JPH04155385A - Graphic processing device - Google Patents

Abstract

PURPOSE:To obtain a clearness of picture element by calculating the intersection when vector data cross each other, then calculating an approximate area rate of an edge picture element including the intersection, and correcting the approximate area rate according to the crossing condition of the vector data. CONSTITUTION:It is detected whether there are two straight lines crossing each other, of the vector data (straight lines) on a scanning line. When there are, the coordinates of the intersection is calculated, and then the picture element including the intersection is calculated. After that, the angle theta of the two straight lines at the painting out side is calculated, and when the angle thetais not 180 deg. < theta < 360 deg., it is decided that the position of the intersection in the edge picture element is at the lower side. On the other hand, when the angle theta is as 180 deg. < theta < 360 deg., the H0 direction, the H1 direction, the V0 direction, and the V1 direction are decided from the inclination of an imaginary line to divide the theta into two equal angles, and the direction of the opening not painted out. After that, the up and down relation of the intersection to the picture element is decided. And only when the intersection P is at the upper side of the picture element, the approximate area rate of the edge picture element including the intersection is corrected.

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 suppress thickening of intersection points and obtain sharp images.

[Prior Art] 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(b) 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 kicf 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 H degree (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 account 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 to the weighted averaging method, which simply counts the number of sub-pixels that are in The effects are different. Note that the weight at this time is given using a filter.

19121(a) and (b), FIG.
a) ,,l! : Same image data, same division method (N=
41=7), and the weighting shows an example in which the averaging method is implemented.

FIG. 19(a) shows a filter (here, conef
ilter), and the corresponding sub-vixel 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 (b)
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. In addition, as a filter, Fig. 20 (a), (
Filters shown in 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 'xN' pixels to correspond to pixels of the equal-averaging method or the weighted averaging method. 21st
The figure shows a convolution method with 3x3 pixel references. In this figure, the pixel whose brightness is to be determined is 2101
Indicated by 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 the hector 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 hector 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 Des
criptionLanguage: Hereafter, PDL
It belongs to a language genre called ``Japanese language'', 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 systems such as this, and vector fonts are used as character fonts in such systems. Therefore, even if the characters are scaled, the print quality can be significantly improved compared to systems using bitmap fonts (for example, conventional word processors).
Another advantage is that character fonts, graphics, and images can be mixed and printed.

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.

Problems to be Solved by the Invention] However, according to the graphic processing device applying the conventional anti-aliasing processing, the gradation value (density data) is calculated based on the percentage of area to be filled in as described above. Therefore, when anti-aliasing processing is applied to the intersection of two vector data, the intersection becomes thick and the sharpness decreases.

Specifically, for example, as shown in FIG. 22(a), a straight line D1 passes through pixels G1 and G2, and pixels G2 and G3
When straight line D2 passes through pixel c1., when calculating the proximal area ratio by dividing the pixel into 4*4 subpixels (uniform averaging method), pixel c1. The approximate area ratio of G2゜G3 is 1/
4.1/2.5/8.

Therefore, pixel G2 appears to have a bulge.

Also, Fig. 22 rb): As shown, the pixel G44 includes the intersection C1 defined as the outline data.
Similarly, if there are two, the intersection will be thicker.

The present invention has been made in view of the above, and an object of the present invention is to apply anti-aliasing processing to edge pixels including intersection points, and to do so without impairing sharpness.

[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 uses anti-aliasing to smoothly express jagged edges (aliases) of the output image. In a graphic processing device to which the processing method is applied, an intersection calculation means that calculates an intersection point when vector data intersects, and an approximation that calculates an approximate area ratio of an edge pixel including the intersection point using an anti-aliasing processing method. The present invention provides a graphic processing device that includes an area ratio calculation means and an approximate area ratio correction means for correcting the approximate area ratio according to the degree of intersection of vector data in edge portion pixels including intersection points.

In addition, 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 smoothly expresses jaggedness (alias) at the edge portion of the output image. In a graphic processing device to which an anti-aliasing processing method is applied, an intersection calculation means for calculating an intersection point when vector data intersects, and an approximate area ratio of an edge pixel including the intersection point is calculated using the anti-aliasing processing method. an approximate area ratio calculation means for calculating an intersection angle θ on the filled side of two vector data forming an intersection; The present invention provides a graphic processing device equipped with approximate area ratio correction means for correcting the approximate area ratio based on the position of the intersection in the area and the filling direction of the image area in the cut/edge part pixels.

In the above configuration, the approximate area ratio correction means is configured such that the slope φ of the virtual line dividing the intersection angle θ into two equal parts is 0≦φ<45
°, or in the range of 135°≦φ<180, and the opening that is not filled is on the right side of the pixel, in the H0 direction,
H if the opening that is not filled is to the left of the pixel
8 directions, the slope φ of the virtual line that bisects the intersection angle θ is in the range of 45°≦φ<135, and the opening that is not filled is in the upper direction of the pixel. direction, if the opening that is not filled is in the lower direction of the pixel, it is defined as ■1 direction;
When the directions of the openings that are not filled are in the H0 direction and the H1 direction, it is determined whether or not to correct the approximate area ratio based on the X coordinate value of the intersection, and the direction of the openings that are not filled is ■. In the case of the direction and the force direction, it is desirable to determine whether or not to correct the approximate area ratio based on the X coordinate value of the intersection point.

Further, in the above-described configuration, it is preferable that the approximate area ratio correcting means corrects the approximate area ratio by multiplying the approximate area ratio by a coefficient set in advance based on the magnitude of the approximate area ratio.

Furthermore, in the above configuration, the preset coefficient S is s=0.5 when the approximate area ratio k is 0.25≦≦0.75.
, otherwise it is desirable that s=1.

[Effect]

In the graphic processing device of the present invention, the intersection calculation means calculates the intersection when the vector data intersects. Next, a near area ratio calculation means calculates an approximate area ratio of the edge portion pixels including the intersection point using an anti-aliasing processing method.

Thereafter, the approximate area ratio correction means corrects the approximate area ratio of the edge portion pixels including the intersection according to the degree of intersection of the vector data.

〔Example〕

Hereinafter, an image forming system to which the graphic processing device of the present invention is applied will be described as an example. ■Outline of approximate area ratio correction according to the present invention, block diagram of the zero image forming system, ■Configuration and operation of PDL controller, ■Image processing device 1.The configuration and operation of the multi-valued color laser printer, 2.The multi-valued drive of the driver will be explained in detail in this order.

■Outline of approximate area ratio correction according to the present invention.

The graphic processing device of the present invention corrects the approximate area ratio of edge pixels including the intersection obtained by anti-aliasing processing by the approximate area ratio correction means based on the degree of intersection of vector data forming the intersection. This makes it possible to obtain clear images without thickening at the intersections.

The approximate area ratio correction according to the present invention will be described in detail below.

In this example, as shown in FIG. 1(a), when the angle θ formed by two straight lines satisfies 180° < θ < 360° and the area side of this angle θ is filled in, approximate area ratio correction processing is performed. implement. In the anti-aliasing process, all vector data is approximated to a straight line vector, so the vector data will be explained below assuming that it is a straight line.

First, the angle θ formed by two straight lines will be defined.

As shown in FIG. 1(b), when a straight line 11 having end points T and T2 intersects a straight line ρ2 having end points T3 and T4, the intersection P of these two straight lines is the end point T, 9. T2
A straight line! It is calculated by deriving the equation of , deriving the equation of straight line 12 from the end points T, , T, and solving these simultaneous equations. The pixel including the coordinates of this intersection P becomes the target edge pixel (note that even if T2 and T3 match, the intersection P can be found in the same way).

Next, since the area to be filled can be determined from the determination of the left and right edges, the angle formed by the two straight lines on the side of the area to be filled is determined as θ with the intersection point P as a reference.

The angle θ obtained in this way is 180°〈θ〈360°
When the following is satisfied, the following approximate area ratio correction process is executed.

The positional relationship between the pixels of the intersection point P is determined.

First, as shown in FIGS. 1(C) and (d), the slope φ of the virtual up3 that divides the angle θ into two is determined, and the slope φ is 0≦
In the range of 45° or 135°≦φ<180,
H if the opening that is not filled is on the right side of the pixel.
The 0 direction and the case where the unfilled opening is to the left of the pixel are defined as the H direction.

Also, the slope φ of the virtual line 13 that divides the angle θ into two equal parts is 45
V if the opening that is not filled is in the upper direction of the pixel in the range of °≦φ<135. The direction is defined as the v1 direction when the opening that is not filled is in the lower direction of the pixel.

H0 direction, H1 direction, ■ defined as above.

The relationship between the direction, the V1 direction, and the slope θ is shown in FIG. 1(e).

Next, H0 direction, H1 direction, ■. Direction, (1) Using the coordinates of the direction and the intersection P, find the positional relationship at the pixel of the intersection P.

In this example, when the directions of the openings that are not filled are in the H0 direction and the H1 direction, the respective directions are set as the bottom, and
Based on the coordinate values of the intersection P, the vertical relationship of the intersection P to the pixel is determined. Specifically, when the opening is in the H6 direction, if the decimal part of the X coordinate is smaller than 0.5, it is upper, 0.
If it is 5 or more, it is determined as lower, and if the opening is in the H1 direction,
If the decimal part of the X coordinate is less than 0.5, it is determined to be lower, and if it is 0.5 or more, it is determined to be upper. Therefore, the intersection P in FIG. 1(d) is determined to be below.

Also, the direction of the opening that is not filled is ■. Direction and ■1
In the case of a direction, the vertical relationship of the intersection point P with respect to the pixel is determined based on the X coordinate value of the intersection point P, with the direction shown as the bottom. Specifically, when the opening is in the V0 direction,
If the decimal part of the ,0. If it is 5 or more, it is determined to be upper. Therefore, the intersection P in Fig. 1(C)
is determined to be above.

The vertical relationship determined in this manner indicates that when the intersection P is located above the pixel, the filled area within the pixel is small, and when it is located below, it indicates that the filled area within the pixel is large. Therefore, when the filled area within a pixel is small, the thickening of the intersection point becomes noticeable, so the approximate area ratio of the edge pixel including the corresponding intersection point is corrected only when the intersection point P is located above the pixel. .

The approximate area ratio is corrected by the approximate area ratio k obtained by anti-aliasing processing. is performed using a predetermined correction coefficient S as follows.

k = s X k o ■ Here, the correction coefficient S is set as follows using the darkness values of 0.25 and 0.75.

When 0.25≦ko≦0.75, s=0.5; otherwise, s=1 (same as no correction).

In the first figure), the intersection point is at the top, but the area ratio is over (
ko > 0.75), Fig. 1 (The button has an intersection position at the bottom, so the approximate area ratio is not corrected. Fig. 1 (h) shows an example of processing when the intersection position is above. , an example of processing when correcting the approximate area ratio is shown.

Alternatively, a method that simplifies this example may be considered, except for the condition of the intersection position, and simply multiplying the area ratio by three at all intersections according to the approximate area ratio.

■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).
The configuration is such that image formation can be performed using image information of both hector data written in the PDL language (hereinafter referred to as PDL language) and image images read by an image reading device. The configuration of the image forming system of this embodiment will be described below with reference to FIG.

The image forming system includes a host computer 100 that creates a document written in PDL language (Postscript language is used in this embodiment);
The PDL controller 200, which applies anti-aliasing processing to the PDL language sent in pages from an image reading device 300 that reads image information via the PDL controller 20;
0. Alternatively, 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 printer that prints the multi-value image data output from the image processing device 400. laser·
A printer 500 and a PDL controller 200. Image reading device 3003 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 203, a RAM 204 that stores the PDL language transferred from the receiving device 201 via the internal system 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 RAM 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. , B, and 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 processing performed by the CPU 202. As described above, the PDL controller 200 processes the PDL language sent page by page from the host computer 100 while processing it in 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 fill-in filling processing using scanning lines. For example, in Figure 4 (
When performing the pass fill 5 process shown in b), the elements of the side across the scanning line yc to be processed and the real value of the X coordinate across the scanning line yc (XI X2 shown in Figure 4)
X3 Xa) and AET (Active Edge T
able: registered in a table that records the X coordinate of the enon 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. be registered. Therefore, after the AET is registered, the elements on each side within the AET are sorted in descending order of X coordinate. And AET
Pair the first two elements 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 the AET, update the scanline (update the X coordinate), until all edges in the AET have been processed, in other words
Similar processing is repeated until all elements within one pass are processed.

Above processing 1. Processing 2. The work in process 3 is executed pass by pass and repeated until all buses 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) Five line vectors AB, BC, CD, DE, and EA (represented by real numbers) (El) Color and brightness values inside the figure As shown in Figure 5, etc., this figure is mainly Seven straight line vectors extending in the scanning direction (real number representation)
divided into 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 the vector elements ((a) above) forming the starting point and ending point of the straight line vector (d) Slope information (near ) Characteristic information of the start point and end point of the straight line vector (right edge, left edge, information that the vector data is vertical, 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, in sub-vixel filling processing, a filling area for each sub-pixel is calculated using a 3*3 sub-pixel division method (S401). This process is repeated for all vectors that cross the scanning line (5402).

Next, in the density determination process, the approximate area ratio of each pixel is calculated in order from the first pixel of the target scanning line using a uniform averaging method (anti-aliening processing method) filter (S403). .

Next, in the approximate area ratio correction process, when the angle θ formed by the two straight lines satisfies 180°<θ<360° and the area side of this angle θ is filled in, the approximate area ratio correction process is performed (5404).

Each color of the figure (BK, R, G, B
Calculate the gradation value (density) of the four colors.

Here, if the figure in FIG. 5(a) has a white background color (
The figure color is red (maximum brightness: 25) on top of (maximum brightness: 255)
5), the luminance of each color of the figure (F!K r (red), 9 (green),
Kb (blue) is obtained based on the following formula.

Kr'= KRtXk 10KRZX(1k)K9=
Kc, +Xk + Kczx(1k)Kb −
+zXk 1KB□X(1-k) However, K R+,
K c + and K s + are respectively the above ([1)
KH2, KG□, and KH2 indicate the brightness values of each previously painted color. Note that K, □, KG□, and KB□ refer to data in each plane memory section corresponding to RGB of the page memory 206 (5405).

Thereafter, the page memory drawing process is performed to write the gradation values of each color into the page memory 206 (S406).

Furthermore, the processes from 5403 to 5406 described above are repeatedly executed for all pixels of one line (5407).

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

Next, approximate area ratio correction processing will be described with reference to the flowchart in FIG. 4(d).

First, it is determined whether there are two intersecting lines among the vector data (straight lines) on the scan line (S408). Here, if there are no intersecting straight lines, the process ends.

If there are straight lines that intersect, calculate the coordinates of the intersection, then
Pixels including the intersection are calculated (5409.410).

Next, calculate the angle θ of the example of filling in two straight lines541
2) If the angle θ is 180° <θ<360'
3), proceed to 5417.

On the other hand, if the angle θ is 180°<θ<360°, set θ to 2
The slope of the virtual line that divides into equal parts, and the H8 direction, H1 direction, and v from the direction of the opening that is not filled. The direction, v1 direction, is determined as follows. Find the slope φ of the imaginary line that bisects the angle θ, and find if the slope φ is 0≦φ〈45° or 135
In the range of °≦φ<18o, when the opening that is not filled is on the right side of the pixel, the H6 direction is, and when the opening that is not filled is on the left side of the pixel, it is the H1 direction, and the slope φ is 45°≦ In the range of φ<135, the case where the unfilled opening is located above the pixel is determined as the V0 direction, and the case where the unfilled opening is located below the pixel is determined as ■1 direction (5414).

Subsequently, the vertical relationship between the intersection points and the pixels is determined. Specifically, when the opening is in the H0 direction, the decimal part of the X coordinate is 0.
．． If it is smaller than 5, it is above, 0. If it is 5 or more, it is determined to be lower, and if the opening is in the H1 direction, the decimal part of the X coordinate is 0.
If it is less than 5, it is determined to be lower, and if it is 0.5 or more, it is determined to be upper (5415).

After that, it is necessary to judge whether the upper or lower judgment is upper or not (5416),
If it is above, the area near the pixel including the intersection (0 area ratio k. is 0.2
5417), 0.
If the range is 25≦ko≦0.75, set the correction coefficient S to 0.5.
, and obtain the corrected approximate area ratio k using the formula k=5Xko (5418.5420).

On the other hand, if the upper/lower judgment is lower, and if the approximate area ratio of the pixel including the intersection point is not 0.25≦ or 0≦0.75, the correction coefficient S is set to 1, and k=5Xko Obtain the approximate area ratio k after correction using the formula (5419.5420
).

In this embodiment, the approximate area ratio correction process is shown separately from the density determination process, but it may be included in the density determination process.

(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 (Y), magenta (M), and cyan (C)
) into each recording signal. Further, the RGB image data given from the PDL controller 200 described above is similarly converted into black (BK), yellow (Y), magenta (M), and cyan (C) recording signals. Here, the mode in which image signals are input from the image reading device 300 is called a copying machine mode, and the mode in which ROB image data is input from the PDL controller 200 is called a 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 take (RGB image take) output from the PDL controller 200 according to the aforementioned mode;
A γ correction circuit 40 receives the 8-bit data (color gradation data) output from the multiplexer 402, changes the gradation according to the characteristics of the photoreceptor, and outputs it as 6-bit data.
3, and red (R) and green (
G).

Convert 6-bit, G gradation data indicating the gradation of blue (B) to gradation data (6-bit, G) of cyan (C), magenta (M), and yellow (Y), which are the respective complementary colors. Complementary color generation circuit 405 and Y, M output from complementary color generation circuit 405
, C, and a masking processing circuit 406 that performs predetermined masking processing on each gradation data of Y, M,
A UCR processing/black generation circuit 407 inputs each gradation data of C and executes UCR processing and black generation processing, and Y outputted from the UCR processing/black generation circuit 407.

Each 6-bit tone data of M, C, and BK is converted into 3-bit tone data Yl, ML C1, and BKI, and is sent to the laser drive processing section 502 inside the multivalued color laser printer 500. It is composed of a gradation processing circuit 408 for outputting, and a synchronization control circuit 409 for synchronizing each circuit of the image processing apparatus 400.

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

Further, as the algorithm used in the gradation processing circuit 408, a multi-value dither method, a multi-value error diffusion method, etc. can be used. For example, a dither matrix of the multi-value dither method can be
x3, multilevel color laser printer 500
The two-round frequency is 3 x 3 area gradation and 3 bits (i.e. 8
It is the product of the multi-value levels of the stages), and 3X3X8=72 (
gradation).

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

The arithmetic expression for the masking process of the masking processing circuit 406 is generally expressed by the following expression, and the arithmetic expression for the tJcR process of the UCR processing/black generation circuit 407 is also generally expressed by the following expression.

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

(... . . . j aa+ aaz a<3 In this example, a new coefficient (al+", etc.) that performs this masking processing and UCR processing simultaneously is calculated in advance,
Furthermore, using the new coefficients, the masking processing circuit 40
6 scheduled input values Y,,M□.

Output value corresponding to Ci (6 bits each) (Y0', 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,
, M, and C are corrected to values obtained by subtracting the black component data BK.

In the above configuration, the T 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 (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 Heyer 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. The details will be explained later, but the development and development of BK data is
A black developing/transfer section 501bk& that performs transfer, a cyan developing/transfer section 501c that develops/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 inputting the 3-bit data of Y, M, C, and BK output from 00 (in this case, image density data). Input 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.

Note that the blank developing/transfer section 5 of the photoreceptor development processing section 501
01bk, the laser drive processing unit 502 laser diode 504bk, and the driver 5-05bk are called a blank recording unit BKU (see FIG. 11). Similarly, the cyan developing/transfer section 501c,
Laser diode 504c, driver 505c,
and buffer memo') 503c, a combination of cyan recording unit CU (see Figure 11), magenta developing/transfer section 501m, laser diode 504m,
A combination of a driver 505m and a buffer memory 503m is connected to a magenta recording unit MU (see FIG. 11),
The yellow developing/transfer section 501y, laser diode 504y, driver 505y, and 9 buffer memory 503y are combined into a yellow recording unit 1-YU.
(See Figure 11). As shown in the figure, each of these recording units includes a blank recording unit BKU from the recording paper conveyance direction around a conveyor belt 506 that conveys the recording paper.
, cyan recording unit CU, magenta recording unit MU, and yellow recording unit (UNISO) YU.

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

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

The multivalued color laser printer 500 includes a transport heald 506 that transports recording paper, and a transport bell (as described above).
Each recording unit YU, MU, arranged around 506
(, U, BKU, and paper feeding power cents 50 containing recording paper)
7a, 507b, and paper feed rollers 508a, 508 that feed the recording paper from 507a, 507b, respectively.
b, and a registration roller 509 that aligns the recording paper sent out from the paper feed rollers 507a and 507b,
The recording units BKU and CU are transported by the transport heald 506.
, MU, and YU and fixes the transferred image on the recording paper, and a paper discharge roller 511 that discharges the recording paper to a predetermined discharge section (not shown). Here, each recording unit YU, MU, CU, BK
U represents photoreceptor drums 512y, 512m, 512c, 5
12bk, and photoreceptor drums 512y and 512m, respectively.
.

Charger 513y that uniformly charges 512c and 512bk
, 513m, 513c, 513bk, and photosensitive drum 5
Polygon mirrors 514y, 514m for guiding the laser beam to 12y, 512m, 512c, 512bk,
514c, 514bk and motor 515y, 515m,
515c, 515bk, and photosensitive drums 512y, 51
toner developing devices 516y, 516m, 516c, and 516bk that develop the electrostatic latent images formed on 2m, 512c, and 512bk using toners of corresponding colors;
Transfer charger 517 that transfers the developed toner image onto recording paper
y, 517m, 517c, and 517bk, and a cleaning device 518y 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 same 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 521y.

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 5, as shown in FIG.
08a (or 508b), and the registration roller 509 records the black (unisolated) BKL.
In synchronization with the formation of the toner image I, the toner image is transferred onto the recording paper conveyed by the conveyor belt 506.

The other recording units I-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 516bk to form and transfer a black toner image, the cyan recording unit CU is equipped with a cyan toner developing device 516C to form and transfer a cyan toner image, and the magenta recording unit MU is equipped with a cyan toner developing device 516C to form and transfer a cyan toner image. A toner developing device 516m is provided to form and transfer a magenta toner image.

■The multi-value drive drivers 505y, 505m, 505c, and 505bk are Y, M, C, and B sent from the image processing device 400.
Based on K's 3-bit, Todek, laser diode 504y, 504m that corresponds to 3.

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, Triba 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-focus image density data (
Here, the D/A converts Y data) into an analog signal.
A converter 551 and a constant current circuit 552 that inputs an analog signal based on the image density value from the D/A converter 551 and supplies a current (LD drive current) Id for driving the laser diode 504y to the laser diode On10 f f circuit 550. It consists of

Here, the LD drive blocker is defined as on at '1°' and off at '0', and as shown in FIG. 13(b), the laser diode on10ff circuit 550 turns on and 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 Id based on the image density data value, the laser beam power output corresponding to the image density data value can be obtained. It turns out.

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 504y 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.
becomes.

Next, referring to FIG. 13(C), a laser diode on/off circuit 550. D/A converter
5 shows a specific circuit configuration of the circuit 551 and the constant current circuit 552. The laser diode on/off circuit 550 has TTL inverters 553, 554 and an on/off circuit.
Differential switching circuit 5 with loff toggle operation
55, 556, and when VGI>VC2, the differential switching circuit 555 is on, and the differential switching circuit 556 is on.
is off, and when VGI<VC2, the differential switching circuit 555 is off.

A resistor R, which forms a voltage divider circuit that generates VC,2 that satisfies the conditions for the differential switching circuit 556 to be turned on.
It is composed of R3. Therefore, when the LD drive clock is "1", the output of the inverter 554 generates VGI, the above condition (VGI>VO2) is satisfied, the differential switching circuit 555 is turned on, and the differential switching circuit 555 is turned on.
56 is turned off and the laser diode 504y is turned on.
do.

Conversely, when the LD drive clock is "0", there is no output from the inverter 554, so the above condition (VGI<
VO2), and the differential switching circuit 555
ff, the differential switching circuit 556 turns on and turns 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 a maximum output value V ref, and a V rat generator 558 that provides image density data and a maximum output value V ref.
3-bit D/ that outputs analog data Vd based on
A converter 559. Furthermore, here Vd
The relationship between the image density data and the maximum output value V ref 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 R, , R6. The output Vd from D/A converter 551 is applied to the base 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 1d flowing through the laser diode 504y is controlled by Vd.

No. 1311D(d) is the output of the aforementioned launch 557.

5 is a timing chart showing the relationship between VGI, Vd, and Id. Here, Vd is Vrl, f based on image density data (3 focus data: 8 gradation data from 0 to 7).
It takes a value in 8 steps from ×0/7 to 7/7, and Id is this V
Based on the dO value, 1. Shows 8 levels from ~17. The laser diode 504y is placed on the photosensitive drum 512y at the 14th level according to the 8 levels of this Id (1, - level 0111 - level . . . , I7 - level 7).
A latent image as shown in the figure is formed.

In an image forming system to which the graphic processing device of the present invention is applied, the configuration and operation described above can be used, for example, as shown in FIG.
Edge pixels including the intersections shown in a), (b), and (C) are processed as shown in FIGS. 16(a), (b), and (C).

As is clear from the illustration, the thickness at the intersection is gone,
A clear image can be obtained.

〔Effect of the invention〕

As explained above, the graphic processing device of the present invention adjusts the output of edge portion pixels of vector data based on the area ratio to be filled, and jagged edge portions (
In a graphics processing device that uses an anti-aliasing processing method that smoothly expresses aliases, there is an intersection calculation means that calculates the intersection point when vector data intersects, and an anti-aliasing method that calculates the approximate area ratio of edge pixels including the intersection point. Approximate area ratio calculation means that calculates using an aliasing processing method, and in pixels including intersection points,
Since it is equipped with an approximate area ratio correction means that corrects the approximate area ratio according to the degree of intersection of the vector data, anti-aliasing processing is performed on edge pixels including intersection points,
Moreover, it is possible to obtain an image without losing sharpness.

In addition, the graphic processing device of the present invention adjusts the output of edge portion pixels of vector data based on the area ratio to be filled, and performs anti-aliasing processing to smoothly express jaggedness (alias) at the edge portion of the output image. In a graphic processing device that is compatible with the method, an intersection calculation means that calculates an intersection point when vector data intersects, and an approximate area that calculates an approximate area ratio of an edge pixel including the intersection point using an anti-aliasing processing method. an intersection angle calculation means for calculating an intersection angle θ on the filled side of two vector data forming an intersection; Position of.

and approximate area ratio correction means for correcting the approximate area ratio based on the filling direction of the image area in the edge area pixels, so that anti-aliasing processing is performed on the edge area pixels including the intersection points, and Images can be obtained without losing sharpness.

[Brief explanation of the drawing]

FIGS. 1(a) to Q'1) are explanatory diagrams showing the approximate area ratio correction processing of the present invention, FIG. 2 is an explanatory diagram showing the configuration of the image forming system of this embodiment, and FIG. An explanatory diagram showing the configuration, FIG. 4(a) is a flowchart showing the operation of the PDL controller, FIG. 4(b) is an explanatory diagram showing path filling processing, and FIG. 4(C) is a flowchart showing anti-aliasing processing. , FIG. 4(d) is a flowchart of approximate area ratio correction processing, FIG. 5(a), (
b) is an explanatory diagram showing the linear hector side of the figure, Fig. 6 is an explanatory diagram showing the configuration of the image processing device, Fig. 7 is an explanatory diagram showing the conversion graph for r correction of the T correction circuit, and Fig. 8 ( a),
(b) and (C) are explanatory diagrams showing conversion graphs for complementary color generation used in the complementary color generation circuit, and Figure 9 is a Heyer type 3 × 3
FIG. 10 is a control program diagram showing a multi-value color laser printer.
11 and 11 are explanatory diagrams showing the configuration of a multivalue color laser printer, FIGS. 12(a) and 12(b) are explanatory diagrams showing the configuration of the exposure system of the yellow recording unit, and FIG. 13 (
a), (b). (C), (d) are explanatory diagrams showing multi-level driving by power modulation, Figure 14 is an explanatory diagram showing the state of latent images depending on the level of power modulation, and Figures 15 (a), (b), (C ) is an explanatory diagram showing the intersection before correction processing, FIG. 16(a),
(b) and (C) are explanatory diagrams showing after the correction processing of the intersection portion according to the present invention, Fig. 17 (a) and (b) are explanatory diagrams showing the conventional anti-aliasing processing, and Fig. 18 (a)
, (b) is an explanatory diagram showing anti-aliasing processing using the uniform averaging method, Fig. 19 (a), (b) is an explanatory diagram showing anti-aliasing processing using the weighted averaging method, Fig. 20 (a) . (b), (C), and (d) are explanatory diagrams showing examples of filters used in the weighted averaging method; Fig. 21 is an explanatory diagram showing a convolution method with 3 x 3 pixel reference; a
). (b) is an explanatory diagram showing conventional problems. Explanation of symbols 100 ----- Host computer 200 --- PDL controller 201 ---
--- Receiving device 202 --- CPU U203-
---Internal system lotus 204----RAM 205---ROM2O6-
-Page memory 207--Transmitting device 208--
-I/O device 300---One image reading device 400---Image processing device 500---Multi-value color laser printer 600-
---System control section

Claims (4)

[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. Intersection point calculation means for calculating an intersection point when vector data intersects; Approximate area ratio calculation means for calculating an approximate area ratio of edge pixels including the intersection point using an anti-aliasing processing method; A graphic processing device comprising: an approximate area ratio correcting means for correcting an approximate area ratio in accordance with the degree of intersection of vector data in edge portion pixels including the image data. (2) 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. Intersection point calculation means for calculating an intersection point when vector data intersects; Approximate area ratio calculation means for calculating an approximate area ratio of edge pixels including the intersection point using an anti-aliasing processing method; an intersection angle calculating means for calculating an intersection angle θ on the filling side of two vector data to be formed; when the intersection angle θ is 180°<θ<360°, a position of the intersection within the edge pixel; Based on the filling direction of the image area in the edge area pixel,
A graphic processing device comprising approximate area ratio correction means for correcting the approximate area ratio. (3) In the second aspect, the approximate area ratio correcting means is configured such that an inclination φ of a virtual line dividing the intersection angle θ into two equal parts is 0≦φ<45°, or 135°.
In the range of °≦φ<180, the case where the unfilled opening is on the right side of the pixel is defined as the H_0 direction, and the case where the unfilled opening is on the left side of the pixel is defined as the H_1 direction, and the intersection angle θ is divided into two. The slope φ of the virtual line is 45°
In the range of ≦φ<135, when the opening that is not filled is in the upper direction of the pixel, the direction is V_0, and when the opening that is not filled is in the lower direction of the pixel, it is the direction V_1, and the direction of the opening that is not filled is H_0 direction and H_
In the case of one direction, it is determined whether or not to correct the approximate area ratio based on the x-coordinate value of the intersection point, and if the direction of the unfilled opening is in the V_0 direction and the V_1 direction, the y-coordinate value of the intersection point is determined. A graphic processing device that determines whether or not to correct the approximate area ratio based on. (4) In claim 3, the approximate area ratio correction means corrects the approximate area ratio by multiplying the approximate area ratio by a coefficient set in advance based on the magnitude of the approximate area ratio. A graphic processing device characterized by: (5) In claim 4, the preset coefficient s is such that the approximate area ratio k is 0.2.
A graphic processing device characterized in that when 5≦k≦0.75, s=0.5, and in other cases, s=1.