing device characterized by comprising data replacement means for replacing data at a level of .