JPH0512426A - Compressor for bit map font - Google Patents

Abstract

PURPOSE:To provide the compressor for a bit map font which can realize satisfactory compression efficiency in the case of compressing a lot of bit map fonts. CONSTITUTION:The plural bit map fonts are inputted to an input device 1, and these bit map fonts are read by a read part 2 and applied to a calculation part 3. The calculation part 3 successively identifies whether respective patterns shown by the respective bit map fonts are symmetrical in right and left sides or not, and these bit map fonts are applied to an extraction part 4 together with the identified result for each bit map font. The extraction part 4 extracts the left part of the bit map font which is identified symmetrical in right and left parts, and this left part and the entire bit map font identified asymmetrical in the right and left parts are successively arranged to form a bit map font train. Then, this bit map font train is applied to a compression part 5. The compression part 5 compresses the bit map font train, and the compressed data are stored in a font storage memory 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bitmap font compression apparatus for efficiently converting a bitmap font showing characters into compressed data.

[0002]

2. Description of the Related Art A bitmap font is for expressing patterns of characters, symbols, etc., and is formed by arranging a plurality of pixels each indicating "white" or "black" in a matrix direction. A plurality of bits (“1” and “0”) corresponding to each pixel of the pixel matrix.
Each of which is shown) is arranged in the matrix direction.

In the case of storing such a bitmap font, if a small number of bitmap fonts are stored, the storage capacity of the memory is small, but a large storage capacity is required to store a large number of bitmap fonts. Requires memory. For this reason, when a large number of bitmap fonts are stored, compression processing is performed on these bitmap fonts and the compressed data obtained by this is stored, thereby reducing the storage capacity of the memory. ..

Conventionally, as a bit map font compression process, a bit pattern is generally sequentially compressed for each line of one bit map font, but in order to further improve the compression efficiency, the bit pattern is used in both directions. A method of compression has also been proposed (Japanese Patent Laid-Open No. 60-176084).
No. Whichever of these methods is used, the compression process is still performed for each of a plurality of bitmap fonts, and each compressed data corresponding to each bitmap font is generated.

Therefore, if there is data in the format including a plurality of bitmap fonts as shown in FIG. 7, the data in the format as shown in FIG. 8 is created as a result of the compression processing of this data. As a result, the data shown in FIG. 8 is stored in the memory. Here, the data of the format shown in FIG. 7 includes a header part 71 for describing a font name, a typeface name, a copyright, a version number, etc., and a plurality of metrics information parts 72-
1-72-n and these metrics information parts 72-1
Bit map units 73-1 to 7-7 arranged for each 72-n
It consists of 3-n. Each metric information section 72-1 to 72
In -n, a character code for identifying characters, symbols, etc., widths and heights of characters, symbols, etc., and metric data indicating a baseline, etc. are respectively described, and each bit map portion 73-1 to 73 is described. Bitmap fonts such as characters and symbols indicated by the character code described in the immediately preceding metrics information section are stored in -n. On the other hand, the data in the format shown in FIG. 8 is the same as the header section 71 shown in FIG. 7, and the header section 81 for describing the font name, typeface name, copyright, version number, etc., and the header section 81 shown in FIG. In the same manner as the metric information section, each metric information section 82-1 to 82-82 in which a character code, widths and heights of characters and symbols, and metric data indicating a baseline are described respectively.
-N and these metrics information parts 82-1 to 82-n
Each of the compressed data sections 83-1 to 83-n arranged for each of the bit map sections 73-1 to 73-n shown in FIG. 7 is included in each of the compressed data sections 83-1 to 83-n. Each compressed data obtained by performing the compression process on each bitmap font stored in is stored.

[0006]

However, whichever of the above two conventional methods is used, when compressing a large number of bitmap fonts, the compression processing is performed for each bitmap font. Therefore, a memory having a storage capacity corresponding to the number of bitmap fonts is required. Therefore, it has been desired to further improve the compression efficiency and save the storage capacity of the memory.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a bitmap font compression device which can realize a better compression efficiency when performing compression processing on a large number of bitmap fonts.

[0008]

According to the present invention, the determining means determines whether or not each pattern indicated by a plurality of bitmap fonts is symmetrical, and the bitmap font string forming means performs the symmetry by the determining means. From the bitmap font showing the pattern determined to be, the portion that can reproduce the pattern is extracted based on the symmetry of the pattern, and the pattern determined to be not symmetric by the determination means is displayed. A bitmap font and a bitmap font string formed by arranging the portions extracted from the bitmap font indicating the pattern determined to be symmetric by the determination unit are formed, and the conversion unit compresses the bitmap font string. I am trying to convert it to data.

[0009]

According to the present invention, the bitmap font string forming means forms a bitmap font string indicating a non-symmetrical pattern and a bitmap font string formed by arranging portions extracted from the bitmap font indicating a symmetrical pattern. However, the converting means converts the bitmap font string into compressed data. Here, the compressed data obtained by performing the compression processing on the bitmap font indicating the symmetrical pattern and the compression processing on the portion extracted from the bitmap font indicating the symmetrical pattern. It can be said that the latter compressed data has a smaller data amount when compared with the compressed data obtained by. Further, rather than performing compression processing for each of a plurality of bitmap fonts, it is possible to perform compression with better efficiency by arranging these bitmap fonts and compressing each bitmap font at once. Therefore, the compressed data obtained by compressing the bitmap font string in the present invention has a smaller data amount than the compressed data obtained by performing the compression processing for each bitmap font as in the conventional case.

[0010]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a compression device according to the present invention. In the figure, the input device 1
The data of the format shown in Fig. 7 is input to
This data is read by the reading unit 2 and given to the arithmetic unit 3.

When the arithmetic unit 3 obtains the bitmap fonts of the bitmap units 73-1 to 73-n in the data, it successively determines whether or not the respective patterns indicated by these bitmap fonts are symmetrical. It is determined and the determination result for each bitmap font is given to the extraction unit 4 together with the data.

The extraction unit 4 extracts the left portion of the bitmap font determined to be left-right symmetric among the bitmap fonts, and determines that the left portion of the extracted bitmap font is not left-right symmetric. And the entire bitmap font are sequentially arranged to form a bitmap font string, and the bitmap font string is included in the header portion 71 and each metric information portion 72.
It is given to the compression unit 5 together with -1 to 72-n.

The compression unit 5 performs a compression process on the bitmap font string, and the compressed data obtained by the compression process is processed by the header unit 71 and the metrics information units 72-1 to 72-2.
Store in font storage memory 6 together with -n.

The processing for the bitmap font performed by the arithmetic unit 3, that is, the determination as to whether or not the bitmap font is bilaterally symmetrical is performed according to the flowchart shown in FIG.

First, when the arithmetic unit 3 obtains the bitmap font of the bitmap unit 73-1 in the data shown in FIG. 7, the line direction in the bitmap font,
That is, it is determined whether or not the number of bit arrays in the horizontal direction is divisible by 2 (step 101). Here, for example, the bitmap font of the bitmap portion 73-1 is as shown in FIG. 3, and the pixel matrix corresponding to this bitmap font is 16 pixels in the row direction and 16 pixels in the column direction as shown in FIG. If there are 16 pixels, the number "16" of bit arrays in the row direction in this bitmap font is 2
Since it is divisible by (step 101, YES), the process proceeds to the next step 103. If the number of bit arrays in the row direction in the bitmap font is not divisible by 2 (step 101, NO), the pattern indicated by this bitmap font is not symmetrical,
The flag indicating whether or not the bitmap font of the bitmap portion 73-1 is bilaterally symmetrical is set to a value "0" (step 102), and the processing is ended.

The number of bit arrays in the row direction in the bitmap font of the bitmap unit 73-1 is "16".
Can be divided by 2 and can be divided exactly into the left part and the right part (step 101, YES). Therefore, the variable x indicating the bit position in the row direction in the bitmap font is initialized to the value “0” and the bitmap font A variable y indicating a bit position in the column direction is initialized to the height of the bitmap font, that is, the number "16" of bit arrays in the column direction (step 103).

Next, the coordinate position I in the left part of the bitmap font is the coordinate position (the value of x, the height of the bitmap font is "16" -the value of y), that is, the coordinate position of the upper left corner of the bitmap font ( (0, 0) (step 104). In addition, the coordinate position r in the right part of the bitmap font is the coordinate position ((bitmap font width "16" -1) -x value, bitmap font height "16" -y value), that is, bit The coordinate position (15,0) in the upper right corner of the map font is set (step 105). That is, the coordinate position I and the coordinate position r respectively indicate the leftmost bit and the rightmost bit of the bit array of the first line in the bitmap font.

When the coordinate position I and the coordinate position r are obtained in this way, the coordinate position I in the bitmap font is calculated.
It is determined whether or not the value of the bit of 1 and the value of the bit of coordinate position r match (step 106). Here, as shown in FIG. 3, the bit value of the coordinate position I (0,0) is “0” and the bit value of the coordinate position r (15,0) is “0”. Since the values of 1 match (step 106, YES), the process proceeds to the next step 107. If the values at the coordinate positions do not match (step 106, NO), the pattern indicated by this bitmap font is not bilaterally symmetric, so the flag is set to "0" (step 102), and the process ends. ..

Next, it is determined whether or not the value of (x + 1) and the value of ((width of bitmap font "16" -1) -x) match (step 107). Here, (x
+1) is the value "1", ((width of bitmap font "16" -1) -x value) is the value "15", and the values do not match (step 107, NO), x Is updated to (x + 1) = 1 (step 108), and the process returns to step 104.

When the value of x is updated to "1", the coordinate position I obtained in the step 104 is the coordinate position (1 indicating the second bit from the left side of the bit array on the first line in the bitmap font (1 , 0), and the coordinate position r obtained in the step 105 is the coordinate position (1) that indicates the second bit from the right side of the bit array in the first row.
4,0). Then, it is determined whether or not the bit value of the coordinate position I (1,0) and the bit value of the coordinate position r (14,0) match (step 106), and the value of each coordinate position matches. Then, it is determined whether or not (x + 1) and ((value of bit map font width "16" -1) -x) match (step 107). If these values do not match, the value of x is updated to (x + 1) = 2 (step 108) and the process returns to step 104.

Thus, steps 104 to 10
Each time the process up to 8 is repeated, a pair of each bit value from the left side of the first line in the bitmap font and each bit value from the right side of the same line is selected, and a pair of each bit is selected. Confirm that the values of match. Then, when the value of the last bit on the left side (coordinate position I (7,0)) and the value of the last bit on the right side (coordinate position r (8,0)) in the first row match (step 106, YES). ),
(X + 1) = 8 and ((width of bitmap font "1
6 "-1) -x value) = 8 (step 107, YES), the process proceeds to the next step 109. That is, the value of each bit from the left side of the first row,
If it can be confirmed that each pair with the value of each bit from the right side of the same line all match, then the next step 1
Go to 09.

The first in the bitmap font
If even one pair of bit values from the left side of the line and bit values from the right side of the same line do not match (step 10
6, NO) and set the flag to the value "0" (step 1
02), and the process ends.

In step 109, x is set to the value "0" like the initial value, and y is set to the value "15" obtained by subtracting the value "1" from the initial value "16". Then, after confirming that the newly set value "15" of y is a positive integer (step 110, YES),
Returning to step 104 above.

After passing through each of the steps 109 and 110, the coordinate position I (value of x, height of bitmap font "16" -value of y) is the leftmost position of the second line in the bitmap font. Of the coordinate position r ((width of bitmap font "16" -1) -x, height of bitmap font "16" -y) (step 104). The value) is set to the rightmost coordinate position (15, 1) on the second line.

Subsequently, it is confirmed that the bit value of the coordinate position I (0,1) and the bit value of the coordinate position r (15,1) match (step 106, YES), and further (step 106). x + 1) and ((width of bitmap font “16”
-1) -value of x) does not match (step 107), after which the value of x is updated to (x + 1) = 1 (step 108), and the process returns from step 104.

By repeating the processing from step 104 in this manner, the value of each bit from the left side of the second line in the bitmap font and the value of each bit from the right side of the same line are selected one by one, It is sequentially confirmed that the values of each pair of bits match. Then, when the value of the last bit on the left side of the second row matches the value of the last bit on the right side (step 106, YES), (x + 1) = 8
And ((width of bitmap font "16" -1) -x
Value is equal to 8 (step 107, YES)
), The value of y is updated in each of the following steps 109 and 110, and after it is confirmed that the updated value of y is a positive integer, the process returns to step 104.

Similarly, for each row from the third row to the sixteenth row, a pair of a value of each bit from the left side and a value of each bit from the right side of the same row is selected, and 1 pair is selected. It is sequentially confirmed that the value of each bit of the pair matches. here,
The value of the last bit on the left side (coordinate position I (7,15)) and the value of the last bit on the right side (coordinate position r (8,15)) in the 16th row match (step 106, YES), and x +
1) = 8 and ((width of bitmap font “16” −
1) -value of x) = 8 (step 107,
YES), and in the next step 109, the value of y "0" is obtained. Then, when it is determined that the value "0" of y is not a positive integer (step 110, NO), it means that the processing from step 104 to step 108 has been completed for all the lines of the bitmap font. Therefore, the flag is set to the value "1" (step 111), and the process ends.

As described above, if it is possible to confirm that the value of each bit from the left side and the value of each bit from the right side are matched for each line in the bit map font of the bit map section 73-1. , The pattern shown by this bitmap font is symmetrical, in which case the flag is set to the value "1".

When the computing unit 3 determines that the pattern indicated by the bitmap font of the bitmap unit 73-1 is bilaterally symmetrical and sets the flag for this bitmap font to the value "1", this value "1" is set. The 1 "flag is written in the metrics information unit 72-1 corresponding to the bitmap unit 73-1.

Similarly, the arithmetic unit 3 sequentially determines whether the bitmap fonts of the bitmap units 73-2 to 73-n in the data shown in FIG. 7 are symmetrical or not, If the pattern indicated by the bitmap font in the bitmap portion is bilaterally symmetric, a flag of the value "1" is written in the metric information portion corresponding to the bitmap portion, and the pattern indicated by the bitmap font in the bitmap portion is changed. If it is not left-right symmetric, the value "0" is set in the metrics information part corresponding to the bitmap part
Write the flag of. When the computing unit 3 finishes the determination of the bitmap fonts of all the bitmap units, the header unit 71 and the metrics information units 72-1 in which the flags of the value "1" or the value "0" are written respectively.
-72-n and each metric information section 72-1 to 72-
-Each bit map unit 73-1 to 73- arranged for each n
n is given to the extraction unit 4.

The extraction unit 4 includes a header unit 71, metrics information units 72-1 to 72-n, and bitmap units 7.
3-1 to 73-n, the bitmap fonts of these bitmap portions are sequentially arranged to form a bitmap font string. When forming this bitmap font string, the extraction unit 4 uses each metric information unit 7
Check the value of each flag written in 2-1 to 72-n one by one, and the flag in the metrics information part has the value "1".
If so, the left half bitmap font portion is extracted from the bitmap font of the bitmap portion corresponding to the metric information portion, and this bitmap font portion is arranged in the bitmap font string. If the flag in the metrics information section has the value "0", the entire bitmap font of the bitmap section corresponding to the metrics information section is arranged in the bitmap font string. For example, if the flag in the metrics information section 72-1 has the value "1", the bitmap section 7 corresponding to this metrics information section
The left half bitmap font portion is extracted from the bitmap font 3-1 and this bitmap font portion is arranged in a bitmap font string. If the flag in the metrics information section 72-2 has the value "0", the bit map section 7 corresponding to this metrics information section.
Arrange the entire 3-2 bitmap font in the bitmap font string. In other words, if the pattern indicated by the bitmap font in the bitmap portion is bilaterally symmetric, the left half bitmap font portion is extracted from this bitmap font, and this bitmap font portion is arranged in the bitmap font string. .. If the pattern indicated by the bitmap font in the bitmap portion is not bilaterally symmetrical, the entire bitmap font is arranged in the bitmap font string.

The bitmap font string thus formed is as shown in FIG. 5, for example. In this bitmap font string, the left half bitmap font portion extracted from the bitmap font indicating the symmetrical character "A" is arranged first, and subsequently the non-symmetrical character "E" is indicated. The entire bitmap font is arranged, and further, the left half bitmap font portion extracted from the bitmap font indicating the character "H" which is symmetrical is arranged.
Similarly, for a bitmap font that shows a symmetrical pattern, only the left half bitmap font part extracted from the bitmap font is arranged.For a bitmap font that shows a pattern that is not symmetrical, the entire bitmap font. Are arranged.

The bitmap font string thus formed has a header portion 71 and each metric information portion 72-1.
~ 72-n are transmitted from the extraction unit 4 to the compression unit 5. The compression unit 5 performs a compression process on the bitmap font string to form compressed data. And
The compression unit 5 forms the storage data in the format shown in FIG. 6 including the compressed data, the header unit 71, and the metrics information units 72-1 to 72-n, and stores the storage data in the font storage memory 6. Store.

As the compression processing, a one-dimensional coding method for compressing the bit pattern for each row of the bitmap font string may be applied, or the bit pattern in the matrix direction of the bitmap font string may be compressed 2. A dimensional coding method may be applied and any method may be used.

As described above, in the present embodiment, it is determined for each of a plurality of bitmap fonts whether or not the pattern indicated by the bitmap font is bilaterally symmetrical, and the bitmap showing the pattern determined to be bilaterally symmetrical. Extract the left half bitmap font part from the font,
A bitmap font string is formed by sequentially arranging the extracted left half bitmap font part and the entire bitmap font that indicates a pattern that is determined not to be bilaterally symmetrical, and compresses this bitmap font string. The compressed data thus obtained is stored. Here, when comparing the compressed data obtained by compressing the entire bitmap font with the compressed data obtained by compressing the left half of the bitmap font, it is clear that the latter compressed data has a smaller data amount. Further, comparing the compression of a plurality of bitmap fonts separately and the compression of a bitmap font string formed by arranging a plurality of bitmap fonts at once,
Since the latter can perform more efficient compression, it is clear that the amount of compressed data obtained by compressing the bitmap font string at once is smaller. Therefore, compressing the bitmap font string in the present embodiment is to compress the data with good efficiency, and the amount of compressed data obtained by this is smaller than that in the conventional example. The memory capacity to be stored can be saved.

Although the left half of the bitmap font showing the symmetrical pattern is extracted in the above embodiment, the invention is not limited to this, and the bitmap font showing the symmetrical pattern is determined, Either the upper half or the lower half of the bitmap font may be extracted and the bitmap font portion may be arranged in the bitmap font string.

By the way, when reproducing each bitmap font based on the data of the format shown in FIG. 6 stored in the font storage memory 6, first, the compressed data is decoded to form a bitmap font string. ,
Bitmap fonts are reproduced one by one from the beginning of this bitmap font string. That is, the leading metric information 72-1 of each metric information section 72-1 to 72-n is selected, and a flag indicating whether or not it is bilaterally symmetric is read from this metric information section, and the flag has the value If it is 1 "and it indicates a symmetrical pattern, the bitmap font part corresponding to the left half of the bitmap font is cut out from the beginning of the bitmap font string, and the cut out bitmap font part is used. The right half pattern portion is generated from the left half pattern portion shown, and the entire bitmap font showing the original pattern is reproduced. Subsequently, the flag indicating whether or not it is bilaterally symmetric is read from the next metric information 72-2, and if the flag is a value “0” and it is not a bilaterally symmetric pattern, the entire bitmap font Is cut out from the bitmap font string and the entire bitmap font is played. Similarly, if the flag of the value "1" is described in the metrics information part, the bitmap font part is cut out from the bitmap font string and the entire bitmap font is reproduced based on the cut out bitmap font part. If the flag of the value "0" is described in the metrics information part, the entire bitmap font is cut out from the bitmap font string.

[0039]

As described above, according to the present invention, a bitmap font showing a non-symmetrical pattern and a bitmap font string in which parts extracted from a bitmap font showing a symmetrical pattern are arranged. Since it is formed and this bit map font string is converted into compressed data, it is possible to compress a large number of bit map fonts with good efficiency and convert into compressed data.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a compression device according to the present invention.

FIG. 2 is a flowchart used for explaining a process by an arithmetic unit in the embodiment apparatus shown in FIG.

FIG. 3 is a diagram showing an example of a bitmap font.

4 is a diagram showing a pixel matrix corresponding to the bitmap font shown in FIG.

5 is a diagram exemplifying a bitmap font string formed in the apparatus of the embodiment shown in FIG.

6 is a diagram showing a format of data stored in a font storage memory in the apparatus of the embodiment shown in FIG.

FIG. 7 is a diagram illustrating a format of data including a plurality of bitmap fonts.

8 is a diagram showing a data format obtained when the plurality of bitmap fonts shown in FIG. 7 are compressed by a conventional method.

[Explanation of symbols]

1 ... Input device, 2 ... Reading unit, 3 ... Calculation unit, 4 ... Extraction unit, 5 ... Compression unit, 6 ... Font storage memory.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 1/411 8839-5C

Claims (1)

Claim: What is claimed is: 1. A bitmap font compression apparatus for converting a plurality of bitmap fonts representing respective patterns into compressed data, wherein the respective patterns represented by the respective bitmap fonts are symmetrical. A determination unit that determines whether or not the pattern is determined, and a bitmap font that indicates the pattern that is determined to be symmetric by the determination unit extracts a portion that can reproduce the pattern based on the symmetry of the pattern. At the same time, a bitmap font showing a pattern which is determined not to be symmetric by the determining means, and a bitmap font in which the portions extracted from the bitmap font showing a pattern determined to be symmetric by the determining means are arranged. Bitmap font to form columns Stage and bitmap font compression apparatus characterized by comprising a conversion means for converting the bit map font string in the compressed data.