JPH0492987A - Image forming device - Google Patents

Abstract

PURPOSE:To make the bit map development of an image at high speed by dividing a polygon shown by vector information by a scan line passing the vertexes into the minimum number of triangles and a quadrangle whose two sides are parallel to these. CONSTITUTION:The polygon given by the vector information is divided into the minimum number of triangles and a trapezoid whose two sides are parallel to the scan line by a straight line parallel to the scan line passing the vertexes. Each side is made approximate to an integral coordinate. However, when the side is parallel to the scan line, the approximation to the side is not executed. And, an edge list is prepared and registered on a RAM. Then, it is judged whether the coordinate registered on the edge list is the starting point to paint- out, or not, and in case of the starting point, the paint-out to the next coordinate is executed. The process is finished when the paint-out is completed. Thus, a process speed is improved without a decimal arithmetic or a half-adjust.

Description

[Detailed description of the invention] [Industrial application field] This invention is a page printer (laser printer).

The present invention relates to an image forming apparatus such as an LED printer (LED printer, etc.), and particularly relates to an image forming apparatus that generates data of a filled polygon on a memory that is viewed as a matrix of pixels.

[Prior Art] For example, in a laser printer, when outputting a polygon represented by vector information as shown in FIG. 9 to a printer engine, the positions of pixels (squares) constituting the polygon are calculated, Generally, the results are written into a bitmap memory, and when the data for one page is complete, it is output to a printer engine for printing.

Note that the vertex A (X + + 3' t ) r in the same figure
B (X + + ym) +C(x m + y
s ) + D (x − + y −) is a pixel position indicating the vertex of the filled polygon to be calculated.

Incidentally, there is a scan conversion method as a method of determining the pixel positions constituting the polygon from vector information.

This scan conversion method generates image data by selecting pixels to be filled in in the order in which scan lines occur.
．． 5.30 issue).

Therefore, when drawing the polygon shown in Figure 9 on the bitmap memory using this scan conversion method, the points where each scan line intersects with the polygon are calculated as shown in Figure 10. demand.

However, since each of these points becomes the start and end points of the filled area, accurate pixels cannot be determined if the number of points is odd or if the sides of the polygon are on the scan line.

Therefore, in such a case, a half scan line as shown in FIG. 11 is used, in which the scan line passes through the middle of the pixel rows.

When the positions of the pixels forming the polygon are determined in this way, the address containing the pixel on the bitmap memory and the bit position of that pixel are determined, and the data to be drawn is written into the bitmap memory.

[Problem to be solved by the invention]

However, when half scan lines are used, it is necessary to perform processing such as decimal operations and rounding when selecting pixels to determine the start and end points of the filled area, which causes the problem of slowing down the processing speed. there were.

This invention has been made in view of the above points, and an object thereof is to increase the processing speed of polygon drawing using vector information.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an image forming apparatus that converts vector information into bitmap information, records it in a bitmap memory, and outputs the result. A first means of dividing the scan line into the minimum number of triangles and rectangles whose two sides are parallel to the scan line, and determining the pixels constituting each figure divided by this means, and storing the results in a bitmap memory. A second writing means is provided.

[For production]

In the image forming apparatus according to the present invention, the first means divides the polygon indicated by the vector information into the minimum number of triangles or rectangles whose two sides are parallel to the scan line by the scan line passing through the vertices of the polygon, and The means calculates the positions of the pixels constituting each of the divided figures, and writes the results into the bitmap memory.

That is, since the start and end points of the filled area for each divided figure can be determined using the Plessenham method, the filling process is faster than when half scan lines are used.

[Example] Hereinafter, an example of the present invention will be specifically described based on the accompanying drawings.

FIG. 2 shows the configuration of a laser printer system which is an embodiment of the present invention.

This system includes a host system 1, a controller 2, a print engine (hereinafter simply referred to as the "engine") 3, a host interface 4 that connects these, and a laser printer video interface (hereinafter referred to as rLPVIJ).
(abbreviated as )5. Note that each part except the host system 1 constitutes a laser printer.

The host system 1 is a host machine such as a word processor, an office computer, or a personal computer that sends print information such as character information, image information, vector information, and overlay information.

The controller 2 is an image processing device that analyzes character information, image information, or vector information received from the host system 1, and generates image information that is bitmap information for each page of print paper.

The print engine 3 is an image forming device that modulates a laser according to image information sent from the controller 2 and prints a visible image on paper.

The host interface 4 is an interface for connecting the host system l and the controller 2, and is an interface for connecting the host system l and the controller 2.
3232C, Centronics I/F, etc. are well known.

LPVI5 is a standard interface that connects the controller 2 and the engine 3. It unifies the video interface hardware, which was previously determined individually for each engine (each model), so that it is not affected by the engine's functions. be.

FIG. 3 shows the hardware configuration of the controller 2 in the laser printer.

The controller 2 includes a CPU 20° program ROM 21 . RAM22. Font ROM23. Non-volatile RAM 24, operation panel 25, option interface 27. Video control section 28. Engine interface 29 and the aforementioned host interface 4 and LP
It consists of the controller side part of VI5, and each part has a CPU
connected by bus.

The CPtJ20 is a central processing unit that centrally controls the entire controller 2, and is a general-purpose 16-bit or 32-bit
Uses Bit CPU.

The program ROM 21 stores microcode (program) for controlling the CPU 20.

RAM22 is a large capacity random access memory,
It is mainly used for the following purposes.

(a) System memory (b) Input buffer (c) Page buffer (d) Font file (e) Macro file (f) Image file (g) Vector file (h) Print control file (i) Video buffer , shows the flow of data processing and the relationship between each buffer and file in this RAM 22.

Information sent from the host system 1 is stored in the input buffer 22b via the host interface 4.

The data stored in this input buffer 22b is
The data is extracted by the data processing unit 201 and registered in either the page buffer 22c, font file 22d, macro file 22e, image file 22f, vector file 22g, or print control file 22h depending on the type of data.

That is, print sequence control data (specifying the paper transport path, ability to specify the number of print sheets) is stored in the print control file 22h, page layout information (relationship between print data and print position, etc.) is stored in the page buffer 22c,
Image information is registered in the image file 22f, downloaded fonts are registered in the font file 22d, overlay information, etc. are registered in the macro file 22e, and vector information is registered in the vector file 22g.

The image information processing unit 202 generates the image file 22f according to the contents of the page buffer 22c.

The contents of the font file 22d and the font ROM 23 are developed into the video buffer 22i, which is a bitmap memory, and the data such as polygons indicated by the vector information in the vector file 22g are stored in the video buffer 22.
Generate on i.

When the printing data for one page is completed in the video buffer 22i, the print control unit 2.3 starts the engine 3 via the LPVI 5 according to the contents of the print control file 22h, and when the engine 3 reaches the image recording timing, the print data is stored in the video buffer 22i. The bitmap information in the buffer 22h is sent to the engine 3 via the LPVI 5 by the video control unit 28.
Send to.

The engine 3 prints the bitmap information sent through the LPVI 5 on paper.

Returning to FIG. 3, the font ROM 23 stores font data for converting character information sent from the host system 1 via the host interface 4 into image information.

The nonvolatile RAM 24 is a memory that stores information for controlling the operating state of the printer after the power is turned on, and mainly stores the following items.

(a) Print direction (b) Font (c) Character size (d) Line spacing (e) Paper feed slot (f) Paper output slot (g) Host interface The memory contents of this non-volatile RAM 24 are stored in the operation panel 25
Updated from.

The host interface 4 is an interface that connects the host system 1 and the controller 2, and is provided with two types: Centronics-compliant parallel and R3-232C, and is selected by operating the operation panel 25.

The option interface 27 is an interface for externally supplying fonts and programs to expand functionality, and can handle two IC cards 6 in this example.

The IC card 6 is a commercially available one, and depending on the type of data stored, there are cards that store a font card, a program card, or both, but they are physically the same.

The video control unit 28 serially converts the video data stored in the video buffer 221 in FIG. 4 with the bus width (16 bits or 32 bits) of the CPU 20, and
It is sent to engine 3 via PVI5.

The engine interface 29 has a serial communication (transmission/reception) function that detects the state of the engine including its resolution using bidirectional serial signals via the LPVI 5, and controls the engine 3 by sending commands.

Next, regarding the polygon drawing process in this example,
This will be explained in detail with reference to the flowchart of FIG. 1 (steps ① to ①) and FIGS. 5 to 8.

Note that the X coordinate is taken in the scan direction, and the X coordinate is taken in the page feed direction.

Step ■ Create an n-gon P as shown in Figure 5 given by vector information.
, P, . . . Pn is divided into a minimum number of triangles with a straight line parallel to the scan line passing through its vertices and a quadrilateral (in the illustrated example, a trapezoid) with two sides parallel to the scan line.

Here, the divided triangles and quadrilaterals are divided into divided figures 1 shown in FIG. II, m, and the processing corresponding to that figure will be described hereafter.

Step■ Each side P, -P,,' P, -P,,... shown in Figure 5
. . . p, -p are approximated to integer coordinates as shown in FIG. 6 using the generally well-known Presenham method. However, if a side is parallel to the scan line (sides P, -P, in the example of FIG. 5), no approximation is performed for that side.

Steps ■~■ Using the processing results of steps ■ and ■ above, create an edge list of pentagons P, P,...P, shown in FIG. 5 using the following method, and register it in the RAM 22 in FIG. 3. .

The edge list is a list indicating the intersections (integer approximated pixel positions) between the outline of a polygon and a scan line, and the X coordinates of the intersections on each scan line are registered.

In addition, the X coordinates of the vertices of polygons P, P, ...Pn are y (max), y (max -1),
+・+y (min+1).

y (min), and the scan is y = y (max
) and decrease by 1 until y = y (min).

That is, scanning starts from y = y (max) shown in Fig. 7, and for the first divided figure shown in Fig. 5, the edge list corresponding to each scan line between y = y (max -1) is Create.

Note that if there are multiple points that intersect with the l scan line, the X coordinate values indicating each point are registered in descending order.

Next, from y=y(max-1) to y=y(max
-2), the divided figure I intersects with the scan line
, It, create an edge list corresponding to each scan line.

Furthermore, from y = y (max= 2), y =
y (min), an edge list corresponding to each scan line is created for the divided figure m that intersects with the scan line, and when the creation is completed, the edge list shown in the following table is completed.

[Edge list] Steps ■~■ Based on the edge list obtained in this way, the fourth
The pentagonal fill data shown in FIG. 5 is created in the video buffer 22i shown in the figure.

That is, on each scan line, it is checked whether the coordinates registered in the edge list are the vertices of the pentagon, and it is determined whether or not they are the starting point of filling, and if it is the starting point, filling is performed up to the next coordinate, As shown in Figure 8, the maximum y coordinate of the edge list is y = y (max)
The process ends when filling from y=y (min) to the minimum is completed.

In this way, in this embodiment, a polygon (n-gon) indicated by vector information is divided into a minimum number of triangles and a trapezoid (a quadrilateral whose two sides are parallel to the scan line) using a scan line passing through its vertices. Then, the positions of the pixels that make up each divided figure are determined using the Plessenham method, and the results are written to the bitmap memory, so decimal operations, rounding, etc. There is no need to perform processing, and the processing speed is improved accordingly.

Note that depending on the shape of the polygon indicated by the vector information, it may be divided into only a plurality of triangles, or into triangles, rectangles, or parallelograms.

The embodiments in which this invention is applied to a laser printer have been described above, but this invention applies to all devices that can convert vector information into bitmap information and draw images, including other optical printers such as LED printers and liquid crystal shutter printers, and digital copying machines. The present invention is applicable to image forming apparatuses.

[Effects of the Invention] As explained above, according to the present invention, when performing the filling process of a polygon indicated by vector information,
Since there is no need to perform decimal operations, rounding, etc., it is possible to speed up image bitmap development.

[Brief explanation of the drawing]

1 is a flow diagram showing the polygon drawing process by the CPU in FIG. 3, FIG. 2 is a block diagram showing the configuration of a laser printer system that is an embodiment of the present invention, and FIG. Figure 4 is a block diagram showing the configuration of the controller in the controller, and Figure 4 shows the flow of data processing and the RAM in Figure 3.
Figures 5 to 8 are explanatory diagrams for explaining the operation of this embodiment, and Figures 9 to 11 are for explaining the conventional clustering point. FIG. 2... Controller 3... Print engine 2o... Central processing unit (CPU) 21... Program ROM 22... RAM
22g...Vector file 221...Video buffer (bitmap memory) Figure 9

Claims (1)

[Claims] 1. In an image forming apparatus that converts vector information into bitmap information, records it in a bitmap memory, and outputs the result, a polygon indicated by the vector information is converted into scan lines passing through its vertices. A first means of dividing into a minimum number of triangles or rectangles whose two sides are parallel to the scan line, and determining the positions of pixels constituting each figure divided by the means, and storing the results in a bitmap memory. 1. An image forming apparatus comprising: a second means for writing on the image forming apparatus.