JPH09319656A - Device and method for displaying character - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a character display device with which the display speed of characters is accelerated by switching the type of font data to be stored in a cache memory based on a face and a size. SOLUTION: A cache input switching device 3 discriminates whether compressed font data outputted from a font memory 2 or extended font data outputted from an extending device 6 is to be stored in a cache memory 4 as the font data of display instructed characters from letter style data and size data transmitted from a document memory 1 and based on the discriminated result, the input of the cache memory 4 is switched. Thus, the cache memory 4 can be effectively utilized and display speed can be accelerated as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character display device and a character display control method in which a character to be displayed is designated by character data, typeface data and size data, and in particular, font data stored in a cache memory is compressed. The present invention relates to a character display device and a character display control method that realize effective use of a cache memory and improvement of display speed by appropriately switching between font data and expanded font data.

[0002]

2. Description of the Related Art In recent years, the spread of electronic devices such as personal computers and word processors has been remarkable,
Along with this spread, the opportunity to handle electronic documents has increased significantly.

FIG. 6 shows a schematic structure and a processing flow for displaying a document on a screen in such a device. Reference numeral 11 denotes a document storage device, which stores character data forming a document, typeface data indicating a typeface (Mincho, Gothic, etc.), and size data when characters are displayed, and these are sequentially output. .

Reference numeral 12 is a font memory in which fonts of all characters are compressed and stored as compressed font data. When the above-mentioned character data and typeface data are input, the compressed font data specified by these is output. There are already many specific compression methods, and here, as an example, a method using coordinate data of the outline of a character is used as shown in FIG. 7. In the figure, (a) exemplifies the shape of characters (image data), and (b) shows
It shows the coordinate data of the contour line of the character shown in (a). As shown in FIG. 7, having the contour line data as a numerical value makes it possible to significantly reduce the amount of data compared to having the character shape as image data. As described above, it is a general method to reduce the capacity of the font memory by using the contour line data.

A decompressing device 13 decompresses the compressed font data described above in a size indicated by size data,
Output as expanded font data. Reference numeral 14 is a cache memory that temporarily stores expanded font data of some characters. Then, if the expanded font data corresponding to the character data, the typeface data, and the size data is stored, it is output. Although font data can be output at a higher speed than the font memory 12, its storage capacity is significantly limited as compared with the font memory 12.

Reference numeral 15 denotes a selection device, which outputs the expanded font data from the cache memory 14 if it is output, and otherwise outputs the output of the expansion device as output font data.

A display device 16 displays output font data. In such a configuration, a font of one typeface contains a large number of fonts and is therefore often compressed and stored in the font memory 12, but the font memory 12 still has a large size. Capacity is needed. Therefore, an inexpensive low-speed memory is often used, but in that case, the display speed of characters decreases. A means for preventing this is the cache memory 14, which stores font data developed in the past. When the same character is displayed again with the same typeface and size, the expanded font data stored in the cache memory 14 can be used without expanding again, and therefore the display processing is speeded up. However, since the cache memory 14 is a high-speed, small-capacity storage device, it cannot store the expanded font data of all characters. In general, when the cache memory 14 is full, the cache is erased in order from the oldest accessed time. Therefore, the display speed as a whole greatly changes depending on how many characters of expanded font data are stored in the cache memory.

[0008]

Since the expanded font data for large characters becomes large, the number of characters that can be stored in the cache memory decreases when cached, and the overall display speed decreases. There is also a method of not storing large characters in the cache memory, but in that case, compressed font data must be extracted from the slow font memory and expanded each time the same character is displayed again. However, the processing speed becomes slow.

The present invention has been made in view of the above circumstances, and stores large decompressed font data in a cache memory when the character size is small, and compressed font data when the character size is large, for example. (EN) Provided are a character display device and a character display control method, which do not occupy a cache memory with expanded font data, and in which the cache can be effectively used to display at a higher speed than before. With the goal.

[0010]

SUMMARY OF THE INVENTION The present invention is a character display device in which a character to be displayed is designated by character data, typeface data and size data, and font data specified by the character data and typeface data is used as a font. In a character display device that takes out from the memory and expands and displays the compressed font data in a size specified by the size data, the compressed font data and the expanded font data can be mixed and stored. Determining means for determining which of the compressed font data and the expanded font data should be stored in the cache memory as the font data of the character instructed to be displayed, from the cache memory and the typeface data and the size data. Based on the judgment of the judgment means Te, characterized by comprising; and a switching means for switching font data to be stored into said cache memory between the compressed font data and expanded font data.

According to the present invention, since the type of font data stored in the cache memory is dynamically switched according to the typeface data and size data, the cache memory is fixedly stored in either compressed font data or expanded font data. Compared with the case, the resources of the cache memory can be effectively used, and the display speed as a whole can be improved.

This determination may be made by comparing the average data amount of the expanded font data and the compressed font data for each character type classified by the combination of the typeface and the size, and adopting the smaller one. For each of the character types described above, the average display processing time when only one of the expanded font data and the compressed font data is stored in the cache memory is compared, and the smaller one may be adopted. Judgment based on this average display processing time can be made by comparing the average data amount per character of the expanded font data for the typeface and size obtained from the typeface data and size data with the threshold value obtained from the typeface data. When the average data amount per character of the expanded font data exceeds the threshold value, the compressed font data may be stored. As a result, the limited capacity of the cache memory can be effectively used, and the overall display speed can be increased.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a character display device according to an embodiment of the present invention. A document memory 1 outputs character data, typeface data, and size data. The character data is data indicating the characters written in the document. The typeface data indicates a typeface such as Mincho typeface or Gothic typeface. Further, the size data indicates the size when a character is displayed, such as 16 × 16 dots.

Reference numeral 2 is a font memory, which is a large-capacity memory that stores compressed font data of all characters. Compressed font data corresponding to these is output from character data and typeface data. The same compression method as the conventional one can be used.

Reference numeral 3 denotes a cache input switching device. The cache input switching device 3 temporarily stores either compressed font data or expanded font data, which will be described later, depending on the typeface data and size data or the size of font data. Output as font data that should be retained.

A cache memory 4 stores the font data output from the cache input switching device 3. Then, if the font data corresponding to the character data, the typeface data, and the size data is stored, it is output. The cache memory 4 is faster and has a smaller capacity than the font memory 2, and cannot store all characters. When full,
Data is erased in order from the oldest accessed time to secure space for new data.

Reference numeral 5 denotes a first selection device, which outputs the font data from the cache memory 4 if the font data is output and is compressed from the font memory 2 in other cases. Select and output the compressed font data.

The expanding device 6 expands the font data selected and output by the selecting device 5 and outputs it as expanded font data. In this embodiment, the compression method shown in FIG. 7 described as the conventional technique is used.

Reference numeral 7 is a second selection device, and if the font data is output from the cache memory 4 and it is not compressed, the data is output, and in other cases, the expansion device 6 outputs the expansion data. Outputs font data as output font data.

A display device 8 displays the expanded font data selected and output by the selection device 7. The cache input switching device 3, the selection device 5, and the selection device 7 in the figure are configured as application programs whose execution is controlled by the CPU mounted on the character display device.

The operation of the character display device of this embodiment when displaying characters will now be described. When the character data, the typeface data, and the size data are output from the document memory 1, the character data and the typeface data are sent to the font memory 2, which causes the compressed font data of the corresponding character to be output from the font memory 2. Is output.

The compressed font data is sent to the selection device 5. In the selection device 5, if the compressed font data is sent from the cache memory 4, it is not sent or is compressed. If not, the compressed font data sent from the font memory 2 is selected and output.

The font data selected and output by the selecting device 5 is expanded by the expanding device 6 and becomes expanded font data. The decompressed font data is sent to the selection device 7, and the selection device 7 sends uncompressed font data from the cache memory 4 if it is not sent or is compressed. To the expanded font data output from the expansion device 6. The font data selected and output by the selection device 7 is displayed on the display device 8.

As described above, the following three types of font data are displayed. (1) Font data stored in the cache memory in the expanded form.

When only one character is viewed, the time required to display it is shortest. However, if the size is large, a large amount of area is required for storage in the cache memory, and the overall display speed is reduced. (2) Font data stored in a compressed form in the cache memory.

Since the processing for expanding is necessary, the time until display is increased as compared with the case of (1). However, with a large size, the amount of data becomes smaller than in (1), and it does not take up space on the cache memory. (3) Font data that is not stored in the cache memory and is output from the font memory.

The display speed is the slowest because it is output from the low-speed font memory and further expanded. The compressed font data output from the font memory 2 and the expanded font data output from the expansion device 6 are both sent to the cache input switching device 3. In the cache input switching device 3, the cache memory 4
Which font should be stored in the cache memory 4 and sends the selected font data to the cache memory 4.

On the other hand, the cache memory 4 stores it, and if the character data and the typeface data sent from the document memory 1 have the corresponding character data, the data is output.

If the compressed font data is cached when the expanded font data is large as in the present embodiment, the cache is effectively used and the overall display speed is improved (optimum average display time). )). Therefore, the average size of the expanded font data is compared with a certain threshold value for each character type classified by the typeface and the size, and if the average size is large, the compressed font data is cached. An example of a concrete threshold value determination method is shown below.

Average time T required to display one character T
When aye is stored in the cache memory 4 together with the compressed font data and the decompressed font data, it can be calculated by the following formula, if it is generalized.

Tave = (n ₁ · T ₁ + n ₂ · T ₂ + (n ₀ −n ₁ −n ₂ ) T ₀ ) / n ₀ Equation (1) where n ₀ : one typeface and one size Total number of characters (constant) n ₁ : Average number of characters of compressed font data stored in cache memory n ₂ : Average number of characters of expanded font data stored in cache memory T ₀ : Compressed font data in font memory is displayed on the display device Average time until display (constant) T ₁ : Average time until display of compressed font data in cache memory on display device (constant) T ₂ : Display of expanded font data in cache memory on display device Average time until constant (constant) Since n ₁ and n ₂ are both stored in the cache memory 4, there is the following relationship.

N ₁ · C ₁ + n ₂ · C ₂ = C ₀ (2) where C _{1 is} the average data amount per character of the compressed font data (depending on the typeface) C ₂ : is the character of the expanded font data Average data amount (depending on typeface / size) C ₀ : Total capacity of cache memory (constant) From equations (1) and (2), Tave = (n ₁ (C ₁ (T ₀ −T ₁ ) − _{C 2 (T 0 -T 1)} ) + C 0 (T 2 -T 0) + n 0 · C 2 · T 0) / (n 0 · C 2) ... (3) Thus equation, C _2> (C ₁ (T ₀ −T ₂ ) / (T ₀ −T
_In the case of ₁ ), it can be seen that Tave is minimized by setting n ₂ to 0 and otherwise n ₁ to 0. The average data amount on the left side of this equation depends on the typeface and size, and the threshold value on the right side depends on the typeface. In this way, the relationship between the average data amount and a certain threshold value is calculated in the cache input switching device 3, and the data stored in the cache memory 4 is dynamically switched according to the magnitude relationship. It is a feature. The cache input switching device 3 does not calculate which of compressed font data and expanded font data is to be stored in the cache memory 4 each time, but a calculation result is previously stored for each combination of typeface data and size data. It is also effective to secure as.

For example, consider the case of displaying a document as shown in FIG. In (1), the typeface is Mincho and the size is full-width "A". In (2), the size is changed to double-width and "A" is displayed. Also,
In (3), the typeface is Gothic and the size is changed to full-width to display "A", and in (4), the size is changed to double-width and "A" is displayed.

In such a case, as shown in FIG.
In (1), typeface data indicating Mincho, size data indicating full-width, and character data indicating "A" are input. After that, when the characters of Mincho type and full-width characters are continuously displayed, only the character data is input. Further, in (2), the changed size data is added and the character data is input, and similarly,
In (3), font data and size data are added, and in (4), size data is added and character data is input.
Therefore, the cache input switching device 3 may switch the storage method in the cache memory 4 only when at least one of the typeface data and the size data changes.

FIG. 4 shows a table holding a storage method for each combination of typeface data and size data. When at least one of the typeface data and size data transmitted from the document memory 1 changes, the cache input switching device 3 refers to this table and switches the method of storing font data in the cache memory 3. FIG. 5 shows the result of storing the font data of the data shown in FIG. 3 in the cache memory 3 based on the table shown in FIG.

As described above, by dynamically switching the font data stored in the cache memory 3 according to the typeface data and size data, the resources of the cache memory can be effectively utilized and the display speed can be improved as a whole. Becomes

Up to now, the description has been made assuming that the data amount of the expanded font data is larger than the data amount of the compressed font data. However, when the character size is small as in the print preview screen, the expanded font data is used. The data may be smaller. In order to deal with such a case, it is also effective to store the smaller one of the compressed font data and the expanded font data in the cache memory. In this case, the cache input switching device compares the data amounts of the compressed font data and the expanded font data, and outputs the smaller one as the storage font data. In the above example, the average display time is optimized (minimized), but in this case, the number of characters inside the cache is optimized (maximized). Which one is more efficient overall depends on the implementation.

By selecting the data to be stored in the cache memory in this manner, the limited capacity of the cache memory is effectively used and the overall display speed is increased.

[0039]

As described above in detail, according to the present invention, the font data to be stored in the cache memory is compressed between the compressed font data and the expanded font data according to the font and size of the characters to be displayed. Since it is switched dynamically with, it becomes possible to effectively use the cache memory even when displaying large characters.
In addition, high-speed document display is possible as a whole.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a character display device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a document display of the same embodiment.

FIG. 3 is a view showing an example of input data according to the same embodiment.

FIG. 4 is an exemplary view showing a table holding a storage method for each combination of the typeface and size of the embodiment.

FIG. 5 is a conceptual diagram showing a storage image of a cache memory of the same embodiment.

FIG. 6 is a diagram showing a configuration and a flow of processing for displaying a conventional document on a screen.

FIG. 7 is a conceptual diagram for explaining one compression method of font data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Document memory 2 ... Font memory 3 ... Cache input switching device 4 ... Cache memory 5 ... Selection device 6 ... Expansion device 7 ... Selection device 8 ... Display device

Claims (6)

[Claims] 1. A character display device in which characters to be displayed are designated by character data, typeface data, and size data, wherein font data specified by the character data and typeface data is taken out from a font memory,
In a character display device that expands and displays the compressed font data in a size specified by the size data, a cache memory that can store the compressed font data and the expanded font data in a mixed manner, Determining means for determining which of the compressed font data and the expanded font data should be stored in the cache memory as the font data of the character instructed to be displayed, from the typeface data and size data; A character display device, comprising: switching means for switching the font data to be stored in the cache memory between the compressed font data and the expanded font data based on the determination. 2. The determining means stores in the cache memory only one of the compressed font data and the expanded font data for each character type classified by a combination of the typeface data and size data. 2. The character display device according to claim 1, wherein it is determined that one having a smaller average display time should be stored in the cache memory when it is assumed that the character display is performed. 3. The determination means, when the average data amount per character of the expanded font data in the typeface and size obtained by the typeface data and size data exceeds a threshold value obtained by the typeface data. 2. The character display device according to claim 1, wherein it is determined that the compressed font data should be stored. 4. The character display device according to claim 1, wherein the determination unit determines that one of the compressed font data and the expanded font data having a smaller data amount should be stored. 5. A character display device in which a character to be displayed is designated by character data, typeface data and size data, wherein font data specified by the character data and typeface data is taken out from a font memory,
In a character display device for expanding and displaying the compressed font data in a size specified by the size data, a cache capable of selectively storing one of the compressed font data and the expanded font data. A memory, setting means for setting which of the compressed font data and the expanded font data the font data of the display-instructed character is stored in the cache memory, and based on the setting of the setting means A character display device comprising: switching means for switching font data to be stored in the cache memory between the compressed font data and the expanded font data. 6. A character display control method for a character display device in which a character to be displayed is designated by character data, typeface data and size data, wherein font data specified by the character data and typeface data is retrieved from a font memory. In the character display control method of the character display device, which expands and displays the compressed font data in a size specified by the size data, the compressed font data and the expansion data are extracted from the typeface data and the size data. It is determined which of the selected font data should be stored in the cache memory as the font data of the character instructed to be displayed, and based on the result of the determination, the font data to be stored in the cache memory is compressed and expanded. Font data Character display control method characterized by switched.