WO2009107168A1

WO2009107168A1 - Character plotting device

Info

Publication number: WO2009107168A1
Application number: PCT/JP2008/000385
Authority: WO
Inventors: 鳥居晃; 加藤義幸; 根岸博康; 石田良平; 濱田雅樹; 木皿大介
Original assignee: 三菱電機株式会社
Priority date: 2008-02-28
Filing date: 2008-02-28
Publication date: 2009-09-03

Abstract

When a character size is large and a contour information data size generated by a contour plotting unit (3) exceeds a memory size of a contour buffer (4), a control unit (8) outputs to the contour plotting unit (3), an instruction to divide the character into a plurality of regions and generate contour information for each of the divided regions. Thus, it is possible to realize a high-speed plotting with a small hardware size.

Description

Character drawing device

The present invention relates to a character drawing apparatus for drawing an outline font.

The outline font has a feature in which the outline of the character is defined by a mathematical expression and can be easily deformed such as enlarging, reducing, and rotating.
When the outline font is displayed on a display device such as an LCD, it is necessary to convert it to raster data. After performing coordinate conversion and converting to a desired size, the outline is drawn according to the formula of the outline. Processing to fill the contour is required.
Such processing is normally performed by software processing by the CPU. However, when the performance of the CPU is low in an embedded device or the like, a long processing time may be required.

Therefore, a character drawing apparatus that speeds up character drawing by hardware has been proposed (see, for example, Patent Document 1).
However, in this character drawing apparatus, since all the outline information of the character is written in the outline drawing memory and then the filling process is performed, an outline drawing memory corresponding to the size of the character is required. Therefore, when dealing with large characters, a large-capacity contour drawing memory is required.
If the contour drawing memory is externally attached, it is possible to deal with large characters, but since the external memory is frequently accessed, the drawing speed may be reduced.

Japanese Patent Laid-Open No. 4-199094 (FIG. 2)

Since the conventional character drawing apparatus is configured as described above, a contour drawing memory corresponding to the size of the character is required, and a large-capacity contour drawing memory is required when dealing with large characters. was there.
If the contour drawing memory is externally attached, it is possible to deal with large characters, but since the external memory is frequently accessed, there is a problem that the drawing speed becomes slow.

The present invention has been made to solve the above-described problems, and an object thereof is to obtain a character drawing apparatus capable of realizing high-speed drawing with a small hardware scale.

In the character drawing device according to the present invention, when the size of the character is large and the data size of the contour information generated by the contour information generating unit exceeds the memory size of the contour buffer, the control unit divides the character into a plurality of regions. Thus, an instruction for generating contour information for each divided region is output to the contour information generating means.

This has the effect of realizing high-speed drawing with a small hardware scale.

It is a block diagram which shows the character drawing apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the data structure of the vector data which comprises the outline of a character. It is explanatory drawing which shows the relationship between a character and the outline buffer. FIG. 10 is an explanatory diagram illustrating processing contents in a region (1) of the contour drawing unit 3; It is explanatory drawing which shows an example of the outline buffer 4, the flag buffer 5, and the auxiliary | assistant buffer 6 at the time of finishing the production | generation process of the outline information of area | region (1). It is a flowchart which shows the processing content (Pixel generation process in one scan line direction) of the pixel generation part. It is explanatory drawing which shows an example of the auxiliary | assistant buffer 6 at the time of the pixel production | generation result of an area | region (1), and the production | generation process of the pixel of an area | region (1) having been complete | finished. It is explanatory drawing which shows the processing content in the area | region (2) of the outline drawing part 3. FIG. It is explanatory drawing which shows an example of the outline buffer 4, the flag buffer 5, and the auxiliary | assistant buffer 6 at the time of complete | finishing the production | generation process of the outline information of area | region (2). It is explanatory drawing which shows an example of the auxiliary | assistant buffer 6 at the time of the pixel production | generation result of an area | region (2), and the production | generation process of the pixel of an area | region (2) having been complete | finished. It is a block diagram which shows the character drawing apparatus by Embodiment 2 of this invention. It is explanatory drawing which shows the content of the outline buffer 4, the density | concentration buffer 12, and the flag buffer 5 at the time of processing of the area | region (2) of a character.

Hereinafter, in order to describe the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a character drawing apparatus according to Embodiment 1 of the present invention. In FIG. Perform the process of converting to the upper coordinates. The coordinate conversion unit 1 constitutes coordinate conversion means.

The input buffer 2 is a memory that stores vector data whose coordinates are converted by the coordinate conversion unit 1.
The contour drawing unit 3 reads out the straight lines and the vertices of the curve from the vector data after the coordinate conversion stored in the input buffer 2 and divides the curve into minute straight lines and configures the contour. Rasterization processing is performed on the straight lines and the minute straight lines, and processing for generating contour information indicating coordinates corresponding to the contour of the character is performed. The contour drawing unit 3 constitutes contour information generating means.

The contour buffer 4 is composed of a double buffer, and stores the contour information generated by the contour drawing unit 3.
The flag buffer 5 is composed of a double buffer, and holds a flag indicating whether or not the contour information stored in the contour buffer 4 is valid contour information.
The auxiliary buffer 6 is a memory that holds contour information for one vertical column.

The pixel generation unit 7 refers to the flag held in the flag buffer 5, reads only valid contour information from the contour buffer 4, generates a pixel to be drawn according to the contour information, and stores the pixel in the frame buffer 9. Execute the process of writing to. The pixel generation unit 7 constitutes a pixel generation unit.

When the vector data for one character is stored in the input buffer 2, the control unit 8 outputs a processing start command to the contour drawing unit 3, and the contour information generated by the contour drawing unit 3 is large in character size. If the data size exceeds the memory size of the contour buffer 4, the character is divided into a plurality of regions, and an instruction to generate contour information for each divided region is output to the contour drawing unit 3. The control unit 8 constitutes a control means.
The frame buffer 9 is a memory that holds an image of a drawing result.

Next, the operation will be described.
In the initial state, the input buffer 2 is empty, and the contour buffer 4, the flag buffer 5, and the auxiliary buffer 16 are initialized with the initial value “0”.

When the character drawing device draws a character, an attribute indicating the color of the character is designated, and vector data constituting the outline of the character is input.
Alternatively, the character drawing device may read the vector data stored in the external memory.
Here, the vector data is data that defines a contour by the vertices and control points of straight lines and curves as shown in FIG. In the following description, it is assumed that the origin of the XY coordinates exists at the upper left.

When the vector data constituting the outline of the character is input, the coordinate conversion unit 1 uses a preset conversion matrix (conversion matrix for performing character enlargement / reduction, rotation, translation, etc.), and The coordinates are converted into coordinates on the frame buffer 9.
When the coordinate conversion unit 1 converts the coordinates of the vector data into the coordinates on the frame buffer 9, the coordinate conversion unit 1 stores the vector data after the coordinate conversion in the input buffer 2.
When the coordinate conversion of the vector data for one character is completed and all the vector data for one character is stored in the input buffer 2, the coordinate conversion unit 1 notifies the control unit 8 to that effect.

As shown in FIG. 3, the coordinate conversion unit 1 stores the minimum value (Xmin, Ymin) of the X coordinate / Y coordinate of the vector data constituting the outline of the character and the maximum value of the X coordinate / Y coordinate. (Xmax, Ymax) is stored.
In the first embodiment, for convenience of explanation, since the size of characters is large, it is assumed that the data size of contour information generated by the contour drawing unit 3 described later exceeds the memory size of the contour buffer 4.
Specifically, the data size of the contour information generated by the contour drawing unit 3 is assumed to be within the memory size for four contour buffers 4 as shown in FIG.

When the control unit 8 receives notification from the coordinate conversion unit 1 that all vector data for one character has been stored in the input buffer 2, the control unit 8 instructs the contour drawing unit 3 to start processing for generating contour information.
However, in the first embodiment, since the character size is large and the data size of the contour information exceeds the memory size of the contour buffer 4, the character is divided into a plurality of regions and contour information is generated for each divided region. The contour drawing unit 3 is instructed as follows.
That is, as shown in FIG. 3, the control unit 8 divides the character into four regions (1) to (4), and first starts the processing for generating the contour information of the region (1). 3 is instructed.

When the contour drawing unit 3 receives an instruction to start processing for generating the contour information of the region (1) from the control unit 8, the contour drawing unit 3 reads the characters in the region (1) from the vector data after coordinate conversion stored in the input buffer 2. The contour information indicating the coordinates corresponding to the contour is generated.
Hereinafter, the processing content of the outline drawing part 3 is demonstrated concretely.
FIG. 4 is an explanatory diagram showing processing contents in the region (1) of the contour drawing unit 3.

When the contour drawing unit 3 receives an instruction to start the processing for generating the contour information of the region (1) from the control unit 8, the contour drawing unit 3 reads the vector data after coordinate conversion stored in the input buffer 2, and reads the X of the vector data. In order to make the minimum value (Xmin, Ymin) of the coordinates and Y coordinates correspond to the origin (0, 0) of the contour buffer 4, as shown in FIG. The process of subtracting the minimum value Xmin of the Y coordinate is performed, and the process of subtracting the minimum value Ymin of the Y coordinate from the value of the Y coordinate of the vector data is performed.

Next, the contour drawing unit 3 determines whether or not a straight line or a curve constituting the contour of the character is completely outside the contour buffer 4.
The contour drawing unit 3 discards the straight lines and curves located outside the contour buffer 4 as shown in FIG.
That is, the straight lines and curves located in the areas (2) to (4) other than the area (1) are discarded. However, the vertices of the straight lines / curves in the regions (2) to (4) connected to the vertices of the straight lines / curves in the region (1) are left without being discarded.

Next, as shown in FIG. 4C, the contour drawing unit 3 performs a process of dividing the curve constituting the contour of the character into minute straight lines.
Since the process of dividing a curve into minute lines is a known technique, a detailed description thereof will be omitted, but a method of dividing a curve into a plurality of minute lines by dividing the curve by the number of divisions according to the curvature of the curve. Can be considered.

Next, the contour drawing unit 3 determines whether or not a plurality of minute straight lines divided from the curve are completely outside the contour buffer 4.
The contour drawing unit 3 discards a minute straight line located outside the contour buffer 4 as shown in FIG.
That is, the minute straight lines located in the areas (2) to (4) other than the area (1) are discarded. However, the vertices of the minute lines in the regions (2) to (4) connected to the vertices of the minute lines in the region (1) are left without being discarded.

Next, the contour drawing unit 3 performs rasterization processing on the straight lines and minute straight lines constituting the contour, and generates contour information indicating coordinates corresponding to the contour of the character.
That is, the contour drawing unit 3 performs rasterization processing on the straight lines and minute lines constituting the contour, obtains the intersection of the scan line, the straight line, and the minute line, and writes the value in the portion of the contour buffer 4 corresponding to the intersection. Process.

At this time, when the direction of the straight line and the minute straight line at the intersection is upward (when it is an upward straight line), as shown in FIG. 5B, “1” is added to the portion of the contour buffer 4 corresponding to the intersection. When the direction of the straight line and the minute line at the intersection is downward (when it is a downward straight line), “1” is subtracted from the portion of the contour buffer 4 corresponding to the intersection.
However, if the coordinates of the intersection point exceed the size of the contour buffer 4, no value is written.
Further, when a value is written to the contour buffer 4, the corresponding bit of the flag buffer 5 is set to “1” (see FIG. 5C).

5A shows an example of the auxiliary buffer 6 at the time when the contour information generation process for the region (1) is completed, and FIG. 5B shows the contour information generation processing for the region (1). An example of the contour buffer 4 at the time is shown, and FIG. 5C shows an example of the flag buffer 5 at the time when the generation processing of the contour information of the region (1) is completed.
However, for simplification of the drawing, it is assumed here that the contour buffer 4 has a capacity of 16 × 16 pixels. The flag buffer 5 is assumed to be composed of 1 bit per 2 pixels in the horizontal direction.

When the contour drawing unit 3 generates the contour information of the region (1), the control unit 8 instructs the pixel generation unit 7 to start processing for generating pixels according to the contour information of the region (1).
When receiving a pixel generation processing start instruction from the control unit 8, the pixel generation unit 7 refers to the flag held in the flag buffer 5 and reads only valid contour information from the contour buffer 4. Then, a pixel to be rendered is generated and a process of writing the pixel to the frame buffer 9 is performed.
Hereinafter, the processing content of the pixel generation part 7 is demonstrated concretely. FIG. 6 is a flowchart showing the processing contents of the pixel generation unit 7 (one pixel generation process in the scan line direction).

Upon receiving an instruction to start pixel generation processing from the control unit 8, the pixel generation unit 7 generates pixels by repeating pixel generation in the scan line direction by the vertical resolution of the contour buffer 4.
That is, in the process of the scan line with Y = 0 (the top scan line in FIG. 5), the pixel generation unit 7 first sets the current X coordinate to “−1” and supports the current Y coordinate. The value in the buffer 6 is read, and the value in the auxiliary buffer 6 is set as the number of intersections W with the current contour (step ST1).
In the example of FIG. 5, since the value of the auxiliary buffer 6 is initialized to “0”, the number of intersections W with the contour is “0” at this time.

Next, the pixel generation unit 7 reads all the flags held in one line of the flag buffer 5 corresponding to the current Y coordinate (step ST2).
In the example of FIG. 5C, one line of the flag buffer 5 is 8 bits, and each flag is 1 bit. Accordingly, since the flag held in one line is 8 bits and the number of bits is small, it is easy to read all the flags held in one line at a time.

Next, the pixel generation unit 7 detects a flag whose value is “1” (a flag indicating that it is valid contour information) from the read flags for one line, and corresponds to the flag. A process of sequentially reading values (valid contour information) in the contour buffer 4 from the left side is performed (step ST3).
In the scan line of Y = 0, the leftmost flag of the flag buffer 5 is “1”, and the coordinates of the contour buffer 4 corresponding to the flag are (0, 0) and (1, 0). The values of coordinates (0, 0) and (1, 0) are read out.

When the pixel generation unit 7 reads the value “+1” of the coordinate (0, 0) in the contour buffer 14, the value of the X coordinate of the coordinate (0, 0) is set to Xnew.
Further, the value “+1” of the coordinate (0, 0) is added to the number of intersections W with the current contour, and the addition result is set as Wnew (step ST4).
That is, the pixel generation unit 7 sets Xnew = 0 and Wnew = 1.

Next, the pixel generation unit 7 determines whether or not the number of intersections W with the current contour is other than “0” (step ST5).
At this stage, since W = 0, it is determined that the number of intersections W with the current contour is not “0”, and the process proceeds to the process of step ST7 without proceeding to the process of step ST6 for generating a pixel. To do.
In step ST7, the pixel generation unit 7 updates the current X coordinate and the value of the number of intersections W with the contour. That is, X = Xnew = 0 and W = Wnew = 1.

Next, the pixel generation unit 7 determines whether or not the process of reading valid contour information from the contour buffer 4 is finished (step ST8).
Here, since the reading is not completed, the coordinates (1, 0) which is the next position of the contour buffer 4 is read (step ST3).

When the pixel generation unit 7 reads the value “0” of the coordinate (1, 0) of the contour buffer 14, the value of the X coordinate of the coordinate (1, 0) is set to Xnew.
Further, the value “0” of the coordinate (1, 0) is added to the number of intersections W with the current contour, and the addition result is set as Wnew (step ST4).
That is, the pixel generation unit 7 sets Xnew = 1 and Wnew = 1.

Next, the pixel generation unit 7 determines whether or not the number of intersections W with the current contour is other than “0” (step ST5).
At this stage, since W = 1, it is determined that the number of intersections W with the current contour is other than “0”, and the process proceeds to the process of step ST6 for generating pixels.
In step ST6, the pixel generation unit 7 generates pixels in the scan line direction from X to Xnew-1.
At this stage, since X = 0 and Xnew = 1, only the pixel with X = 0 is generated.
When the pixel generation unit 7 generates a pixel in the scan line direction, the pixel generation unit 7 updates the current X coordinate and the value of the number of intersections W with the contour (step ST7). That is, X = Xnew = 1 and W = Wnew = 1.

The processing corresponding to the leftmost flag in the flag buffer 5 is completed by the processing so far. However, since the seventh flag from the left in the flag buffer 5 is also “1”, the contour buffer 4 corresponding to this flag. Similar processing (steps ST3 to ST7) is performed for the coordinates (12,0) and (13,0).
That is, since the value “0” of the coordinate (12, 0) in the contour buffer 4 is read out and Xnew = 12, Wnew = 1, pixels with the X coordinate from “1” to “11” are generated. Thus, X = 12, W = 1.
Next, the value “−1” of the coordinate (13, 0) of the contour buffer 4 is read out, and Xnew = 13 and Wnew = 0. Therefore, a pixel having an X coordinate of “12” is generated, and X = 13, W = 0.

With the above processing, the processing for reading all effective contour information corresponding to the flag “1” in the flag buffer 5 from the contour buffer 4 in the scan line of Y = 0 is completed.
When the reading of valid contour information is completed, the pixel generation unit 7 again determines whether or not the number of intersections W with the current contour is other than “0” (step ST9).
At this stage, since W = 0, it is determined that the number of intersections W with the current contour is not “0”, and the process proceeds to the process of step ST11 without proceeding to the process of step ST10 for generating a pixel. To do.
In step ST11, the pixel generation unit 7 writes the value W of “0” in the position corresponding to the current Y coordinate of the auxiliary buffer 6, and ends the pixel generation processing for each scan line (step ST11).

When the pixel generation process in the Y = 0 scan line ends, the pixel generation unit 7 starts the pixel generation process in the Y = 1 scan line.
In the flag buffer 5 in the scan line of Y = 1, only the leftmost flag is “1”, so the coordinates (0, 1) and (1, 1) of the contour buffer 4 corresponding to this flag are step ST3. Processes ST7 to ST7 are performed.

That is, the initial state is X = −1, W = 0, the value “1” of the coordinate (0, 1) of the contour buffer 4 is read, and Xnew = 0 and Wnew = 1.
Next, since the value “0” of the coordinate (1, 1) in the contour buffer 4 is read out and Xnew = 1 and Wnew = 1, a pixel having an X coordinate of “0” is generated, and X = 1, W = 1.

With the above processing, the processing for reading all effective contour information corresponding to the flag “1” in the flag buffer 5 from the contour buffer 4 in the scan line of Y = 1 is completed.
At this stage, since W = 1, pixels up to the right end of the region of the contour buffer 4 (X coordinates from “1” to “15”) are generated (step ST10).
Then, W value “1” is written at the position corresponding to the current Y coordinate of the auxiliary buffer 6, and the pixel generation processing for each scan line is completed.

When the pixel generation process in the Y = 1 scan line ends, the pixel generation unit 7 similarly starts the pixel generation process in the Y = 2 scan line.
In the scan line of Y = 2, the pixels with the X coordinate from “5” to “10” and the pixels with the X coordinate from “14” to “15” are generated at the corresponding positions in the auxiliary buffer 6. Is written with the value “1” of W.

By repeating the above processing up to the scan line of Y = 15, all the pixels that need to be drawn are generated in the region of the contour buffer 4.
When all the pixels that need to be drawn are generated, the pixel generation unit 7 adds the Xmin value to the X coordinate value of the pixel, and adds the Ymin value to the Y coordinate value, whereby the frame buffer 9 The coordinates are converted into the upper coordinates and drawn in the frame buffer 9 with a preset drawing color.

The contour drawing unit 3 and the pixel generation unit 7 perform the above-described processing by pipeline processing, and finish the operation when all the pixels that need to be drawn are drawn in the frame buffer 9.
FIG. 7A shows an example of the pixel generation result of the region (1), and FIG. 7B shows an example of the auxiliary buffer 6 at the time when the pixel generation processing of the region (1) is completed.

In the description of the pixel generation unit 7 described above, the contour information is read from the contour buffer 4 one pixel at a time. However, a plurality of pixels may be read at a time to perform pixel generation processing. Good.
In the example of FIG. 5, the flag buffer 5 is configured with one bit per two horizontal pixels. In this case, the contour buffer 4 also reads two horizontal pixels simultaneously, It is preferable to perform the pixel generation process.

When reading from the contour buffer 4 and the flag buffer 5 is performed, the pixel generation unit 7 performs an initialization process of writing a “0” value to the read address immediately after the reading.
If the contour buffer 4 and the flag buffer 5 are constituted by a two-port memory, the initialization and the next data can be read simultaneously, so that the initialization time can be completely hidden. Reading and initialization may be performed alternately.
As a result, since the contour buffer 4 and the flag buffer 5 are all initialized when the operation of the pixel generation unit 7 is finished, when the next drawing is performed, the contour buffer 4 and the flag buffer 5 Processing such as initialization of the entire area becomes unnecessary, and high-speed operation becomes possible.

When the drawing of the character region (1) is completed by the above processing, the control unit 8 instructs the contour drawing unit 3 to start processing for generating the contour information of the region (2).
When the contour drawing unit 3 receives an instruction to start processing for generating the contour information of the region (2) from the control unit 8, the contour drawing unit 3 reads the characters in the region (2) from the vector data after coordinate conversion stored in the input buffer 2. The contour information indicating the coordinates corresponding to the contour is generated.
Hereinafter, the processing content of the outline drawing part 3 is demonstrated concretely.
FIG. 8 is an explanatory diagram showing the processing contents in the region (2) of the contour drawing unit 3.

When the contour drawing unit 3 receives an instruction to start processing for generating the contour information of the region (2) from the control unit 8, the contour drawing unit 3 reads the vector data after coordinate conversion stored in the input buffer 2 and reads the region (1). In order to associate the coordinates (Xmin + 16, Ymin) on the right with the origin (0, 0) of the contour buffer 4, as shown in FIG. A process of subtracting the value Xmin + 16 of the right adjacent coordinate is performed, and a process of subtracting the minimum value Ymin of the Y coordinate from the Y coordinate value of the vector data is performed.

The other processing contents in the contour drawing unit 3 are the same as in the case of generating the contour information of the area (1), and thus the description thereof is omitted.
FIG. 9A shows an example of the auxiliary buffer 6 at the time when the contour information generation processing for the region (2) is completed, and FIG. 9B shows the contour information generation processing for the region (2) completed. An example of the contour buffer 4 at the time is shown, and FIG. 9C shows an example of the flag buffer 5 at the time when the processing for generating the contour information of the region (2) is completed.

When the contour drawing unit 3 generates the contour information of the region (2), the control unit 8 instructs the pixel generation unit 7 to start processing for generating pixels according to the contour information of the region (2).
When receiving a pixel generation processing start instruction from the control unit 8, the pixel generation unit 7 refers to the flag held in the flag buffer 5 and reads only valid contour information from the contour buffer 4. Then, a pixel to be rendered is generated and a process of writing the pixel to the frame buffer 9 is performed.

The processing content in the area (2) of the pixel generation unit 7 is to add the value of Xmin + 16 to the value of the X coordinate of the pixel in order to make the origin of the contour buffer 4 correspond to the coordinates (Xmin + 16, Ymin) on the frame buffer, Except for adding the value of Ymin to the value of the Y coordinate, it is the same as the processing content in the area (1), and therefore detailed description thereof is omitted.

In addition, as shown in FIG. 9A, the auxiliary buffer 6 when the pixel generation unit 7 starts processing stores the value of the number of times of intersection with the contour of the rightmost pixel in the region (1). Therefore, by using this value as an initial value, it is possible to accurately generate a pixel without causing pixel omission between the regions (1) and (2).
However, when generating a pixel in steps ST6 and ST10 in FIG. 6, control is performed so that a pixel having an X coordinate of “−1” is not generated.

FIG. 10A shows an example of the pixel generation result of the region (2), and FIG. 10B shows an example of the auxiliary buffer 6 at the time when the pixel generation processing of the region (2) is completed.
Since there are no pixels to be drawn on the right side of the area (2), the values of the auxiliary buffer 6 are all “0”.

When the drawing of the character region (2) is completed by the above processing, the control unit 8 instructs the contour drawing unit 3 to start processing for generating the contour information of the region (3).
When the contour drawing unit 3 receives an instruction to start processing for generating the contour information of the region (3) from the control unit 8, the contour drawing unit 3 reads the characters in the region (3) from the vector data after coordinate conversion stored in the input buffer 2. The contour information indicating the coordinates corresponding to the contour is generated.

The processing content in the region (3) of the contour drawing unit 3 is that the X coordinate / Y coordinate (Xmin, Ymin + 16) of the vector data is associated with the origin (0, 0) of the contour buffer 4 so as to correspond to the X coordinate of the vector data. Except for subtracting the value of Xmin from the value of Y and subtracting the value of Ymin + 16 from the value of the Y coordinate of the vector data, the description is omitted because it is the same as the processing content in the region (1).

When the contour drawing unit 3 generates the contour information of the region (3), the control unit 8 instructs the pixel generation unit 7 to start processing for generating pixels according to the contour information of the region (3).
When receiving a pixel generation processing start instruction from the control unit 8, the pixel generation unit 7 refers to the flag held in the flag buffer 5 and reads only valid contour information from the contour buffer 4. Then, a pixel to be rendered is generated and a process of writing the pixel to the frame buffer 9 is performed.

The processing content in the region (3) of the pixel generation unit 7 is to add the value of Xmin to the X coordinate value of the pixel in order to make the origin of the contour buffer 4 correspond to the coordinates (Xmin, Ymin + 16) on the frame buffer, Except for adding the value of Ymin + 16 to the value of the Y coordinate, it is the same as the processing content in the area (1), and therefore detailed description thereof is omitted.

When the drawing of the character region (3) is completed by the above processing, the control unit 8 instructs the contour drawing unit 3 to start processing for generating the contour information of the region (4).
When the contour drawing unit 3 receives an instruction to start processing for generating the contour information of the region (4) from the control unit 8, the contour drawing unit 3 reads the characters in the region (4) from the vector data after coordinate conversion stored in the input buffer 2. The contour information indicating the coordinates corresponding to the contour is generated.

The processing content in the region (4) of the contour drawing unit 3 is that the X coordinate / Y coordinate (Xmin + 16, Ymin + 16) of the vector data is made to correspond to the origin (0, 0) of the contour buffer 4 and the vector data Except for subtracting the value of Xmin + 16 from the value of Y and subtracting the value of Ymin + 16 from the value of the Y coordinate of the vector data, the description is omitted because it is the same as the processing content in the region (1).

When the contour drawing unit 3 generates the contour information of the region (4), the control unit 8 instructs the pixel generation unit 7 to start processing for generating pixels according to the contour information of the region (4).
When receiving a pixel generation processing start instruction from the control unit 8, the pixel generation unit 7 refers to the flag held in the flag buffer 5 and reads only valid contour information from the contour buffer 4. Then, a pixel to be rendered is generated and a process of writing the pixel to the frame buffer 9 is performed.

The processing content in the region (4) of the pixel generation unit 7 is to add the value of Xmin + 16 to the X coordinate value of the pixel in order to make the origin of the contour buffer 4 correspond to the coordinates (Xmin + 16, Ymin + 16) on the frame buffer, Except for adding the value of Ymin + 16 to the value of the Y coordinate, it is the same as the processing content in the area (1), and therefore detailed description thereof is omitted.

When the drawing of the character area (4) is completed by the above processing, the control unit 8 determines that all the drawing in the character bounding box has been completed, and that the drawing of the character has been completed. The stored vector data is discarded and the operation is terminated.

In the first embodiment, the contour drawing unit 3 and the pixel generation unit 7 are alternately operated. However, by configuring the contour buffer 4 and the flag buffer 5 with double buffers, for example, the pixel generation unit 7 While performing the processing of the region (1), the control unit 8 operates the contour drawing unit 3 and the pixel generation unit 7 in parallel so that the contour drawing unit 3 performs the processing of the region (2). You may do it.

As apparent from the above, according to the first embodiment, when the character size is large and the data size of the contour information generated by the contour drawing unit 3 exceeds the memory size of the contour buffer 4, the control unit 8 Since the character is divided into a plurality of regions and an instruction to generate contour information for each divided region is output to the contour drawing unit 3, the effect of realizing high-speed drawing with a small hardware scale is achieved. Play.

That is, according to the first embodiment, since the contour buffer 4 is built in, the number of accesses to the external memory can be reduced and the operation can be performed faster than when the contour buffer 4 is placed in the external memory. can do.
Further, since the built-in contour buffer 4 requires only a small memory, the hardware scale can be reduced, and even when drawing a large character, the contour buffer 4 is shifted several times while shifting the coordinates in units of the size of the contour buffer 4. This can be done by drawing.

According to the first embodiment, the contour buffer 4 is configured as a double buffer, and the control unit 8 performs the contour information generation processing by the contour drawing unit 3 and the pixel generation processing by the pixel generation unit 7 in parallel. Since it is configured to execute, there is an effect that high-speed drawing can be realized.

According to the first embodiment, the auxiliary buffer 6 that holds the vertical-line outline information is provided, and when the outline drawing unit 3 generates the outline information for each divided region, the pixel generation unit 7 holds the auxiliary information in the auxiliary buffer 6. Since the pixel to be drawn is generated with reference to the vertical outline information that is displayed, the pixel is accurately generated without causing the occurrence of missing pixels between adjacent regions. There is an effect that can be.

According to the first embodiment, the flag buffer 5 that holds a flag indicating whether or not the contour information stored in the contour buffer 4 is valid contour information is provided, and the pixel generation unit 7 generates a pixel. In this case, the flag stored in the flag buffer 5 is referred to so that only valid contour information is read from the contour buffer 4, so that it is not necessary to read invalid contour information that does not need to be read. There is an effect that the operation can be speeded up.

According to the first embodiment, the configuration is such that the contour buffer 4 and the flag buffer 5 are initialized immediately after reading from the contour buffer 4 and the flag buffer 5, so that the initialization time is concealed, There is an effect that the operation can be speeded up.

Embodiment 2. FIG.
11 is a block diagram showing a character drawing apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG.
The contour drawing unit 11 performs the same processing as that of the contour drawing unit 3 in FIG. 1, and when generating contour information, obtains the pixel density from the distance between the pixel and the contour of the pixels near the contour, and the density of the pixel Is stored in the density buffer 12. The contour drawing unit 11 constitutes contour information generating means.
The density buffer 12 is a memory that stores the density of pixels.

The pixel generation unit 13 performs the same processing as that of the pixel generation unit 7 of FIG. 1, and also calculates a density value for each pixel from the contour information stored in the contour buffer 4 and the pixel density stored in the density buffer 12. The process which asks for is implemented. The pixel generation unit 13 constitutes a pixel generation unit.
The pixel calculation unit 14 performs blend processing with the frame buffer 9 based on the density value for each pixel obtained by the pixel generation unit 13.
The pixel calculation unit 14 constitutes a pixel calculation means.

In the first embodiment, the case where the drawing of characters by anti-aliasing is not considered has been described. However, the anti-aliased character may be drawn.
FIG. 12 is an explanatory diagram showing the contents of the contour buffer 4, the density buffer 12, and the flag buffer 5 when the character area (2) is processed.

As illustrated in FIG. 12A, the contour drawing unit 11 generates contour information in the same manner as the contour drawing unit 3 in FIG. 1, and stores the contour information in the contour buffer 4.
Further, as shown in FIG. 12B, the contour drawing unit 11 calculates the density of the pixel near the contour from the distance between the pixel and the contour, and calculates the density of the pixel. Stored in the density buffer 12.
For example, if the distance between the pixel and the outline is “0”, the density of the pixel is set to “0.5”. The longer the distance between the pixel and the outline, the lower the density of the pixel is less than “0.5”. Set to value.
If the distance between the pixel and the contour is longer than “0.5”, the density of the pixel is set to “0”.
At this time, in the flag buffer 5, as shown in FIG. 12C, a flag corresponding to writing valid data in at least one of the contour buffer 4 and the density buffer 12 is set to “1”. .

The pixel generation unit 13 generates a pixel to be rendered in the same manner as the pixel generation unit 7 in FIG. 1, and also uses the contour information stored in the contour buffer 4 and the pixel density stored in the density buffer 12. The density value for each pixel is calculated.
For example, if the contour information stored in the contour buffer 4 is valid contour information, the density value of the pixel is obtained by subtracting the pixel density stored in the density buffer 12 from “1.0”. Set.
On the other hand, if the contour information stored in the contour buffer 4 is invalid contour information, the density value of the pixel is set to the value stored in the density buffer 12.
As shown in FIG. 12D, the pixel calculation unit 14 performs a known blend process with the frame buffer 9 from the density value for each pixel calculated by the pixel generation unit 13, so that the frame buffer 9 Write pixel to.

As apparent from the above, according to the second embodiment, the pixel calculation unit 14 is configured to perform blend processing with the frame buffer 9 from the density value for each pixel obtained by the pixel generation unit 13. As a result, it is possible to draw an anti-aliased outline font at high speed.

As described above, the character drawing device according to the present invention is suitable for a device that needs to draw an outline font at high speed.

Claims

Coordinate conversion means for converting the coordinates of the vector data constituting the outline of the character into coordinates on the frame buffer, and the straight lines and the vertices of the curve constituting the outline of the character are read from the vector data whose coordinates are converted by the coordinate conversion means. Contour information generating means for dividing the curve into minute straight lines and performing rasterization processing on the straight lines constituting the contour and the minute straight lines to generate contour information indicating coordinates corresponding to the contours of the characters; A contour buffer for storing the contour information generated by the contour information generating means; a pixel generating means for generating a pixel to be rendered in accordance with the contour information stored in the contour buffer and writing the pixel in the frame buffer; The outline information generated by the outline information generating means is large in size of the character A character having control means for dividing the character into a plurality of areas and outputting an instruction to generate outline information for each divided area to the outline information generating means when the data size exceeds the memory size of the outline buffer; Drawing device.
The contour buffer is constituted by a double buffer, and the control means causes the contour information generation process by the contour information generation means and the pixel generation process by the pixel generation means to be executed in parallel. Character drawing device.
When an auxiliary buffer for holding contour information for one vertical column is provided and the contour information generating unit generates the contour information for each divided region, the pixel generating unit refers to the vertical column of contour information stored in the auxiliary buffer. The character drawing apparatus according to claim 1, wherein a pixel to be drawn is generated.
A flag buffer for holding a flag indicating whether or not the outline information stored in the outline buffer is valid outline information is provided, and the flag held in the flag buffer when the pixel generation means generates a pixel. The character drawing apparatus according to claim 1, wherein only valid contour information is read from the contour buffer.
2. The character drawing apparatus according to claim 1, wherein the pixel generation means initializes the contour buffer immediately after the contour information is read from the contour buffer.
When the contour information generating means generates the contour information, the pixel density is obtained from the distance between the pixel and the contour for the pixels near the contour, and the pixel density is stored in the density buffer. The pixel generating means is stored in the contour buffer. A pixel for which a density value is obtained for each pixel from the contour information stored in the density buffer and the density of the pixel stored in the density buffer, and blend processing is performed between the density value for each pixel obtained by the pixel generation unit and the frame buffer. The character drawing apparatus according to claim 1, further comprising a calculation unit.