JPH0468662A - Line density converter for binary picture - Google Patents

Abstract

PURPOSE:To reduce the time required for line density conversion processing by providing a picture element thinning means which thins picture elements of original picture information in response to a conversion magnification in each region to be segmented by an original picture segmentation means to the pre-stage of the original picture segmentation means. CONSTITUTION:A picture element thinning section 15 and a thinned picture memory 20 are provided between an original picture memory 12 and an original picture segmentation section 11. Picture elements are thinned before the segmentation processing by the original picture segmentation section 11 to decrease a data quantity being an object of the segmentation processing and to reduce the time required for the line density conversion processing. A thinning rate by the picture element thinning section 15 and a conversion magnification in a line density conversion section 10 are decided in response to the desired conversion magnification. For example, in the case of 1/6 reduction processing, after 1/2 thinning processing in the picture element thinning section 15, the line density conversion section 10 applies 1/3 reduction processing to the result. Moreover, the thinning rate in the picture element thinning section 15 is decided in response to the resolution of the original picture. The picture obtained as the result of the thinning processing is a picture indicated in the picture memory 20.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a density conversion device for binary images, particularly for facsimile machines, DTP (Desk Top Pub)
The present invention relates to a device for converting the linear density of a binary image in an optical filing device or the like.

Prior Art Conventionally, in this type of linear density conversion device for binary images,
Processing is performed to reduce or enlarge original image information composed of binarized image information according to a desired magnification. The conventional linear density conversion device for binary images will be explained with reference to FIG.

FIG. 2 is a block diagram showing the configuration of a conventional linear density conversion device for binary images. In the figure, the conventional binary image linear density conversion device includes an original image cutting section 11. This original image cutting section 11 cuts out an original image block 13 consisting of a collection of pixels according to a conversion magnification specified by a magnification specifying section (not shown) from an original image memory 12 in which binarized image information is stored. It is supplied to the total sum calculating section 14. Here, the conversion magnification is vertical p
When the original image is multiplied by q times in width and q times in width, the original image cutting portion 11 cuts out pixels of the original image consisting of 1/p1 in height and 1/q in width as an original image processor 13.

The sum calculation unit 14 calculates the density sum value 16 of the original picture block 13 by setting the density to 1' when the pixel of the original picture is a black pixel indicating black, and setting the density to '0' when the pixel is a white pixel.

The correction unit 17 corrects the total density value 16 by adding the density correction value 19 inputted from the error buffer 18, and supplies the corrected density value 21 to the converted pixel density determination unit 22. Note that all zeros are stored in the error bar 18 as initial data.

The converted pixel density determination section 22 includes a comparator 23 and a threshold calculation section 24. The converter 23 binarizes the corrected density value 21 using the threshold value 25 manually input from the threshold calculation unit 24 and outputs it as a converted pixel density value 26 .

The converted pixel density value 26 is stored in a predetermined area of the converted pixel memory 27 corresponding to the converted original image block 13 .

The threshold calculation section 24 calculates a threshold according to a magnification specified by a magnification specifying section (not shown), or outputs a threshold set by an operator.

The converted density error calculation section 28 includes a weight multiplication section 29 . The weight multiplier 29 converts the pixel density value 26 to (1/p)
(1/q) and the density value of one pixel after conversion is (1
/p) Original picture block 1 consisting of (1/q) pixels
Correct the weight to be equal to the density value of 3.

The subtractor 31 calculates the difference between the corrected density value 21 before conversion and the corrected converted pixel density 30, and outputs a density error 32.

The density error 32 is supplied to a density error distribution section 33, and is distributed to the surrounding area of the converted original image block. The density error 32 is input to the allocation peripheral block determining section 34, and the original picture blocks 13 to be allocated and the allocation ratio are determined.

The distribution ratio multiplier 35 multiplies the original picture blocks determined by the distribution peripheral block determining unit 34 and the weights according to their distribution ratios, and outputs the distribution density 36. In this embodiment, the conversion error density 32 of the original image block in row g and column m is expressed as
It is arranged to distribute 50% to the original picture block in column m, and 50% to the original picture block in row g and column (m+1).

Each distributed concentration 36 output from the concentration error distribution section 33 is
The data is stored in each area of the error buffer 18 corresponding to the allocated original image block. The total value of the error density 36 for each original image block is supplied to the correction unit 17 as a density correction value 19 when converting that original image block.

Next, the operation of the binary image linear density conversion device configured as described above will be described. Note that the linear density conversion rate of the binary image linear density conversion device can take any value, but for the sake of simplicity, a case where the conversion magnification is 1/2 will be described.

In order to increase the line density by half, it is sufficient to convert four pixels of the original image to one pixel of the conversion surface. Therefore, the operator
By operating the magnification specifying section (not shown),
Set to 2x and set the conversion magnification.

When a conversion magnification of 1/2 is set in a magnification specifying section (not shown), the original image cutting section 11 cuts out an original image block 13 composed of four pixels from the original image memory 12.

The original picture block 13 cut out by the original picture cutting unit 11 is placed in g rows and m
column. The original image block 13 is supplied to a total sum calculation section 14, and its density sum value 16 is calculated. In the case of the original image memory 12 schematically shown in FIG. 2, there is one black pixel and three white pixels in the original image block 13 in row g and column m, so the total density value 16 is "1'.This total density value 16 is supplied to the correction section 17.

The correction unit 17 adds "0.4" of the density correction value 19 supplied from the error buffer 18 to "1" of the density total value 16.
are added to obtain a corrected density error 21 "1°4", which is output. “0.4” of the density correction value 19 for the original picture block 13 in row g and column m is the density distribution due to the conversion of the original picture block in row (I-1) and column m, and in row g and column (m-1). The total value is 36.

The corrected density value 21 of the original image block 13 outputted by the correction section 17 is input to the comparator 23 of the converted pixel density determination section 22 . The comparator 23 binarizes the corrected density value 21 using the threshold value 25 inputted from the threshold value calculation section 24 . The comparator 23 receives as a threshold value 25 a half value of the number of pixels "4" of the original image block 13 determined by the threshold value calculating section 24, that is, "2".

Since the corrected density value 21 is "1.4", the converted pixel density value 26 for the original image block 13 is determined to be 0''.In other words, the original image block 13 of 2 rows and m columns output from the converted pixel density determination unit 22 is divided into two. The converted pixel after converting to 1x is “
This converted pixel density value 26 "0" is stored in row g and column m, which is an area of the converted pixel memory 27 corresponding to the converted original image block 13.

Further, the converted pixel density value 26 is input to the weight multiplication unit 29 of the converted density error calculation unit 28 . Since the density weight of one converted pixel corresponds to four pixels of the original image, the weight multiplier 2
9 multiplies the converted pixel density value 26 by a weight “4” and inputs the corrected converted pixel density 30 to the difference unit 31 . The differentiator 31 is
The difference between the corrected density value 21 before conversion and the corrected converted pixel density 30 is determined, and a density error 32 is output. Correction conversion pixel density 3
Since 0 is "O" and the corrected density value 21 is "1.4", the density error 32 of the original block 13 in row g and column m is "1.4".
becomes.

The density error 32 calculated by the converted density error calculation unit 28 is supplied to the density error distribution unit 33, and is distributed to the surrounding area of the converted original image block 13 in row g and column m to the peripheral block determination unit 34. In this embodiment, the value "0.7" obtained by multiplying 1.4" of the concentration error 32 by a weight of 1/2 in the distribution ratio multiplication unit 35 is applied to row (g+1), column m, and row g, and - Error buffer 18 as the distribution density 36 of the original picture block located in the column
Add to. The density correction value 19 in row g and column (m+1) of the error buffer 18 is based on the distribution density 36 "0°2" due to the change in the original block in row (11-1) and column (m+1) in row g and column m. Value "0.9'" added with distribution concentration "0.7"
It is.

In addition, the density correction value 19 in row (I+1) and column m of the error buffer 18 is set to "0.7°" of the distributed density 36 in row g and column m.
The distribution density 36 of the +1) row and the (m-1) column is added and determined.

The density correction value 19 obtained in this way is
7, and the density sum value 16 of each corresponding original image block 13 is corrected. Thereafter, the process is similarly repeated from the upper left to the lower right of the original image memory 12.

In the conventional example explained above, the conversion error density of the original image block of row g and column m is set to 50% for the original image block of row (N+1) and column m.
%, 5 in the original block at row (j7+1) and column (m+1)
Although the conversion error density is distributed at a rate of 0%, the peripheral blocks to which the conversion error density is distributed and their distribution ratios are not particularly limited.

For example, convert the conversion error density of row g and column m to row (j)+1) and m
40% of the original image block in the column, 40% to the original image block in the (N+1) row and (m+1) column, and 30% to the original image block in the (N+1) row and (m+1) column, and furthermore, these It is also possible to distribute it to the periphery at a predetermined ratio.

As described above, since the density of the converted image is determined by phytohacking the density difference between the original image and the converted image, it is possible to obtain a converted image close to the density of the original image. Furthermore, even if the original image is a halftone image, by feeding back density errors to the original image, the periodicity of linear density conversion calculations is reduced, making it less likely that interference with the halftone period will occur, making moiré less noticeable. . Furthermore, since the density error to be fed back is distributed to the peripheral area of the converted original image block, the randomness of the correction value increases and moiré is less likely to occur. Furthermore, since the density error is determined by weighting the converted image so that it is equal to the original image, it is possible to obtain a converted image that is even closer to the density of the original image, and the density preservation of the converted image with respect to the original image is further improved. It becomes expensive.

However, in the conventional linear density conversion device described above, it is necessary to count all the density values of all pixels of the original image, so linear density conversion processing is performed on images with high resolution and high redundancy in terms of image quality. In this case, since the amount of data to be processed is large, the disadvantage is that linear density conversion takes a long time.

OBJECTS OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional drawbacks, and its purpose is to provide a linear density conversion device for binary images in which the time required for linear density conversion processing is shortened.

Structure of the Invention The linear density conversion device for a binary image according to the present invention includes an original image cutting means for cutting out an original image block of an area according to a desired conversion magnification from original image information constituted by binary image information; a total sum calculating means for calculating the total density value of the original image blocks cut out by the original image cutting means; a correcting means for correcting the total density value obtained by the sum calculating means and outputting a corrected density value; a converted pixel density determination unit that binarizes a corrected density value and outputs a converted pixel density for the original image block; and a value obtained by weighting the converted pixel density according to the conversion magnification, and a corrected density output by the correction unit. an error calculating means for calculating a density error between the two pixels; and an error calculating means for distributing the density error obtained by the error calculating means to peripheral blocks of the original image block binarized by the converted pixel density determining means, and for use in correction processing in the correcting means. a linear density conversion device for a binary image, the device comprising: a feedback means for performing a feet hack; It is characterized in that it is provided before the original image cutting means.

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a linear density conversion device for a binary image according to the present invention, and parts equivalent to those in FIG. 2 are designated by the same reference numerals.

In the figure, the difference between the binary image linear density conversion device according to the embodiment of the present invention and the conventional one is that there is a pixel deflection section] 5 and a deflection image memory 20 between the original image memory 12 and the original image cutting section 11. This is a point that is provided. In other words, by dividing the pixels before the clipping process by the original image clipping section 11, the amount of data subject to the clipping process is reduced and the time required for the linear density conversion process is shortened. Note that the conversion processing in the linear density conversion section 10 is the same as the conventional one.

What is important here is to determine the magnification in the pixel magnification section 15 and the conversion magnification in the linear density conversion section 10 in accordance with the desired conversion magnification.

In other words, the final conversion magnification is determined by the magnification factor in the pixel magnification section 15 and the conversion magnification in the linear density conversion section 10. For example, in the case of 1/6 reduction processing, the pixel adjustment section 15 performs 1/2 reduction processing, and then the linear density conversion section]0 performs 1/3 reduction processing.

Note that the pixel adjustment rate in the pixel adjustment section 15 may be determined according to the resolution of the original image.

In addition, the steering method in the steering section 15 is 4 in this example.
This is a simple diagonal method in which each pixel is one pixel. That is,
The four pixels in row 9 and column m in the figure are spread out so that the lower right pixel in the area is the one pixel. Therefore, as a result of the magnification process, the resulting image is the image shown in the image memory 20. In other words, it is sufficient to mask at regular intervals.

Furthermore, the steering method in the steering section 5 is not only the above-mentioned simple steering method, but also the well-known 9-division method, D.D.A.
(Digital Dirrerential Ana
lyzer) method may be used, and an appropriate method may be adopted depending on the resolution of the original image, etc.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention performs linear density conversion by magnifying the original pixels before performing linear density conversion processing, and performing conversion processing on the image after the magnification at a magnification according to the magnification rate. This has the effect of reducing the number of pixels to be processed and shortening the processing time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a binary image linear density conversion device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional binary image linear density conversion device. Explanation of symbols of main parts 10...Density conversion unit 12--Original image memory 15...Pixel adjustment section 20--Adjustment image memory

Claims (1)

[Claims] (1) An original image cutting means for cutting out an original image block in an area according to a desired conversion magnification from original image information composed of binarized image information, and a total density value of the original image blocks cut out by this original image cutting means. a total sum calculation means for calculating the total density value, a correction means for correcting the density sum value obtained by the sum calculation means and outputting a corrected density value, and a correction means for binarizing the corrected density value output from the correction means and converting it to the original image block. a converted pixel density determining means for outputting a pixel density; an error calculating means for calculating a density error between a value obtained by weighting the converted pixel density according to the conversion magnification and a corrected density output by the correcting means; and this error. linear density conversion of a binary image, comprising: feedback means for distributing the density error obtained by the calculation means to peripheral blocks of the original image block binarized by the converted pixel density determining means and feeding it back for correction processing in the correction means; 2. The apparatus is characterized in that a pixel diversion means is provided at a stage upstream of the original image cutting means to spread pixels of the original image information according to the conversion magnification in each region to be cut out by the original image cutting means. Linear density conversion device for value images.