JPH04157980A - Graphic processor - Google Patents

Abstract

PURPOSE:To quickly calculate the area rate by using (y) coordinate values of feature points to calculate the area rate in the case of 0 deg.<=¦theta¦<45 deg. or 135 deg.<=¦theta¦<180 deg. where theta is the inclination of vector data and using (x) coordinate value of feature points in the case of 45 deg.<=¦theta¦<135 deg.. CONSTITUTION:A CPU 202 stores the page description language(PDL) received by a reception equipment 201 in a RAM 204 through an internal system bus 203 in accordance with the program stored in a ROM 205. When one page of the PDL is received and stored in the RAM 204 thereafter, the area rate is calculated by a prescribed method, and graphic elements in the RAM 204 are subjected to anti-aliasing processing, and multilevel RGB image data is stored in the plane memory part of a page memory 206. Data in the page memory 206 is sent to a picture processing device 400 through a transmission equipment 207 thereafter.

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 performs 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 antialiasing 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 Fig. 15(a) to visually change the display image as shown in Fig. 15(b).
) as shown in the figure.

In conventional graphic processing devices, 1) Uniform averaging method 2) Weighting is an averaging method, 2) Convolution integral method, etc. are generally applied as anti-aliasing processing methods.

■Uniform averaging method calculates each pixel (pixel) to 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 16 (a
) and (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 pixel is decomposed into 7*7 sub-pixels as shown in the same figure (b), and the pixels covered by the image are divided into 7*7 sub-pixels. Count the number of sub-vixels. 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 is distorted at each pixel.

■Weighting is an averaging method The weighting and averaging method is a partial modification of the uniform averaging method. In contrast to the weighted averaging method, which gives a weight to each subpixel, the influence on the brightness kid of that subpixel depends on which subpixel the image falls on. Trying to be different. Note that the weight at this time is given using a filter.

With reference to FIGS. 17(a) and (b), FIG. 16(a)
An example is shown in which the same image data is weighted using the same dividing method (N=M=7) and the averaging method.

FIG. 17(a) shows a filter (here, conef
i I ter ), and the corresponding sub-pixel is given a weight equal to 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, the number of weighted subpixels in the image is 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. In addition, as a filter, Fig. 18 (a
L (b), (cL (do) The filter characteristics shown are excellent.

■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
``×N'' pixels are considered to correspond to pixels of the equal-averaging method or the weighted averaging method. 19th
The figure shows a convolution method with 3x3 pixel references. In this diagram, the pixel whose brightness we are trying to determine is 1901
Indicated by The image continues to the bottom right of the diagonal line, and the subpixels painted in 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 is a page description language (Page Descriptor).
scriptionLanguage: Hereafter, PD
It belongs to a language genre called ``L'', and describes the form of the contents of a document, including the text (letter part), graphics, and their arrangement and appearance. It is a programming language for writing characters, and in such systems, vector fonts are used as character fonts. Therefore, even if characters are scaled, the print quality can be significantly improved compared to systems that use focus map fonts (for example, conventional word processors, etc.). It has the advantage that it is possible to print a mixture of

However, the resolution of the laser printers used in these systems is at most 240dpi to 400dp.
There are many i, computer graphics C
Similar to RT display, there is a problem in that aliasing occurs due to the low resolution. For this reason, antialiasing processing is now being applied to printing using a laser printer in order 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 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 it is an object of the present invention to quickly calculate the area ratio without dividing subpixels or counting the number of filled pixels.

[Means for Solving the Problems] In order to achieve the above object, the present invention adjusts the output of edge portion pixels of vector data based on the area ratio to be filled, and eliminates jaggedness ( In a graphic processing device to which an anti-aliasing processing method is applied to smoothly express images (aliases), a feature point calculation means for calculating feature points for edge pixels of vector data;
Feature point.

The present invention also provides a graphic processing device including an area ratio calculation means for calculating an area ratio to be filled based on the slope of the vector data.

Furthermore, in addition to the above-described configuration, the area ratio calculation means includes:
When the slope θ of the vector data is 0≦101〈45° or 135°≦1θl〈180°, the area ratio is calculated using the X coordinate value of the feature point, and the slope θ of the vector data is
However, when 45°≦|θ|<135°, the present invention provides a graphic processing device that calculates the area ratio using the X coordinate value of the feature point.

Further, in the above-described configuration, it is preferable that the feature point is an intersection point when vector data passes through an edge pixel, and an intersection point when a plurality of hex-1-hel data intersect within an edge pixel.

[Operation] In the graphic processing device of the present invention, the feature point calculating means calculates feature points for edge pixels of vector data.

The area ratio calculation means is the slope θ of the vector data ′
However, 0≦1θI〈45°, or 135°≦]θl<
In the case of 180°, the area ratio is calculated using the X coordinate value of the feature point, and the slope θ of the vector data is 45°≦|θ|<1
In the case of 35°, the area ratio is calculated using the X coordinate value of the feature point.

〔Example〕

Hereinafter, an image forming system to which the graphic processing device of the present invention is applied will be described as an example.
A detailed explanation will be given in the following order: (1) configuration and operation of the PDL controller, (2) configuration of the image processing device, (2) configuration and operation of the multi-value color laser printer, and (2) multi-value drive of the driver.

■Overview of anti-aliasing processing
0) is based on the feature points for the edge pixels of the vector data and the slope of the vector data.
This calculates the area ratio to be covered. Hereinafter, 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).

First, prior to explanation, feature points will be defined. Feature points are intersection points (input/output coordinate values) when vector data passes through edge pixels;

This shows an intersection point where a plurality of vector data intersect within an edge pixel.

As shown in FIG. 1(a), if one pixel (i.e., an edge pixel) through which vector data on the yo-y scan line passes is a closed interval, when the vector data passes through the closed interval, As shown in the figure, there are two intersection points (input and
output coordinate values).

Actually, when two vector data intersect and pass through one edge pixel, as shown in Fig. 1(b),
An intersection point Xc is created by the intersection.

The intersection points Xa and Xb are the straight line information of the vector data (coordinates and slope of the start and end points of the vector) and Y o
'Y + Y of scan line. It can be easily determined by an equation from the coordinates of and Yl. Further, the intersection point Xc is determined by an equation from the straight line information of the two intersecting vector data.

In this embodiment, as shown in FIG. 1C, based on the slope θ of the vector data that crosses the edge pixel, θ at around 1 is O≦|θ|<45°, or.

The case where 135°≦jθ1<180° is classified as an H region (horizontal region), and the case where the inclination θ is 45°≦)θ1<135° is classified as a V region (vertical region).

For example, FIG. 1(d) shows an example where vector data exists in the V area, and FIG. 1(e) shows an example where vector data exists in the H area.

Here, if the vector data is on the left edge (the image part exists on the right side of the vector data), the actual area ratio for both is the area of trapezoid abcd.

Paying attention to the coordinates of the intersection of pixel and vector data, for example,
The coordinates of the intersection in Figure 1(d) are (xo, O).

(x,, 1), since the area of the hector data is close to the vertical line, it can be regarded as χ.XI.Then, the coordinates of the center line (
XO+XI)/2, the area ratio of trapezoid abcd is approximate rectangle a'
It can be replaced with the area ratio of bed' (I XO'').

Similarly, as shown in Figure 1(e), in the case of the slope of the HVii region, the coordinates of the intersection are (0, yo), (1, y+
, ), then the center line y. The area ratio y of the rectangle a'b'cd, where the coordinates of '' are yo'-(yo + y+)72. ” is found.

In this way, vector data belonging to the VjJ region is
For vector data belonging to the Hjl region, the area ratio can be calculated using the X coordinate. In other words, the area ratio to be filled can be calculated based on the feature points for the edge pixels of the vector data and the slope of the vector data.

Next, a special example will be described. This refers to a case where there is an end point within a pixel or a case where one pixel has two vector data. Note that the area ratio can be found in the same way in other complicated cases, for example, when three vector data exist in one pixel, but in this example, an arbitrary value is set as a fixed value by default. .

FIG. 1(f) shows a case where vector data in the y6N area (denoted as vector data V) and vector data in the Hf1l area (described as vector data H) exist within one pixel. In this case, the respective coordinates X based on the method described above. Find Z yo+.

Then, the center lines intersect, forming a rectangle like abcd.

Therefore, the area ratio can be calculated as (1xo') x (1-yo').

Figure 1 (The turbidity is vector data of two V regions per pixel (
A case in which vector data (2) and vector data (Vz) exist is shown. At this time, since the X coordinates overlap and the area ratio increases, including the X coordinate of the end point P (referring to the case where the intersection of vector data and vector data coincides with the start and end points of vector data), (xo-xz ) and (x+ −
The magnitude of χ0) is compared, and the coordinate value with the largest difference is used for calculation.

Here, since (χ.-xz)>(χ,-x.), use χ0 and x2 to find the area ratio X.゛ from Xo''-(χ.+X2)/2. , two vector data are both in the HjJf range, the comparison is similarly performed and processed.

In this way, since the area ratio to be filled is calculated by approximating a rectangle, processing speed can be increased.

Furthermore, since the area ratio required is the same as the actual area, the accuracy of anti-aliasing processing can be improved.

■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)) and image information read by an image reading device. 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 (Postscript language is used in this embodiment);
A PDL controller (graphic processing device of the present invention) that applies anti-aliasing processing to the PDL language sent page by page from ) 200, an image reading device 300 that reads image information via an optical system unit, and a PDL controller 200. Or.

An image processing device 400 that inputs the image output from the image reading device 300 and performs image processing (details will be described later), and a multi-value color laser printer that prints the multi-value image data output from the image processing device 400. printer 50
0, PDL controller 2001 image reading device 30
01 Image processing device 400. and a system control section 600 that controls the multivalued color laser printer 500.

■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, an internal system bus 203, a RAM 204 that stores PDL language transferred from the receiving device 201 via the internal system bus 203, and a ROM 205 that stores anti-aliasing programs and the like.
, a page memory 206 that stores multivalued RGB image data subjected to anti-aliasing processing, a transmitting device 207 that transfers the RGB image data stored in the page memory 206 to the image processing device 400 , and a system control unit 600 . It is composed of an I10 device 208 that performs transmission and reception.

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 hash 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 R'AM 204 are subjected to anti-aliasing processing based on the flowchart described later, and the multivalued RGB image data is stored in the plain memory section of the page memory 206 (the page memory 206 is ,G,B plain memory parts,
(consisting of a feature information memory section).

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 FIGS. 4(a) and 4(b).

FIG. 4(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 converts it to red (R).

It is developed into three-color images: green (G) and blue (B).

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 linear 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 elements on the side across which the scanning line yc to be processed and the real value of the X coordinate across the scanning line yc (not shown in Figure 4)
X3X4) and AET (8active Edge Ta
ble: Register in the table (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. 4 is processed first, X3 is first registered in AET as the be done. Therefore, after registering AET, the elements of each side in AET are
Sort in ascending order of coordinates. Then, pair the first two elements of AET and fill in the space between them. 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 AET and update the scan line (update the X coordinate)
In other words, 1 until all edges in AET are processed.
The same process is repeated until all elements in one path are processed.

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).

Here, for example, in process 1 of FIG. 4(a),
), this figure has the following elements.

(B) Line vector of 5 trees AB, BC, CD, DE, EA (represented by real numbers) (I+) Color and brightness value inside the figure This figure is created by the above operation as shown in Figure 5 (b). , is divided 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 and ending points of the straight line vectors of the seven trees. That is, (c) Starting point coordinate values (real number expression) of the vector elements ((a) above) that constitute the starting point and ending point of the straight line vector (d) Slope information (ho) of the vector element that constitutes the starting point and ending point of the straight line vector ) Characteristic information of the start point and end point of a straight line vector (right edge, left edge, end point of a figure, intersection of straight lines, etc.) When an edge pixel is detected in the scan line filling process, the information shown in Fig. 4(c) Execute the antialiasing process shown in the flowchart.

First, we need to determine whether there is one vector of vector data that crosses the edge pixel (5401), and if it is one hectare, then
Based on (around θ) of hector data, ■ area (45°
It is determined whether ≦]θ]<135° (S402).

■If it is an area, calculate the X coordinate and calculate the area ratio X based on the following formula (1). " is calculated (S403).

x o' - (x o x +) / 2---41
) ■ If it is not the region (that is, if it is the H region), then the following formula (2
) based on the area ratio y. is calculated (3404).

yo"-(yo + y +) / 2----12
) On the other hand, if it is not 1 hectare, it is determined whether there are 2 vectors (S405). If it is 2 hectares, determine whether the two vector data are the same area 5406), if the same area, ■ determine whether they are areas 5407), ■ If the area, compare the X coordinates and find the coordinates with a large difference. Using , the area ratio χ. is calculated (S408).

(2) If it is not a region (that is, if it is an H region), the X coordinates are compared and the coordinate with the largest difference is used to calculate the area ratio yo゛ (5409).

If the areas are not the same, calculate the X coordinate and calculate the area ratio X based on the following formula (1). is calculated (S410).

Xo+−(χ0+χ, ) / 2−−−−−−− (
1) Also, if it is not 2 vectors, a preset fixed value is set as the area ratio of the corresponding edge pixel (
3411).

The CPU 202 repeats the above process up to the last pixel of the scanning line (X coordinate).

(2) 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.
Black (BK) necessary for recording the three-color image signals read by D7r, 7g, and 7b.

Yellow I: Converts to l-(Y), magenta (M), and cyan (C) recording signals. In addition, the PDL mentioned above
Similarly, RGB image data given from the controller 200 is converted into black (BK), yellow (Y), magenta (M), and cyan (C) recording signals. Here, the mode for inputting image signals from the image reading device 300 is set to copy machine mode, and the PDL controller 20
The mode in which RGB image data is input from 0 is called graphics 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 sensitivity variations, etc. 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 (RGB image data) output from the PDL controller 200 according to the above-described mode;
A T 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 a 6-hint data.
3, and red (R) and green (
G).

Complementary color generation circuit that converts 6-bit gradation data indicating the gradation of blue (B) into gradation a cycle data (6 bits) of each complementary color, cyan (C), magenta (M), and yellow (Y). 405, Y output from the complementary color generation circuit 405,
A masking processing circuit 406 that performs predetermined masking processing on each of M and C gradation data, and a masking processing circuit 406 that performs predetermined masking processing on each gradation data of M and C, and
, a UCR processing/black generation circuit 407 that inputs each gradation data of C and executes OCR processing and black generation processing;
The 6-bit gradation data of Y, M, C, and BK outputted from the processing/black generation circuit 407 are converted into 3-bit gradation data YLMI, CI, and 3-bit gradation data.

Convert to BKI and use multilevel color laser printer 50
The image processing apparatus 400 includes a gradation processing circuit 408 that outputs output to the laser drive processing section 502 inside the image processing apparatus 400, and a synchronization control circuit 409 that synchronizes each circuit of the image processing apparatus 400.

Although details will be omitted, the T 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
x3, multilevel color laser printer 500
The number of gradations is the product of 3×3 area gradations and 3-bit (that is, 8 steps) multivalue level, and is 3×3×8=72 (gradations).

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 Y o,
M o, Co: data after masking process, and U
The arithmetic expression for UCR processing of the CR 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.

A new coefficient (a11'', etc.) that simultaneously performs the process is calculated in advance, and the new coefficient is used to calculate the scheduled input values Y,, M, of the masking processing circuit 406.

Output value corresponding to Ci (6 bits each) (yo', etc.: value that is the calculation result of the UCR processing/black generation circuit 407)
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 a set of ROMs, and the data at the address specified by the inputs Y, M, and C of the masking processing circuit 406 is given as the output of the UCR processing/black generation circuit 407.

In addition, for boat fishing, the masking processing circuit 406 performs Y and M according to the characteristics of the spectral reflection wavelength of the toner for forming a recorded image.
, C signals, and the UCR processing/black generation circuit 407 performs correction for color balance in overlapping toners of each color. UCR processing/black generation circuit 4
07, black component data BK is generated by combining the input three color data of Y, M, and C, and the output Y,
The M and C color component data are corrected to values obtained by subtracting the black component data BK.

In the above configuration, the γ correction circuit 403 executes processing based on the T correction conversion graph shown in FIG. 7, and the complementary color generation circuit 405 executes processing as shown in FIGS. 8(a) and 8(b).

Processing is executed based on the conversion graph for complementary color generation shown in (C), and then the masking processing circuit 406 and the UCR processing/black generation circuit 407 execute processing based on the following equation.

Thereafter, the gradation processing circuit 408 performs gradation processing using a Bayer type 3×3 multivalued dither matrix shown in FIG.

■Multi-value color laser printer configuration First, the 10th
The schematic configuration of the multivalued color laser printer 500 will be described with reference to the control block diagram shown in the figure.

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. Details will be given later, but BK Deday's development and
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.
The laser beam is output by manually inputting the 3-bit data of Y, M, C, and BK (in this case, image density data) output from 00; Manual buffer memory 503y, 503m
, 503c, and a laser diode 504y that outputs laser beams corresponding to Y, M, C, and BK, respectively.
Drivers 505y, 505m, 505c, and 5 drive the laser diodes 504y, 504m, 504c, and 504bk, respectively.
It consists of 05bk.

In addition, the black developing/transfer section 5 of the photoreceptor development processing section 501
01bk, the laser drive processing section 502, the laser diode 504bk, and the driver 505bk are called a black recording unit BKU (see FIG. 11). Similarly, a cyan developing/transfer section 501c, a laser diode 504c, a driver 505c, and
The buffer memory 503C is combined with a cyan recording unit CU (see Figure 11) and a magenta developing/transfer section 501m.
, laser diode 504m, driver 50
5m and a buffer memory 503m are combined into a magenta recording unit (MU) (see Figure 11), a yellow developing/transfer section 501y, and a laser diode 504y.
, driver 505y, and.

The combination of buffer memories 503y is called a yellow recording unit YU (see FIG. 11). As shown in the figure, each of these recording units is connected to a conveyor belt 506 that conveys the recording paper.
Blank recording unit B from the recording paper conveyance direction around
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 5 for blank 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 multilevel color laser printer 500 will be specifically explained with reference to FIG.

The multilevel color laser printer 500 includes a conveyance heald 506 that conveys recording paper, and recording units YU, MU, and YU arranged around the conveyance heald 506 as described above.
Paper feed case that stores CU, BKU, and recording paper) 507
a, 507b, and paper feed rollers 508a, 508b that feed recording paper from paper feed cassettes) 507a, 507b, respectively.
, a registration roller 509 that aligns the recording paper sent out from the paper feed cassettes 507a and 507b, and a conveyance heald 506 that moves the recording units BKU, CO, and M.
A fixing roller 510 transports U and YU sequentially and fixes the transferred image onto the recording paper, and the recording paper is transferred to a predetermined ejection section (
(not shown). Here, each recording unit YU, MU, CU, BKU has photosensitive drums 512y, 512m, 512c, 512.
bk, and photoreceptor drums 512y and 512m, respectively.

Charger 513y that uniformly charges 512c and 512bk
, 513m, 513 (513bk and photoconductor tram 51
Polygon mirrors 514y, 514m, 5 for guiding laser beams to 2y, 512m, 512c, 512bk
14c, 514bk and motor 515y, 515m, 5
15c, 515bk, and photosensitive drums 512y, 512
toner developing devices 516y, 516m, 516c, and 516bk that develop the electrostatic latent images formed on the surfaces m, 512c, and 512bk using toners of corresponding colors; and a transfer charging device that transfers the developed toner images to recording paper. Vessel 517y
, 517m, 517c, and 517bk, and a cleaning device 51.8y that removes toner remaining on the photoreceptor drums 512y, 512m, 512c, and 512bk after transfer.
, 518m.

It consists of 518c and 518bk.

Note that 519y, 519m, 519c, and 519bk are photosensitive drums 512y and 512m, respectively.

This shows a toner adhesion density measuring device for reading test patterns provided on 512c and 512bk, and is composed of a CCD line sensor and an LED light source arranged in the thrust direction.

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

Figure 12 (a) and (b) are yellow recording unit YU.
The configuration of the exposure system is shown. 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 520y, and further passes through a mirror 521. y.

522y and is irradiated onto the photosensitive drum 512y through the dustproof glass 523y. At this time, since the polygon mirror 514y is rotated at a constant speed by the motor 515y, the laser beam moves in a direction along the axis of the photosensitive drum 512y (main scanning direction). Furthermore, in this embodiment, a photosensor 524y 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 504y outputs recording data (
Since the photoreceptor drum 504y is activated to emit light based on the 3-bit data from the image processing device 400, multivalue exposure corresponding to the recording data is performed on the surface of the photoreceptor drum 504y. 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 transferred from the cassette 507a (or 507b) to the paper feed roller 50, as shown in FIG.
8a (or 508b), 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.

Other recording units BKU, CU, and MU have similar configurations and perform similar operations, but the blank recording unit BKU
is equipped with a black toner developing device 516bk to form and transfer a black toner image, and the cyan recording unit CO is equipped with a cyan toner ring (& ?ilf 516c) to form and transfer a cyan toner image, and to form and transfer a magenta toner image. The recording unit (MU) includes a magenta toner developing device 516m, and forms and transfers a magenta toner image.

■ Multi-value drive drivers 505y, 505m, 505c, and 505bk drive Y, M, C, and B signals sent from the image processing device 400.
Based on a 3-bit deck of K.

Applicable laser diodes 504y, 504m.

It performs control for multi-value driving of 504c and 504bk, 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. 13(a), (b), (C), and (d). In addition, drivers 505y, 505m
.

505c, 505bk, and laser diode 50
4y, 504m, 504c, and 504bk each have the same configuration, so here, the driver 505y and laser diode 504y will be explained as an example.

As shown in FIG. 13(a), the driver 505y turns the laser diode 504y on and off based on a predetermined LD drive clock.
n10ff circuit 550 and 3-bit image density data (
Here, the D/A converts Y data) into an analog signal.
A constant current circuit 552 inputs an analog signal based on the image density value from the converter 551 and the D/A converter 551, generates a current Id for driving the laser diode 504y (LD drive current), and supplies it to the laser diode ON10ff circuit 550. It consists of

Here, the LD drive black is "1" and on゛'0.
As shown in FIG. 13(b), the laser diode on10ff circuit 550 turns off the laser diode 504y accordingly. Furthermore, since there is a proportional relationship between the LD drive current 1d and the laser beam power, 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. 13(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 552, The laser beam power of the laser diode F504y is level 4. Also, the image density data value is "7" (
In the case of 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 is level 7. Next, refer to FIG. 13(C). Then, the laser diode ON10ff circuit 550. A specific circuit configuration of the D/A converter 551 and the constant current circuit 552 is shown. The laser diode on10ff circuit 550 includes TTL inverters 553 and 554, differential switching circuits 555 and 556 that perform an on101'f toggle operation, and a VG
When I>VC2, the differential switching circuit 555 is turned on.
, differential switching circuit 556 is off, VGI<V
At C2, the differential switching circuit 555 is off.

Resistors R2 and R form a voltage dividing circuit that generates VC2 that satisfies the conditions for the differential switching circuit 556 to turn on.
It consists of 3. Therefore, when the LD drive clock is "1", the output of the inverter 554 generates VGI, the above condition (vcl>vG2) is satisfied, the differential switching circuit 555 is turned on, and the differential switching circuit 555 is turned on.
6 is turned off and the laser diode 504y is turned on.

On the other hand, when the LD drive blackout is "0°",
Since there is no output from the inverter 554, the above conditions (VC,
1<VC2), and the differential switching circuit 555
is off, the differential switching circuit 556 is on,
Turn off the laser diode 504y.

The D/A converter 551 has a latch 5 that latches the input image density data while the LD drive clock is '1'.
57, a V rat generator 558 that provides maximum output values V r,, f, and a 3-bit D/A that outputs analog data Vd based on the image density data and the maximum output value r0.
converter 559. Incidentally, the relationship between Vd, image density data, and maximum output value ■r is expressed by the following equation.

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 R4 and R5. The output Vd 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. 13(d) shows the output of the latch 557 mentioned above.

Timing showing the relationship between VC, 1, Vd, and Id
'It's Guchiyad. Here, Vd takes values in 8 stages from V,, if ■ Based on the value. 8 levels of ~I7 are shown. The laser diode 5゜4y controls the photosensitive drum 5 according to the eight levels of this Icl (■o-level 0゜■, -level..., I7-level 7).
A latent image as shown in FIG. 14 is formed on 12y.

In the image forming system to which the graphic processing device of the present invention is applied, the area ratio can be determined at high speed by the above-described configuration and operation without performing subpixel division or counting the number of filled pixels.

Furthermore, since the area ratio is determined by the actual area ratio, anti-aliasing processing can be performed without damaging the image of the actual image.

〔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 graphic processing device to which an anti-aliasing processing method is applied to smoothly express aliasing, a feature point calculation means for calculating feature points for edge pixels of vector data, and a feature point calculation means that calculates feature points for edge pixels of vector data, and based on the feature points and the slope of the vector data, Since the present invention includes an area ratio calculation means for calculating the area ratio to be filled, the area ratio can be calculated at high speed without dividing subpixels and counting the number of filled pixels.

Furthermore, in addition to the above-described configuration, the area ratio calculation means includes:
When the slope θ of the vector data is 0≦]θ1〈45°, or 135°≦1θ]〈180°, the area ratio is calculated using the X coordinate value of the feature point, and the slope θ of the vector data is
However, when 45° ≦ | θ | In addition, anti-aliasing processing can be performed with high accuracy.

[Brief explanation of the drawing]

FIGS. 1(a) to (g) are explanatory diagrams showing an outline of the anti-aliasing process of the present invention, FIG. 2 is an explanatory diagram showing the configuration of the image forming system of this embodiment, and FIG. 3 is the configuration of the PDL controller. 4 (al is a flowchart showing the operation of the PDL controller, FIG. 4(b) is an explanatory diagram showing path filling processing, FIG. 4(C) is a flowchart showing anti-aliasing processing, Figure 5 (
at (b) is an explanatory diagram showing linear vector division of a figure,
FIG. 6 is an explanatory diagram showing the configuration of the image processing device, and FIG. 7 is a T
An explanatory diagram showing a conversion graph for γ correction of the correction circuit, Fig. 8 (
a), (b), and (c) are explanatory diagrams showing conversion graphs for complementary color generation used in the complementary color generation circuit, FIG. 9 is an explanatory diagram showing a Bayer type 3×3 multivalued dither matrix, and FIG.
The figure is a control block diagram showing a multi-value color laser printer, Fig. 11 is an explanatory diagram showing the configuration of a multi-value color laser printer, and Figs. 12 (a) and (b) are the exposure system of the yellow recording unit. An explanatory diagram showing the configuration of, Fig. 13 (
a), (b), (c), and (d) are explanatory diagrams showing multi-level driving by power modulation, Fig. 14 is an explanatory diagram showing the state of the latent image depending on the level of power modulation, and Fig. 15 ( a),
(b3 is an explanatory diagram showing conventional anti-aliasing processing, Fig. 16 (a), (t)) is an explanatory diagram showing anti-aliasing processing by uniform averaging method, Fig. 17 (a)
L (b) is an explanatory diagram showing anti-aliasing processing using weighted averaging method, Figure 18 (a), (b),
(C) and (d) are explanatory diagrams showing examples of filters used in the weighted averaging method, and FIG. 19 is an explanatory diagram showing a convolution method with reference to 3×3 pixels. Explanation of symbols 100 --- Host computer 200 --- PDL controller 201
----------- Receiving device 202 -------- CP
U203--Internal system bus 204--RAM 205-----RO
M206------ Page memory 207------
----- Transmitting device 208-111111-I/O device 300-----1 image reading device 400-----Image processing device 500----1 Value Color Laser Printer 600---System Control Unit

Claims (3)

[Claims] (1) In a graphic processing device that applies an anti-aliasing processing method that adjusts the output of edge pixels of vector data based on the area ratio to be filled, and smoothly expresses jagged edges (aliases) of the output image. A feature point calculation means for calculating a feature point for the edge pixel of the vector data; and an area ratio calculation means for calculating an area ratio to be filled based on the feature point and the slope of the vector data. A graphic processing device characterized by: (2) In claim 1, the area ratio calculation means is configured such that the slope θ of the vector data is 0≦|θ|<45°, or 135°≦|θ|<1
In the case of 80°, the area ratio is calculated using the y-coordinate value of the feature point, and the slope θ of the vector data is 45°≦|θ
A graphic processing device characterized in that when |<135°, an area ratio is calculated using the X coordinate value of the feature point. (3) In claims 1 and 2, the feature point is an intersection point where the vector data passes through the edge pixel, and an intersection point where a plurality of vector data intersect within the edge pixel. A graphic processing device characterized by the following.