JP3368143B2 - Image processing apparatus and method - Google Patents

Description

Detailed Description of the Invention

The present invention relates to an image processing apparatus and a method thereof, for example, image processing for outputting an image in high quality.

[0002]

2. Description of the Related Art An image forming system has been proposed which comprises a controller that receives image data from a host computer and sends the image data to an image forming apparatus, and an image forming apparatus that forms an image based on the image data sent from the controller. There is. For example, a color copying machine (for example, Canon CLC500: registered trademark) is used as an image forming apparatus, and an image forming system in which it is combined with various controllers is commercialized.

A color copying machine, which is an image forming apparatus, has a plurality of output color components C (Cyan), M (Magenta), and Y (Yel).
Low) and K (blacK) are laser-type color electrophotographic printers that perform image formation in a frame-sequential manner, and realize a halftone by driving a laser with a signal obtained by pulse-width-modulating an image signal.

There are a first method of modulating the pulse width in pixel units and a second method of modulating the pulse width in units of a plurality of pixels as the method of performing the pulse width modulation. In the first method, since a pulse is output for each pixel, high resolution can be obtained. On the other hand, in the second method, a pulse is output for each of a plurality of pixels, so the resolution is poor, but the amount of the pulse width that changes with changes in image data is larger than in the first method, so It becomes easy to faithfully reproduce changes in data, in other words, high gradation can be obtained.

Such a color copying machine is, for example, 400 dpi.
With the resolution of 1 and the first method modulates the pulse width for each pixel, the screen frequency is 400 lines per inch, so it is called 400 lines. Since the screen frequency is 200 lines per inch because the pulse width is modulated, it is called 200 lines.

Then, the operator of the image forming apparatus or the controller selects whether the image formation based on the image data output from the controller is performed by 200 lines or 400 lines. Alternatively, the type of image is determined by the determination unit of the image forming apparatus main body, and in the case of a character or line drawing, 400
An image is formed by lines, and in the case of a photograph, an image is formed by 200 lines.

Further, for each element of image processing such as γ correction, spatial filter, masking / UCR, and luminance-density conversion in the image forming apparatus, similarly, one processing or parameter is uniquely selected and set. Alternatively, the processing and parameters can be switched according to the determination result of the determination unit of the image forming apparatus main body.

[0008]

However, the above-mentioned technique has the following problems. In other words, if the screen frequency of the image forming device is fixed to 200 lines, the resolution will deteriorate when the character image output from the controller is formed, and if it is fixed to 400 lines, the gradation image such as a photograph output from the controller will be displayed. However, there is a problem in that the gradation property is deteriorated.

Further, when the image type is determined by the determination means of the image forming apparatus main body, there is an erroneous determination that the character portion is the photograph portion and the photograph portion is the character portion. Further, since the image type is determined in image block units, it is necessary to perform one of the processes (200 lines or 400 lines) in block units for the character portion included in the photograph portion. Therefore, there is an adverse effect that the processing is switched and the trace of the detected character portion included in the photograph portion is reflected in the output image in a textured manner.

The present invention is for solving the above-mentioned problems individually or collectively, and it is possible to correctly determine the image type,
The purpose is to perform appropriate image processing on a pixel-by-pixel basis.

Another object is to output a high quality image at low cost.

[0012]

The present invention has the following structure as one means for achieving the above object.

The image processing apparatus according to the present invention includes a generation means for generating an image signal and a characteristic signal representing a characteristic of each pixel of the image signal from information described in a page description language, and the image signal. A processing unit that performs image processing according to the characteristic signal for each pixel, and the generation unit includes
The feature signal is obtained by performing a predetermined logical operation on the result of determining the feature of each pixel based on each of the image type, the image type and the image attribute in the page description language.

According to the image processing method of the present invention, an image signal and a characteristic signal representing a characteristic of each pixel of the image signal are generated from information described in a page description language, and each pixel of the image signal is generated. And a step of performing image processing according to the feature signal, wherein the feature signal determines the feature for each pixel based on each of the image type, the image type and the image attribute in the page description language. It is characterized by being generated by applying a predetermined logical operation to the result.

[0015]

DETAILED DESCRIPTION OF THE INVENTION An image processing apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0016]

First Embodiment [General Description of Apparatus] FIG. 1 is a schematic view of an image forming system according to an embodiment of the present invention.

In the figure, 101 is a host computer and 102 is a controller. Reference numeral 103 denotes an image forming apparatus that copies a document placed on a document table in color and outputs a color image sent from the computer 101 via the controller 102. Here, so-called DTP (Desk Top Publishing) application software runs on the host computer 101 to create / edit various documents and figures. Create host computer 101
/ Edited documents and figures are described in Page Description Language (PDL: Page
Information described in Discription Language (commands and data, referred to below as "PDL data")
To the controller 102 via the connection cable 243.

The controller 102 is the host computer 1
Performs raster image processing (RIP) to translate the PDL data sent from 01 and convert it to raster image data. The raster image data is sent to the image forming apparatus 103 via the connection cable 242, and the image is output.

[Overview of Image Forming Apparatus] FIG.
First, the operation of the image forming apparatus 103 as a copying machine for copying an original image will be described with reference to the schematic view of 03.

A document 202 placed on the platen glass 201 is illuminated with light by an illumination 203. The reflected light from the original 202 is
CCD sensor 2 by optical system 207 via mirrors 204, 205, 206
Image on 08. In addition, the motor 209 causes the mirror 204
The first mirror unit 210 including the light 203 and the illumination 203 is mechanically driven at the speed V, and the second mirror unit 211 including the mirrors 205 and 206 is driven at the speed 1 / 2V to scan the entire surface of the original 202. It

The image processing section 212 processes the image information output from the CCD sensor 208 as an electric signal, temporarily holds it in a memory 108 described later, and outputs it as a print signal. The print signal output from the image processing unit 212 is sent to a laser driver (not shown) to drive four semiconductor laser elements (not shown). One of the laser beams emitted by the four semiconductor laser elements is scanned by the polygon mirror 213 and passes through the mirrors 214, 215 and 216 to form a latent image on the photosensitive drum 217. Each of the other laser beams is also scanned by the polygon mirror 213, forms a latent image on the photosensitive drum 221 via the mirrors 218, 219, 220, forms a latent image on the photosensitive drum 225 via the mirrors 222, 223, 224, and mirrors 226, 227, 228.
Then, a latent image is formed on the photosensitive drum 229.

In this way, the latent images formed on the respective photosensitive drums are respectively a developing device 230 for supplying yellow (Y) toner and a developing device 23 for supplying magenta (M) toner.
1, developing device 232 that supplies cyan (C) toner, black
It is developed by the developing device 233 which supplies the toner of (K).
The developed four-color toner image is transferred to a recording paper, and a full-color output image can be obtained.

The recording paper supplied from one of the recording paper cassettes 234 and 235 or the manual feed tray 236 is adsorbed on the transfer belt 238 via the registration roller 237 and conveyed. On the photosensitive drums 217, 221, 225, 229, toner images of respective colors have been developed in advance in synchronization with the paper feed timing.
The toner image is transferred onto the recording paper as the recording paper is conveyed.
The recording paper on which the four-color toner images have been transferred should be
Is separated from the fixing belt 2 and conveyed by the conveyor belt 239.
The toner is fixed by 40 and is discharged to the paper discharge tray 241.

The four photosensitive drums are arranged at equal intervals with a distance d, and the recording belt is conveyed at a constant speed V by the conveyor belt 238. The element is driven.

[Flow of Image Signal] FIG. 3 is a block diagram showing the flow of the image signal.

The image information of the original 202 is read by the CCD sensor 208 by red (R), green (G) and blue representing the target image.
The image signals of the three color components (B) are converted and output as digital signals.

Reference numeral 112 denotes an input masking unit, which converts the input RGB signals (R0, G0, B0) into standard RGB signals by the calculation shown in the following equation.
Convert to color space signals. However, cij (i = 1,2,3
j = 1,2,3) is a device-specific constant that takes into consideration various characteristics such as the sensitivity characteristics of the CCD sensor 208 and the spectral characteristics of the illumination 203.

Reference numeral 104 denotes a LOG conversion unit for performing brightness / density conversion, which is R
It is composed of a lookup table of AM or ROM, and performs the operation shown in the following equation. C = -K ・ log (R / 255) M = -K ・ log (G / 255)… (2) Y = -K ・ log (B / 255) where K is a constant and the base of logarithm is 10

An output masking / UCR unit 106 converts the MCY signal (M1, C1, Y1) into the YMCK signal which is the toner color of the image forming apparatus 103 by the calculation shown in the following equation. However, the following expression ai
j (i = 1,2,3,4 j = 1,2,3,4) is a constant peculiar to the apparatus in consideration of the tint characteristics of the toner. However, K = min (C1, M1, Y1)… (4)

From the above equations (1) to (4), the CCD sensor 208
The RGB signal output from is converted into a YMCK signal corresponding to the spectral distribution characteristic of the toner and output.

On the other hand, reference numeral 105 denotes an image area determination unit for detecting a character / line drawing portion, which determines whether or not each pixel in the original image is a part of a character or a line image and generates a determination signal TEXT. 107c
Reference numerals 107d and 107d denote a compression circuit and an expansion circuit, which compress the CMY image signal and the determination signal TEXT to reduce the amount of information and then store the same in the memory 108 and expand the data read from the memory 108 to generate the CYM image signal and Play judgment signal TEXT.

Denoted at 107c and 107d are a compression circuit and a decompression circuit, respectively, which are image signals (R, G, B) and character / line drawing determination signals TE.
The XT is compressed, the amount of information is dropped, and then stored in the memory 108, and the data read from the memory 108 causes
The image signal (R, G, B) and the character / line drawing determination signal TEXT are expanded.

The compression / expansion algorithm used in the compression / expansion circuits 107c and 107d is arbitrary and is not particularly limited. For example, the so-called JPEG (Joint Photographic Experts Gr
block coding using orthogonal transformation such as
DPCM (Differential Pulse Co) using the difference value for each pixel
de Modulation) encoding or the like can be used. Further, in the present embodiment, an example in which the image data is compressed / decompressed by hardware has been shown, but it may be performed by software.

Controller 10 controlled by CPU 110
2 stores the YMCK image signal that matches the above-described toner spectral sensitivity characteristic in the memory 109, and stores the YMCK image signal in the memory 109 in synchronization with the image forming timing of the image forming apparatus 103.
Read MCK image signal. The memory 109 may hold the computer image sent from the host computer 101 and the image signal read by the CCD sensor 208.

Further, the selector 132 is provided with the image signal and the TEXT signal inputted from the controller 102 and the decompression circuit 107d.
The image signal and the TEX signal expanded by are switched.

[Copier Operation] In the system of this embodiment, the operation of the copier alone (hereinafter referred to as "copier operation")
, And "system operation" including the controller 102 exist, the operation of the copying machine will be described first.

In the case of the operation of the copying machine, the image signal output from the CCD sensor 208 is the input masking section 112 and the LOG converting section 10.
After being compressed by the compression circuit 107c through 4, the memory 108
Written in. The determination signal TEXT output from the image area determination unit 105 is also written in the memory 108 after being compressed by the compression circuit 107c. Then, the data read from the memory 108 is expanded by the expansion circuit 107d, and in synchronization with the image forming timing of the copying machine, the masking / UCR unit 106,
A spatial filter 133 that performs processing such as edge enhancement and smoothing on the image signal, a γ correction unit 134 that performs gamma correction according to the printer characteristics on the image signal, and a laser driver via a PWM circuit 115 for pulse width modulation of the laser. Sent.

FIG. 4 is a diagram showing writing / reading timing of image data in the operation of the copying machine. In the figure, the image signal is stored in the memory 10 at the timing indicated by reference numeral 1301.
It is written in 8 and is read at the timing shown by reference numerals 1302-1305. As shown in the drawing, the timing relationships indicated by reference numerals 1302 to 1305 each have a read start interval of time d / V. Here, as described above, d is the distance between the four photosensitive drums arranged at equal intervals, and V is the conveyor belt 2
The transport speed is 38. Needless to say, the read start timing of the Y stage indicated by reference numeral 1302 is later than the write start timing indicated by reference numeral 1301.

[System Operation] Next, the controller 102
The system operation including will be described.

The PDL data expansion operation is performed by the host computer 101 expanding the PDL data into a full-color image,
This is an operation of writing in the memory 109 of the controller 102. This full-color image is stored in the memory 109 as image data separated into four colors of yellow (Y), magenta (M), cyan (C), and black (K) in accordance with the image forming apparatus 103. . At this time, an identification signal for identifying the character / line drawing portion detected by the character / line drawing extraction described later and the other portion is also written in the memory 109. Then, the identification signal is read out from the memory 109, sent to the image forming apparatus 103, and printed out at the timing shown in FIG.

In the printout operation, the memory 109
The full-color image stored in the and the TEXT signal, which is a character / line drawing identification signal, are stored in the four photosensitive drums 217, 221, 22.
It is read out in synchronization with the rotation of 5,229 and sent to the laser driver via the PWM circuit 135.

The controller 102 controls these operations.
CPU 110 of. The CPU 110 is, for example, a one-chip CPU, and a control program and the like are stored in advance in an internal ROM, and control and processing are performed by using the internal RAM as a work memory.

[Image Area Determining Section] FIG. 5 is a block diagram showing a configuration example of the image area determining section 105. The image area determining section 105 extracts characters and line drawing parts from an RGB image signal obtained by reading an original, Set to '1' if the pixel constitutes a character or line drawing part,
Otherwise, the judgment signal TEXT which becomes "0" is generated.

In FIG. 5, reference numeral 1601 denotes an ND signal generator, which generates an ND signal which is a lightness signal in consideration of human visibility characteristics from a full-color RGB image signal by a product-sum operation shown in the following equation. However, d1, d2, and d3 are constants considering human visibility characteristics.

Reference numeral 1602 denotes a character / line drawing determination unit which extracts a character / line drawing portion from the brightness signal ND and generates "1" when the pixel constitutes a character or line drawing portion, and "0" otherwise. . Since this type of circuit is known, its detailed description is omitted.

[Judgment signal TEXT] FIG. 6 is a diagram for explaining the judgment signal TEXT. 1401 shows an example of an original document to be read or an image to be printed out, and 1402 shows the judgment signal TEXT in the image 1401 two-dimensionally. Is the image shown in. That is, the character / line drawing portion in the image 1401 is shown in “black” in the image 1402, and the others are shown in “white”. 14
03 is an image obtained by enlarging a part of the image 1402, and the pixels indicated by the symbol 1404 are the pixels forming the character / line drawing part,
The TEXT signal becomes '1'. On the other hand, indicated by reference numeral 1405
The pixel of the mark is a pixel which configures other than the character / line drawing, and the TEXT signal becomes “0”.

[Structure of Memory 109] FIG. 7 is a diagram for explaining the structure of data held in the memory 109 and how to read it. Reference numeral 1501 denotes an address map in the memory 109. Yellow (Y) image data 1502, magenta (M) image data 1503, cyan (C) image data 1504, black
The (K) image data 1505 has 8-bit information per pixel. The data 1506 of the judgment signal TEXT is
Each pixel has 1 bit of information.

Reference numeral 1507 conceptually shows how each of the above data is read. In other words, Y image data 150
2 is the M image data 150 in synchronization with the image formation on the photosensitive drum 217.
3 is the C image data 150 in synchronization with the image formation on the photosensitive drum 221.
4 is the K image data 150 in synchronization with the image formation on the photosensitive drum 225.
5 is read in synchronization with the image formation on the photosensitive drum 229. Further, the data 1506 of the determination signal TEXT is read out simultaneously in four systems (in parallel) in synchronization with all the four photosensitive drums.

[PWM circuit] yellow (Y), magenta (M),
The image data color-separated into four colors of cyan (C) and black (K) is sent to the laser driver via the respective PWM circuits 135,

FIG. 8 is a block diagram showing an example of the structure of one color of the PWM circuit 135. Reference numeral 1001 denotes a D / A converter which converts an input digital image signal (any one of Y, M, C and K) into an analog signal. Convert to. A triangular wave generator 1002 is used when importance is attached to gradation, and generates a triangular wave of one pixel period. On the other hand, 1003 is a triangular wave generator used when importance is attached to the resolution and generates a triangular wave with a two-pixel cycle. A selector 1004 receives a TEXT signal, which is a character / line drawing identification signal, as a selection signal and switches between two triangular waves according to the TEXT signal.

In other words, in the character and line drawing portion of the image, the triangular wave generated by the triangular wave generator 1003 and emphasizing the resolution and the analog image signal are compared by the comparator 1005.
The pulse train (PWM signal) having the pulse width as the comparison result is input to the laser driving unit 1006 that drives the laser element 1007. On the other hand, in the image portion other than the characters and the line drawing, the triangular wave generated by the triangular wave generator 1002 that emphasizes gradation is compared with the analog image signal, and the PWM signal as the comparison result is the laser driving unit 1006.
Is input to.

The period of the triangular wave that emphasizes gradation is not limited to two pixels, but may be set to a three-pixel period or a four-pixel period in relation to the resolution of the image forming unit.

FIG. 9 is an example of a timing chart in the PWM circuit. The upper part of the figure shows the PWM timing when the gradation is emphasized, and the output 1801 of the D / A converter 1001 and the triangular wave 1802 of the two-pixel period are compared. From the comparator 1005 to PW
The M signal 1803 is output. On the other hand, the lower part of the figure shows the PWM timing when the resolution is important, and the D / A converter 10
The output 1804 of 01 and the triangular wave 1805 with one pixel period are compared,
The PWM signal 1806 is output from the comparator 1005.

Practically, the PWM signal is generated by the TEXT signal indicating whether each part of the image to be output is the character / line drawing part where the resolution is important or the part other than the character / line drawing where the gradation is important. 1803 and 1806 are adaptively switched to perform preferable image formation.

[PDL] PostScript (registered trademark) of Adobe Systems Incorporated
PDL is a language for describing one page image by combining the following elements. (a) Image description with character code (b) Image description with figure code (c) Image description with raster image data

10A and 10B are views for explaining the PDL data, and L100 to L102 in FIG. 10A are examples of description by character codes. L100 is a description that specifies the color of characters. The values in parentheses represent cyan, magenta, yellow, and black densities in order from the left, with the minimum being 0.0 and the maximum being 1.0.
In other words, L100 specifies that the text is black.

Next, L101 is a description for substituting the character string "IC" into the variable string1. L102 is a description for instructing the layout of the character string.The first and second parameters are the xy coordinate mark indicating the start position of the character string on the recording paper, the third parameter is the character size, and the fourth parameter is the fourth parameter. Is the character spacing, the fifth parameter is the string to be laid out,
Shown respectively. In short, L101 and L102
The size of the character string assigned to string1 from the coordinates (0,0)
It is instructed to lay out at 0.3 and 0.1 intervals.

L103 and L104 in FIG. 10A are examples of description by graphic codes. L103 is a description for designating the line color, and the arrangement of parameters is the same as that of L100, and cyan is designated here.

Next, L104 is a description that specifies that a line is drawn, and the first and second parameters are xy indicating the start of the line.
Coordinates, third and fourth parameters indicate the end of the line
The xy coordinates. The fifth parameter indicates the line thickness.

L105 and L106 of FIG. 10A are examples of description by raster image data. L105 is a raster image variable imag
The first parameter represents the image type and the number of color components of the raster image, the second parameter represents the number of bits per color component, and the third and fourth parameters represent the raster image. Represents the size in the x and y directions. The fifth parameter and subsequent parameters are raster image data, and the number of raster image data is the product of the image sizes in the x direction and the y direction multiplied by the number of color components forming one pixel. In the example of L105, since the CMYK image is composed of four color components, the number of raster image data is 5 × 5 × 4 = 100.

Next, L106 is 0.5 × 0 from the coordinates (0,0.5).
The size of 5 is instructed to lay out the raster image data assigned to the variable image1.

FIG. 10B is a diagram showing the result of raster image processing by interpreting the PDL data of FIG. 10A. The image R100 is from L101 to L1.
From the description of 02, the image R101 is from the description of L103 and L104,
The image R102 is an image developed from the description of L105 and L106. These image data are actually expanded in the memory 109 for each CMYK color component, and C = 0, M = 0, Y = 0, K = 255 are written in the memory portion corresponding to the image R100, for example. Rare, image R
C = 255, M = 0, Y = 0, K = 0 is written in the memory portion corresponding to 101.

That is, the PDL data sent from the host computer 101 or the like is converted into raster image data by the above-described raster image processing, and then the controller 102.
Is written in the memory 109 of.

[PDL Data Expansion Process] FIG. 11 is a control flowchart of the controller 102, which is a process started by the CPU 110 when the controller 102 is powered on or reset.

In step S11, the interface mode is received from the connected image forming apparatus 103. This interface mode is applied to the connected image forming apparatus 10
It indicates whether to send RGB data or CMYK data to 3.

Next, in step S12, one unit of PDL data is received from the host computer. This unit may be several bytes or one page as long as it is a unit suitable for processing.
For example, it may be one line unit shown in FIG. 10A. In step S13,
Determine whether the received PDL data is the data to be raster image processed (eg L102, L104, L105 in FIG. 10A),
If so, raster image processing is performed in step S14 and written in the memory 109. If the received data is other than the data to be rasterized (for example, L100 in FIG. 10A), processing such as setting to an internal variable is performed in step S15.

Although FIG. 11 shows an example in which data is received in step S12 for each processing unit in steps S13 to S15, when data larger than the processing unit in steps S13 to S15 is received in step S12, Steps S13 to S15 are repeated for each received processing unit. If the unit received in step S12 is smaller than the processing unit in steps S13 to S15, the process waits for receiving the processing unit in step 12, and then the process proceeds to step S13.

In step S16, it is determined whether PDL data for one page has been received and expanded, and if PDL data for one page has not been received, steps S12 to S15 are repeated. Since normal PDL data includes information indicating the end of a page such as an EOF (End Of File) code and information instructing the start of printing, the determination is performed using this.

When the PDL data for one page has been received, it is determined in step S17 whether the interface mode is RGB or CMYK. In RGB mode, memory in step S18
The RGB raster image data stored in 109 is read and sent to the image forming apparatus 103 as it is, and an image for one page is formed. On the other hand, in the CMYK mode, memory 1 is set in step S19.
The RGB raster image data stored in 09 is read, the RGB image data is converted into CMYK image data by logarithmic conversion, the converted CMYK data is sent to the image forming apparatus 103, and an image for one page is formed.

[Generation of TEXT data from PDL] Next, referring to FIG.
Consider a case where an image as shown in FIG. 13A is formed by PDL data as shown in FIG.

The image R100 shown in FIG. 13A is the same as the image with the character code shown in FIG. 10A. Similarly, image R1
01 is an image (line image) based on the figure code shown in FIG. 10A.
Is the same as. Further, instead of the image R102 of FIG. 10B, an image R103 is drawn in FIG. 13A, the image R103 has a magenta outline, and a yellow disk-shaped image inside,
The center coordinates are (0.3, 0.7), the radius of the circle is 0.3, and the width of the outline is
It is 0.05.

Here, only the character part and the line part and the contour line part of the figure of FIG. 13A are black (TEXT = '1'), and the others are white (TEXT = '0'). Figure 13
It is B. This generation of TEXT data is performed at the same time as the PDL data expansion processing, and is stored in the memory 109 as TEXT data. That is, at the same address of the memory 109, 8 CMYKs each
33-bit image data and 1-bit TEXT data
Bits will be stored.

[Line Number Switching Based on TEXT Data] FIG. 14 is a flowchart for explaining line number switching control based on TEXT data in the image forming apparatus 103.
This is a process executed by a control unit (not shown) composed of M, RAM and the like.

After the power is turned on, in step S21, the line number control mode is set from the operation unit (not shown). This does not have to be input, and if the previous setting mode is held in non-volatile memory such as battery-backed memory, it can be used, and if not input, the default mode is used. You can also The line number control mode may be sent from the controller 102 instead of being input from the operation unit. The input of the line number control mode is not limited to immediately after the power is turned on, and can be set at any time during the image forming operation.

The line number control mode includes the following modes.

(1) 200-line fixed mode: a mode in which an image is formed with 200-line fixed. The whole surface is suitable for forming a gradation image like a photograph

(2) 400-line fixed mode: a mode for forming an image with 400-line fixed. Suitable for forming images that consist only of characters and line drawings

(3) Image area separation switching mode: For each image area, it is determined whether the image included in the area is a character / line drawing or a photograph, and accordingly, the character / line drawing area is 400 lines, and the photograph area is
Mode to form with 200 lines. It is suitable for forming an image in which characters / line drawings and photographs are mixed and it is possible to correctly determine whether characters / line drawings or photographs. Alternatively, for each area of the image, it is determined whether the image data included in the area has a specific value, and accordingly, the specific value area has 400 lines, and the others have 2 lines.
Mode formed by 00 lines. Suitable for forming images in which characters / line drawings and photographs are mixed and the characters / line drawings have specific values.

After setting the line number control mode, in step S22, the print request command from the controller 102 is awaited,
When a print request command is received, steps S29 and S
At 30, the line number control mode is determined. That is, in the 200-line fixed mode, the screen frequency is set to 200-line fixed in step S33, and in the 400-line fixed mode, step S32.
Set the screen frequency to 400 lines with. If the line number control mode is neither the 200-line fixed mode nor the 400-line fixed mode, it is the image area separation switching mode.
To set image area separation switching.

When the image area separation switching mode is set,
At the timing shown in 4, the TEXT data stored in the memory 109 is read in synchronization with the image data. The TEXT data stored in the memory 109 is 1 bit / pixel, but according to the timing of each color component shown in FIG.
The same data may be read from the head address.

When it is difficult to access different addresses of the same memory at the time of reading, it is necessary to divide the same data into 3 planes or 4 planes.
It may be stored in 9, and read from each plane at the read timing of each color component.

[Generation of TEXT Signal Based on PDL Data Parameter] FIG. 15 is a list in which the image shown in FIG. 16A is described in PDL. Images R201 to R204 represent the letters "IC" with sizes of 0.05, 0.1, 0.2, and 0.3, respectively. Similarly, in images R205 to R207, the line thickness is
It represents the 0.02, 0.05. 0.1 line. And FIG. 16B shows
Character size in Figure 16A is less than 0.3, and line width is 0.
It is a figure which shows the binary data which makes TEXT data corresponding to the thing less than 1 into "1".

That is, the CPU 110 determines from the description of FIG. 15 to L2013,
Determine the value of the third parameter of L2023, L2033, L2043, and if the parameter is 0.3 or more, set TEXT = '0' to 0.3.
If it is less than, TEXT = '1' is written in the memory 109. Furthermore, the value of the fifth parameter of L2052, L2062, L2072 is judged, and if the parameter is 0.1 or more, TEXT = '0'
Is less than 0.1, TEXT = '1' is written in the memory 109.

Therefore, the image data written in the memory 109 and the TEXT data are synchronously read, and the read TEXT data is input to the selector 1004 (FIG. 8), whereby the screen frequency is 400 lines / 200 lines. The image can be formed by switching to. Fig. 17 is a diagram showing the result of switching the screen frequency.The solid black portion in the figure is the image area with emphasis on resolution expressed by 400 lines, and the part expressed by stripes is expressed by 200 lines. It is an image part that emphasizes gradation.

[Generation of TEXT Signal at Overlapping Portion] FIG.
19B is a list in which the image shown in FIG. 19A is described in PDL. Image R3
Both 01 and R302 represent the character “IC”, of which the image R302 is represented within the figure R303 by overlapping with the figure R303. In this case, of course, the TEXT data of the image R301 is "1". Further, the TEXT data of the image R302 becomes "1", and the TEXT data of the graphic R303 becomes "0". Therefore, for the overlapping portion of the image R302 and the graphic R303, TEXT data = '1' is given priority.

This priority order is, for example, (character>line>
Contours> Inside a figure> Base), etc., and if the ones with higher priority than the contours overlap, unconditionally TE
If the XT data is set to '1', or if at least one of the TEXT data is set to '1' in the overlapping portion of a plurality of images, a rule such as TEXT data = '1' may be determined. Then, the TEXT data generated in this way is written in the memory 109. FIG. 19B is a diagram showing the TEXT data written in the memory 109 by the above processing.

Therefore, by reading the image data and the TEXT data written in the memory 109 in synchronization with each other and inputting the read TEXT data to the selector 1004 (FIG. 8), the screen frequency is 400 lines / 200 lines. The image can be formed by switching to. Figure 20 is a diagram showing the results of switching the screen rulings.The solid black portion in the figure is the resolution-oriented image portion represented by 400 lines, and the portion represented by stripes is represented by 200 lines. It is an image part that emphasizes gradation.

As described above, according to the present embodiment, by using the information described in PDL, an image in which resolution is important such as characters / fine lines / contours and other gradation characteristics are used. When an image to be emphasized is discriminated and the image is formed, an appropriate screen ruling is automatically set according to the discrimination result, and an image with high image quality can be formed.

[0089]

[Second Embodiment] An image processing apparatus according to a second embodiment of the present invention will be described below. In the second embodiment,
The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The second embodiment is a spatial filter shown in FIG.
As shown in FIG. 21, the characteristics of the 133 and the γ correction unit 134 are TE
It is switched according to the XT data.

[Switching of spatial filter] Spatial filter 13
In 3, the TEXT data is used as the selection signal of the selector 1205, and the spatial filter has the characteristics that emphasize the gradation.
1201 and spatial filter 1203 with characteristics that emphasize resolution
Switch between and. That is, when the TEXT data is '0' (gray level is emphasized), the spatial filter 1201 is selected, the filtering process having the characteristic indicated by reference numeral 1202 is performed, and smooth gray level is reproduced. On the contrary, when the TEXT data is '1' (resolution priority), the spatial filter 1203 is selected and the code 1204
The filtering process with the characteristics as shown in is performed to emphasize the edges and reproduce the edges of characters / fine lines / contours clearly.

[Switching gamma correction] Similarly, the gamma correction section
In 134, the TEXT data is used as a selection signal of the selector 1210, and a lookup table (LUT) 1206 having a characteristic that emphasizes gradation is used, and an L table having a characteristic that emphasizes resolution.
Switch between UT1208. That is, when the TEXT data is '0' (gray level is important), the LUT 1206 is selected, the linear characteristic correction as indicated by reference numeral 1207 is performed, and the gray level is given priority to all the densities. Conversely, the TEXT data is '1'
When (Emphasis on resolution) is selected, LUT1208 is selected and the code is 1209.
The steep characteristics are corrected as shown in, and characters / fine lines /
The contour lines are clearly reproduced.

As described above, according to this embodiment, the same effect as that of the first embodiment can be obtained, and in addition, the γ table and the spatial filter adapted to the character / line drawing and the gradation image are automatically set. Therefore, it is possible to form an image with higher image quality.

[0094]

Third Embodiment An image processing apparatus according to the third embodiment of the present invention will be described below. Incidentally, in the third embodiment,
The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 22 is a block diagram showing a configuration example of the image forming apparatus of the third embodiment, in which the position of the external I / F 131 shown in FIG. 3 is moved from the CMYK signal section to the RGB signal section. Therefore, the selector 132 switches between the image signal and TEXT signal input from the controller 102 and the image signal and TEXT signal input from the input masking unit 112 and the image area determination unit 105.

Then, in the third embodiment, as shown in FIG. 23, the LOG conversion unit 104 and the masking / UCR unit 106 also have T
EXT data is input, and LOG conversion characteristics and masking / UCR characteristics are switched according to TEXT data.

[Switching of LOG conversion] In the LOG converter 104, the TEXT data is used as a selection signal of the selector 1305, and a conversion table 1301 having characteristics with emphasis on gradation is provided.
The conversion table 1303, which has characteristics that place importance on resolution, is switched. That is, when the TEXT data is '0' (gray scale is emphasized), the conversion table 1301 is selected, the characteristics shown by reference numeral 1302 are converted, and smooth gray scale is reproduced. On the other hand, when the TEXT data is '1' (resolution-oriented), the conversion table 1303 is selected, the characteristics shown by reference numeral 1304 are converted, and characters / fine lines / contours are clearly reproduced.

[Switching of masking coefficient and UCR amount]
Similarly, in the masking / UCR unit 106, the TEXT data is used as the selection signal of the selector 1310, and the black generation unit 1306 and the masking unit 1307 which have the characteristics that emphasize the gradation property.
And the black generation unit 1308 and the masking unit 1309, which have the characteristics of emphasizing resolution. That is, when the TEXT data is '0' (gray level is emphasized), the black generation section 1306 and the masking section 1307 are selected, and the gray level is given priority to all the densities. On the contrary, when the TEXT data is '1' (resolution-oriented), the black generation unit 1308 and the masking unit 1309 are selected, and characters / fine lines / contour lines are clearly reproduced.

More specifically, in the case of TEXT data = '0' (gradation is emphasized), black is generated by the equation (6), and TEXT data =
In the case of '1' (resolution is important), black is generated according to equation (7). K = min… (6) K = min × (min / MAX) + min × (1-min / MAX) (min / 255) ² … (7) where min = min (Y, M, C) MAX = MAX (Y, M, C)

Further, when TEXT data = “0”, masking processing is performed by the equation (8), and when TEXT data = “1”, masking processing is performed by the equation (9). Where aij (i, j = 1 to 8) and bij (i, j = 1 to 8) are different numbers.

As described above, according to the present embodiment, the same effects as those of the first and second embodiments can be obtained, and in addition, the LOG conversion table and the masking / UCR suitable for the character / line drawing and the gradation image can be obtained. Since the processing can be automatically set, it is possible to form an image with higher image quality.

[0102]

Other Embodiments Even when the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus including one device (for example, a copying machine). Machine, facsimile machine, etc.).

Further, an object of the present invention is to supply a storage medium having a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to supply a computer (or CPU or M or CPU) of the system or apparatus.
Needless to say, this is also achieved by the PU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM,
CD-R, magnetic tape, non-volatile memory card, ROM, etc. can be used.

Moreover, not only the functions of the above-described embodiments are realized by executing the program code read by the computer, but also the OS (operating system) operating on the computer based on the instructions of the program code. It is needless to say that this also includes a case where the above) performs a part or all of the actual processing and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that a case where the CPU included in the function expansion card or the function expansion unit performs some or all of the actual processing and the processing realizes the functions of the above-described embodiments is also included.

When determining the image type from the PDL data, character styles (standard / bold / italic / blank / shadow characters, etc.) and line types (solid line / dot line / dot chain line or straight line / curve / freehand) Etc.), presence / absence of arrowheads of lines, type of figure (closed loop / non-closed loop etc.), shape of figure (rectangle / non-rectangle / freehand etc.), type of contour line of figure (solid line / dotted line / dashed line or straight line / Curve / freehand, etc.),
Patterns inside the figure (vertical stripes / horizontal stripes / diagonal lines, etc.) can also be used.

When the image type is determined from a plurality of characteristics and attributes, a logical operation (logical product or logical sum) is performed on the plurality of determination results, or a majority decision is made.
It may be a signal for switching the image processing. Alternatively, the image processing may be switched depending on the determination result of the image located on the uppermost surface (the frontmost surface) of the finally formed image.

[0108]

As described above, according to the present invention,
It is possible to correctly determine the image type and perform appropriate image processing for each pixel.

Further, a high quality image can be output at low cost.

[Brief description of drawings]

FIG. 1 is a schematic view of an image forming system according to an embodiment of the present invention,

FIG. 2 is a schematic view of the image forming apparatus shown in FIG.

FIG. 3 is a block diagram showing the flow of an image signal,

FIG. 4 is a diagram showing writing / reading timing of image data in a copying machine operation;

5 is a block diagram showing a configuration example of an image area determination unit shown in FIG.

FIG. 6 is a diagram for explaining a determination signal TEXT,

7 is a diagram for explaining the structure of data stored in the memory 109 shown in FIG. 3 and how to read it;

8 is a block diagram showing a configuration example of one color of the PWM circuit shown in FIG. 3,

[FIG. 9] Example of timing chart in PWM circuit,

FIG. 10A is a diagram for explaining PDL data,

10B is a diagram showing a result of raster image processing by interpreting the PDL data of FIG. 10A;

11 is a control flowchart of the controller shown in FIG.

FIG. 12 is a diagram showing an example of PDL data,

13A is a diagram showing a result of interpreting the PDL data of FIG. 12 and performing raster image processing;

13B is a diagram showing TEXT data corresponding to FIG. 13A,

FIG. 14 is a flowchart illustrating a line number switching control based on TEXT data in the image forming apparatus,

FIG. 15 is a list in which the image shown in FIG. 16A is described in PDL;

16A is a diagram showing an example of an image, FIG.

16B is a diagram showing TEXT data corresponding to FIG. 16A,

FIG. 17 is a diagram showing the result of switching the screen ruling for the image of FIG. 16A;

FIG. 18 is a list in which the image shown in FIG. 19A is described in PDL;

FIG. 19A is a diagram showing an example of an image;

FIG. 19B is a diagram showing TEXT data corresponding to FIG. 17A;

FIG. 20 is a diagram showing a result of switching the screen ruling for the image of FIG. 17A;

FIG. 21 is a spatial filter and γ in the second embodiment.
Block diagram showing a configuration example for switching the characteristics of the correction unit,

FIG. 22 is a block diagram showing a configuration example of an image forming apparatus according to a third embodiment,

FIG. 23 is a block diagram showing a configuration example in which characteristics, a masking coefficient, and a UCR amount of a LOG conversion unit are switched in the third embodiment.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G06T 11/00 100 B41J 2/00 B41J 5/30 G06F 3/12

Claims (18)

(57) [Claims] 1. From information described in a page description language,
An image signal, and generating means for generating a feature signal representing a feature of each pixel of the image signal, for each pixel of the image signal, have a processing means for performing image processing corresponding to the characteristic signal, said The generation means is an image tag in the page description language.
Type, image type and image attributes,
A predetermined logical operation is performed on the result of judging the characteristics of each pixel.
An image processing apparatus, characterized in that the characteristic signal is obtained by performing the processing. 2. The image processing apparatus according to claim 1, wherein the generation unit determines a feature of each pixel based on an image type in the page description language. 3. The image processing apparatus according to claim 2, wherein the image type includes at least one of a character code, a graphic code, and raster image data. 4. The image processing apparatus according to claim 1, wherein the generation unit determines a feature for each pixel based on an image attribute in the page description language. 5. The image attributes include at least characters,
5. The image processing apparatus according to claim 4, wherein one of a line, a figure, a contour line, and the inside of the figure is included. 6. The image processing apparatus according to claim 1, wherein the generation unit determines a characteristic of each pixel based on an attribute of an image in the page description language and a parameter indicating the content thereof. . 7. The image attributes and the parameters representing the contents thereof include at least a character font, a character size, a character style, a character color or density, a line thickness,
Line type, line color or density, line length, line angle, figure type, figure shape, figure size, outline thickness,
Contour type, contour color or density, contour length,
Contains one of the following: the angle of the contour line, the pattern inside the figure, the color or density inside the figure, the density of the dots inside the figure, the coordinates of the image, the pattern of the raster image, the color or density of the raster image, and the density of the dots. 7. The image processing device according to claim 6, wherein 8. The image processing apparatus according to claim 4, wherein the generation unit determines a feature for each pixel based on a priority order corresponding to an attribute of the image. 9. The image processing apparatus according to claim 1 , wherein the logical operation for obtaining the characteristic signal is a logical product. 10. The image processing apparatus according to claim 1 , wherein the logical operation for obtaining the characteristic signal is a logical sum. 11. The image processing apparatus according to claim 1 , wherein the logical operation for obtaining the characteristic signal is a majority decision. 12. The generating means determines the characteristics of each pixel based on each of the image type, the image type and the image attribute in the page description language, and determines the top surface or the top surface of the formed image. The image processing apparatus according to claim 1, wherein the determination result of the image located at is used as the characteristic signal. 13. The image processing apparatus according to claim 1, wherein the processing unit switches between image processing that emphasizes gradation and image processing that emphasizes resolution based on the characteristic signal. . 14. The image processing performed by the processing means includes at least processing for controlling a pulse width of a signal for forming an image according to the image signal , gamma correction processing, and space processing.
Filtering, masking, black generation or black extraction
14. The image processing apparatus according to claim 1 or 13 , wherein the image processing apparatus includes one of the above. 15. to the processing means performs image processing, at least a luminance - image processing apparatus according to claim 1 or claim 13, characterized in that includes density conversion processing. 16. An image processing apparatus according to any one of claims 1 to 15, wherein the image signal and the characteristic signal, characterized in that it is synchronous transfer. The method according to claim 17, wherein the image signal and the characteristic signal, once stored in memory, claim from claim 1 is read out from said memory, characterized in that it is synchronous transfer 16
The image processing device described in any one of 1. From 18. The information described in a page description language, and an image signal to generate a feature signal representing a feature of each pixel of the image signal, for each pixel of the image signal, corresponding to the characteristic signal have a respective step of performing image processing, the feature signal, data of an image in the page description language
Type, image type and image attributes,
A predetermined logical operation is performed on the result of judging the characteristics of each pixel.
An image processing method characterized by being generated by application .