JPH09281948A - Character cache control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time required for generating bit map data of characters from data of characters in a character cache control device outputting bit map data of characters to a computer, printer, or the like. SOLUTION: An edge data generation section 4 detects an edge indicating a boundary line between a white pixel and a black pixel, data related to the detected edge is cached in an edge storage section 6, when the character is outputted, a bit map generation section 5 generates bit map data based on the edge data. Further, edge data is coded, and it is cached in a coding storage section 15 as coded data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for generating character bitmap data on the basis of character outline data in a device such as a printer for outputting characters, and more particularly to high speed using a cache memory. The present invention relates to a technique for generating bitmap data.

[0002]

2. Description of the Related Art Conventionally, when a document created by a computer is output by a printer or the like, character bit map data is generated based on character outline data stored in advance in a memory or the like, and the bit map data is stored. It is outputting. However, generally, it takes a lot of time to generate bitmap data from outline data. Therefore, in order to avoid generating bitmap data many times and to speed up access to the memory where the bitmap data is stored, once the frequently used characters are A character cache control device that uses a cache system in which a character is saved in a cache memory and the bit map data is read from the cache memory when the character is output again is widely used.

Further, in recent character cache control devices, in order to efficiently use the limited area of the cache memory, the bitmap data is compressed once without being saved in the cache memory as it is. , The compressed bitmap data is saved in the cache memory. Then, when outputting the character, the compressed bitmap data is read from the cache memory, and the compressed bitmap data is decompressed to be returned to the regular bitmap data and output. By such compression / expansion processing, as many characters as possible can be cached in a finite cache memory area.

[0004]

By the way, the conventional character cache control device having the above-mentioned compression / expansion function cannot execute the process of compressing or expanding the bitmap data in a short time. Therefore, even if the bitmap data for many characters can be saved in the cache memory, it takes a lot of time to compress and decompress each bitmap data. There was a problem that the time could not be shortened.

[0005]

The present invention employs the following structure in order to solve the above problems. <Structure 1> A font data storage unit for storing font data representing outlines of a plurality of characters, an edge data generation unit for generating edge data representing a boundary between white pixels and black pixels from the font data, and edge data. A character cache control device comprising: an edge storage unit for caching; and a bitmap generation unit for generating bitmap data indicating white pixels and black pixels from the edge data cached in the edge storage unit.

<Structure 2> The edge data generator divides a plurality of white pixels and black pixels into a plurality of regions based on the connection of pixels of the same color, and each region is represented by the color of the pixel and the number of pixels. Configuration 1 characterized by generating edge data
Character cache controller.

<Structure 3> The character cache control device according to Structure 1, wherein the edge data generation unit generates edge data indicating a position of a boundary between a white pixel and a black pixel for each row.

<Structure 4> A code table showing a correspondence relationship between the number of continuous white pixels and the number of continuous black pixels and a code value representing the number assigned according to the number and the appearance frequency. The number of white pixels and the number of black pixels are calculated from the stored code table storage unit and the position of the boundary between the white pixel and the black pixel in the edge data, and the calculated number of white pixels and the number of black pixels are calculated based on the code table. Character of configuration 1, comprising an encoding processing unit that generates encoded data by encoding the number of pixels into a code value, and an encoding storage unit that stores the generated encoded data. Cache controller.

<Structure 5> The relationship between the length of the continuous white pixels and the continuous length of the continuous black pixels with respect to the length of the line forming the character, and the code value representing the ratio. And a code table generation unit for generating a code table based on the reference table.

<Structure 6> A character cache according to structure 5 having a code table determination unit for checking whether or not there is a code table corresponding to an input character by searching a code table storage unit. Control device.

<Structure 7> The structure 6 is characterized in that the code table determination unit confirms whether or not there is a code table corresponding to the input character based only on the font size of the input character. Character cache controller.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

<Structure of Concrete Example 1> Hereinafter, a character cache control device of the present invention will be described with reference to an embodiment. FIG.
3 is a block diagram of a character cache control device of Specific Example 1. FIG. The character cache control device C includes a cache determination unit 1, a bitmap / edge determination unit 2, a font data storage unit 3, an edge data generation unit 4, a bitmap generation unit 5, a bitmap storage unit 6, an edge storage unit 7, It is composed of the image storage unit 8.

The cache determination unit 1 determines whether a character input from a computer, a printer or the like (not shown) is a character to be cached, and a cache necessity flag of the bitmap storage unit 6 and an edge storage unit. The determination is made by referring to the cache necessity flag of No. 7. The bitmap / edge determination unit 2 determines whether the bitmap data of the character to be cached should be cached or the edge data should be cached. The determination is made by referring to the no flag or the cache necessity flag of the edge storage unit 7.

The font data storage unit 3 stores in advance vector data indicating the outline of each character. The edge data generation unit 4 develops the font data as an analog quantity on a two-dimensional coordinate, then extracts and quantizes the contour so as to express the contour of the character as a digital quantity, and then extracts and quantizes the contour. The white pixels and the black pixels are distinguished from each other based on the contour, and the white pixels and the black pixels are further divided into a plurality of regions based on the connection of the pixels, and finally each region exists in the region. Only by the number of pixels,
Alternatively, the edge data is generated by representing the number of pixels existing in the area and their colors. The bitmap generation unit 5 reproduces white pixels and black pixels on two-dimensional coordinates based on the edge data,
Generate bitmap data.

The bitmap storage unit 6 stores bitmap data 6a and bitmap registration information 6b. The bitmap data 6a is stored in the bitmap generation unit 5
It is the bitmap data itself generated by. On the other hand, the bitmap registration information 6b is composed of a cache necessity flag and a cached non-flag, and the cache necessity flag is a flag indicating whether the character is a character to be cached, The cached unflagged flag is a flag indicating whether or not the character is cached. The edge storage unit 7, like the bitmap storage unit 6, has edge data 7a and edge registration information 7b.
And remember. The edge data 7a is the edge data itself generated by the edge data generation unit 4. On the other hand, the edge registration information 7b includes a cache necessity flag and a cached non-flag, and their functions are exactly the same as those of the bitmap registration information 6b. The image storage unit 8 temporarily stores the bitmap data of each character and outputs the bitmap data as output data.

<Operation> Next, the operation of the character cache control device of the present invention will be described. 2, 3 and 4 are operation flowcharts of the character cache control device of the present invention. Further, FIG. 5 is a diagram showing a process of processing the character “A” to be cached as edge data, and FIG. 6 is a diagram showing an edge pixel string and edge data of the character “A”. Hereinafter, regarding the operation of the character cache control device of the present invention, with the processing for the character "A",
A description will be given along these operation flowcharts. In addition,
It is assumed that the edge data of the character "A" has not been cached yet.

<Data Input> Step S100: The character cache control device C receives a document composed of characters and the like as input data from a computer or printer (not shown). Step S110: The cache determination unit 1 refers to the bitmap registration information 6b and the edge registration information 7b for each character existing in the received document to determine whether or not the character is a character to be cached. judge. Here, for the character "A", the cache necessity flag of the bitmap registration information 6b is "no", but the cache necessity flag of the edge registration information 7b is "necessary". "A" will proceed to the cached process.

<Processing of Characters to be Cached> Step S200: Bitmap / Edge Determination Unit 2
Indicates whether the character to be cached is a character to be cached as bitmap data or a character to be cached as edge data, and a cache necessity flag of the bitmap registration information 6b and an edge. The determination is made by referring to the cache necessity flag of the registration information 7b. Here, since the cache necessity flag of the edge registration information 7b is "necessary" for the character "A", the character "A" proceeds to the process of caching the edge data (step S260). Become.

<Processing of Characters in which Bitmap Data is Cached> Step S210: If the character is a character cached as bitmap data, the bitmap / edge determination unit 2 determines that the character is already a bit. Whether cached as map data or not yet cached as bitmap data is determined by referring to the cached unflagged flag of the bitmap registration information 6b. Step S220: If the character is already cached as bitmap data, the bitmap data 6a is read from the bitmap storage unit 6. Step S230: If the character is not yet cached as bitmap data, the edge data generation unit 4 reads the font data from the font data storage unit 3 and writes the font data, as will be described later (Step S280). Generate edge data based on Step S240: Furthermore, the bitmap generation unit 5
Generates bitmap data from the edge data, as will be described later (step S290). Step S250: The bitmap storage unit 6 stores the generated bitmap data and sets the cached unflagged flag of the edge registration information 7b to “done”.

<Processing of Character whose Edge Data is Cached> Step S260: If the character is a character that is cached as edge data, the bitmap / edge determination unit 2 determines that the character is already edge data. Whether it is cached or not yet cached as edge data is determined by referring to the cached unflagged flag of the edge registration information 7b.
In the edge registration information 7b for the character "A", the cache flag "not yet" is set, so the character "A" is displayed.
Is a process for generating edge data (step S28).
It will proceed to 0). Step S270: If the character is already cached as edge data, the edge data 7a is read from the edge storage unit 7.

Step S280: If the character is not cached as edge data yet, read the font data from the font data storage unit 3,
Generate edge data. Here, the generation of the edge data of the character "A" will be described. First, by expanding the font data of the character "A" stored in the font data storage unit 3, that is, the vector data, on the two-dimensional coordinates (17 rows x 18 columns), as shown in FIG. ) Create an outline of the letter "A" as shown in (). At this time, correction processing such as hint processing and approximation processing such as curve smoothing are executed as necessary. It should be noted that, on these two-dimensional coordinates, each portion surrounded by the grid corresponds to a pixel of the finally created bitmap data.

Second, a sampling process and a quantization process are executed so that the generated outline is suitable for digital processing. Here, as the sampling process, an auxiliary lattice (dotted line in the figure) extending in the horizontal direction is virtually set at the center of each lattice under the scan conversion process, as shown in FIG. 5B. ,
The intersections (black dots) of those auxiliary grids and outlines are extracted. Then, by quantizing the value of the X coordinate of each intersection, each intersection is approximated to the closest grid, as shown in FIG. 5C, and as a result, an edge (black dot) is obtained.

Thirdly, the numerical value "1" meaning black is assigned to the pixels forming the character "A" itself, while the numerical value meaning white is assigned to the pixels forming the margin. Assign "0". In each row, the pixel between the odd-numbered edge and the next even-numbered edge is
While it is “black”, the pixels between the even-numbered edge and the next odd-numbered edge are “white”. Therefore, "1" or "0" can be assigned to each pixel by referring to whether each edge is an odd number or an even number. As a result, for example, to the pixels located in the fourth row, numerical values of 0000001111000000 (white × 6, black × 2, white × 1, black × 2, white × 6) are sequentially assigned from the left side. .

Fourth, by arranging all the pixels (306 pixels: 17 × 18 pixels) to which the numerical values of “1” and “0” are assigned in a line, edge pixels as shown in FIG. Create a column. Thereby, for example, FIG.
1st row pixel in
00 (white × 7, black × 3, white × 7) is positioned at the beginning of FIG. 6A, and the pixel 00000011 in the second row is
111,000,000 (white x 6, black 5, white x 6) is positioned to the right of it. Similarly, the pixels of the following rows are positioned one after another.

Finally, this edge pixel array is divided into pixels of the same color, and each divided portion is represented by a color and the number of pixels. As a result, as shown in FIG. 6A, this edge pixel row is white × 7, black × 3, white × 13, black × 5, white × 1.
2, ..., White x 1, Black x 3, White x 11, Black x 6, White x 1
1 represents black × 3. Further, since the series of white pixels and the series of white pixels are alternately repeated, the redundancy of the edge pixel row, that is, the extra information about the color is deleted if only the first color of the edge pixel row is clarified. It becomes possible to do. Therefore, this edge pixel row is white,
7, 3, 13, 5, 12, ..., 1, 3, 11, 6, 1
It can be represented by edge data 1 and 3. As a result, for example, 40 bits (bits) required to represent the first 40 pixels (pixels in the first row + pixels in the second row + six pixels in the third row) are 17 bits (1 + 3 + 2 +).
4 + 3 + 4).

Step S290: The edge storage unit 7
The generated edge data is stored. Step S300: Based on the generated edge data or the read edge data, the bitmap generation unit 5 makes the character portion a black pixel and the blank portion a white pixel. As a result, bitmap data is generated. Here, regarding the character “A”, FIG.
Bitmap data as shown in (d) is generated.

<Processing of Non-Cached Characters> Step S400: If the character is a non-cached character, the edge data generation unit 4 causes the font data storage unit 3 to operate as described above (Step S280).
The font data is read from and the edge data is generated based on the font data. Step S410: As described above (step S290), the bitmap generation unit 5 generates bitmap data based on the generated edge data.

<Data Output> Step S120: The read bit map data and the generated bit map data are stored in the image storage unit 8.
Is stored. Step S130: After the bitmap data of all the characters are stored in the image storage unit 8, the character cache control device C outputs the bitmap data to a device (not shown) such as a computer or a printer.

As described above, in the character cache control device of this specific example, the edge data generation unit 4 generates data indicating the edge which is the boundary between the white pixel and the black pixel from the font data of the character, and this edge is generated. Cache data in edge store. Then, when outputting the character, the bitmap generation unit reads the edge data from the edge data storage unit and generates bitmap data indicating the positions of the white pixels and the black pixels based on the edge data. Therefore, the bitmap data is not cached in the cache memory as it is, but is cached in the cache memory in the form of edge data having a smaller data amount than the bitmap data. It can be used more efficiently.

<Generation of Edge Data by Other Method> Unlike the above specific example, the edge data generation unit 4
However, it is also possible to store only the “position” of the edge for each row as the edge data in the edge storage unit 7. Using this method, the first line is 7, 1 for the character "A".
Can be represented as 0, the second row can be represented as 6, 11, the 18th row can be represented as 0, 3, 14, 17, and so on for the other rows. it can. As a result, each row that normally requires 17 bits to represent can be represented by 7 bits (3 + 4) for the first row and 7 bits (3 + 4) for the second row, for example.
It can be represented by bits, and the 18th row can be represented by 12 bits (1 + 2 + 4 + 5). As a result, the amount of data stored in the cache memory for each character can be reduced to about half of the amount of data stored by the conventional technique.

<Structure of Concrete Example 2> Next, a character cache control device of Concrete Example 2 will be described. FIG. 7 is a block diagram of the character cache control device of the second specific example. The functional difference between the character cache control device of the specific example 2 and the character cache control device of the specific example 1 is that in the device of the specific example 2, a code table is generated from a reference table prepared in advance, and the generated code is used. This is to generate encoded data by encoding the edge data generated by the device of the first specific example based on the table. Therefore, the character cache control device of the second specific example has all the units 1 to 8 in the character cache control device of the first specific example, and further includes the code table determination unit 10 and the code table generation unit 1.
1, reference table storage unit 12, code table storage unit 1
3, a coding processing unit 14, a coding storage unit 15, and a decoding processing unit 16.

Here, the reference table means that the length of a certain white line or the length of a black line occupies the length of a line forming a character regardless of the type of character, font size, etc. A table showing a correspondence relationship between a ratio and a code value indicating the ratio.The code table is based on the reference table, for each font size of characters, in the font size, etc., It is a table showing how many pixels the above-mentioned sequence corresponds to and the corresponding relationship with the above-mentioned code value.

The character cache control device of the second specific example will be described below, focusing on the configuration unique to the character cache control device of the second specific example and the operation of the configuration. Although there is no difference in the essential function, for convenience of explanation, the name of the bitmap / edge determination unit 2 in the specific example 1 is changed to the bitmap / edge / coding determination unit 2 for description.

<Structure / Operation Common to Specific Example 1> The operations from the cache determination unit 1 to the image storage unit 8 that are common to the structure of Specific example 1 are substantially the same as those of Specific example 1. The only difference is that the bitmap / edge / encoding determination unit 2 should cache bitmap data, cache edge data, or cache data for a character to be cached, or Whether or not the encoded data should be cached is determined by a cache necessity flag in the bitmap storage unit 6, a cache necessity flag in the edge storage unit 7, and the encoding storage unit 1.
The determination is made by referring to the cache necessity flag in 5.

<Structure / Operation Different from Specific Example 1> The operations of the code table determination unit 10 to the decoding processing unit 16 different from the structure of the specific example 1 are as follows. The code table determination unit 10 determines whether or not there is a code table corresponding to the font size or the like based on the font size or the like of the input character. The code table generation unit 11 generates a code table from the reference table prepared in advance in the reference table storage unit 12. The code table storage unit 13 stores the code table generated by the code table generation unit 11. The encoding processing unit 14 converts the edge data generated by the edge data generation unit 4 into
Encoding is performed based on the code table stored in the code table storage unit 13 to generate encoded data. The encoding storage unit 15 stores the generated encoded data. The decoding processing unit 16 reads out the encoded data from the encoding storage unit 15 and refers to the code table corresponding to the encoded data to execute the decoding process of reproducing the encoded data into edge data. To do.

<Operation of Concrete Example 2> FIG. 8 is an operation flowchart of the entire apparatus of Concrete Example 2, and FIG. 9 is a concrete example 2
3 is an operation flowchart showing an encoding process which is an operation peculiar to the device of FIG. The operation will be described below with reference to these operation flowcharts. As in the case of the first specific example, assuming that the character “A” is a character to be cached in the form of encoded data, the process will be described together. However, it is assumed that the character "A" has not been cached yet, and that the character having the same font size as that of the character "A" has not been cached yet.

Step S100: The character cache controller C receives, as input data, a document composed of characters or the like from a computer or printer (not shown). Step S110: The cache determination unit 1 determines whether or not each character existing in the received document is a character to be cached, the bitmap registration information 6b, the edge registration information 7b, and the encoding registration. Information 15
It judges by referring to b. Here, for the character "A", the cache necessity flag of the bitmap registration information 6b and the cache necessity flag of the edge registration information 7b are "no", while the cache necessity of the encoding registration information 15b is "NO". Since the flag is "necessary", the character "A"
Will proceed in the direction of cached processing.

Step S120: Whether the character to be cached is a character to be cached as bitmap data or a character to be cached as edge data is determined by the bit / edge / encoding determination unit 2. Alternatively, whether the character is a character to be cached as encoded data, the bitmap registration information 6
The cache necessity flag of b, the cache necessity flag of the edge registration information 7b, and the cache necessity flag of the encoded registration information 15b are referred to for the determination. Here, as for the character "A", since only the cache necessity flag of the encoding registration information 15b is "necessary", the character "A" advances toward the process of being cached as encoded data. It will be. When the data is cached as bitmap data, as described in the concrete example 1, step S
If the processing of 210 or less is executed and the data is cached as edge data, similarly, step S26 is performed.
The processing of 0 or less is executed.

<Processing of Character Cached as Encoded Data> Step S310: If the character is a character cached as encoded data, the bitmap / edge / encoding determination unit 2 determines that the character is It is determined by referring to the cached unflagged flag of the coding registration information 15b whether it has already been cached as coded data or has not been cached as coded data. Here, the coded registration information 15b of the character "A"
Indicates that the cached unflagged flag is "not yet" indicating that it has not been cached yet. Therefore, the character "A" is displayed.
Will proceed to the process of generating encoded data.

Step S320: If the character is already cached as encoded data, the encoded data is read from the encoding storage unit 15 and the code table for the font size of the character is set in the code table. It is read from the storage unit 12. Step S330: The decoding processing unit 16 reproduces the edge data by decoding the read coded data based on the code table.

<Preparation of Code Table> Step S340: If the character is not cached as coded data yet, the coded table is created, the edge table is created, the coded data is created, etc. Step S340a: The code table determination unit 10 checks the code table storage unit 13 as to whether or not there is a code table corresponding to the font size of the character. Step S340b: When the code table corresponding to the font size of the character is searched, the code table determination unit 10 instructs the encoding processing unit 14 to read the code table. Then, the encoding processing unit 14
Reads the retrieved code table from the code table storage unit 13.

Step S340c: If the code table corresponding to the font size of the character is not searched, the code table determination unit 10 instructs the code table generation unit 11 to generate the code table. Under the instruction, the code table generating unit 11 generates a code table from the reference table. In this way, the code table determination unit 10 determines the presence or absence of the code table. Therefore, if there is no code table, it is possible to immediately shift to the process of creating the code table, and if there is a code table. Can avoid the wasteful processing of creating the same code table as the code table again. Further, since the code table is generally judged only based on the font size on which it most depends, it is possible to quickly judge the presence or absence of the code table.

<Description of Reference Table and Code Table> FIG. 11 is a diagram showing the relationship between the reference table and the code table. The reference table is a table showing a correspondence relationship between a ratio of continuous black or white connections to a length of a line forming a character and a code value indicating the ratio. For example, when the length of one line is 50 (no unit), a run having a length of 10 is converted into a binary code value 010.
When encoding to 0, 0.2 (= 10/50) and 0
It means that 100 and 100 correspond. Similarly, a correspondence relationship between the proportion of connections having lengths of 0, 10, 30, 40 ... And the code value indicating the proportion is also prepared. Furthermore, this correspondence is determined based on the length of the run and the frequency of occurrence of the run, and more specifically, the higher the frequency of occurrence and the longer the run, the smaller the code. Set to sign to value. As a result, the more frequently the data is generated, the more the data can be represented by the smaller amount of data.

On the other hand, the code table includes the above reference table and the font size of the actual character, more accurately,
Based on the number of pixels forming one row, the correspondence relationship between the number of pixels corresponding to the series and the code value that is the same as the code value is shown. Therefore, for example, if a code table for a font size including 17 pixels per row is generated based on a reference table including a correspondence relationship between the ratio 0.2 and the code value 0100, the number of pixels is 3 (more accurately). Is a sequence of the number of pixels 3.4 (17 × 0.2) and the code value 001
A code table including a correspondence relationship with 0 will be generated. Similarly, when a code table for a font size including 30 pixels per line is generated, the number of pixels is 6 (3
(0 × 0.2) and a code value of 0100 will be generated as a code table. Here, one line is 17
For the character "A" composed of pixels, the font
Since the code table for size 17 has not been generated yet, the code table for that font size 17 will be generated.

Step S340d: The code table generation unit 11 stores the generated code table in the code table storage unit 13 and delivers the code table to the encoding processing unit 14.

<Generation of Encoded Data> Step S350: The encoding processing unit 14 reads the font data from the font data storage unit 3 in the same manner as Step S280 in the first specific example and the other methods in the first specific example. Generate edge data. FIG.
It is a figure which shows conversion from edge data to encoding data about a character "A". As shown in FIG. 12A, for each line of the character "A", the edge data (7, 10) of the first line, the edge data (6, 11) of the second line,
The edge data (6, 11) of the line 10, the edge data (3, 6, 11, 14) of the line 10, and the edge data (0, 3, 14, 17) of the line 18 are generated. In addition,
This edge data does not include information on whether the leading pixel is a white pixel or a black pixel. For example, the first seven pixels in the first row include information such as white or black, and the first six pixels in the second row include information such as white or black. Not at all. However, the series of pixels located first in each row is always a white pixel,
Next, the sequence of pixels located is always black.
Similarly, a series of white pixels and a series of black pixels are alternately repeated. Therefore, there is no need for information on whether the sequence of the first pixel in each row is a white pixel or a black pixel, and similarly, the sequence of pixels thereafter is also a white pixel or a black pixel. No information about that is needed.

Step S360: Encoding processing section 14
Calculates the number of consecutive white pixels and the number of consecutive black pixels from the edge data. Here, for the character “A”, for example, the edge data (3, 6, 1
1 and 14), as shown in FIG. 12B, by subtracting the numbers representing the boundary between the series of white pixels and the series of black pixels, the number of white pixels forming the series of white pixels and The number of black pixels forming a series of black pixels is obtained. As a result, subtraction data (3, 3, 5, 3) can be obtained.

Step S370: Encoding processing unit 14
Converts the subtraction data indicating the number of white pixels and the number of black pixels into a code value, that is, encoded data, based on the code table described above. Here, in the subtraction data (3, 3, 5, 3) on the 10th line of the character “A”, “3” is “0”.
The coded data (0010, 0010, 0) is converted into "0" and "5" into "0100".
100,00100 will be obtained. Step S380: The encoding storage unit 15 stores the encoded data that has been encoded. Step S390: If the bitmap data generation failure 5
Based on the edge data reproduced in step S330 or the edge data newly generated in step S350, the character itself is made a black pixel and the margin is made a white pixel. As a result, bitmap data is generated.

As described above, in the character cache control device of this specific example, the number of consecutive white pixels is determined based on the code table showing the correspondence relationship between the number of pixels in the edge data and the code value representing the number. Alternatively, encoded data is generated by converting the number of consecutive black pixels into a code value. Then, the encoding storage unit stores the generated encoded data. Here, in this code table, the correspondence relationship between the number of consecutive pixels and the code value representing the number is determined based on the number and the appearance frequency. Therefore, the continuous pixel can be represented by the encoded data having a data amount smaller than the data amount required when the continuous data is represented by the edge data. Therefore, it is possible to cache the encoded data, which is a data amount smaller than the data amount of the edge data, in the cache memory, so that the area of the cache memory, which is a finite space, can be used more effectively and the access time is also increased. It is possible to shorten it further.

In addition, the reference table storage unit does not depend on the font size of the character, the type of character, etc., and the length of the continuous white pixels and the length of the continuous black pixels with respect to the length of one line. It stores a reference table showing a correspondence relationship between the ratio of the total occupied area and the code value representing the ratio.
Then, the code table generation unit refers to the reference table stored in the reference table storage unit based on the font size and the like of the input character, and thereby the font size and the like of the input character is suitable. Generate a code table. Therefore, the code table storage unit does not store a large number of code tables that can support a large number of font sizes and various character types, and one reference table stored in the reference table storage unit or a small number of reference tables. It suffices to store a small number of code tables generated by the code table generation unit based on the tables. As a result, it is possible to avoid storing even the code table that is less likely to be used, and it is possible to effectively use the memory area.

Furthermore, the code table determination unit checks whether or not there is a code table suitable for the input character by searching the code table storage unit. Therefore, if there is already a code table corresponding to the input character, edge data can be immediately converted to coded data based on the code table, while If there is no compatible code table, the code table generation unit can newly generate a code table. Therefore, it is possible to avoid generating the same code table, and proceeding with the encoding process without generating the code table that has to be generated.

Then, the code table determination unit searches the code table storage unit based on only the font size of the input character to determine whether or not the code table corresponding to the input character exists. Confirm. Therefore, since the presence or absence of the code table is confirmed based only on the font size of the character, it is possible to quickly confirm whether or not the code table exists.

[Brief description of drawings]

FIG. 1 is a block diagram of a specific example 1.

FIG. 2 is an operation flowchart (overall) of the first specific example.

FIG. 3 is an operation flowchart of specific example 1 (when cached).

FIG. 4 is an operation flowchart of specific example 1 (when not cached).

FIG. 5 is a diagram showing a process in which a character “A” is processed.

FIG. 6 is a diagram showing an edge pixel string and edge data of a character “A”.

FIG. 7 is a block diagram of a second specific example.

FIG. 8 is a flowchart of the operation of the second specific example (overall).

FIG. 9 is an operation flowchart of specific example 2 (encoding process).
It is.

FIG. 10 is an operation flowchart (preparation of a table) of the second specific example.

FIG. 11 is a reference table and a code table according to the second specific example.

FIG. 12 is a diagram showing encoded data according to a second specific example.

[Explanation of Codes] C Character Cache Control Device 3 Font Data Storage Unit 4 Edge Data Generation Unit 5 Bitmap Generation Unit 6 Edge Storage Unit 7 Bitmap Storage Unit

Claims (7)

[Claims] 1. A font data storage unit for storing font data representing outlines of a plurality of characters; an edge data generation unit for generating edge data representing a boundary between white pixels and black pixels from the font data; A character cache comprising: an edge storage unit that caches edge data; and a bitmap generation unit that generates bitmap data indicating white pixels and black pixels from the edge data cached in the edge storage unit. Control device. 2. The edge data generation unit divides a plurality of white pixels and black pixels into a plurality of regions based on the connection of pixels of the same color, and represents each region by the color of the pixel and the number of pixels. The character cache control device according to claim 1, wherein 3. The character cache control device according to claim 1, wherein the edge data generation unit generates edge data indicating a position of a boundary between a white pixel and a black pixel for each row. 4. A code table is stored which shows a correspondence relationship between the number of consecutive white pixels and the number of consecutive black pixels, and a code value representing the number, which is assigned according to the number and the appearance frequency. The number of white pixels and the number of black pixels are calculated from the code table storage unit and the position of the boundary between the white pixel and the black pixel in the edge data, and the calculated number of white pixels and the number of black pixels are calculated based on the code table. 2. The encoding processing unit that generates encoded data by encoding the number of symbols into a code value, and the encoding storage unit that stores the generated encoded data. Character cache controller. 5. A relationship between a ratio of a continuous length of continuous white pixels and a continuous length of continuous black pixels to a length of a line forming a character, and a relationship between a code value representing the ratio and The character cache control device according to claim 4, further comprising a reference table storage unit that stores the reference table shown, and a code table generation unit that generates the code table based on the reference table. 6. The character cache according to claim 5, further comprising a code table determination unit for checking whether or not there is a code table corresponding to an input character by searching a code table storage unit. Control device. 7. The code table determination unit confirms whether or not there is a code table corresponding to the input character based on only the font size of the input character. Character cache controller.