JPH08149284A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] In an image forming apparatus, whisker-like noise, disappearance of fine lines, and thickening of a graphic that occur at the time of enlargement / reduction are reduced, and high quality printing is enabled. A selection means (10) for selecting a pixel window having a central pixel composed of a plurality of pixels in a plurality of continuous image data in a temporary storage means (7) and a comparison means for comparing data in the pixel window. 11 and a conversion means 12 for converting the data of the central pixel when the comparison result indicates that the central pixel needs to be converted, and the image conversion is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention enlarges / reduces a black and white binary image, forms a pseudo multi-valued image, and performs error diffusion processing on the image to obtain a black and white binary electrophotographic image. The present invention relates to an image forming apparatus capable of obtaining an output image with improved image quality, such as a fax machine, a digital copier, a printer, etc.

[0002]

2. Description of the Related Art Conventionally, a printing apparatus using an electrophotographic system has a superiority in terms of printing speed and printing quality, and further has been reduced in price in recent years.
A printer as an output terminal such as a workstation
It is rapidly spreading to plain paper fax machines and digital copiers.

In these devices, a function of reducing and outputting faxes such as B4 and A3 to A4, and a function of enlarging and reducing in digital copier are essential. As an example of a conventional image forming apparatus, a binary image forming apparatus having a scaling function will be described below with reference to FIG.

FIG. 10 is a block diagram of a conventional image forming apparatus. The image forming apparatus 1 is composed of a controller section 2 and an image recording means 3 using an electrophotographic method. The image forming apparatus 1 receives the bitmap image data transferred from the outside by the external interface unit 4 in the controller unit 2. External interface means 4
The received data of the bitmap received in step 1 is sequentially stored in the received data storage means 5. The received data accumulated in the received data storage means 5 is enlarged / reduced by the enlargement / reduction means 6 if necessary.

Here, the enlarging / reducing process by the enlarging / reducing means 6 will be described. 11 and 12 show the bitmap data and the image thereof stored in the reception data storage means 5, where 0 corresponds to a white dot and 1 corresponds to a black dot.
A case where this image is reduced to 3/4 times (9/16 times in area) will be described. First, the binary original image is multivalued (FIG. 13, 256 gradation in the example, 0: white dot, FF black dot). Further, this image is tripled vertically and horizontally (see FIG. 14).
(A)) The average density of a 4 × 4 matrix is obtained and used as the image density of the pixel (FIG. 14 (b)). This process is performed for all the data in the received data storage means 5.
FIG. 15 shows the result of performing the above processing on all the data in FIG.

Further, in the case of multiplying by 4/3, multivalued image data may be multiplied by 4 in length and width, and an average density may be obtained by a 3 × 3 matrix and used as pixel image data. Generally, if the image data is enlarged by the value of the numerator, the average density of the denominator values in the matrix is obtained, and the pixel image data is obtained, the enlargement / reduction can be performed at any magnification.

The image data scaled by the scaling means 6 is stored in a temporary storage means 7 for temporarily storing the image data. The error diffusion means 8 is acted on the multi-valued data to generate binary bit map image data, which is transferred to the image recording means 3 through the engine interface means 9 and printed on paper by the electrophotographic method.

[0008]

However, when the error diffusion means 8 is acted on the reduced image data of FIG. 15 in the above-mentioned conventional configuration, it becomes as shown in FIG. 16 (a) and FIG. 16 (b). Whisker-like noise was generated, which significantly deteriorated the output image.

When the data used for ruled lines such as the table shown in FIG. 17A is reduced to 1/3 by the conventional method, the ruled lines are interrupted as shown in FIG. Disappears. Further, when the image is enlarged 7/4 times by the conventional method as shown in FIG.
As in (b), there is a problem that the figure is relatively thick and the thin line is crushed.

SUMMARY OF THE INVENTION The present invention solves the above problems, and an object of the present invention is to provide an image forming apparatus capable of high-quality printing by reducing whisker-like noise, disappearance of fine lines, and thickening of graphics that occur during enlargement / reduction. I am trying.

[0011]

To achieve this object, an image forming apparatus of the present invention comprises an interface means for receiving bitmap image data, a reception data storage means for temporarily storing bitmap reception data, and a bitmap image. A scaling means for scaling up and down the data, a temporary storage means for temporarily storing the scaled image data, and a central pixel composed of a plurality of pixels in a plurality of consecutive image data in the temporary storage means Selecting means for selecting a pixel window having the same, comparing means for comparing the data in the pixel window, and conversion for converting the data of the central pixel when the comparison result requires conversion for the central pixel Means, a converted image storage means for accumulating data that has been converted by the converting means, and an image in the converted image storage means. Those with an error diffusion means for performing error diffusion processing on the data.

[0012]

According to the present invention, the print data is converted by image processing according to the above-mentioned configuration, thereby reducing whisker-like noise, disappearance of thin lines, and thickening of graphics, which occur during enlargement / reduction,
Enables high quality printing.

[0013]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. The image forming apparatus 1 receives the bitmap image data transferred from the outside by the external interface unit 4 in the controller unit 2. The received data of the bitmap received by the external interface means 4 is sequentially accumulated in the received data storage means 5. Received data storage means 5
If necessary, the received data stored in
The scaling process is performed by.

The image data scaled by the scaling means 6 is stored in a temporary storage means 7 for temporarily storing the image data. The image data accumulated in the temporary storage means 7 is
As shown in FIG. 2, the selection means 10 selects a pixel window having a central pixel composed of a plurality of pixels in a plurality of continuous image data in the temporary storage means 7. Although a 3 × 3 pixel window is used in this embodiment, any pixel window having a central pixel may be used.

As shown in FIG. 3, the comparison means 11 converts the data in the pixel window selected by the selection means 10 if the center pixel is vertically, horizontally or diagonally the same. The central pixel conversion request is issued to the means 12. In the present embodiment, when there is a conversion request, the conversion means 12 sets FF (black dot) to 8 if the data of the central pixel is 80 (hexadecimal number) or more.
If it is less than 0, it is converted to 0 (white dot). If there is no conversion request, the value of the central pixel is output as it is. The data processed by the conversion means 12 is stored in the converted image storage means 13. The selection means 10 is operated so that each pixel of the data shown in FIG. 15 is the central pixel, and the comparison means 11 and the conversion means 12 are operated. The result is as shown in FIG. 4, and the error diffusion means is applied to this image. When 8 is applied, an output image as shown in FIG. 5 is obtained, and whisker-like noise is reduced.

This output image is transferred to the image storage means 3 through the engine interface means 9 and printed on a sheet by electrophotography. In the present embodiment, the comparison unit 11 issues a conversion request to the conversion unit 12 when any of the vertical direction, the horizontal direction, and the diagonal direction is equal to the central pixel, but depending on the input image, only the vertical direction may be changed. The conversion request may be issued only in the horizontal direction, only in the diagonal direction, or in the case of a combination of two of these conditions. Further, in the present embodiment, the conversion means 12 sets the threshold value to 80 when a conversion request is made, and FF (black dot) if it is 80 (hexadecimal number) or more and 0 (if it is less than 80). Although it is designed to be converted into white dots), the threshold value may be arbitrarily determined depending on the image.

(Embodiment 2) Another embodiment of the present invention will be described below with reference to the drawings. Conventional Example and Example 1
The same parts as the above are given the same numbers and their explanations are omitted.

When the image is reduced, the conversion means 12 of the first embodiment is converted into FF (black dot) when the data in the vertical direction, the horizontal direction and the diagonal direction are equal and have an intermediate value as shown in FIG. To do so. This conversion means 12 is shown in FIG.
It is applied to the image data of (a) and reduced to 1/3. Other than this, when the same processing as that of the first embodiment is performed, the result is as shown in FIG. 7, and it is possible to prevent the thin lines such as ruled lines from being interrupted or disappeared.

(Embodiment 3) Still another embodiment of the present invention will be described below with reference to the drawings. The same parts as those in the conventional example and the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

When enlarging an image, the conversion means 12 of the first embodiment converts the image into 0 (white dot) when the data in the vertical direction, the horizontal direction, and the diagonal direction are equal and have an intermediate value as shown in FIG. Try to convert to. This conversion means 12 is applied to the image data of FIG. 18A to enlarge it to 4/7. By performing the same processing as in the first embodiment except for this, the result is as shown in FIG. 9, and it is possible to prevent the fatness of the figure and the generation of whisker-like noise, and to obtain an output image with sharp image quality.

[0022]

As is apparent from the above embodiments, the present invention selects a pixel window having a central pixel composed of a plurality of pixels in a plurality of consecutive image data in the temporary storage means. The selecting means, the comparing means for comparing the data in the pixel window, the converting means for converting the data of the central pixel when the comparison result requires conversion for the central pixel, and the comparing means. By forming a converted image storage unit for accumulating the data after the conversion processing, the image formation capable of reducing the whisker-like noise, the disappearance of thin lines, and the thickening of characters generated at the time of enlarging / reducing and enabling high-quality printing The device can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing selected pixel windows according to the first embodiment of the present invention.

FIG. 3 is a diagram showing conditions under which the comparison means issues a conversion request in the first embodiment of the present invention.

FIG. 4 is a diagram showing a result of converting the data of FIG. 15 in Example 1 of the present invention.

FIG. 5 is a bitmap data diagram (a) and its image diagram (b) in which error diffusion is performed on the data of FIG. 4 in the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conversion unit according to the second embodiment of the present invention.

FIG. 7 is an image diagram in the second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a conversion unit according to the third embodiment of the present invention.

FIG. 9 is an image diagram in Example 3 of the present invention.

FIG. 10 is a configuration diagram showing a conventional image forming apparatus.

FIG. 11 is a diagram showing an example of bitmap data accumulated in a reception data storage unit.

FIG. 12 is an image diagram of the bitmap data of FIG. 11 accumulated in the reception data storage means.

FIG. 13 is a diagram in which the bitmap data of FIG. 11 is multivalued.

FIG. 14 is a diagram in which the data in FIG. 13 is tripled in length and width (a) and an image data diagram in which an average density is obtained (b).

15 is a diagram showing the reduction result (multivalued data) of FIG. 11.

16 is a bitmap data diagram (a) and its image diagram (b) when error diffusion processing is performed on the data of FIG. 15.

FIG. 17 is a bitmap data diagram (a) showing an example of ruled lines.
And (b) showing the reduction result by the conventional example.

FIG. 18 is a bitmap data diagram (a) showing another example and a diagram (b) showing an enlargement result according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Controller section 3 Image recording means 4 External interface means 5 Received data storage means 6 Enlargement / reduction means 7 Temporary storage means 8 Error diffusion means 9 Engine interface means 10 Selection means 11 Comparison means 12 Conversion means 13 Converted image storage means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 1/405 H04N 1/40 C

Claims (10)

[Claims] 1. An external interface means for receiving bitmap image data, a reception data storage means for temporarily storing bitmap reception data, an enlarging / reducing means for enlarging and reducing the bitmap image data, and an enlarging / reducing image data. The data in the pixel window is compared with a temporary storage means for temporarily storing and a selection means for selecting a pixel window having a central pixel composed of a plurality of pixels in a plurality of consecutive image data in the temporary storage means. A comparing means, a converting means for converting the data of the central pixel when the comparison result requires conversion for the central pixel, and a converted image for accumulating the data after the conversion processing by the converting means. It has a storage means and an error diffusion means for performing an error diffusion process on the image data in the converted image storage means. An image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, wherein the comparison means is a comparison means for comparing whether or not the data in the vertical direction of the central pixel is equal to the data of the central pixel. 3. The image forming apparatus according to claim 1, wherein the comparing means is a comparing means for comparing whether or not the data in the left-right direction of the central pixel is equal to the data of the central pixel. 4. The image forming apparatus according to claim 1, wherein the comparing means is a comparing means for comparing whether or not the data in the diagonal direction of the central pixel is equal to the data of the central pixel. 5. The image forming apparatus according to claim 1, wherein the comparison means is a combination of the comparison means according to any one of claims 2 to 4. 6. The image forming apparatus according to claim 1, wherein the conversion means converts the intermediate value data of the central pixel into white dots. 7. The image forming apparatus according to claim 1, wherein the conversion means converts the intermediate value data of the central pixel into black dots. 8. The image according to claim 1, wherein the converting means converts the intermediate value data of the central pixel into a black dot in the case of reduction, and converts the intermediate value data of the central pixel into a white dot in the case of enlargement. Forming equipment. 9. The image forming apparatus according to claim 1, wherein the conversion means converts the data of the central pixel into either a white dot or a black dot, whichever is closer. 10. The image forming apparatus according to claim 1, wherein the conversion unit has a variable threshold value and converts the data of the central pixel into either a white dot or a black dot according to the threshold value. apparatus.