JP2000108419A - Imaging method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gray scale representation faithful to an original image by generating a pixel gray level reference direction data based on the bit map pattern information of a high resolution region image data and determining the gray level of each pixel constituting the bit map pattern of a high resolution region based on a reference gray level data. SOLUTION: An image data read out from an image processor is inputted to a decoder 211 at an image signal converting section and an image data selecting/processing section 260 and the value of MSB in the image data is determined by the decoder 211. When the MSB is 1, the image data is a profile region data and an image data representative of a bit map pattern number is decoded. Subsequently, a plurality of bit map patterns are read out along with a pixel gray level reference direction indicative of the reference direction of a pixel for determining the pixel gray level in the ON/OFF pixel regions of the bit map pattern. Thereafter, gray level of each pixel in high resolution region is determined based on a gray level reference direction data and a plurality of screen signals are generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method capable of outputting high-quality images. More specifically, the present invention relates to an image forming apparatus having a plurality of low-resolution and high-resolution outputs. The present invention relates to an image forming apparatus and an image forming method that enable high-resolution output without losing density information. Especially for printers connected to computers and printers connected to networks,
It processes character information and graphic information input in a page description language (PDL) or the like, and realizes output of a high-quality print image.

[0002]

2. Description of the Related Art Many computer printers and network printers that are currently commercialized convert a character code into a bitmap image of a printer and print it in a printing process of coded character information. This is to match the bit configuration on the computer side with the bit configuration on the printer side.It is determined whether the character code sent from the computer is dot-printed or not in the resolution unit of the printer. A bitmap image is generated based on the bitmap image. Even if the printer itself is a multi-valued printer capable of expressing a halftone image (for example, 8 bits, 256 gradations) for each pixel, it is necessary to process a pixel as a bitmap image in which one pixel is assigned to a binary value of 0 or 255. General. As a result, step-like jaggies (jaggies) in the resolution unit of the printer occur at the edges of characters, line drawings, and graphics, deteriorating the image quality.

In order to solve the problem of image quality deterioration, fine pixels finer than the basic resolution are generated, and the density level of the pixel of interest is determined depending on how much the original image occupies the fine pixels. . With this configuration, a jagged portion (also called an alias) can be made a visually smooth image. This is called an anti-aliasing process, but in many cases, the background color can only correspond to a solid color, that is, an alias on the white background, which is the color of the transfer medium. Aliases may have white border-like defects, or anti-aliasing may cause jagged edges in text, line art, and graphics at printer resolution units. Image quality is degraded.

On the other hand, Japanese Patent Application Laid-Open No. 7-273994 discloses an image forming apparatus that converts a bitmap image into a bitmap image with a different resolution for each image area, forms an image for each resolution, and superimposes. However, when images are formed and superimposed a plurality of times as in this image forming apparatus, not only does the recording speed decrease in inverse proportion to the number of superimpositions, but also misregistration occurs during superimposition, resulting in large image quality. Highly likely to damage.

[0005] In addition, it is widely known that in the conventional anti-aliasing processing, a thin gray line or a thin line due to an adjacent line is likely to be generated, thereby deteriorating the image quality.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus which does not cause a defect even if the resolution of aliases of characters, line drawings and graphics on a background color is increased. An object of the present invention is to provide an image forming method. Still another object of the present invention is to provide an image forming apparatus and an image forming method that do not impair the recording speed and image quality with a simple configuration.

[0007]

An image forming apparatus according to the present invention, which achieves the above object, has a high resolution area based on input image data in an image forming apparatus having a configuration capable of outputting at a plurality of resolutions. A decoder for generating pixel density reference direction data for obtaining density information of each pixel constituting the high-resolution bitmap pattern based on bitmap pattern information of the image data; and the pixel density reference direction output by the decoder. Based on the data, reference is made to the density data of the pixel data in the low resolution area at the position indicated by the pixel density reference direction data, and based on the reference density data, each pixel constituting the bitmap pattern in the high resolution area is referred to. Density determining means for determining the density.

Further, in the image forming apparatus of the present invention,
The density determination unit is configured to determine a shortest distance low-resolution area located in a direction indicated by pixel density reference direction data of the high-resolution area image data from a plurality of low-resolution area image data having density information in the input image data. The image data is selected, and the image density of the selected low-resolution area image data is determined as the pixel density of the high-resolution area image data.

Further, the image forming apparatus of the present invention comprises a screen signal generating means for generating a plurality of screen signals according to the pixel density of the high resolution area image data determined by the density determining means, and the screen signal generating means. And a synthesizing means for synthesizing the screen signal generated in the above and a serial signal obtained by serializing bitmap pattern data of high-resolution area image data, and generating multi-tone data in the high-resolution area. I do.

Further, in the image forming apparatus of the present invention,
The synthesizing unit has a configuration in which screen signals corresponding to a plurality of different pixel densities forming a bitmap of the high resolution area image data determined by the density determining unit are selected and output.

Further, in the image forming apparatus of the present invention,
The synthesizing means is configured to synthesize and output a screen signal based on pixel density information of the low resolution area image data and a screen signal based on pixel density information of the high resolution area image data determined by the density determining means. It is characterized by having.

Further, in the image forming apparatus of the present invention,
The synthesizing means is constituted by a logical operation element.

Further, in the image forming apparatus of the present invention,
The pixel density reference direction data generated by the decoder is determined based on a pattern distribution of a bitmap pattern corresponding to input high-resolution image data.

Further, in the image forming apparatus of the present invention,
The high resolution area image data is contour area data in the image data, and the low resolution area is data other than the contour area in the image data.

Further, according to the image forming method of the present invention, there is provided an image forming method for an image forming apparatus having a configuration capable of outputting at a plurality of resolutions, wherein a bit map pattern of high-resolution area image data based on input image data is provided. A decoding step of generating pixel density reference direction data for obtaining density information of each pixel constituting the high-resolution bitmap pattern based on the information; and a pixel density reference direction data generated in the decoding step. Referring to the density data of the pixel data of the low resolution area at the position indicated by the pixel density reference direction data, and determining the density of each pixel forming the bitmap pattern of the high resolution area based on the reference density data. And a density determination step.

Further, in the image forming method of the present invention,
The density determination step is a step of, from a plurality of low resolution area image data having density information in the input image data, a shortest distance low resolution area located in a direction indicated by pixel density reference direction data of the high resolution area image data. The image data is selected, and the image density of the selected low-resolution area image data is determined as the pixel density of the high-resolution area image data.

Further, the image forming method according to the present invention further comprises a screen signal generating step of generating a plurality of screen signals according to the pixel density of the high-resolution area image data determined in the density determining step; Combining a screen signal generated in the step and a serial signal obtained by serializing bitmap pattern data of the high-resolution area image data to generate multi-gradation data in the high-resolution area. I do.

Further, in the image forming method of the present invention,
The synthesizing step is characterized by selecting and outputting screen signals corresponding to a plurality of different pixel densities constituting a bitmap of the high resolution area image data determined in the density determining step.

Further, in the image forming method of the present invention,
The synthesizing step includes synthesizing and outputting a screen signal based on the pixel density information of the low-resolution area image data and a screen signal based on the pixel density information of the high-resolution area image data determined in the density determining step. Features.

Further, in the image forming method according to the present invention, the pixel density reference direction data generated in the decoding step is determined based on a pattern distribution of a bitmap pattern corresponding to the input high-resolution image data. It is characterized by.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of an image forming apparatus and an image forming method according to the present invention will be described below.

[0022]

FIG. 1 is a schematic diagram showing a system to which an image forming apparatus according to the present invention is applied. The image processing apparatus 1 shown in FIG. 1 includes a plurality of client computers 3A, 3B,
Are connected via a network 5 to another device group 4 (hereinafter collectively referred to as a device group) including a client computer group 3, a server computer 4A and an image processing device 4B.

The image processing apparatus 1 includes various PDLs (Page Descriptions) sent from the group of apparatuses.
The print information described in (Language: page description language) is analyzed, and the analyzed image data is written to a buffer memory (not shown) as needed.

The PDL includes, for example, PostScript (trademark of Adobe in the United States, hereinafter referred to as PS), Interpress (trademark of Xerox in the United States), etc., and shape information such as resolution, contour, position, and rotation angle. And color information.

The image data written in the image processing apparatus 1 is read out in synchronization with the image forming apparatus 2 by a control signal sent from the image forming apparatus 2, passed to the image signal conversion unit 210, and passed to the laser driving apparatus. A laser modulation signal for driving 220 is generated and supplied to image exposure unit 200.

FIG. 12 is a schematic view of the image exposure section 200. The image exposure unit 200 includes a photoconductor 201, a laser diode 202, a collimator lens 203, a first cylinder lens 205, a mirror 206, a polygon mirror 207,
The f-θ lens 208 and the second cylinder member 209 are constituent elements. The laser diode 202 is driven by the driving of the laser driving device 220, and a light beam modulated according to image information is formed on the photoconductor 201.

FIG. 2 shows image data generated by the image processing apparatus 1. The image processing device 1 analyzes the PDL sent from the device group and develops it into image data.

The image data has a 12-bit configuration as shown in FIG. The contours of characters, lines, graphics, and the like shown in the PDL are 2 which is the basic resolution of the image forming apparatus.
It is developed at 96 dpm higher than 4 dpm. The resolution of the image forming apparatus will be briefly described with reference to the sample of FIG. The upper part (a) of FIG. 13 is the image data expressed in PDL, and when it is developed in the image forming apparatus, the display is as shown in the middle part (b) or the lower part (c) of FIG. In this example, the basic resolution of the image forming apparatus is 24 dpm, and the high resolution is 96 dpm. In this case, 24 dpm is a large matrix in FIGS. 13B and 13C, and 96 dpm is a small matrix. A high resolution of 96 dpm is used in the outline data portion, and portions other than the outline data are displayed at the basic resolution of 24 dpm of the image forming apparatus, which is similar to the upper part (a) of FIG. 13, which is image data expressed in PDL. It can be displayed in a manner. In order to enable such display, the image data has different data configurations in the outline area (data A) and the area outside the outline (data B) as shown in FIG.

The contour area (data A) holds numbers for identifying 2048 types of patterns, some of which are shown in FIG. 3, as high-resolution pattern data (0 to 2047). Further, data 1 indicating a contour portion is added as the MSB of the data.

On the other hand, the portion (data B) other than the contour portion is
8-bit density data developed at a resolution of 24 dpm equal to the basic resolution of the image forming apparatus;
Screen select (S_SEL) data to be selected at 10 is generated, and data 0 indicating that it is outside the contour is added to the MSB of the data.

The screen select data is data used to select a screen signal which is an actual display or a print pattern when a display corresponding to the designated density is executed. For example, when displaying or printing at a certain density, several patterns for displaying or printing the density can be selected, and data for selecting one screen signal from the plurality of selectable screen signals is displayed on the screen. This is select data.
Here, 0, indicated by the S_SEL field in FIG.
S_SEL from four types of patterns corresponding to 1, 2, and 3
One of the screen signals is selected based on the screen select data specified in the field.

As understood from the data structure of FIG.
There is no area for storing density data and screen select data in the data (data A) indicating the contour area.
Therefore, only the contour area data cannot have density information, and cannot express the original accurate density in the high resolution area. The image forming apparatus of the present invention solves this problem.
In order to determine the pixel density and the background density in the high resolution pattern, respective density reference direction information is generated. This configuration will be described later.

FIG. 4 is a schematic diagram of the image signal converter 210. FIGS. 5, 6, and 7 show the image signal converter 2 shown in FIG.
10 is a schematic diagram showing the operation of the decoder 211 in FIG. FIG. 8 is a block diagram of the image data selection processing unit 260 in the image signal conversion unit 210. 9 is a schematic diagram of a conversion method of the parallel-serial converter 212 in the image signal conversion unit 210, and FIG. 10 is a block diagram of a combiner 215 in the image signal conversion unit. Hereinafter, details of each component will be described with reference to the drawings.

The image data read from the image processing apparatus 1 (see FIG. 1) is transmitted to an image signal conversion section 210 (see 21 in FIG. 1).
0, detailed configuration is input to FIG. As shown in FIG. 2, the input image data has different data structures between the outline region and the outside of the outline region, and the processing is executed based on each data.

As shown in FIG. 4, the image signal converter 210 includes a decoder 211, a parallel / serial converter 212,
Image data selection processing section 260, screen generator 213, screen selector 214, combiner 21
5, etc. are provided. PCKL is used for each processing unit.
A buffer, a delay circuit, a data latch, and the like (not shown) for synchronizing with the above are included.

The image data read from the image processing apparatus 1 is input to the decoder 211 of the image signal converter 210 and the image data selection processor 260.

For the image data input to the decoder 211, the value of the MSB in the image data is first determined, and the MSB value is determined.
Is 1, this is contour area data as described in FIG. 2, and image data representing a bitmap pattern number is decoded from the data. If the MSB is 0, this is data outside the contour and 0 data is output.

In the decoder 211, when the MSB is 1,
As shown in FIG. 5, the image data representing the bitmap pattern number is decoded, and from the plurality of bitmap patterns shown in FIG. 3, a 16-bit bitmap pattern (Bitmap pattern) indicating a specific pattern and a bitmap pattern Each indicating the reference direction of a pixel to be referred to in order to determine the density of the pixel density
A bit flag (pixel density reference direction) and a 4-bit flag (Back Gro) indicating the reference direction of a pixel to be referred to in order to determine the density of the background pixel density, which is the pixel area where the bitmap data is turned off.
und density reference direction) is bitmap pattern generation Ta
ble. The direction indicated by the 4-bit flag indicating the reference direction is 16 directions when the upper side of the target pixel is set to the north, east, west, north and south.

As described above, the decoder 211 generates pixel density reference direction data for obtaining density information of each pixel constituting the bitmap pattern based on the bitmap pattern information of the image data in the high resolution area which is the contour area. Is done. In order to generate the direction data, the decoder detects the pattern configuration of the pixels forming the bitmap, and obtains the reference direction based on the area of the pattern. For example, if ON pixels are unevenly distributed in the upper left, the upper left is determined as the reference direction.

As a specific example, the lower part of FIG. 5 shows an example in which the decoder 211 decodes image data whose MSB is "1" and whose bitmap pattern number is "No. 6". Input pattern No. Reference numeral 6 denotes data as shown in FIG. 3, and a 16-bit bitmap pattern indicating this pattern is output. Further, in this case, a 4-bit flag (pixel density reference direction) indicating the reference direction of the pixel to be referred to in order to determine the density of the pixel density of the pixel area where the bit map pattern is turned ON indicates the upper left (northwest) direction. A 4-bit flag (Back Ground density reference direction) indicating the reference direction of a pixel to be referred to in order to determine the density of the background pixel density, which is a pixel area where the data and bitmap data are turned OFF, is located at the lower right (Southeast ) Data indicating the direction is output from the decoder 211.

The decoder 211 further divides 16 high-resolution 96 dpm bitmaps existing in a 24 dpm bitmap frame into two, and shows two sets of eight bitmap patterns as shown in FIGS. 6 and 7. Such a rearrangement process is performed.

FIG. 6A shows a transition of data after the rearrangement process in the decoder 211 and the parallel-serial conversion of the rearranged data in the parallel-serial converter 212 according to the present invention. FIG. 6B shows a transition of data when parallel-serial conversion is directly performed from a conventional high-resolution bitmap.

The bit map shown at the left end of FIG.
It is a high resolution bitmap of 96 dpm.
11 divides 16 96 dpm bitmaps into two,
Divided into two sets of eight bitmap patterns (area division)
Then, these are rearranged (rearrangement processing) according to the rules shown in FIG.

Each reordering rule shown in FIG. 7 will be described. FIG. 7A shows a case where data is rearranged to the right, which is set as a default. The pixels of interest here are 2 × 4, 2 × 4 pixels surrounded by a thick line in the center of the 4 × 4 pixels shown on the left side of FIG. 7A).
FIG. 7A shows a configuration in which the pattern is not biased to the left or right in these eight pixels. In this case, rearrangement to the left is performed as shown in the right-side diagram of FIG. 7A).

That is, as shown in FIG. 7A), the number of pixels to be turned ON by further dividing the inside of the eight bitmap frames into two right and left is skewed to the left or adjacent to the eight bitmap patterns of interest. In the case where there is no bias on both the left and right including the four bitmap patterns to be performed, the pixels which are turned ON from the first pixel number as shown in FIG.

As shown in FIG. 7B), when the number of ON pixels in the eight bitmap frames of interest is shifted to the right side, rearrangement is right-aligned as shown in the right diagram of FIG. 7B). Is made.

Although the central eight bitmap frames of interest as shown in FIG. 7c) are not biased, the number of pixels that are turned on including the four adjacent bitmaps shifts to the right. If it is determined that they are present, rearrangement to the right is performed as shown on the right side of FIG. 7C).

In any case, the number of pixels that are turned ON is the same as the original bitmap data, and is turned ON from the first pixel number shown in FIG. 7D) depending on whether the right-aligned or left-aligned rearrangement is performed. It is determined whether to turn ON from No. 8 or not, and the original number of ON pixels is turned ON from No. 1 or from No. 8 and rearranged.

The pixels of the eight adjacent bitmaps are shown in FIG.
In the case of a specific form as shown in e), FIG.
As shown in (1), data rearrangement in which ON pixels are moved in parallel between eight adjacent bitmaps is executed.

The rearranged bitmap pattern is output to parallel / serial converter 212. The parallel-serial converter 212 (see FIG. 9) converts the signal output from the decoder 211 into a 1-bit serial signal and outputs it to the combiner 215.

Referring to FIG. 9, a parallel-serial converter 21
Operation 2 will be described. As described above, the parallel-to-serial converter 212 converts the bitmap pattern that has been rearranged in the decoder 211 into a decoder 211.
Receive from For example, the input bitmap pattern is a region surrounded by a thick line at the center on the left side shown in FIG.
Each pixel is assigned a pixel number for explanation. Assuming that the pixels input to the parallel-to-serial converter 212 are two sets of 1 to 8 pixels surrounded by a thick line on the left center shown in FIG. 9, the parallel-to-serial converter 212
The pixels 1 to 8 are arranged in series as shown on the right side of FIG.

On the other hand, the image data input to the image data selection processing section 260 is temporarily stored in a memory 261 in the image data selection processing section 260 as shown in FIG. FIG.
Shows the configuration of the image data selection processing unit 260. The image data selection processing unit 260 has a memory 261 and a controller 262. For data with the MSB of 1 (high-resolution area data forming the outline area), an 8-bit flag indicating the reference direction of the input pixel is sent from the decoder 211 to the controller 262. As shown in FIG. 5, the reference direction data is a total of 8 bits, ie, 4 bits each for the ON pixel density reference direction and the background density reference direction.

Since the contour area data does not have density information in the data as described with reference to FIG. 2, the reference direction is determined by the density reference direction data, and the density data of the pixels in the determined reference direction is determined. Is determined as the density of the high resolution area. As described above, the image data selection processing unit 260 functions as an image density determining unit.

For example, the high resolution bitmap pattern shown in the lower part of FIG. 5 has an upper left pixel (gray) and a lower right background (white). The 4-bit data indicating the density reference direction of these pixels and the background is northwest (upper left) for the upper left pixel (gray), and the 4-bit data indicating the density reference direction of the background is southeast (right). Below), the concentration of each of these is
The determination can be made using the density of the low-resolution data (see data B shown in FIG. 2) existing in the direction indicated by each reference direction data.

The low resolution area image data used for determining the density is, for example, the shortest distance low resolution area image data located in the direction indicated by the pixel density reference direction data of the high resolution area image data. The image density of the area image data is defined as the pixel density of the high-resolution area image data.

According to the 8-bit flag indicating the pixel density reference direction sent to the controller 262, the density data (8 bits) of the pixel to be referred to by the pixel area where the bitmap pattern is turned on, and the bitmap data O
The density data (8 bits) of the pixel to be referred to by the pixel area (background) that becomes the FF is the halftone data (8bi).
t × 2) is output from the memory 261. Further, a pixel area where the screen select data (2 bits) for selecting an output signal by the multiplexer 216 (see FIG. 4) is turned on in the bitmap pattern and a pixel area is turned off in the bitmap data (background)
Are determined for each region of (FL2 [1:
0], FL3 [1: 0]) are output from the memory 261.

As described above, the ON pixels of the high-resolution bitmap constituting the contour area and the density of the background are determined, sent to the screen generator as halftone data, and a screen signal corresponding to the determined density is generated. . There are a plurality of types of screen signals to be generated, and screen select data is used to select an output screen signal from the plurality of types of screen signals. The screen select data is output to the screen select generator 214 for each of the ON pixels of the high resolution bitmap and the background.

The density data (8 bits × 2) output from the image data selection processing unit 260 and the density data included in the image data are input to the screen generator 213, and the output corresponding to each pixel is output by a buffer circuit (not shown) or the like. Timing is achieved and a known method (for example, FIG.
The image signal control configuration shown in (1) generates a screen signal for each of a plurality of screens. It should be noted that a screen signal is also generated for a low resolution area where no contour area is formed, based on the density information of the low resolution area image data.

The configuration of the image signal control unit shown in FIG. 11 will be briefly described. The image signal control unit includes a data latch 301,
D / A converter 302, triangular wave generator 303, comparator 30
4, image data and clock data for timing control are input to the data latch 301. The clock data is supplied to the D / A converter 302 and the triangular wave generator 3
03 is also output. The triangular wave generator 303 generates a triangular wave having a predetermined shape and outputs the generated triangular wave to the comparator 304. The image data output to the D / A converter 302 via the data latch is also D / A converted, output to the comparator 304, and compared with the triangular wave generated by the triangular wave generator 303. The obtained signal is output to the combiner 215. Each signal output timing and comparison timing are controlled by a clock.

The screen select data (2 bits each) for the pixel area where the bitmap pattern is turned on and the pixel area where the bitmap data is turned off, output from the image data selection processing unit 260, are output from the screen select generator 214. And the screen select generator 214 outputs a plurality of screen signals output from the screen generator 213,
A selection signal for selecting the pattern data converted into a serial signal by the parallel-serial converter 212 is generated.

As described above, the plurality of screen signals and serial signals generated are synchronized for each corresponding pixel, and are synthesized by the combiner 215. The combiner 215 is constituted by a logic circuit as shown in FIG.

The structure of the combiner 215 shown in FIG. 10 will be described. The combiner 215 includes a logic circuit 216 and a multiplexer 217 as shown in FIG. The logic circuit includes serial image data (Serial) input from the parallel-serial converter 212.
1 Data) is input, and a plurality of types, here four types, of screen signals (Screen)
n1 to 4), and a screen selection signal (Screen) from the screen select generator 214.
n Select) is input.

The serial image data (Serial Data) input from the parallel-serial converter 212 is input to the combiner in FIG. This data is obtained by rearranging 96 dpm high-resolution bitmap patterns by the decoder 211 as described with reference to FIGS.
Further, data serialized by the parallel-serial converter 212 is input. This high-resolution data is processed as a laser exposure image by parallel-serial conversion as described with reference to FIG.
The data does not have the density information of the N pixels and the density information of the background.

The density information of each of these ON pixels and the density information of the background are determined by a screen signal and screen select information input to the combiner 215. Four types of screen signals (Screen
n1 to 4) are output from the screen generator 213 to the combiner 215. This signal is, for example, a screen signal generated in the image signal control unit configuration of FIG. 11 based on the density data (8 bits × 2) output from the image data selection processing unit 260 and the density data included in the image data. is there.

The combiner 215 shown in FIG. 10 generates and outputs a screen signal based on the density information of each of the ON pixel and the background pixel in the high resolution area. That is, it has a configuration in which screen signals corresponding to a plurality of different densities constituting a bit map of a high resolution area are respectively selected and output.

The combiner 215 combines the serial signal output from the parallel-to-serial converter 212 and a plurality of screen signals output from the screen generator 213 to generate data having 256 gradations and a resolution of 96 dpm.

The screen signal in the low-resolution area can be generated by the screen generator 213 based on the density information of the low-resolution image data, input to the combiner 215, and synthesized.

Data having a resolution of 96 dpm with 256 tones generated by the combiner 215 is input to the multiplexer 216, and the screen is selected according to the configuration of the image data according to the select signal output from the screen selector generator 214. Then, it is output to the laser driving device 220. For example, a screen signal based on the density of a low-resolution ON pixel area outside a certain contour area is Screen1, and a screen signal based on the density of a low-resolution background pixel area is Screen1.
4, the screen signal based on the determined density of the high-resolution ON pixel is Screen1, and the screen signal based on the density of the high-resolution background pixel area is Sc.
In the area different from the former, the screen signal based on the density of the low-resolution ON pixel area outside the outline area is Screen2, and the screen signal based on the density of the low-resolution background pixel area is S2.
If the screen signal based on the determined density of the high-resolution ON pixel is Screen2 and the screen signal based on the density of the high-resolution background pixel area is Screen3, the screen signals 1 to 4 corresponding to the respective pixels are respectively Is selected by the select signal associated with the, and is output via the combiner 215 and the multiplexer 216. Hereinafter, these output results will be described in comparison with the output results of the conventional configuration.

FIG. 13 is a schematic view of an image when a graphic alias is drawn by the image forming apparatus of the present invention and the conventional method. 13A shows an original image represented in PDL, FIG. 13B shows an image processed and output by the image forming apparatus of the present invention, and FIG. 13C shows a drawing process performed by a conventional method. This is the output image.

As shown in FIG. 13A, the original image has a density of 10%.
The background portion has a pixel density of 0% and a density of 10%, and the contour portion is formed of a smooth curve. FIG. 13 shows a comparison with a conventional image processing system which performs processing at a higher resolution (96 dpm) than a region other than the contour region in order to faithfully represent the contour curve in the contour portion processing.

In the conventional image processing system, the contour portion has a higher resolution (96 dpm) than a region (24 dpm) other than the contour region.
pm), at which time pixel density information (density 10
0%), the background density information is output as 0% density.
As shown in FIG. 13C, the result is that matching with the density of the other background area of 24 dpm (density of 10%) is not achieved. That is, the alias is expanded to a high resolution of 96 dpm as in the present invention, and the alias is expanded to 24 dpm and 96 dpm.
FIG. 13C shows a conventional example of a method of switching pm pixels.
Since the alias has no gradation, 24 dpm and 96
When the dpm pixel is switched, a white defect occurs in the alias.

On the other hand, in the image forming apparatus of the present invention, the pixel density information (density 100%) and the background density information (density 10%) in the high resolution (96 dpm) processing in the contour processing. Then, a high-resolution image is generated. Therefore, as shown in FIG. 13B, both the pixel density and the background density have other low resolutions (24
The same density output as in the (dpm) region is obtained.

As described above, in the processing of the decoder 211 described with reference to FIG. 5, the information of the pixel density reference direction and the background density reference direction is generated when the bitmap pattern is generated, and these density reference directions are generated. Are determined by referring to the image densities of the bitmaps existing in the image data.

FIG. 14 shows still another example of an image forming apparatus according to the present invention and a schematic view of an image when drawing by a conventional method. 14A shows an original image represented in PDL, FIG. 14B shows an image processed and output by the image forming apparatus of the present invention, and FIG. 14C shows a drawing process performed by a conventional method. This is the output image. In the example of the conventional method shown in FIG. 14C, the background density information is prioritized, so that it is not possible to extract only the outline region and perform high-resolution processing.
As a result, the processing of the low resolution (24 dpm) is performed in the outline area as in the other areas, and a faithful outline expression cannot be performed. That is, in the conventional example of FIG.
Although no defect occurs as in (c), anti-aliasing is not performed, so that jaggies depending on the resolution are conspicuous, and the shape is considerably different from the original image of FIG. 14 (a).

On the other hand, the image forming apparatus of the present invention
At the time of high resolution (96 dpm) processing in the contour processing, a high resolution image is generated after obtaining pixel density information (density 75%) and background density information (density 10%). Therefore, as shown in FIG. 14B, the same density output as that of the other low-resolution (24 dpm) area can be obtained for both the pixel density and the background density.

In the image forming apparatus of the present invention, since the alias of the contour expression has 256 gradations, it is drawn with no inferiority to the area other than the alias, and an image very close to the original image represented in PDL can be obtained.

[0077]

As described above, according to the image forming apparatus and the image forming method of the present invention, it is possible to output image data at a plurality of different resolutions and to process characters and graphics aliases at a high resolution. In the same way as the low-resolution part other than the alias, the configuration is such that the 256 gradations can be maintained. With this configuration, even when the background color and the alias such as characters overlap, the original image represented in the PDL can be maintained. A faithful gradation expression is possible, and a high-quality image can be output.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a system to which an image forming apparatus according to the present invention is applied.

FIG. 2 is a diagram illustrating a configuration of image data processed in the image forming apparatus of the present invention.

FIG. 3 is a diagram showing a bitmap pattern used in the image forming apparatus of the present invention and a part of the bitmap pattern number.

FIG. 4 is a block diagram of an image signal conversion unit in the image forming apparatus of the present invention.

FIG. 5 is an operation schematic diagram (1) of a decoder in an image signal conversion unit of the image forming apparatus of the present invention.

FIG. 6 is a schematic diagram (2) of the operation of the decoder in the image signal conversion unit of the image forming apparatus of the present invention.

FIG. 7 is an operation schematic diagram (3) of a decoder in the image signal conversion unit of the image forming apparatus of the present invention.

FIG. 8 is a block diagram of an image data selection processing unit in an image signal conversion unit of the image forming apparatus of the present invention.

FIG. 9 is a schematic diagram of a conversion method of a parallel-serial converter in an image signal conversion unit of the image forming apparatus of the present invention.

FIG. 10 is a block diagram of a combiner in an image signal conversion unit of the image forming apparatus of the present invention.

FIG. 11 is a schematic diagram of an image signal control unit of the image forming apparatus of the present invention.

FIG. 12 is a schematic view of an image exposing unit of the image forming apparatus of the present invention.

FIG. 13 is a schematic diagram (1) of an image formed by the image forming apparatus of the present invention and a conventional method.

FIG. 14 is a schematic view (2) of an image formed by the image forming apparatus of the present invention and a conventional method.

[Explanation of symbols]

 Reference Signs List 1 image processing device 2 image forming device 3 client computer group 4 other device group 5 network 200 image exposure unit 201 photoconductor 202 laser diode 203 collimator lens 205 first cylinder lens 206 mirror 207 polygon mirror 208 f-θ lens 209 second Cylinder member 211 Decoder 212 Parallel-serial converter 213 Screen generator 214 Screen selector generator 215 Combiner 216 Multiplexer 220 Laser driver 260 Image data selection processor 261 Memory 262 Controller 301 Data latch 302 D / A converter 303 Triangular waveform generator 304 Comparator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA05 AA17 AB07 DA03 DA18 5B021 AA30 BB03 DD07 5B057 CA08 CA18 CB08 CB16 CE05 5C077 LL05 LL19 MP01 NN17 PP54 TT03

Claims (14)

[Claims] 1. An image forming apparatus having a configuration capable of outputting at a plurality of resolutions, wherein said high-resolution bitmap pattern is generated based on bitmap pattern information of high-resolution area image data based on input image data. A decoder for generating pixel density reference direction data for obtaining density information of each constituent pixel; and a low resolution area at a position indicated by the pixel density reference direction data based on the pixel density reference direction data output by the decoder. Density determining means for determining density of each pixel constituting the bitmap pattern of the high resolution area based on the density data included in the pixel data of the image forming apparatus. apparatus. 2. The image processing apparatus according to claim 1, wherein the density determining unit determines, from a plurality of low resolution area image data having density information in the input image data, a shortest one positioned in a direction indicated by pixel density reference direction data of the high resolution area image data. 2. The configuration according to claim 1, wherein the low-resolution area image data at a distance is selected, and the image density of the selected low-resolution area image data is determined as the pixel density of the high-resolution area image data. Image forming device. 3. The image forming apparatus further comprises: a screen signal generating unit configured to generate a plurality of screen signals according to a pixel density of the high resolution area image data determined by the density determining unit; Synthesizing means for synthesizing the screen signal generated in the above and a serial signal obtained by serializing bitmap pattern data of high-resolution area image data to generate multi-tone data in the high-resolution area. The image forming apparatus according to claim 1. 4. The composition means for selecting and outputting screen signals corresponding to a plurality of different pixel densities constituting a bitmap of the high-resolution area image data determined by the density determination means, respectively. The image forming apparatus according to claim 3, wherein: 5. The combining means combines a screen signal based on pixel density information of low resolution area image data and a screen signal based on pixel density information of high resolution area image data determined by the density determining means. The image forming apparatus according to claim 3, wherein the image forming apparatus has a configuration for performing output. 6. An image forming apparatus according to claim 3, wherein said synthesizing means comprises a logical operation element. 7. The apparatus according to claim 1, wherein the pixel density reference direction data generated in the decoder is determined based on a pattern distribution of a bitmap pattern corresponding to input high-resolution image data. Image forming apparatus. 8. The image processing apparatus according to claim 1, wherein the high resolution area image data is contour area data in the image data, and the low resolution area is data other than the contour area in the image data. An image forming apparatus according to any one of the above. 9. An image forming method for an image forming apparatus having a configuration capable of outputting at a plurality of resolutions, wherein the high-resolution area is determined based on bitmap pattern information of high-resolution area image data based on input image data. A decoding step of generating pixel density reference direction data for obtaining density information of each pixel constituting the bitmap pattern; and, based on the pixel density reference direction data generated in the decoding step, the pixel density reference direction data A density determining step of referring to density data of the pixel data of the low resolution area at the indicated position and determining the density of each pixel constituting the bitmap pattern of the high resolution area based on the reference density data. An image forming method comprising: 10. The method according to claim 1, wherein the step of determining a density includes, from a plurality of low-resolution area image data having density information in the input image data, a shortest one positioned in a direction indicated by pixel density reference direction data of the high-resolution area image data. 10. The configuration according to claim 9, wherein the low-resolution area image data at a distance is selected, and the image density of the selected low-resolution area image data is determined as the pixel density of the high-resolution area image data. Image forming method. 11. The image forming method further comprises: a screen signal generating step of generating a plurality of screen signals according to a pixel density of the high-resolution area image data determined in the density determining step; And synthesizing the screen signal generated in and the serial signal obtained by serializing the bitmap pattern data of the high-resolution area image data to generate multi-gradation data in the high-resolution area. The image forming method according to claim 9, wherein: 12. The synthesizing step selects and outputs screen signals corresponding to a plurality of different pixel densities constituting a bitmap of the high-resolution area image data determined in the density determining step. The image forming method according to claim 11, wherein: 13. The combining step combines a screen signal based on the pixel density information of the low-resolution area image data and a screen signal based on the pixel density information of the high-resolution area image data determined in the density determining step. 13. The image forming method according to claim 11, wherein the image is output. 14. The apparatus according to claim 9, wherein said pixel density reference direction data generated in said decoding step is determined based on a pattern distribution of a bitmap pattern corresponding to input high-resolution image data. The image forming method as described in the above.