JPH0546141A - Character cache system - Google Patents

Abstract

PURPOSE:To decrease the frequency of execution of bit map development processing based upon outline font data irrelevantly to the size of a character cache area, the array of characters in a character string to be drawn, etc. CONSTITUTION:The frequency and range of appearance on the character string to be drawn are analyzed as to each of the character the character string before the bit map development processing is started and a set M of characters which appear plural times and are extracted as cache candidates is generated (step 101). According to the analytic result of the step 101, a character cache control table where the sections of the character cache area are assigned in the decreasing order of the frequencies of appearance of the respective characters in the set M is generated (step 102). Then the bit maps of the characters obtained by the bit map development processing are cached according to the character cache control table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character cache system in a document drawing system for drawing a character string by a bitmap expansion process based on outline font data.

[0002]

2. Description of the Related Art A document drawing system that draws a character string by bitmap expansion processing based on outline font data uses a bitmap expansion processing algorithm incorporated in the system to outline the characters obtained from the outline font data. Generate a bitmap in which the bits inside are filled in on the image memory.

An algorithm for bitmap expansion processing is generally of a complicated structure, and if the processing by this algorithm is repeated for each character, the drawing processing will take a long time. Therefore, generally, in a document drawing system that draws a character string by bitmap expansion processing, the character cache method is used to speed up the character string drawing processing.

A conventional character cache system will be described.

With the character cache method, for a character once created by a bit map expansion process, the bit map is held in a character cache area (a part of memory) equipped in the system, and the character is stored again. At the time of drawing, by copying the bitmap held in the character cache area to the image memory, it is not necessary to generate a bitmap by a normal bitmap expansion process, and the speed of the character string drawing process is increased. It is a thing.

Even if the characters are the same, the bitmaps will not be the same if the type of font (Mincho or Gothic in Japanese) or the size of the character (such as the number of points) is different. Therefore, the character cache area must be held separately.

All the characters in the character string illustrated below are
It is assumed that the font type and character size match.

In the conventional character cache system, every time one character to be drawn next is extracted from the character string to be drawn, it is checked whether or not the bitmap of the character is held in the character cache area. If it is held, it is copied and used. If it is not held, a bitmap is newly generated by the bitmap expansion processing based on the outline font data and drawn. At this time, the generated bitmap is held in the character cache area so as to be prepared for the next appearance of this character.

Usually, the character cache area has a size enough to accommodate a bitmap for hundreds of characters. Since the size is still limited, it may happen that the bitmap cannot be retained anymore, but at that time, the oldest bitmap is often discarded and a new bitmap is retained.

[0010]

However, in the above-mentioned conventional character cache system, the original purpose of the character cache system cannot be achieved depending on the arrangement of the characters in the character string unless the character cache area is considerably large. There was a problem that it would end up. This will be described below with a specific example.

It is assumed that the character string "Aa Aa Aa Aa" is drawn in a certain size. However, it is assumed that the size of the character cache area provided in the system can hold a bitmap for two characters but cannot hold for three characters.

In the conventional character cache system, the processing proceeds as follows. First, execute bitmap expansion processing based on the outline font data, and
To draw. These bitmaps are held in the character cache area. Next, draw'U 'in the same way.
Since the bitmap can no longer be retained in the character cache area, "
Overwrite the bitmap of u '.

Then, the process goes to the drawing process of the next character "A". Then, since the'a 'bitmap is no longer held, the bitmap is again generated by the bitmap expansion processing based on the outline font data, and the bitmap is drawn. Then, the part holding the bitmap of "I" is overwritten with the bitmap of "A". Similarly, the writing to the character cache area is repeated for each character.

As a result, the bit map held in the character cache area is not effectively utilized, and the meaning of the character cache method for performing character drawing at high speed is completely lost. On the contrary, it will be slower than if nothing was done for the time to keep the character bitmap in the character cache area.

As described above, in the conventional character cache system, if the character cache area is not quite large, the number of times the bitmap expansion processing based on the outline font data is executed is reduced depending on the arrangement of the characters in the character string. In addition to not being able to achieve the original purpose, there was a problem that the processing efficiency deteriorated.

The present invention has been made in view of the above circumstances, and determines the number of executions of bitmap expansion processing based on outline font data regardless of the size of the character cache area, the arrangement of characters on a character string to be drawn, and the like. An object of the present invention is to provide a character cache method that can achieve the original purpose of the character cache method of reducing the number.

[0017]

According to the character cache method of the present invention, in a document drawing system equipped with a character cache area for holding a bitmap of characters, the character cache of a bitmap created by bitmap expansion processing. The holding processing in the area is executed according to a certain standard.

However, in the document drawing system, when a bit map of a character to be drawn is generated in the image memory, for a character whose bit map is already held in the character cache area, the character cache area By copying the bitmap stored in the image memory to the image memory, a bitmap of the character to be drawn is newly created based on the outline font data. It is assumed to be of the form.

In the character cache system according to the present invention, in order to achieve the object, the character cache area is divided into unit sections for storing a bitmap for one character, and a character to be held in each section and its holding range are divided. It is managed by the character cache management table.

Before the bitmap expansion processing is started, the number of appearances and the appearance range of each character in the character string to be drawn are analyzed, and characters appearing multiple times are cache candidates. A set M extracted as is generated.

Then, when the number of partitions of the character cache area is L, first, L characters are extracted from the set M in descending order of the number of appearances as a first cache candidate,
Each character of the extracted first cache candidate is allocated to each section in the character cache area set in the character cache management table, and a holding range of the allocated character is set for each section.

For the remaining characters of the set M excluding the first cache candidate, the number of appearances is within a range that does not overlap with the holding range of the characters that are already set to be held in each section in the character cache area. In the order of increasing number, the sections are allocated to each section on the character cache area set in the character cache management table, and the holding range of the allocated characters is set for each section.

Then, based on the setting on the character cache management table, the holding process of the bitmap in the character cache area is executed.

[0024]

In the character cache system according to the present invention, the characters in the character string to be drawn are retained in the character cache area provided in the document drawing system in order from the one having the highest appearance frequency, and are effectively used in the drawing process. Will be.

Therefore, regardless of the size of the character cache area or the arrangement of characters on the character string to be drawn, the original purpose of the character cache method is to reduce the number of times the bitmap expansion processing based on the outline font data is executed. can do.

[0026]

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 3, a document drawing system for carrying out an embodiment of the present invention is created by the system body 10, an external storage device 29 storing an outline font data file 30, and the system body 10. CRT 32 that visually outputs image data, and printer 3
4 and. Here, the external storage device 29, CR
The T32 and the printer 34 are connected to the system main body 10 as peripheral devices.

The system main body 10 is an arithmetic processing unit that executes a character string drawing process in a predetermined procedure, and corresponds to, for example, a personal computer main body or a workstation main body. The system main body 10 is equipped with a page data generation module 12 that generates page data such as a page description language and a document drawing module 14 that draws a document.

The page data generation module 12 generates page data by a publishing application program or the like and sends it to the document drawing module 14. The page data output from the page data generation module 12 includes command data that means drawing a character string.

As shown, the document drawing module 14 is composed of a drawing processor 20, a data memory 22, a character cache area 24, an image memory 26 and the like. Here, the data memory 22 stores data such as page data output from the page data generation module 12 and outline font data read from the outline font data file 30.

The drawing processor 20 receives the page data generated by the page data generating module 12 through the data memory 22 and interprets the page data. When the page data includes command data indicating character string drawing, a predetermined value is given. Perform the various processes required to draw a character string by following the procedure.

Further, when drawing a character string, the drawing processor 20 creates a bit map of a character to be drawn based on the outline font data of the outline font data file 30 when necessary. Execute the process. The bitmap created by this bitmap expansion process is normally created in the image memory 26, but the created bitmap can be held in the character cache area 24. Also,
A rectangular transfer function from the character cache area 24 to the image memory 26 is provided, and the bitmap held in the character cache area 24 can be copied to any position on the image memory 26.

Whether or not the drawing processor 20 holds the bitmap created by the bitmap expansion processing in the character cache area 24 depends on the character cache method according to the embodiment of the present invention.

The character cache area 24 is a cache memory for holding a bit map of characters, and holds the bit map created by the drawing processor 20 according to the character cache method of one embodiment. The image memory 26 temporarily holds image data to be drawn, and the CRT 32 or the printer 34 which is a display device.
Output to.

In the character cache system according to one embodiment of the present invention, the character cache area 24 is divided into unit divisions for storing a bitmap for one character, and the character to be retained in each division and its retaining range are defined by character. It is managed by the cache management table. The unit division for storing the bitmap for one character is a rectangular area having a size enough to hold the bitmap for one character, and the size C (n) of each rectangular area in the character string to be drawn. It is a constant value that is determined by the size n of the character (usually represented by the number of points, etc.), and does not change depending on the character (that is, the same when saving the character "a" or "u"). is there).

In the case of the conventional character cache method, the character bitmap is held in the character cache area as the smallest rectangular area surrounding the character, and in order to hold a plurality of characters, the minimum required for each character. The rectangular areas of are arranged in the character cache area so that no space is created. Therefore, conventionally, the size of the rectangular area to be held differs depending on the character even if the number of points is the same. However, in this embodiment, the size of the rectangular area to hold the bitmap (that is, unit division) is The same is true for. In other words, in the case of this embodiment, the unit division is set according to the one that requires the largest rectangular area among the characters to be drawn.

FIG. 4 shows a specific example of the division of the character cache area. In this example, it is divided into three, that is, divisions 1 to 3, and therefore, a bitmap for 3 characters can always be held.

The character cache management table is for managing which character bitmap is held at which stage during the character string drawing process in each section on the character cache area 24. In order to execute the character cache method of the embodiment, it is created in the memory managed by the drawing processor 20.

In the character cache system of this embodiment,
When the character string to be drawn is recognized, the management table creating process is executed before the bitmap expansion process required for drawing is started. This management table creation processing creates a character cache management table in which characters to be held for each section on the character cache area 24 and their holding range are set, and the processing is performed according to the procedure of FIG.

First, for each character in a character string to be drawn, the number of appearances and the range of appearance on the character string are analyzed to generate a set M in which characters that appear multiple times are extracted as cache candidates (step 101). The appearance range in a character string is from the position where the character first appears in the character string (what character it is) to the position where it appears last (this character is also what character). Say.

Next, when the number of partitions of the character cache area 24 is L (L = 3 in this example), first, from the set M, L characters in descending order of appearance frequency are set as the first cache candidate. Each character of the extracted first cache candidate is allocated to each section on the character cache area 24 set in the character cache management table, and a holding range of the allocated character is set for each section. Then, the character extracted as the first cache candidate is excluded from the set M (step 102). The holding range in each section is the range on the character string from the start to the end of saving in each section.

Next, it is judged whether or not there are still characters remaining in the set M excluding the first cache candidate (step 103). When there are no characters remaining, the management table creating process is terminated. , And a series of character string drawing processing (step 104). However, when there are still characters remaining in the set M, the character with the highest number of appearances is extracted from the remaining characters (step 105), and is there a division in the character cache area 24 that can hold that character? It is checked whether or not (step 106).

The process of step 106 is performed by a character holding range which is already held in the character cache management table and a holding range of characters to which a section is assigned.
The appearance range of the character newly extracted from the set M is compared to check whether or not there is a section that can be assigned without overlapping the holding range.

When it is found in the step 106 that there is only one section on the character cache area 24 that can be held, the character is assigned to that section, and
The holding range of the character is set (step 107). Then, the character whose classification is determined to be held in step 107 is deleted from the set M, and the process returns to step 103 (step 108).

When it is determined in step 106 that there is no division in the character cache area 24 that can be held, the process immediately proceeds to step 108, and the character is set M.
, And returns to step 103.

In step 106, when there are two or more sections that can be held in the character cache area 24, the process proceeds to step 109 to select the optimum section.

Step 109 is to select from among a plurality of divisions capable of holding the character, a character cache that enables the leanest character cache. It does as follows. First, if the divisions are i
Assuming that there are individual pieces, those division numbers are set to Ki. In each of these categories, some characters have already been registered together with the holding range. Therefore, in general, in each of the divisions Ki, there is a registered character whose storage range comes before and after the letter X to which a new division is assigned.

Let P (Ki) be the distance between the registered characters whose holding range is immediately before and X, and O (Ki) be the distance between the registered characters whose X is immediately after the holding range and X. .. If there is no registered character immediately before or immediately after, the displacement from the beginning or end of the character string is set to P (Ki) and O (Ki), respectively. Where min
Select one of P (Ki) or O (Ki) having a value of {P (Ki), O (Ki)}, and assign that category Ki to the category holding the character X, and Register the retention range. When the process of step 109 is completed, the process returns to step 103 via step 108.

In the above-described management table creation process, steps 103 to 108 are performed in order from the character cache management table to the character cache management table in the descending order of the number of appearances of the characters remaining in the set M in order to effectively use the character cache area 24 at all times. Is an attempt to register.

When the creation of the character cache management table is completed by the management table creation process described above,
Next, the character string drawing process is executed in the procedure shown in FIG.

Since the character bitmap is created character by character, first, in step 201, the value of the pointer indicating the character on the character string to be drawn is set to the initial value (that is, the first character of the character string is drawn). Make the character pointed to). Next, one character indicated by the pointer is taken out (step 202), and it is judged whether or not the bitmap of the character is already held in the character cache area 24 (step 203). The determination in step 202 is
First, it is performed according to the setting contents of the character cache management table created by the management table creation process. The appearance position of the judgment target character on the character string is within the holding range (holding start) described in the character cache management table. (Excluding the position), it is determined to be held.

When it is determined in step 203 that the character is not already held in the character cache area 24, it is further determined based on the description in the character cache management table whether or not the character should be held in the character cache area (( Step 204). In the character cache management table, the character to which the classification to be retained is not assigned is a character that should not be retained in the character cache area. In that case, the corresponding outline font data is read from the outline font data file 30 and read. A bitmap expansion process is executed based on the outline font data thus generated to generate a bitmap of the corresponding character on the image memory 26 (step 205).

Upon completion of step 205, it is determined whether or not the character is the end (last character) of the character string (step 206). If it is the end, the drawing process is ended, but if it is not the end, The value of the pointer designating the character to be drawn is incremented by 1 (step 207) and the process returns to step 202.

In step 204, if the character is a character to be held in the character cache area (that is, the appearance position of the character to be judged on the character string is within the holding range described in the character cache management table, the start of holding). Outline font data file 3
The corresponding outline font data is read from 0, bitmap expansion processing is executed based on the read outline font data, and a bitmap of the character is generated in the corresponding section on the character cache area 24 (step 208). Next, the bit map on the character cache area 24 is copied to the image memory 26 (step 209), and the process proceeds to step 206.

When it is determined in step 203 that the character cache area 24 has already been held, the process immediately proceeds to step 209, and the character cache area 2 is stored.
4 is stored in the image memory 26.
Image memory 2
Get the desired bitmap on 6.

In the document drawing system shown in FIG. 3, the characters for which the bitmap is generated on the image memory 26 by the drawing process of FIG. 2 are sequentially drawn on the CRT 32, and as necessary (by operator's instruction). Output to the printer 34.

To make it easier to understand the operation and effect of the embodiment of the present invention, the contents of the processing shown in FIGS. 1 and 2 will be described by using a specific example. In this specific example, the character string to be drawn is "Ai No Kaoh Uo Uo",
It is assumed that each character in this character string has a size of 18 points. The character cache area 24 is shown in FIG.
As shown in, it is assumed that the size is such that the bitmap can be stored only for three characters.

First, in the character string analysis process in step 101 of FIG. 1, the number of appearances and the appearance range of each character in the character string are checked. 5 and 6 show the results of this analysis processing. FIG. 5 numerically shows the analysis result, and the appearance range is represented by the first appearance position (rank) and the last appearance position (rank) on the character string. In addition, in FIG. 6, the appearance range is a "line segment" along the character string.
It is represented by the length of. Further, in step 101, a set M of characters appearing a plurality of times on the character string is generated based on the analysis result.

The character "ka" on the character string is not included in the set M because it does not belong to the cache candidates because it appears once. The above analysis results are held in the memory managed by the drawing processor 20 until the management table creating process shown in FIG. 1 is completed.

When the characters of the set M are arranged in descending order of the number of appearances, they are'a ',' i ',' o ',' u ', and'e'. In step 102 of FIG. 1, the upper three characters “A”, “I”, and “O” (all three occurrences) are extracted in descending order of appearance count, and the character cache area holds these characters. Twenty-four sections are assigned, and the holding range (which matches the appearance range of the analysis result) in each assigned section is described for each section. Then, it is further extracted from the set M as a first cache candidate.
Excludes the three letters'a ',' i ', and'o'.

FIG. 7 shows the recorded contents of the character cache management table 27 at the time when the processing of step 102 is completed. In the case of this example, the character'a '
Is held in section 1, the character "i" is held in section 2, and the character "o" is held in section 3. Next, regarding the characters remaining in the set M, steps 103 to 109 in FIG.
By the processing according to (3), whether or not to retain the character cache area 24 is set in descending order of appearance frequency. The letter'U '
In the case of, the appearance range does not overlap with the holding range of the holding character'a 'of Category 1, and the holding character of Category 2'
It does not overlap with the storage range of'i '. Therefore, in step 106, two partitions, partition 1 and partition 2, are recognized as cacheable candidates, and the next step 109
Therefore, the optimum classification is required.

When the character “U” is held in the division 1 or the division 2, the gap between the holding range (appearance range) of the character “U” and the holding range of another adjacent character is the division 1 It becomes smaller when it is decided to hold. Therefore, in the process of step 109, the classification 1 is selected as the holding classification of “U”.

Similarly, steps 103 to 106 are repeated, and the holding section for the character "e" is set to section 2 in step 107, and the management table creating process is completed. FIG. 8 shows the description contents of the character cache management table 27 at the time when the management table creation processing shown in FIG. 1 is completed.

When the management table creation processing is completed, FIG.
Is executed based on the character cache management table 27. Since the character "a" at the beginning of the character string is to be held in the partition 1 of the character cache area 24, the outline font data of the character "a" is used to generate the bitmap in the partition 1, and the bitmap is generated in the image memory. And draw it. Similarly, using the outline font data of "yes", the bitmap is generated in the section 2, and the bitmap is copied to the image memory and drawn.

For the third and fourth characters "i", the bitmap is already cached, so copy it and draw it. According to the character cache management table, the 5th character'e 'is supposed to be stored in Category 2. Therefore, in the section 2 which previously held the'I' bitmap, Generates (overwrites) a bitmap, copies it to image memory, and draws it. By repeating such processing, character drawing proceeds.

In the character cache system as described above, the characters in the character string to be drawn are arranged in the character cache area 2 provided in the document drawing system in descending order of appearance frequency.
4 and is effectively used for drawing processing.

Therefore, regardless of the size of the character cache area 24 or the arrangement of characters on the character string to be drawn, the original purpose of the character cache method is to reduce the number of times the bitmap expansion processing based on the outline font data is executed. Can be achieved.

In the above-described embodiment, for each character in the set M, the character cache area 2 is arranged in descending order of the number of appearances.
Although four divisions are assigned, in principle, when there are the same number of appearances, the character that appears first in the character string to be drawn should be prioritized as a cache candidate.

Further, in the character cache method according to the present invention, during the management table creating process, the first cache candidate character is first allocated to each section of the character cache area 24, and then the remaining characters of the set M are left. Is also assigned to the character cache area 24, but such processing expansion is always performed in the character cache area 24.
The purpose is to retain more characters without waste, and the specific processing procedure is step 103 in FIG.
It is not limited to ~ 109.

The characters remaining in the set M are vacant in the descending order of the number of appearances within a range that does not overlap the holding range of the characters that are already set to be held in each section of the character cache area 24. If there is a case where the appearance range of the characters remaining in the set M overlaps with the holding range of the characters that are already decided to be held in each section, the holding range of the characters to be assigned to the section later may be assigned. It is conceivable to narrow the occurrence range of the character on the character string to avoid duplication.

[0071]

As is apparent from the above description, in the character cache system according to the present invention, the characters in the character string to be drawn are arranged in the character cache area in the document drawing system in descending order of appearance frequency. It will be stored in and will be effectively used for drawing processing.

Therefore, regardless of the size of the character cache area, the arrangement of characters on the character string to be drawn, etc., the original purpose of the character cache method of reducing the number of executions of bitmap expansion processing based on outline font data is achieved. can do.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of management table creation processing according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a character string drawing process using an embodiment of the present invention.

FIG. 3 is a diagram illustrating the configuration of a document drawing system that executes an embodiment of the present invention.

FIG. 4 is an explanatory diagram of a character cache area according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a character string analysis process according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram of character string analysis processing according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram of an example of creating a character cache management table according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram of an example of creating a character cache management table according to an embodiment of the present invention.

[Explanation of symbols]

 10 system main body 12 page data generation module 14 document drawing module 20 drawing processor 22 data memory 24 character cache area 26 image memory 29 external storage device 30 outline font data file 32 CRT 34 printer

Claims (1)

[Claims] 1. A character cache area for holding a bitmap of a character is provided, and when a bitmap of a character to be drawn is generated in an image memory, a character whose bitmap is already held in the character cache area is added to the character cache area. On the other hand, by copying the bitmap held in the character cache area to the image memory, a bitmap of the character to be drawn is newly created based on the outline font data. In a document drawing system for accelerating column drawing processing, a character cache method for executing a holding process of a bitmap created by the bitmap expanding process in the character cache area according to a certain standard, Area is a unit division that stores a bitmap for one character The character cache management table manages the characters held in each section and the holding range. On the other hand, before starting the bitmap expansion processing, the character string for each character in the character string to be drawn is The number of appearances and the range of appearance in the above are analyzed to generate a set M in which characters that appear multiple times are extracted as cache candidates. When the number of partitions of the character cache area is L, first, from the set M, , L characters are extracted as a first cache candidate in descending order of appearance frequency, and each character of the extracted first cache candidate is assigned to each section on the character cache area set in the character cache management table. The retention range of the characters allocated for each division is set, and for the remaining characters of the set M excluding the first cache candidate, the character cache area has already been set. Allocate to each section on the character cache area set in the character cache management table in the descending order of the number of occurrences within the range that does not overlap with the retention range of characters set to retain in each of the above categories, and further Set the retention range of the characters allocated for each, based on the settings on the character cache management table,
A character cache method characterized by executing a process of holding a bitmap in the character cache area.