JPH04158061A - Graphic output device - Google Patents

Abstract

PURPOSE:To enhance an effect of anti-aliasing process by correcting a state that lateral lines are expressed thinner than vertical lines at the time of outputting from a laser beam printer, etc., by using a filter of long vertical length when dividing a pixel to be used into subpixels, filtering it, and adding them in one pixel to calculate an area rate. CONSTITUTION:If a width ratio of a vertical line to a lateral line is c:1 and a subpixel division of m*m is used, when the vertical length of a filter is x=m(c-1)/2, it is extended by a value obtained by multiplying 2/m by the round-up fraction of the x. The total of one pixel part at the center of the filter is obtained, and the standard value of the filter is set to A. Since the filter has a vertical length of one pixel or more, an image to be filtered by the filter needs (1 + (round-up fraction of x) X 2/m) line, and hence image data of the line is always stored while updating the content. The image data of a plurality of the lines is divided into subpixels, and filtered by a filter having long vertical length to obtain an area rate. If the calculated value is larger than the value A of the filter, the value is replaced by a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a graphic output device that performs anti-aliasing processing to remove jagged edges of an output image. ) is divided into subpixels, filtered, summed within one pixel, and calculated area ratio. Graphical output that corrects the aspect ratio of striped horizontal lines by using a reduction filter. Regarding equipment.

[Conventional technology]

In the field of computer graphics, when displaying an image on a CRT, which is an output medium, a technique called anti-aliasing processing is used to make the displayed image more beautiful.

This process applies brightness modulation to the jagged parts (called aliases) on the stairs as shown in Figure 21(a),
This visually smooths the displayed image as shown in FIG. 21(b).

Furthermore, as a method for outputting data after anti-aliasing processing, for example, an electrostatic latent image corresponding to image information is formed on a rotating photoreceptor drum using a laser, and the electrostatic latent image is transferred to the photoreceptor. There is a system in which toner is visualized on a developing sleeve that rotates in contact with a drum.

[Problem to be solved by the invention]

However, when the linear velocity at the contact portion between the photoreceptor drum and the developing sleeve is higher than that of the photoreceptor drum, the latent image in a line perpendicular to the rotation direction is There is a problem that the image is developed thinly.

In other words, the magnitude of the applied friction force varies depending on the angle of the direction of the latent line image on the photoconductor drum with respect to the rotational direction of the photoconductor drum and developing sleeve, resulting in a problem in that the reproduced line width differs. do.

The present invention has been made in view of the above, and includes, for example,
The purpose is to prevent horizontal lines from appearing thinner than vertical lines when outputting images using a laser beam printer, etc., and to enhance the effectiveness of anti-aliasing processing.

[Means to solve the problem]

In order to achieve the above object, the present invention includes an anti-aliasing processing means for smoothly expressing jagged edges (aliases) of a hector image, and outputting image data subjected to anti-aliasing processing from the anti-aliasing processing means. A graphic output device comprising an image output means, a line width ratio detection means for detecting a line width ratio between vertical lines and horizontal lines of an output medium, and a length (n pixels) of a navy blue color of a filter used for the anti-aliasing processing. a first calculation means for calculating, a second calculation means for calculating the number m of lines of the image necessary for the filter processing, a storage means for storing the image data for m lines or more, the filter and the storage. The present invention provides a graphic output device including third calculating means for calculating the area ratio of each pixel based on image data stored in the means.

[For production]

The graphic output device of the present invention divides a target pixel into sub-pixels, applies a filter, calculates the sum within one pixel, and calculates the area ratio. Corrects the situation where horizontal lines appear thinner than vertical lines when output from a beam printer, etc.

[Example] An embodiment of the graphic output device of the present invention will be described below based on the drawings. Configuration ■Configuration of multi-value color laser printer (configuration and operation of developing section of multi-value color laser printer) ■ Multi-value drive of driver ■ Specific operation examples will be explained in detail in this order.

■Summary of the Invention In the graphic output device according to the present invention, a modified filter used for conventional anti-aliasing processing is used. The horizontal length of the filter is kept at 1 pixel, and the vertical length is extended to n pixels. The vertical length of the filter is determined by the vertical/horizontal line width ratio before correction when outputting on each output medium, and its accuracy depends on the number of subpixel divisions.

First, the line width ratio of vertical lines and horizontal lines on the corresponding output medium is detected.

A schematic configuration of a laser beam printer is shown in FIG. 11, which will be described later, and one color in the drawing will be explained.

In the same figure, 512bk is a photosensitive drum, 519bk
This is a toner image measuring device consisting of a CCD line sensor and an LED light source.

In the toner image measuring device, the toner image formed on the photoreceptor drum 512bk moves between the CCD line sensor 519bk and the photoreceptor drum 512bk as the photoreceptor drum 512bk rotates, and in turn moves between the CCD line sensor 519bk and the photoreceptor drum 512bk.
9bk is used to measure the amount of reflected light, and the toner adhesion state of the pattern can be measured. The measured values are sequentially sent and stored in a RAM which is used for pattern storage.

In this embodiment, the first
A test pattern of striped lines and horizontal lines having the same line width as shown in Figure (b) is written, and the toner image formed thereby (Figure 1 (C)) is transferred to the CCD line sensor 519bk
Read at.

Thereafter, the line widths of the successive patterns stored in the RAM are counted for each vertical line and horizontal line, and the ratio is calculated to obtain the line width ratio of the vertical line and horizontal line (FIG. 1(d)).

If the vertical line width is a and the horizontal line width is b, then the ratio is a:b
For convenience of later processing, it is modified to a/b:1.

Below, the line width ratio of striped lines and horizontal lines is c:1, and m
A line width ratio correction method when using *m sub-vixel division will be described.

The length of the dark blue filter is preferably C pixels, but depending on the number of subpixel divisions, the filter is 17
Considering in units of m, the length of the filter blade is extended by the value obtained by rounding up X and multiplying by 2/m. Also, pay attention to the central 1-pixel portion of the filter, calculate the total, and set the standard value of that filter as A.

The area ratio calculation for the target pixel is basically performed using a method similar to the convolution method described later. Since the filter has a length of more than one pixel in the picture, the image area to which the filter can be applied also needs to cover multiple lines.

Specifically, since (1+(round up of x) x2/m) lines are required, that amount of image data is stored while constantly updating its contents. The image data of these multiple lines is divided into sub-vixels as before, and the area ratio is determined by applying a vertical filter. If the calculated value is larger than the filter standard value A, replace the value with aT:.

■Schematic configuration of image forming system The image forming system of this embodiment uses a page description language (P
ageDescriptionLanguage
This configuration allows image formation of both image information, including vector data written in the PDL language (hereinafter referred to as PDL language) and image images read by an image reading device.

The configuration of the image forming system of this embodiment will be described below with reference to FIG. 1(a).

The image forming system includes a host computer 100 that creates a document written in PDL language (Postscript language is used in this embodiment);
A PDL controller (the anti-aliasing processing of the present invention) that applies anti-aliasing processing to the incoming PDL language sent page by page from equipment) 200
an image reading device 300 that reads image information through an optical system unit; and an image processing device that inputs an image output from the PDL controller 200 or the image reading device W300 and performs image processing (details will be described later). A bag W400 and a multivalued color laser printer 5 that prints multivalued image data output from the image processing bag W400.
00, PDL controller 200, and image reading device 3
00, an image processing device 400, and a system control unit 600 that controls a multivalued color laser printer 500.

■Anti-aliasing processing The following methods are known as anti-aliasing processing methods.

i, Uniform averaging method 11. Weighting is an averaging method 1111 convolution integral method Each of the above methods will be explained in turn.

1. Uniform averaging method The uniform averaging method calculates each pixel by N*M (N, M
is a natural number), performs rask calculation at high resolution, and then calculates the brightness of each pixel by taking the average of N*M sub-pixels. Figure 2 (a), (
Anti-aliasing processing using the uniform averaging method will be specifically explained with reference to b).

If the edge of the image overlaps a certain pixel (here, the image is connected to the bottom right of the diagonal line),
When anti-aliasing processing is not performed, the same figure (a)
), the brightness of this pixel (kid L) is the maximum brightness of the gradation that can be displayed (for example, on the second round of the 256th floor, k
id・255) is assigned. N= for this pixel
When performing anti-aliasing processing using the uniform averaging method with M=7, as shown in FIG. 4B, a pixel is decomposed into 7*7 sub-vixels, and the number of sub-vixels covered by the image is counted. The count number (28)
is the total number of sub-vixels in l pixel (49 in this case)
The maximum brightness (255
) to calculate the brightness of that pixel. In this way, in the uniform averaging method, the brightness of each pixel is determined by taking into consideration how the image covers each pixel.

11. Weighting is an averaging method The weighting and averaging method is a partial modification of the uniform averaging method. In contrast, the weighted averaging method assigns a weight to each subpixel, and the brightness of that subpixel (kid) is calculated based on which subpixel the image covers. The impact on the data appears to be different. still,
At this time, weights are assigned using a filter.

Referring to Figures 3(a) and (b), an example in which the same image data as in Figure 2(a) is weighted using the same dividing method (N=M=7) and the averaging method. shows.

FIG. 3(a) shows a filter (here, conefi
lter), and the corresponding sub-pixel is given the same weight as this characteristic. For example, the weight of the upper right corner subpixel is 2. When an image is applied to each subpixel, the weight value given by the filter characteristics becomes the count value of that subpixel. FIG. 6B shows the display pattern of the image changed depending on the weight of the sub-pixels. In this case, if we count the weighted subpixels of the image, we get 1
It becomes 99. This value is divided by the sum of the filter values (336 in this case) corresponding to uniform averaging, averaged, and multiplied by the maximum brightness to calculate the brightness of this pixel. The filters shown in Fig. 4 (a), (b),
Filters shown in (C) and (d) are known.

j15 Convolutional Integral Method The convolutional integral method is a method that also refers to the appearance of surrounding pixels when determining the brightness of one pixel. That is, the area around one pixel whose brightness is to be determined is N
Consider the 'XN' pixels to correspond to the equal-averaging or weighted averaging pixels. FIG. 5 shows the convolution method with 3×3 pixel references. In this figure, the pixel whose brightness is to be determined is indicated at 51.

The image continues below and to the right of the diagonal line, and the subpixels painted black are the subpixels that are counted.

Each pixel is divided into 4*4. Therefore, in this case, a 12*12 filter will be used. This method has the effect of removing high frequency components contained in a vector image.

On the other hand, a publishing system using a personal computer,
With the spread of so-called DTP (desk top publishing), systems for printing vector images, such as those used in computer graphics, have become widely used. A typical example is a system using Adobe's Post Script. PostScript belongs to the language genre of page description languages, and is used to describe the contents of a single document, such as the text (text), graphics, etc.
Alternatively, it is a programming language for describing forms including their arrangement and appearance, and such systems employ vector fonts as character fonts. Therefore, even when characters are scaled, the print quality can be significantly improved compared to systems that use Bitma/Nobu fonts (for example, conventional word processors, etc.). It has the advantage that it is possible to print a mixture of images.

However, according to the conventional anti-aliasing processing method and its device, one pixel is divided into a plurality of sub-pixels (for example, 49 sub-pixels), and the number of filled-in sub-pixels is counted to calculate the area ratio. (brightness), it takes time to calculate the area ratio, which poses a problem in that it hinders improvement in display speed or printing speed. In particular, the convolution method has problems in that it requires a large amount of calculation and affects multiple pixels, making it difficult to improve processing speed.

In view of the above, an anti-alias song method has also been proposed that calculates the area ratio at high speed without dividing sub-vixels or counting the number of filled pixels.

1. Method for obtaining approximate area ratio of edge pixels This anti-aliasing processing method involves determining the presence or absence of an intersection between hector data and a predetermined group of straight lines when edge pixels are divided by a predetermined group of straight lines; Based on the type of edge, the area ratio near the edge of the pixel of the edge/knob portion is obtained. Below, the 6th
A method for obtaining an approximate area ratio from the presence or absence of an intersection and the type of edge will be described in detail with reference to FIGS.

Straight line L1 (hereinafter referred to as vector straight line L) given by vector data and each line y in the sub-scanning direction y
. +V++yz at the intersection X, as shown in FIG. 6(a). + X l + X 2, the equation of this vector straight line L1 is, for example,
yo) and (χ++y"1) using the following equation (1).

X + X.

On the other hand, focusing on the pixel P, a new χ"y" coordinate system is set, and as shown in FIG. 6(b), the pixel P is aligned in a straight line,
It, i! , z, l-, is, Eb, ! 7.
It is divided by eight straight lines (hereinafter referred to as dividing straight lines) of I2s. Here, the equation of each straight line is the following equation (3)
~θ0).

Dividing straight line 1 +: x = O------(3)
j22: x = 1/3 −−−−−− (4)
i! , 3: χ−2/ 3 −=−−−(5) 14: x
= 1 ------- (6) p, 2y=o-
−−−−−(7) 1, : y = 1/3−−−−−− (8)
127: y = 2 / 3 ---- (9) fe
:y=1 ・------(10) Also, the equation of the vector straight line L1 obtained using the above equation (1) is y=-(1/3)X+ (7/6) -(2) Assuming that, the dividing straight line f +, Rz, E that divides this vector straight line L1 and the pixel P 3. IL4. I
! , s.

16.1! , 'r, and the coordinates of the intersections with in are shown in the following table.

Table Here, the range of χ゛ and y゛ of pixel P in the x'y'' coordinate system is 0≦X゛≦1.0≦y゛≦1, so there is no intersection within the range of this pixel P. There are three dividing straight lines R3 and E4#e.Conversely, within the range of this pixel P, the three dividing straight lines f3.f-, I
The equation of the Kutle line, which has only 8 points of intersection, is the 6th
As shown in figure (C), if the intersection points are A and B, the coordinates of the intersection point A are (1/3<x'≦2/3.y'
-1) The coordinates of intersection B are (x'=1.2/3<y'<1)
It will definitely pass through the range. For this reason, 1. the three dividing straight lines 1. The area ratios of pixels P divided by vector straight lines that intersect only with ff+14+l s show close values; in other words, the vector straight line groups that have intersections with the predetermined dividing straight line group are set as one set. case,
The area ratio of the pixel P divided by the hector straight line group C2 of the set indicates a similar area ratio within a predetermined range. Therefore, the vector straight line and the dividing straight line z1p2. p3. p,,p,
,, p6. The individual area ratios of the set classified based on the intersection information with p, , p8 can be approximated to one area ratio.

Therefore, in this anti-aliasing processing method, a set of vector straight lines is created based on the intersection information and edge information indicating which edge is on the left or right, and an approximate area ratio is calculated for each set in advance. For example, a LUT (Look Up Table) as shown in FIG. 6(d) is created which includes intersection information, edge information, and approximate area ratio. Then, when performing anti-aliasing processing,
Instead of performing subpixel division and calculating the area ratio of edge pixels, based on intersection information and edge information,
The output adjustment for edge pixels is performed by inputting the corresponding approximate area ratio from the LUT.

In the LUT shown in FIG. 6(d), the edge information flag indicates a left edge when the left edge flag is -1 and the right edge flag is -0, and when the left edge flag is -0 and the right edge flag is -1, it indicates a right edge. .

Also, when left edge flag - right edge flag = 1,
11D represents the vertices as shown in (e), and when the dividing straight line flag is -1, the dividing straight lines 1+, 12 . z.

・・・・・・! 8 and the vector straight line intersect (that is, there is an intersection). LUT data D
The figure (e) shows straight lines that can be considered under 10 conditions, and the data D1 also includes the approximate area ratio of the diagonally shaded portion shown in the figure (e) as information. Similarly, the straight line that can be considered under the conditions of the data D2 of the LUT is shown in (Figure 1), and the data D2 includes the approximate area ratio of the shaded portion shown in Figure (Figure 2) as information. Therefore, for example, in the same figure (e
) to find the area ratio of the vector line, cough hector line and dividing line! 1. Find the intersection with nz,...16, then use the edge information determined by the PDL specifications to determine whether the edge is a left edge, edge, or right edge, and use these intersection information and edge information. Based on this, the corresponding approximate area ratio is obtained from the LUT.

■Configuration and operation of PDL controller FIG. 7(a) shows the configuration of the PDL controller 200.
A receiving device 201 that receives a language, a CPU 202 that performs storage control and anti-aliasing processing for the PDL language received by the receiving device 201, and an internal system Has2
03 and the receiving device 20 via the internal system HAS 203.
A RAM 204 that stores the PDL language to be transferred from 1, and a ROM that stores anti-aliasing programs, etc.
205 and multivalued R with anti-aliasing processing
a page memory 206 that stores GB image data;
It is composed of a transmitting device 207 that transfers RGB image data stored in the page memory 206 to the image processing device 400, and an I10 device 208 that transmits and receives data to and from the system control unit 600.

Here, the CPtJ 202 transfers the PDL language received by the receiving device 201 to the RAM 204 through the internal system hash 203 according to the program stored in the ROM 205.
Store in. After that, when the PDL language for one page is received and stored in the RAM 204, the graphic elements in the RAM 204 are subjected to an anti-aliasing processing method, and the multivalued RG
B image data is stored in the plain memory section of the page memory 206 (the page memory 206 is stored in the plain memory section of the page memory 206 as shown in FIG.
As shown in FIG. 2, it consists of an R, G, and B plane memory section 206a and a feature information memory section 206b).

The data in the page memory 206 is then transferred to the transmitter 2
07 to the image processing device 400.

The operation of the PDL controller 200 will be described below with reference to FIG.

FIG. 8(a) shows a flowchart of the processing performed by the CPU 202. As described above, the PDL controller 200 performs anti-aliasing processing on the PDL language sent page by page from the host computer 100, and generates three-color images of red (R), green (G), and blue (B). Expand to.

In the PDL language, graphics and characters are all described using hector data, and as the name "page description language" indicates, image information is processed in units of pages. Furthermore, one page is made up of at least one path, with each path being made up of one or more elements (graphic elements and text elements).

First, when PDL language is input, it is determined whether the element is a curved vector, and if it is a curved vector, it is approximated to a straight line vector and registered as a straight line element (line) in the work area. This is performed for all V-shaped and character elements within one path, and straight line elements are registered in the work area for each path (processing 1).

Then, the linear elements of the work area registered for each path are sorted based on the starting y-coordinate of the straight line (processing 2).

Next, in process 3, the ylu marks are updated one by one and filled with scanning lines. For example, when performing the path filling process shown in FIG.
Real value of the X coordinate across (X+ shown in Figure 8(b)
X2 X3 X4) and AET (＾active Ed
geTable: a table for recording the X coordinate of the edge portion appearing on the scanning line).

Here, the order of the elements registered in the work area is the order in which they were registered in process 1, so they are not necessarily registered in order of decreasing X coordinate across the scanning line yc. For example, in process 1, if a straight line element passing through scanning lines yc and x3 in FIG. 8(b) is processed first, be registered first. Therefore, after the AET is registered, the elements on each side within the AET are sorted in descending order of X coordinate. Then, the first two elements of the AET are paired and the space between them is filled in (filling process using scanning lines). Anti-aliasing processing is achieved by adjusting the density and brightness of pixels in the edge portion in accordance with the near area ratio in this filling processing. Then, remove the processed edge from the AET and update the scanline (X
coordinates) until all edges in the AET have been processed, in other words, all elements in one path have been processed.
Repeat the process.

The operations of process 1, process 2, and process 3 described above are executed pass by pass, and repeated until all passes for one page are completed.

Next, FIG. 8 (C
), will be explained based on the flowchart of FIG. 8(d).

FIG. 8(C) is a flowchart showing the flow of filter determination.

First, detect the vertical/horizontal line width ratio of the output medium (step 5
301). Second, the number of subpixel divisions is determined (step 5302). Third, the vertical length of the filter is calculated from C and m described in section 2 (step 5303), and the filter is determined.

Next, FIG. 8(d) is a flowchart showing the flow of area ratio determination.

First, calculate the area ratio (Step S 305), and second, determine whether the area ratio is A (Step 5306).
. Area ratio〈If it is determined that it is not A, change the area ratio to A.
shall be. On the other hand, if it is determined that the area ratio is A,
The area ratio calculated in 5UTEPUS 305 is used, and the area ratio determination process for that pixel ends.

0 Configuration of Image Processing Apparatus The configuration of the image processing apparatus 400 will be explained with reference to FIG.

The image processing device 400 is a CC in the image reading device 300.
The three-color image signals read by D7r, 7g, and 7b are converted into black (BK), yellow (Y), magenta (M), and cyan (C) recording signals necessary for recording. Further, the RGB image data given from the PDL controller 200 described above is similarly blanked (BK
), yellow (Y), magenta (M), and fan (
C) into each recording signal. Here, the mode for inputting an image signal from the image reading device 300 is a copying machine mode,
The mode that inputs RGB image data from the PDL controller 200 is called a graphics node mode.

The image processing device 400 includes CCDs 7r, 7g, and 7b.
The color gradation data obtained by A/D converting the output signal of
a shading correction circuit 401 that performs correction for variations in anger level of internal terminal elements of 7r, 7g, and 7b;
a multiplexer 402 that selectively outputs either the color gradation data output from the shading correction circuit 401 or the color gradation data (ROB image data) output from the PDL controller 200 according to the aforementioned mode;
A γ correction circuit 40 receives the 8-bit data (color gradation data) output from the multiplexer 402, changes the gradation according to the characteristics of the photoreceptor, and outputs it as 6-bit data.
3, (R) and green (G) output from the γ correction circuit 403.
), 6-bit gradation data indicating the gradation of blue (B) is converted into gradation data (6 bits) of the respective complementary colors cyan (C), magenta (M), and yellow (Y). Y output from the color generation circuit 405 and the complementary color generation circuit 405
A masking processing circuit 406 performs predetermined masking processing on each gradation data of , M, and C, and a masking processing circuit 406 that performs predetermined masking processing on each gradation data of Y,
a tJcR processing/black generation circuit 407 that inputs M and C gradation data and executes UCR processing and black generation processing;
Y, M, C output from CR processing/black generation 8407
Gradation processing that converts each 6-bit gradation data of 1 and BK into 3-bit gradation data YLMI, CL, and BKI, and outputs it to the laser drive processing section 502 inside the multi-valued color laser printer 500. A synchronization control circuit 4 for synchronizing the circuit 408 and each circuit of the image processing device 400
09.

Although details will be omitted, the γ correction circuit 403 has a configuration in which the gradation can be arbitrarily changed using an operation button on the console 700.

Further, as an algorithm used in the gradation processing circuit 408, a multi-value dither method, a multi-value error diffusion method, etc. can be applied. For example, a dither matrix of the multi-value dither method is
x 3, the number of gradations of the multilevel color laser printer 500 is the product of the area gradation of 3 x 3 and the multilevel level of 3 bits (that is, 8 levels), and 3X3X8 = 72 (8 rounds of floors). becomes.

Next, the processing of the masking processing circuit 406 and the UCR processing/black generation circuit 407 will be explained.

Generally, the arithmetic expression for masking processing of the masking processing circuit 406 is as follows: Y, , M, , C,: masking processing unit data Yo, Mo
, co: data after masking processing is used.

Further, the arithmetic expression for UCR processing of the TJCR processing/black generation circuit 407 is also generally expressed as follows.

Therefore, in this embodiment, new coefficients are obtained from these equations using the product of both coefficients.

et al: 1 ・ 10° (BK,' In this embodiment, new coefficients (al, ", etc.) for performing this masking processing and UCR processing simultaneously are calculated in advance,
Furthermore, using the new coefficients, the masking processing circuit 40
6 scheduled input values Y,,M,.

Output value (yo” etc.: UC) corresponding to C8 (6 bits each)
This is the calculation result of the R processing/black generation circuit 407 (I is calculated and stored in a predetermined memory in advance).

Therefore, in this embodiment, the masking processing circuit 406 and U
The CR processing/black generation circuit 407 is composed of l ROMs, and the data at the address specified by the masking processing circuit 406 (D inputs Y, M, and C) is given as the output of the UCR processing/black generation circuit 407.

In addition, for boat fishing, the masking processing circuit 406 sets Y= according to the characteristics of the spectral reflection wavelength of the recorded image forming toner.
The UCR processing/black generation circuit 407 corrects the M and C signals, and the UCR processing/black generation circuit 407 performs correction for color balance in overlapping toners of each color. After passing through the UCR processing/black generation circuit 407, black component data BK is generated by combining the input three color data of Y, M, and C, and the output Y
, , M, and C color components are corrected to values obtained by subtracting black component data BK.

■Configuration of multi-value color laser printer (configuration and operation of developing section of multi-value color laser printer) First, the schematic configuration of multi-value color laser printer 5000 will be explained with reference to the control block diagram shown in FIG. do.

A photoreceptor development processing unit 501 uniformly charges the surface of a photoreceptor drum (described later), exposes the charged surface to a laser beam to form a latent image, develops the latent image with toner, and transfers it to recording paper. The details will be explained later, but the development and development of BK data is
A black developing/transfer section 501bk that performs transfer, a cyan developing/transfer section 501c that develops and transfers C data,
A magenta developing/transfer section 50 that develops/transfers M data.
1m, and a yellow developing/transfer section 501y that develops and transfers Y data.

The laser drive processing unit 502 includes the image processing device 4 described above.
It outputs a laser beam by inputting the 3-bit data of Y, M, C, and BK output from 00 (in this case, image density data). Hanwha Memory 503y, 503m to input
, 503c, and a laser diode 504y that outputs laser beams corresponding to Y, M, C, and BK, respectively.
Tribars 505y, 505m, 505c, and 5 drive the laser diodes 504y, 504m, 504c, and 504bk, respectively.
It is composed of 05bk.

Note that the blank developing/transfer section 5 of the photoreceptor development processing section 501
01bk, the laser drive processing unit 502, the laser diode 504bk, and the driver 505bk are called a blank recording unit BKU (see FIG. 11). Similarly, the combination of the cyan developing/transfer section 501c, laser diode 504c, driver 505c, and Hasofa Memo'J 503c is used in the cyan recording unit C.
U (see Figure 11), magenta developing/transfer section 501m,
A combination of a laser diode 504m, a driver 505m, and a fa memory 503m is connected to a magenta recording unit MLJ (see Figure 11), a yellow developing/transfer section 501y, a laser diode 504y, and a driver 5o.
5y and the yellow sofa memory 503y are called yellow recording unit 1-YU (see FIG. 11). As shown in the figure, these recording units are arranged around a conveyor belt 506 that conveys the recording paper in the direction of conveyance of the recording paper: a blank recording unit hBKU, a cyan recording unit CU, a magenta recording unit MU, and a yellow recording unit YU.
They are arranged in this order.

Due to this arrangement of each recording unit, the laser diode 5 for black exposure starts exposure first.
04bk, and the laser diode 504y for yellow exposure starts exposure last. Therefore,
There is a time difference in the order of exposure start between each laser diode,
Data recorded during the time difference (output of the image processing device 400)
In order to hold the data, the laser drive processing unit 502 includes the three sets of buffer memories 503y, 503m, and 503c described above.
is provided.

Next, the configuration of the multivalued color laser printer 500 will be specifically explained with reference to FIG.

The multivalued color laser printer 500 includes a conveyor belt 506 for conveying recording paper, and recording units YU and MU arranged around the conveyor belt 506 as described above.
, CU, BKU, and a paper feed cassette 50 containing recording paper.
7a, 507b, and paper feed cassettes 0508a, 508 that feed recording paper from paper cassettes 507a, 507b, respectively.
b, and a registration roller 509 that aligns the recording paper sent out from the paper feed cassettes 507a and 507b.
The recording units 7, BKu, CU are transported by the transport heald 506.
, MLI, and YU and fixes the transferred image on the recording paper, and a paper discharge roller 511 that discharges the recording paper to a predetermined discharge section (not shown). Here, each recording unit YU, MU, CU, B
KU is photosensitive drum 512y, 512m, 512C1
512bk, and photoreceptor drums 512y and 512, respectively.
Charger 51 that uniformly charges m, 512c, and 512bk
3y, 513m, 513c, 513bk, and polygon mirrors 514y, 514 for guiding the laser beam to the photosensitive drums 512y, 512m, 512C1512bk.
m, 514 c.

5 ] 4 bk and motor 515y, 515m, 51
5C1515bk and photosensitive drum 512y, 512m
, 512c, and 512bk.
Toner developing devices 516y, 516m, and 516C1516bk that develop using toner of the corresponding color, and a transfer charger 517 that transfers the developed toner image to the recording paper.
y, 517m, 517c, 517bk, and a cleaning cartridge 518y for removing toner remaining on the photoreceptor drums 512y, 512m, 512c, 512bk after transfer.
, 518m, 518C1518bk.

Note that 519y, 519m, 519c, and 519bk are photosensitive drums 512y, 512m, 512c, and 519b, respectively.
A COD line sensor for reading a predetermined pattern provided on the color laser printer 12bk is shown, and although the details are omitted, the process status of the multivalued color laser printer 500 is detected by this sensor.

The operation of the above configuration will be explained using exposure, development, and transfer of yellow recording 227 sheets YU as an example.

FIGS. 12(a) and 12(b) show the structure of the exposure system of the yellow recording unit YU. In the figure, a laser beam emitted from a laser diode 504y is reflected by a polygon mirror 514y, passes through an f-theta lens 502y, is further reflected by mirrors 521y and 522y, passes through a dustproof glass 523y, and hits a photosensitive drum 512y. irradiated. At this time, the laser beam is
4y is driven to rotate at a constant speed by the motor 515y, so it moves in the direction along the axis of the photosensitive drum 512y (main scanning direction). Further, in this embodiment, a photosensor 524y is provided to detect the base point of the scanning position tracking in the main scan, so that the laser beam at the non-exposed position is detected. Since the laser diode 504y is activated to emit light based on the recorded data (3-focus data from the image processing device 400), multivalue exposure corresponding to the recorded data is applied to the photoreceptor drum 504y.
performed on the surface of The surface of the photosensitive drum 504y is uniformly charged in advance by the charger 513y as described above, and an electrostatic latent image corresponding to the original image is formed by the exposure. The electrostatic latent image is developed by a yellow developing device 516y to become a yellow toner image. This toner image is
As shown in FIG. 11, paper feed roller 508a (or 508
b), and is transferred by registration rollers 509 onto a recording sheet conveyed by a conveyor belt 506 in synchronization with the toner image formation in the black recording unit (BKU).

The other recording units BKU, CO, and MU have similar configurations and perform similar operations, but the black recording unit BKU is equipped with a blank toner developing device 516bk and forms and transfers a black toner image, and the cyan recording unit C
Unit U is equipped with a cyan toner developing device 516C to form and transfer a cyan toner image, and magenta recording unit MU is equipped with a magenta toner developing device 516m to form and transfer a magenta toner image.

■Multi-value drive of driver Drivers 505y, 505m, 505c.

505bk is Y sent from the image processing device 400.
, M, C, BK 3-bit data, ↓ backing laser diodes 504y, 504m, 504c,
504bk, and power modulation, pulse width modulation, etc. are generally used as the driving method.

Hereinafter, multi-value drive using power modulation, which is used in this embodiment, will be explained in detail. In addition, drivers 505y, 505m, 5
05c, 505bk, and laser diode 504
y, 504m, 504c, and 504bk each have the same configuration, so here, the driver 505y and laser diode 504y will be explained as an example.

The driver 505y, as shown in FIG.
Based on D drive clock, laser diode 5
A laser diode on/off circuit 550 turns on/□ff 04y, a D/A converter 551 converts 3-bit image density data (here, Y data) into an analog signal, and converts the image density value into an analog signal. input the analog signal based on the D/A converter 551,
The current (LD drive current) Id that drives the laser diode 504y is supplied to the laser diode on10ff circuit 55.
0, and a constant current circuit 552 that supplies a constant current to 0.

In the above configuration, the laser diode On/o
f f circuit 550 causes laser diode 504y
emits light, and a laser beam is emitted to the photoreceptor drum 512y.

Here, the LD drive clock is defined as on at 1° and off at 0°, and as shown in FIG. 14, the laser diode on10ff circuit 550 turns on and off the laser diode 504y accordingly.
Since the LD drive current Id and the laser beam power are in a proportional relationship, based on the image density data value <LD drive current 1d
By generating , a laser beam power output corresponding to the image density data value can be obtained. For example, as shown in FIG. 14, the image density data value is "4°" (
In the case of data N-1) in the figure, the corresponding LD drive current Id is supplied by the constant current circuit 552, and the laser beam power of the laser diode 504y is level 4.
becomes. Further, when the image density data value is "7'' (data N in the figure), the corresponding LD drive current 1d is supplied by the constant current circuit 552, and the laser beam power of the laser diode 504y becomes level 7. .

Next, referring to FIG. 15, the laser diode on
/ o f f circuit 550, D/A converter 551
, and the specific circuit configuration of the constant current circuit 552 will be explained. The laser diode on10ff circuit 550 is T
TL inverters 553 and 554, differential switching circuits 555 and 556 that perform onloff toggle operation, and differential switching circuit 555 when VGI>VO2.
is on, differential switching circuit 556 is off, VG
When I<VO2, the differential switching circuit 555 is turned off.
f, a resistor Rz forming a voltage dividing circuit that generates VO2 that satisfies the conditions for the differential switching circuit 556 to be turned on;
, R3, when the LD drive clock is 1'', the output of the inverter 554 generates VGI, the above condition (VG 1 > VG2) is satisfied, and the differential switching circuit 555 is turned on. , the differential switching circuit 556 is off L, and the laser diode 504
Turn on y. Also, conversely, the LD drive black is “
0'', there is no output from the inverter 554, so the above condition (VGl<VG2) is satisfied, the differential switching circuit 555 is off, and the differential switching circuit 556 is off.
turns on and turns off the laser diode 504y.

The D/A converter 551 includes a latch 557 that double-checks the input image density data while the LD drive clock is "1", a V rey generator 558 that provides the maximum output value V ref, and a V rey generator 558 that outputs the image density data and the maximum output value. Output value V re
3-bit D outputting analog data Vd based on f
/A converter 559. Furthermore, here V
The relationship between d, image density data, and maximum output value -0 is expressed by the following equation.

Image density data (manual power value) V d −V ret ×□ The constant current circuit 552 includes the laser diode 504 in the laser diode ON10ff circuit 550 as described above.
y current, and the transistor 560
and resistors R, , R6. The output ■d from D/A converter 551 is applied to the gate of transistor 560 to determine the voltage applied to resistor R4.

In other words, the current flowing through the resistor R4 is the current flowing through the transistor 5.
60, the current Id flowing through the laser diode 504y is controlled by Vd.

FIG. 16 shows the output of the U-nochi 557, VGl,
, Vd, and Id. Here, Vd is image density data (3-bit data:
Based on 8 gradation data from 0 to 7), ■ref
It takes a value in steps of /7 to 7/708, and Id is this VdO
Based on the value, eight levels of Io-17 are shown. The laser diode 504y has 8 levels of this Id (
I0=level 0, 1. - Levelt..., 1. = level 7), a latent image as shown in FIG. 17 is formed on the photosensitive drum 512y.

Further, in this embodiment, multivalue drive using power modulation is applied, but it goes without saying that the same effect can be obtained by using multivalue drive using pulse width modulation.

For reference, FIG. 18 shows changes in latent image form depending on the level of pulse width modulation.

①Specific Operation Example Next, a concrete operation example of the present invention will be explained using FIGS. 19 and 20.

Assume that the line width ratio between vertical lines and horizontal lines is 1.4:I. In this case, the vertical length of the filter should be 1.4 pixels.

However, in this example, 2*2 sub-vixel division is performed, so in order to create a vertically symmetrical filter with reduced length, the vertical length must be at least (1 + 2 x 1/2), that is, at least 2 pixels. must be divided into minutes.

Therefore, a filter as shown in FIG. 19A is used. All numbers in the filter are 1 for ease of explanation.
shall be. Three lines of image data are always held.

The image in FIG. 19(a) is divided into sub-vixels and filtered, and the area ratio of the target pixel is calculated in the conventional manner.

The result is No. 191k(b). If we take the sum of the center 1 pixel part of the filter used, A=4, so in Fig. 19(b), all the parts where the value is larger than 4 are replaced with 4 (Fig. 19( d)).

The value of 4, that is, the state when outputting after adjusting so that the brightness is the highest, is expressed as the size of the circle by the size of the circle.
This is shown in Figure 9(e).

In the original state, vertical lines and horizontal lines are the same thickness, but after processing by this graphic output device, thin dots are placed above and below the horizontal lines, making them thicker than the vertical lines.

For reference, FIG. 19(C) shows the result of outputting the area ratio as shown in FIG. 19(1)).

As can be seen from Figure 19 (C) in Part 2, extra thin dots are placed above and below the horizontal line, making the horizontal line thicker.
A side effect of the filter having long stripes is that the pixel density of the vertical lines is greater than that of the horizontal lines. As a result, when the image is actually output, it becomes difficult to notice the effect of the horizontal line becoming thicker.

Therefore, the processing from FIG. 19(b) to FIG. 19(d) is required.

In addition, since the line widths of the vertical lines and horizontal lines input in Fig. 19 were 1 pixel, Fig. 20 ( Another example is shown in a) to FIG. 20(e).

As described above, according to this embodiment, on an output medium that requires line width correction for vertical lines and horizontal lines, the correction can be performed simultaneously by anti-aliasing processing.

〔Effect of the invention〕

As explained above, according to the graphic processing apparatus according to the present invention, jagged edges (aliases) of hector images
Anti-aliasing processing means that smoothly expresses
In a graphic output device comprising image output means for outputting image data subjected to anti-alias song processing by the anti-alias song processing means, line width ratio detection means for detecting a line width ratio of vertical lines and horizontal lines of an output medium. , a first calculation means for calculating the vertical length (n pixels) of the filter used for the anti-aliasing process, a second calculation means for calculating the number of lines m of the image necessary for the filter process, and m542. Since it is equipped with a storage means for storing the image data for more than 10 minutes, and a third calculation means for calculating the area ratio of each pixel from the image data stored in the filter and the storage means, for example, laser beam blinking, etc. When outputting an image using , horizontal lines can be prevented from appearing thinner than vertical lines, and the effect of anti-aliasing processing can be enhanced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of the image forming system of this embodiment, FIG. 1(b) to FIG. 1(d) are supplementary diagrams for explaining the present invention in detail, and FIG. 2(a) , (b) is an explanatory diagram showing anti-aliasing processing using the uniform averaging method.
Figures (a) and (b) are explanatory diagrams showing antialiasing processing using the weighted averaging method; Figures 4 (a) and (b);
(C) and (d) are explanatory diagrams showing examples of filters used in the weighted averaging method. Figure 5 is an explanatory diagram showing a convolution method with 3x3 pixel reference. Figures 6 (a) and ( b), (C
), (d), (e), ge) are explanatory diagrams showing anti-aliasing processing to obtain the near area ratio of edge portion pixels.
FIG. 7(a) is an explanatory diagram showing the configuration of the PDL controller, FIG. 7(b) is an explanatory diagram showing the configuration of the page memory, FIG. 8(a) is a flowchart showing the operation of the PDL controller, FIG. ) is an explanatory diagram showing the path filling process, FIG. 8(C) is a flowchart showing the flow of filter determination in the graphic output device according to the present invention, and FIG. 8(d) is an explanatory diagram showing the flow of filter determination in the graphic output device according to the present invention. FIG. 9 is an explanatory diagram showing the configuration of the image processing device, FIG. 10 is a control block diagram showing the multi-value color laser printer, and FIG. 11 shows the configuration of the multi-value color laser printer. Explanatory diagram, FIGS. 12(a) and 12(b) are explanatory diagrams showing the configuration of the exposure system of the yellow recording unit.
FIG. 3 is a block diagram showing the configuration of the driver 505y.
Figures 4 and 16 are timing charts showing the operation of the driver, Figure 15 is a circuit diagram showing the configuration of the laser diode ON10ff circuit, etc., Figure 17 is an example of a latent image depending on the power modulation level, and Figure 18 is the pulse width. Examples of latent images depending on the level of modulation, FIGS. 19 and 20 are explanatory diagrams showing specific operation examples according to the present invention, and FIGS. 21(a) and (b) are explanatory diagrams showing the effects of anti-aliasing processing. . Explanation of symbols 100 --- Host computer 110 Laser writing section 11L --- Laser diode 112 Photoreceptor 20
0-PDL controller 201--receiving device 202-CP U2O5-internal system 20t-RAM 205-ROM 206--page memory 207-transmitting device 208-
I10 device 300-Image reading device 400 Image processing device ゛500-Multi-value color laser printer 504-Laser diode 505-Driver 550-Laser diode on10ff circuit 551
- D/A converter 552 constant current circuit

Claims (1)

[Scope of Claims] Anti-aliasing processing means for smoothly expressing jagged edges (aliases) of a vector image; and image output means for outputting image data subjected to anti-aliasing processing by the anti-aliasing processing means. A graphic output device according to the present invention, comprising: a line width ratio detection means for detecting a line width ratio between vertical lines and horizontal lines of an output medium; and a first calculation unit for calculating a vertical length (n pixels) of a filter used for the anti-aliasing process. means, second calculation means for calculating the number m of lines of the image necessary for the filter processing, storage means for storing the image data for m lines or more, and the filter and the image stored in the storage means. A graphic output device comprising a third calculation means for calculating the area ratio of each pixel based on data.