JPH04117581A - Graphic processor - Google Patents

Abstract

PURPOSE:To obtain an area ratio at high speed by reading the gradation value of the group of an applying triangle part based on the inclination of storage means vector data at processing an anti-alien thing and determining the gradation value of an edge part picture element with the area ratio. CONSTITUTION:When one picture element on a scanner line is defined as a closed section, a triangle part formed when vector data intersects and crosses the upper edge and the lower edge of the closed section and the triangle part formed when they intersects and crosses a left side edge and a right side edge are case-classified by the inclination of the vector data in advance. Then, a gradation value K' is set every the group of the triangle part case-classified and is stored as an LUT (recording means), the gradation value K' of the group of the applying triangle part is read based on the ionclination of the vector data at processing an anti-alien thing and a gradation value K of an edge part picture element is determined with the gradation value K'. Thus, an area ratio can be found at high speed without executing subpixel division and the counting of the number of painting-out.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a graphic processing device that performs anti-aliasing processing to remove jagged edges of an output image.
More specifically, the present invention relates to a graphic processing device that can perform anti-aliasing processing at high speed.

[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 is performed on the jagged part (called alias) on the stairs as shown in Fig. 17(a).
Figure 17 (c) visually displays the displayed image by applying brightness modulation to
It is used to smooth the surface as shown in the figure.

In conventional graphic processing apparatuses, (1) uniform averaging method, (2) weighted averaging method, (2) convolution integral method, etc. are generally applied as anti-aliasing processing methods.

■The uniform averaging method calculates each pixel (picture element) to N*M (N,
After decomposing the pixel into sub-pixels (M is a natural number) and performing rask calculation at high resolution, the brightness of each pixel is determined by taking the average of N*M sub-pixels. Figure 18(a)
, (b), anti-aliasing processing using the uniform averaging method will be specifically explained. If the edge of the image overlaps a certain pixel (here, it is assumed that the image is connected to the bottom right of the diagonal line), and when anti-aliasing processing is not performed, as shown in Figure (a),
The brightness kid of this pixel is assigned the highest brightness of the displayable gradations (for example, kid·255 for 256 gradations). When performing anti-aliasing processing on this pixel using the uniform averaging method with N=M=7, the same figure (
As shown in b), the pixel is decomposed into 7*7 sub-pixels and the number of sub-pixels covered by the image is counted. The count number (28) is divided by the total number of sub-vixels in one pixel (49 in this case), normalized (averaged), and multiplied by 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.

■ 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 is calculated based on which subpixel the image focuses on. The effects on the kids are different. still,
At this time, weights are assigned using a filter.

Referring to FIG. 19 (Tsukasa, (b)), an example is shown in which the same image data as in FIG. 18(a) is weighted using the same dividing method (N=M=7) and the averaging method.

FIG. 19(a) shows a filter (here, conef
ilter), 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. Same figure (c)
This figure shows how the display pattern of the image is changed depending on the weight of the sub-pixels. In this case, if we count the weighted subpixels of the image, we get
It becomes 199. 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. Incidentally, as filters, filters shown in No. 20 (a), (b), (C), and (d) are known.

■Convolution integral method The convolution integral method is a method that 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. 21 shows a convolution method with 3×3 pixel references. In this figure, the pixel whose brightness is to be determined is indicated by 2101.

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,
So-called DTP (Desk Top Publishing)
With the spread of computer graphics, 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. Bost° scripts are written in the Page Description Language (Page D).
DescriptionLanguage: PD
It belongs to a language genre called ``L'', and describes the form of the contents of a single document, including the text (letter part), graphics, and their arrangement and appearance. It is a programming language for such systems.
A vector font is used as the character font.

Therefore, even if characters are scaled, the print quality can be significantly improved compared to systems that use bitmap fonts (for example, conventional word processors), and character fonts, graphics, and images can be There is an advantage that printing can be performed in a mixed manner.

However, the resolution of the laser printers used in these systems is at most 240dpi to 400dp.
There are many i, computer graphics CR
Similar to the T display, there is a problem in that aliasing occurs due to the low resolution. For this reason, even in printing using a laser printer, there is a need to perform anti-aliasing processing to improve the quality of the printed image.

[Problem to be solved by the invention]

However, according to a graphic processing device that applies a conventional anti-aliasing processing method, one pixel is divided into multiple sub-pixels (for example, 49 sub-pixels) and the number of sub-pixels to be filled is counted. Since the area ratio (brightness) is calculated, there is a problem in that it takes time to calculate the area ratio, which 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.

The present invention has been made in view of the above, and an object of the present invention is to quickly obtain an area ratio without dividing subpixels or counting the number of filled pixels.

[Means to solve the problem]

In order to achieve the above object, the present invention adjusts the output of edge pixels of vector data based on the area ratio to be filled, and performs anti-aliasing processing to smoothly express jagged edges (aliases) of the output image. In the graphic processing device that executes the processing, when one pixel on the scan line is defined as a closed interval, the triangular part formed when the vector data intersects the upper side and the lower side of the closed interval, and the left side A storage means that divides the triangular parts formed when crossing the side and the right side into cases according to the slope of the vector data in advance, and stores tone values set for each group of the triangular parts divided into cases; and calculation means for reading the gradation value of the corresponding group of triangular parts from the storage means during anti-aliasing processing based on the slope of the vector data, and determining the gradation value of the edge part pixel using this area ratio. The present invention provides a graphics processing device that has the following features.

Further, in the above-described configuration, the calculation means is configured such that the vector data passes across two adjacent sides of the closed interval, and a triangular part formed by the two adjacent sides and the vector data is an image part (a filled part ), the gradation value of the triangle part is the gradation value of the edge pixel, the vector data passes across two adjacent sides of the closed interval, and the two adjacent sides and vector data If the triangular part to be formed is not an image part (filled part), the present invention provides a graphic processing device that subtracts the gradation value of the triangular part from the maximum gradation value of one pixel to obtain the gradation value of the edge part pixel. be.

[Effect]

In the graphic processing device of the present invention, the calculation means reads the gradation value of the group of the corresponding triangular dead part from the storage means based on the slope of the vector data during anti-aliasing processing, and uses this gradation (d). The gradation value of the edge pixel is determined by the calculation means. If the Nito-shaped part to be displayed is an image part (filled part), the gradation value of the Nito-shaped part is taken as the gradation value of the edge part pixel, and the vector data passes through two adjacent sides of the closed section horizontally. death,
In addition, if the triangular part formed by two adjacent sides and vector data is not an image part (filled part), the gradation value of the triangular part is subtracted from the maximum gradation value of one pixel to determine the gradation level of the edge self-pixel. Find the value.

〔Example〕

Hereinafter, an image forming system incorporating the graphic processing device of the present invention as a PDL controller will be described. ) configuration and operation.

■Configuration and operation of multilevel color laser printer,■
A detailed explanation will be given in the order of multi-value driving of the driver.

■Summary of anti-aliasing processing The graphic processing device of the present invention (hereinafter referred to as PDL controller) performs a unique processing for pixels at the edge portion of graphic elements drawn using the same vector data, which is determined from the slope of the vector data. The tone value set based on the area of the triangular part is calculated using LUT (Look [jp T
ble) and determines the gradation value of the edge pixel based on the gradation value of the triangular portion and the gradation value obtained from the area of the remaining rectangular portion. below,
An outline of antialiasing processing in the graphic processing apparatus of the present invention will be explained in detail with reference to FIGS. 1(a) to 1(g).

As shown in FIG. 1(a), the vector data on the Yo-Y1 scan line passes through 1i! When an element (that is, an edge pixel) is a closed interval, when the vector data passes through the closed interval, the Xa , Xb are formed.

On the other hand, when a straight line vector (vector data) having an inclination is subjected to scan line processing, in the main scanning direction of the output medium or the sub-scanning direction of the output medium,
As shown in (C), a plurality of triangular parts having a common area are formed at the same angle. Therefore, for example, if the vector data is the left edge, the gradation value of this triangular part is ' (triangular part The value obtained by converting the area ratio S° based on the number of gradations n-1 for one pixel as a whole: 'ζS'
1) The value obtained by adding ') to the gradation value of the remaining rectangular portion becomes the gradation value of the corresponding edge pixel.

Since the size of one pixel is fixed, the gradation value ' of this common triangular part is uniquely determined by the slope of the vector data. In the present invention, when one pixel on a scan line is defined as a closed interval, a triangular part (as shown in FIG. 1 (b) triangular part),
The triangular portion formed when crossing the left side and the right side (the triangular portion in FIG. 1 (C)) is divided into cases in advance according to the slope of the vector data, and the triangular portion is divided into cases. For each group, set the gradation value to ゛ as shown in Fig. 1(d), and write the LUT (recording means).
, and during anti-aliasing processing, based on the slope of the vector data, ' is read as the gradation value of the group of the corresponding triangular part, and ' is used as the gradation value of 42 to calculate the gradation value K of the edge pixel. Determine. In this embodiment, the number of gradations is set to IO stages from 0 to 9 (the number of gradations corresponding to 3*3 sub-vixel division), and the gradation value is set to '.

Hereinafter, with reference to FIGS. 1(e), 1(f), and ((to)), calculations for the gradation values of edge pixels will be specifically described.

As mentioned above, the gradation value of the edge pixel (1) can be found by adding ° and the gradation value K'' of the rectangular part to the gradation value of the triangular part. First, the gradient of the vector data is Based on this, read ゛ into the corresponding gradation value from the LUT (see M in Figure 1 (d)).Next, the area S of the remaining rectangular part is
” is determined by the formula S”=X”×y, and further S”X9
(9 is the value of 10 (number of gradations) - 1) and rounded off to the nearest whole number, which is calculated as the gradation value K"° of the rectangular part, and K'+
Let the value of K'' be the gradation value of the edge pixel (1).

For edge part pixel (2) and edge part pixel (5), when one pixel is a closed interval, the intersection of the vector data and the closed interval is located on the upper and lower sides, similar to edge part pixel (1). Therefore, each gradation value K can be obtained in a similar manner. In this way, the gradation value of the triangular part can be used repeatedly when calculating the gradation value of the edge pixel of the same vector data, so after the first LUT reference, the LUT can be used again.
It is a good idea to keep it so you don't have to search for the UT.

On the other hand, when the vector data does not pass through the upper and lower sides of the pixel, as in the case of edge pixel (3) and edge pixel (4), but instead passes through two adjacent sides, as shown in FIG. 1(f), (
The gradation value K I+ of the triangular part shown in 6) is determined as a value obtained by rounding off K' (same figure @), the gradation value K of the edge pixel
= K'', and if the triangular part is not a filled part ((f) in the same figure), the gradation value of the edge pixel is set as =
9-K”.

Here, we have explained how to obtain the gradation value of the edge pixel when the vector data passes through the top and bottom sides, but the same applies to the case where the edge pixel passes through the left and right sides. By adding ' to the value and ' to the tone value of the remaining rectangular portion, the tone value K of the edge pixel can be determined. However, in this case, the calculation formula for calculating the gradation value K'' of the rectangular part is different from the above-mentioned case of passing through the upper and lower sides, so whether the vector data passes through the upper and lower sides of the edge pixel or , it is necessary to determine whether it passes through the left side or the right side.The details will be described later, but in this embodiment, two cases are determined using the slope of vector data.

Note that if the end point (start point or end point) of the vector data is included in the edge pixel, the above method cannot be applied, so for example, the gradation value K is determined by the conventional sub-pixel division method. do it like this. However, since the probability that an edge part pixel has an end point in boat fishing is small, the present invention can be applied in most cases to find the gradation value K.
It is possible to speed up anti-aliasing processing.

■Block diagram of the image forming system The image forming system of this embodiment uses the Page Description Language output from DTP (Desk Top Publishing).
e: Hereinafter referred to as PDL language) is converted into an image via a PDL controller to form an image of image information. The configuration of the image forming system of this embodiment will be described below with reference to FIG.

The image forming system includes a host computer 100 that creates a document written in PDL language (Bost script language is used in this embodiment);
While anti-aliasing the incoming PDL language sent page by page from
BK), yellow (Y), magenta (M), and cyan (C) multivalued image data.
A multi-value color laser printer 300 that prints multi-value image data output by the controller 200, and a PD.
L controller 200. And, multivalued color/laser/
The system controller 400 controls the printer 300.

■Configuration and operation of PDL controller FIG. 3 shows the configuration of the PDL controller 200, which includes a receiving device 201 that receives the PDL language sent from the host computer 100, and storage control and control of the PDL language received by the receiving device 201. A CPU 202 that executes anti-aliasing processing, etc., and an internal system bus 203
, a RAM 204 that stores the PDL language to be transferred from the receiving device 201 via the internal system bus 203, and a ROM 20 that stores an anti-aliasing program and the like.
5 and multivalued YMC with anti-aliasing processing
and page memory 206 for storing BK image data.
, a transmitting device 207 that transfers the YMC and BK image data stored in the page memory 206 to the multilevel color laser printer 300, and an I10 device 2208 that performs transmission and reception with the system control section 400.

Here, the CPU 202 receives the P received by the receiving device 201.
The DL language is stored in the RAM 204 through the internal system path 203 according to the program stored in the ROM 205. After that, you will receive one page of PDL language,
Once stored in the RAM 204, the graphic elements in the RAM 204 are subjected to anti-aliasing processing based on a flowchart to be described later, and the multilevel YMC and BK image data is stored in the brain memory section of the page memory 206 (the page memory 206 is , M, consists of a plane memory section of CBK and a feature information memory section).

The data in the page memory 206 is then transferred to the transmitter 2
07 to the multilevel color laser link 300.

Hereinafter, with reference to FIGS. 4(a) and (b), PDL: 1
7) The operation of roller 200 will be explained.

FIG. 4(a) shows a flowchart of 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 processes the PDL language into black (BK), yellow (Y), magenta (
M) and cyan (C).

In the PDL language, graphics and characters are all described using vector 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 graphic and character elements within one path, and linear elements are registered in the work area for each path (processing 1).

Then, the straight line elements of the work area registered in this path unit are sorted by the starting X coordinate of the straight line (processing 2)
.

Next, in process 3, while updating the X coordinate one by one,
Performs filling processing using scanning lines. For example, in Figure 4 (
When performing the path filling process shown in b), the scanning line yc to be processed (in this embodiment, the above-mentioned Yo ・Y1
A scan line with a thickness of one pixel is described as a scan line, and a scan line that indicates a straight line with no thickness is described as a scan line), and the elements of the side that crosses that scan line. Real value of the X coordinate across yc (xI + x2.X 31 X 4 shown in Figure 4 (c)
) and AET (Active Edge Table
: A table that records 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 X in FIG. 4(b) is processed first, x3 is the AET is first registered in

Therefore, after the AET is registered, the elements on each side within the AET are sorted in descending order of X coordinate. Then, make two of the first elements of AET bare and fill in the space between them (
Specifically, for example, filling processing using a scan line formed by scanning line yc and scanning line yc+1)
.

Anti-aliasing processing is achieved by adjusting the density and brightness of pixels in the edge portion in accordance with the approximate area ratio in this filling processing. Then remove the processed edge from the AET, update the scanline (update the Repeat the process.

Above processing 1. Processing 2. The work in process 3 is executed pass by pass and repeated until all passes for one page are completed.

Next, the anti-aliasing process executed during the scan line filling process of process 3 described above will be described in detail with reference to the flowchart of FIG. 4(C).

For example, in process 1 in FIG. 4(a), in FIG.
If a pentagon ABCDE as shown in a) is input, this figure has the following elements.

(a) Five line vectors AB, BC, CD, DE, and EA (represented by real numbers) (b) Color and brightness values inside the figure This figure is created by the above-mentioned operation as shown in Figure 5 (b). , into seven straight line vectors (expressed as real numbers) extending in the main scanning direction. At this time, in this embodiment, the following information is added to the starting points and ending points of the seven straight line vectors. That is, (c) Starting point coordinate values (real number expression) of vector elements ((a) above) that constitute the starting point and ending point of a straight line vector (d) Slope information (dip) of vector elements that constitute the starting point and ending point of a straight line vector Characteristic information of the start point and end point of a straight line vector (right edge, left edge, apex of a figure, cotton of 1 dot or less, intersection of straight lines, etc.) When an edge pixel is detected in the scan line filling process, the fourth The anti-aliasing process shown in the flowchart of Figure 1(C) is executed.
) ~ (As shown in □□□, in the present invention, ゛ is read into the gradation value of the group of the corresponding triangular part based on the slope of the vector data from the LUT, and ゛ is used for this gradation value to create an edge. The gradation value K of a partial pixel is determined at high speed.

First, it is determined whether the end points of the vector are included on the scan line (S401).
). If there is no endpoint of the vector, ' is read from the LUT into the gradation value of the corresponding triangular part based on the slope θ of the straight line vector and held (s402). Next, it is determined whether the slope θ is in the range of π/4≦θ≦3π/4 (S4
03). In other words, it is determined whether there is a possibility that a straight line vector having an inclination θ passes through the upper and lower sides, or whether it has a possibility that it passes through the left and right sides. Here, for example, the slope θ
If is in the range of π/4≦θ≦3π/4, it indicates that the straight line vector has high perpendicularity, and also indicates that it does not intersect both the left and right sides and pass through the pixel. Therefore, if the slope θ is in the range of π/4≦θ≦3π/4, it is necessary to determine whether the straight line vector passes through the upper and lower sides (3404), and if it passes through the upper and lower sides, the area of the rectangular portion is calculated. Then, the gradation value K"° of the rectangular part is obtained (5405). Next, the gradation value of the corresponding edge pixel is obtained by adding " and the gradation value K of the rectangular part" to the gradation value of the triangular part. Determine the adjustment value K (
3406). On the other hand, if it does not pass through the upper and lower sides, the gradation value K'' of the triangular part of the pixel is calculated (S407), and the filled part in the pixel is determined (5408), and if the triangular part is a filled part, the triangular part gradation value K
” to the gradation value of the corresponding edge pixel 5409)
, if the part other than the triangular part is a filled part, the gradation value K of the corresponding edge pixel is set to "9-K" (S4
10). Thereafter, it is determined whether the scan line processing of the edge portion for one line has been completed (5411), and if it has not been completed, the processing is repeated from 5404.

On the other hand, if the slope θ is not within the range of π/4≦θ≦3π/4, it is difficult to determine whether the straight line vector passes through the left side and the right side.
12) When passing through the left and right sides, calculate the area of the rectangular part and further obtain the gradation value K'' of the rectangular part (S
413). Next, the gradation value K of the corresponding edge pixel is determined by adding `` and the gradation value K'' of the rectangular portion to the gradation value of the triangular portion (5414).

If it does not pass through the left and right sides, the gradation value K'' of the triangular part of the pixel is calculated (S415), and the filled part in the pixel is determined (3416), and if the triangular part is a filled part, the gradation value of the triangular part is Set the tone value KH to the tone value of the corresponding edge pixel (5417), and if the area other than the triangular part is a filled area, set the tone value K of the corresponding edge pixel to =9-K'' ( S41B). after that,
Check whether the scan line processing of the edge part for one line has been completed (5419), and if it has not been completed, the process again
Repeat the process from 04.

If one scan line has been completed in steps 5411 and 5419 above, it is determined in step 5420 whether or not the scan line processing of the edge portions of all lines has been completed, and if it has been completed, the processing is performed as an anti-ray. Finish the reasing process. Also, if it is not finished, 540
Repeat the process from 1.

Note that if it is determined in 5401 that the end point of the vector is included on the scan line, the area ratio is calculated by 3*3 sub-vixel division (5421), 5420
Proceed to.

The CPU 202 repeats the above processing up to the last pixel of the scanning line (y coordinate), and at the same time updates the contents of (c) above with the information of (d) above. The gradation values of the figure shown in FIG. 5(a) obtained through the anti-aliasing process in this way have values as shown in FIG.

The gradation values obtained in this way are processed by predetermined YMC and BK conversion processing (details are omitted, but in this embodiment, a YMC and BK conversion program is provided as software). Color and brightness values ((
Based on the information in U), the image is developed into four-color images of black (BK), yellow (Y), magenta (M), and cyan (C), and is stored in the corresponding plain memory section of the page memory 206. is stored as image data. Figures 7(a), (b), (C), and (d) are
Color and brightness value information is C: M: Y= 1:o
, s:o, 3 and the UCR is multiplied by 100%.

■Configuration of multi-value color laser printer First, the general configuration of the multi-value color laser printer 300 will be explained with reference to the control block diagram shown in FIG.

A photoreceptor development processing unit 301 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 301bk that performs transfer, a cyan developing/transfer section 301c that develops and transfers C data,
Cyan development/transfer section 301 that develops/transfers M data
m, and a cyan developing/transfer section 301y that develops and transfers Y data.

The laser drive processing unit 302 receives Y, M, and C signals output from the PDL controller 200 described above.

Buffer memories 303)', 303m input 3-bit BK data (in this case, image density data) and output a laser beam, and input 3-bit Y, M, and C data.

303C, and laser diodes 304y and 3 that output laser beams corresponding to Y, M, C, and BK, respectively.
04m, 304c, 304bk and drivers 305y, 305m, 305c, 30 that drive laser diodes 304y, 304m, 304c, 304bk, respectively.
5b.

In addition, the black developing/transfer section 3 of the photoreceptor development processing section 301
01bk, the laser drive processing unit 302, the laser diode 304bk, and the driver 305bk are called a black recording unit BKU (see FIG. 9).

Similarly, the cyan developing/transfer section 301c, laser diode 304c, driver 305c, and buffer memory 303C are combined into a cyan recording unit C.
U (see Figure 9), magenta developing/transfer section 301m,
Laser diode 304m, driver 305m
, and the buffer memory 303m are combined into a magenta recording unit I-MU (see FIG. 9), a yellow developing/transfer section 301y, a laser diode ao4y, a driver 305y, and.

The combination of buffer memories 303y is called a yellow recording unit (YU) (see FIG. 9). As shown in the figure, each of these recording units is connected to a conveyor belt 306 that conveys the recording paper.
Black recording unit B from the recording paper conveyance direction
KU, cyan recording unit) CU, magenta recording unit MU, and yellow recording unit YU are arranged in this order.

Due to this arrangement of each recording unit, the laser diode 3 for black exposure starts exposure first.
04bk, and the laser diode 304y for yellow exposure starts exposure last. Therefore,
There is a time difference in the order of exposure start between each laser diode,
In order to hold the recorded data (output of the PDL controller 200) during the time difference, the laser drive processing unit 302 has the aforementioned three sets of buffer memories 303)'+303m.
, 303c are provided.

Next, the configuration of the multilevel color laser printer 300 will be specifically explained with reference to FIG.

The multilevel color laser printer 300 includes a conveyor belt 306 that conveys recording paper, and recording units YU, MU, and YU arranged around the conveyor belt 306 as described above.
Paper feed cassette 30 containing CtJ, BKU, and recording paper
7a, 307b, and paper feed rollers 308a, 308 that feed the recording paper from the paper feed cassettes) 307a, 307b, respectively.
b, a registration roller 309 that aligns the recording paper sent out from the paper feed cassettes 307a and 307b,
The recording units I-BKU, CU are transported by the conveyor belt 306.
, MU, and YU are sequentially conveyed and the transferred image is fixed on the recording paper, and a paper discharge roller 311 discharges the recording paper to a predetermined discharge section (not shown). Here, each recording unit YU, MU, CU, BK
U represents photoreceptor drums 312y, 312m, 312c, 3
12bk, and photoreceptor drums 312y and 312m, respectively.
.

Charger 313y that uniformly charges 312c and 312bk
, 313m, 313c, 313bk, and photosensitive drum 3
12y, 312m, 312c.

Polygon mirrors 314y, 314m, 314c, 314bk and motors 315y, 315m, 315c for guiding the laser beam to 312bk.

315bk, photosensitive drum 312)', 312m.

toner developing devices 3163', 316m, 316c316bk that develop the electrostatic latent images formed on 312c, 312bk using toners of corresponding colors; transfer charger 317y that transfers the developed toner images onto recording paper; 3
17m, 317c.

317bk and a photosensitive drum 312y after transfer.

Cleaning device for removing toner remaining on 312m, 312c, 312bk W318y, 318m, 318
c, 318bk.

Note that 319y, 319m, 319c, and 319bk are photosensitive drums 3123', 312m, 312c, and 319bk, respectively.
A CCD line sensor for reading a predetermined pattern provided on 1.2bk is shown, and the details are omitted, but
As a result, the process status of the multivalued color laser printer 300 is detected.

In the above configuration, the operations of the yellow recording unit YU will be explained using exposure, development, and transfer as examples.

Figure 10 (a), Cb) shows the yellow recording unit) YU.
The configuration of the exposure system is shown. In the figure, a laser beam emitted from a laser diode 304y is reflected by a polygon mirror 314y, passes through an f-theta lens 302y, is further reflected by a mirror 321y322y, and is irradiated onto a photosensitive drum 312y through a dustproof glass 323y. Ru. At this time, the laser beam is
4y is driven to rotate at a constant speed by the motor 315y, so it moves in the direction along the axis of the photosensitive drum 312y (main scanning direction). Further, in this embodiment, a photosensor 324y is provided to detect the base point for tracking the scanning position of the main scan, so that the laser beam at the non-exposed position is detected. The laser diode 304y outputs recording data (PDL controller 20
Since the light is energized to emit light based on the 3-bit data (from 0), the multi-value exposure corresponding to the recorded data
This is done on the surface of 04y. Photosensitive drum 304y
The surface of the document is uniformly charged in advance by the charger 313y as described above, and an electrostatic latent image corresponding to the original image is formed by the exposure. The electrostatic latent image is transferred to a yellow developing device 316.
y to form a yellow toner image. This toner image is transferred from the cassette 307a (or 307b) to the paper feed roller 308a (or 3
08b), and is transferred by the registration rollers 309 onto the recording paper conveyed by the conveyor belt 306 in synchronization with the toner image formation in the black recording unit (BKU).

The other recording units BKU, CU, and MU have similar configurations and perform similar operations, but the black recording unit BKU is equipped with a black toner developing device 316bk and forms and transfers a black toner image, and the cyan recording unit C
U includes a cyan toner developing device 316C, which forms and transfers a cyan toner image, and a magenta recording unit M.
U includes a magenta toner developing device 316m, which forms and transfers a magenta toner image.

■The multi-value drive drivers 305y, 305m, 305c, and 305b are as follows:
Y sent from image processing bag W400.

Based on the 3-bit data of M, C, and BK, the laser diodes 304y and 304m correspond to 8.

It performs control for multi-value driving of 304c and 304bk, and power modulation, pulse width modulation, etc. are generally used as the driving method.

Hereinafter, the multivalue drive by power modulation applied in this embodiment will be explained in detail with reference to FIGS. 11(a), (b), (C), and (d). In addition, drivers 305y, 305m
.

305c, 305b, and laser diode 304
y, 304m, 304c, and 304bk each have the same configuration, so here, the driver 305y and laser diode 304y will be explained as an example.

As shown in FIG. 11(a), the driver 305y turns the laser diode 304y on and off based on a predetermined LD drive clock.
n10ff circuit 350 and 3-bit image density data (
Here, the D/A converts Y data) into an analog signal.
a converter 351, and a constant current circuit 352 that inputs an analog signal from the D/A converter 351 and supplies a current (LD drive current) Id for driving the laser diode 304y to the laser diode on10ff circuit 350 based on the image density value. It consists of

Here, the LD drive clock is “1” and on “OI”.
I is defined as off, and as shown in FIG. 11(b), the laser diode on10ff circuit 350 turns off the laser diode 304y accordingly. Furthermore, since the LD drive current Id and the laser beam power are in a proportional relationship, by generating the LD drive current 1d based on the image density data value, the laser beam power output corresponding to the image density data value can be obtained. become.

For example, as shown in FIG. 11(b), when the image density data value is °'4'' (data N-1 in the figure), the corresponding LD drive current Id is supplied by the constant current circuit 352. , the laser beam power of the laser diode 304y is level 4. Also, the image density data value is “7”.
” (data N in the figure), the constant current circuit 352
The corresponding LD drive current 1d is supplied, and the laser beam power of the laser diode 304y becomes level 7.

Next, referring to FIG. 11(C), laser diode on10ff circuit 350. A specific circuit configuration of the D/A converter 351 and the constant current circuit 352 is shown. The laser diode on/o r f circuit 350 has T
TL inverters 353, 354, differential switching circuits 355, 356 that perform onloff toggle operation, and differential switching circuit 355 when VGl>VO2.
is on, the differential switching circuit 356 is off,
When VGI<VO2, the differential switching circuit 355 is off.

Resistors Rz and R form a voltage dividing circuit that generates VO2 that satisfies the conditions for the differential switching circuit 356 to be turned on.
It consists of s. Therefore, when the LD drive clock is "1", the output of the impark 354 generates VGI, the above condition (VCI>VO2) is satisfied, the differential switching circuit 355 is turned on, and the differential switching circuit 356 is turned off and the laser diode 304y is turned off.
Do n.

Conversely, when the LD drive clock is "0", there is no output from the inverter 354, so the above condition (VCI<
VO2), and the differential switching circuit 355
ff, the differential switching circuit 356 is turned on and the laser diode 304y is turned off.

The D/A converter 351 has a latch 3 that latches the input image density data while the LD drive clock is "1".
57, a V ref generator 358 that provides a maximum output value V ref, and a V ref generator 358 that provides image density data and a maximum output value V raf.
Outputs analog data Vd based on 3-bit D
/A converter 359. Furthermore, here V
The relationship between d, image density data, and maximum output value V ref is expressed by the following equation.

The constant current circuit 352 includes the laser diode 304 in the laser diode ON10ff circuit 350 as described above.
y current, and the transistor 360
, and resistors Ra and Rs. The output Vd from D/A converter 351 is applied to the base of transistor 360 to determine the voltage applied to resistor R4.

In other words, the current flowing through resistor R4 is
Since the collector current numbers of 60 are almost equal, the current 1d flowing through the laser diode 304y is controlled by Vd.

FIG. 11(d) shows the output of the latch 357 mentioned above.

5 is a timing chart showing the relationship between VGI, Vd, and Id. Here, Vd is Vr
X takes values in 8 levels from O/7 to 7/7, and Id indicates levels in 8 levels from 10 to I based on this VdO value. The laser diode 304y is placed on the photoreceptor drum 312y at the 12th level according to the 8 levels of this Id (1° = level O2L'' level...■, = level 7).
A latent image as shown in the figure is formed.

In the image forming system to which the anti-aliasing processing and the device of the present invention are applied, the toner image shown in FIG. 13 is finally created for the pentagon ABCDH shown in FIG. 5(a) by the above-described configuration and operation. Formed on recording paper. -Resolution of laser printer for boat fishing is 240~
Considering that it is 400 dpi, the density of the edge portion of the figure becomes visually lighter due to the anti-aliasing process. FIG. 14 shows a toner image of pentagon ABCDE without anti-aliasing processing, and the 13th
As is clear from a comparison between the figure (toner image of the present invention) and FIG.
becomes visually smoother.

Further, in this embodiment, multi-value driving using power modulation is applied, but it goes without saying that similar effects can be obtained by using multi-value driving using pulse width modulation.

For reference, FIG. 15 shows the change in latent image form depending on the level of pulse width modulation, and also shows the toner image when pulse width modulation is applied to the pentagonal ABCDH shown in FIG. 5(a). It is shown in FIG.

〔Effect of the invention〕

As explained above, the graphic processing device of the present invention adjusts the output of the edge portion pixels of vector data based on the area ratio to be filled, and adjusts the output of the edge portion pixels of the output image (
In a graphics processing device that performs anti-aliasing processing to smoothly express images (aliases), when one pixel on a scan line is defined as a closed interval, vector data intersects with the upper and lower sides of the closed interval. The triangular parts formed when crossing the left side and the right side are divided into cases according to the slope of the vector data in advance, and set for each group of triangular parts divided into cases. A storage means for storing tone values of the corresponding triangular portion group is read from the storage means based on the slope of the vector data during anti-aliasing processing, and edge portion pixels are The area ratio can be determined at high speed without dividing subpixels or counting the number of filled pixels.

Furthermore, in the above-described configuration, the calculation means is configured such that the vector data passes across two adjacent sides of the closed interval, and the triangular part formed by the two adjacent sides and the vector data is an image part (a filled part ), the gradation value of the triangular part is the gradation value of the edge pixel, and the vector data passes across two adjacent sides of the closed interval, and is formed by the two adjacent sides and vector data. If the triangular part is not an image part (filled part), the gradation value of the triangle part is subtracted from the maximum gradation value of one pixel to find the gradation value of the edge pixel, so the area ratio can be calculated quickly. can.

[Brief explanation of the drawing]

FIGS. 1(a) to (powder are explanatory diagrams showing the principle of anti-aliasing processing in the graphic processing apparatus of the present invention, FIG. 2 is an explanatory diagram showing the configuration of the image forming system of this embodiment, and FIG.
4(a) is a flowchart showing the operation of the PDL controller; FIG. 4(c) is an explanatory drawing showing the path filling process; FIG. 4(C) is a flowchart showing anti-aliasing processing, FIG. 5(a),
(t)) is an explanatory diagram showing linear vector division of a figure, No. 6
The figure is an explanatory diagram showing gradation values after performing anti-aliasing processing, and Fig. 7 (a), (b), and (C) are explanatory diagrams showing YMC and BK image data stored in the brain memory section of the page memory. 8 is a control block diagram showing a multi-value color laser printer, FIG. 9 is an explanatory diagram showing the configuration of a multi-value color laser printer, and FIG. 10 is a control block diagram showing a multi-value color laser printer.
Figures (a) and (b) are explanatory diagrams showing the configuration of the exposure system of the yellow recording unit, and Figures 11 (a), (b), (c
), (d) is an explanatory diagram showing multi-level driving by power modulation, Fig. 12 is an explanatory diagram showing the state of the latent image depending on the level of power modulation, and Fig. 13 is the pentagon AB shown in Fig. 5 (a).
An explanatory diagram showing the final toner image of CDH, Fig. 14 is a pentagon ABC when anti-aliasing processing is not performed.
An explanatory diagram showing the toner image of DE, Fig. 15 is an explanatory diagram showing the state of the latent image depending on the level of pulse width modulation, and Fig. 16 is an explanatory diagram showing the state of the latent image depending on the level of pulse width modulation. An explanatory diagram showing a toner image in the case, FIG. 17(a)
, (b) is an explanatory diagram showing one conventional anti-aliasing process, FIGS. 18(a) and (b) are explanatory diagrams showing anti-aliasing process using the uniform averaging method, and FIG.
a) and (b) are explanatory diagrams showing anti-aliasing processing using the weighted averaging method; Fig. 20 (a) and (b)
, (C) and (d) are explanatory diagrams showing examples of filters used in the weighted averaging method, and FIG. 21 is an explanatory diagram showing a convolution method with reference to 3×3 pixels. Explanation of symbols 0...Host computer O-----PDL controller 1--
-Receiving device 202...CPU3--Internal system bus 4--RAM 205...--ROM
6.--Page memory 207.--.Transmitting device 8.--.I10 device 0.--Multi-value color laser printer 0.
・−・−System control unit

Claims (2)

[Claims] (1) Scanning is performed in a graphic processing device that adjusts the output of edge pixels of vector data based on the area ratio to be filled and performs anti-aliasing processing to smoothly express jagged edges (aliases) of the output image. When one pixel on a line is a closed interval, a triangular part is formed when the vector data crosses the upper side and the lower side of the closed interval, and the left side and right side. Triangular parts formed when crossing each other are divided into cases according to the slope of the vector data in advance, and storage means for storing gradation values set for each group of the divided triangular parts; , an arithmetic means for reading the gradation value of the corresponding group of triangular parts from the storage means based on the slope of the vector data, and determining the gradation value (density) of the edge pixel using this gradation value; A graphic processing device comprising: (2) In claim 1, the calculation means is configured to allow the vector data to pass across two adjacent sides of the closed interval, and to calculate a triangle formed by the two adjacent sides and the vector data. If the part is an image part (filled part), the gradation value of the triangular part is the gradation value of the edge pixel, and the vector data passes across two adjacent sides of the closed section, and If the triangular part formed by two adjacent sides and the vector data is not an image part (filled part), the gradation value of the triangular part is subtracted from the maximum gradation value of one pixel to determine the gradation of the edge pixel. A graphic processing device characterized by calculating values.