JP2833268B2 - Bitmap font compression device - Google Patents

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 representing a character into compressed data.

[0002]

2. Description of the Related Art A bitmap font is used to represent a pattern of characters, symbols, etc., and is formed by arranging a plurality of pixels each indicating one of "white" and "black" in a matrix direction. A plurality of bits ("1" and "0") corresponding to a pixel matrix and corresponding to each pixel of the pixel matrix.
Are shown in the matrix direction.

When such a bitmap font is stored, 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 storing a large number of bitmap fonts, compression processing is performed on these bitmap fonts, and the resulting compressed data is stored, thereby reducing the storage capacity of the memory. .

Conventionally, as a compression process of a bitmap font, it is general to sequentially compress a bit pattern for each row of one bitmap font. However, in order to further improve the compression efficiency, the bit pattern is compressed in both directions of a matrix. A method of compression has also been proposed (JP-A-60-176084).
Reference). Regardless of which of these methods is used, there is no difference in performing compression processing for each of a plurality of bitmap fonts, and each piece of compressed data corresponding to each bitmap font is generated.

Accordingly, if there is data in a format including a plurality of bitmap fonts as shown in FIG. 7, data in a format as shown in FIG. 8 is created as a result of performing compression processing on this data. Thus, the data shown in FIG. 8 is stored in the memory. Here, the data in the format shown in FIG. 7 includes a header section 71 for describing a font name, a font name, a copyright, a version number, etc., and a plurality of metrics information sections 72-.
1 to 72-n, and these metrics information sections 72-1 to 72-n
Each bitmap section 73-1 to 73-7 arranged for each 72-n
3-n. Each metric information section 72-1 to 72
In -n, a character code for identifying a character, a symbol, and the like, a width and a height of the character, the symbol, and the like, and metric data indicating a baseline are described. In -n, bitmap fonts such as characters and symbols indicated by the character codes described in the immediately preceding metrics information section are stored. On the other hand, the data in the format shown in FIG. 8 includes a header section 81 for describing a font name, a font name, a copyright, a version number, etc., as in the header section 71 shown in FIG. Each of the metric information sections 82-1 to 82-2 in which a character code, width and height of characters, symbols, and the like, and metric data indicating a baseline are described in the same manner as the metric information section.
-N and these metrics information sections 82-1 to 82-n
Each of the compressed data sections 83-1 to 83-n includes a corresponding one of the bit map sections 73-1 to 73-n shown in FIG. Each compressed data obtained by performing a compression process on each bitmap font stored in.

[0006]

However, no matter which of the above two conventional methods is used, when a large number of bitmap fonts are compressed, compression processing is performed for each bitmap font. Therefore, since a memory having a storage capacity corresponding to the number of bitmap fonts is required, it has been desired to further improve the compression efficiency and reduce the storage capacity of the memory.

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

[0008]

According to the present invention, it is determined by a determining means whether or not each pattern represented by a plurality of bitmap fonts is symmetrical. The bitmap font string forming means is symmetrical by the determining means. And extracting a portion that can reproduce the pattern based on the symmetry of the pattern from the bitmap font indicating the pattern determined to be, and indicating the pattern determined to be non-symmetric by the determination unit. A bitmap font string is formed by arranging the bitmap font and the portion extracted from the bitmap font indicating the pattern determined to be symmetric by the determination means, and the conversion means compresses the bitmap font string. It is converted to data.

[0009]

According to the present invention, the bitmap font string forming means forms a bitmap font string indicating an asymmetric pattern and a bitmap font string formed by arranging portions extracted from the bitmap font indicating a symmetric pattern. The conversion means converts the bitmap font string into compressed data. Here, compressed data obtained by performing compression processing on a bitmap font indicating a symmetric pattern, and compression processing on a portion extracted from the bitmap font indicating the symmetric pattern are performed. In comparison with the compressed data obtained by the above, it can be said that the latter compressed data has a smaller data amount. Also, rather than performing compression processing for each of a plurality of bitmap fonts, it is possible to perform compression with higher efficiency by arranging these bitmap fonts and compressing the bitmap fonts at once. Therefore, the amount of compressed data obtained by compressing the bitmap font sequence in the present invention is smaller than that of the conventional compressed data obtained by performing a compression process for each bitmap font.

[0010]

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

FIG. 1 is a block diagram showing an embodiment of a compression apparatus according to the present invention. In the figure, the input device 1
Is input with data in the format shown in FIG.
This data is read by the reading unit 2 and provided to the calculation unit 3.

When the arithmetic section 3 obtains the bitmap fonts of the bitmap sections 73-1 to 73-n in the data, it sequentially determines whether or not each pattern indicated by these bitmap fonts is symmetrical. Judgment is made, and the judgment result for each bitmap font is provided to the extraction unit 4 together with the data.

The extraction unit 4 extracts the left part of the bitmap font determined to be symmetrical among the bitmap fonts, and determines that the left part of the extracted bitmap font is not symmetrical to the left part. The entire bitmap font is sequentially arranged to form a bitmap font row, and this bitmap font row is stored in the header section 71 and each metric information section 72 included in the data.
This is given to the compression unit 5 together with -1 to 72-n.

The compression section 5 performs a compression process on the bitmap font sequence, and compresses the obtained compressed data into a header section 71 and metrics information sections 72-1 to 72-1.
-N is stored in the font storage memory 6 together with -n.

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

First, the arithmetic section 3 obtains the bitmap font of the bitmap section 73-1 in the data shown in FIG.
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 section 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 the column direction as shown in FIG. Assuming that there are 16 pixels, the number “16” of bit arrays in the row direction in this bitmap font is 2
(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 in the bitmap section 73-1 is symmetric is set to a value of "0" (step 102), and the process ends.

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

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

When the coordinate position I and the coordinate position r are obtained in this manner, the coordinate position I in the bitmap font is obtained.
It is determined whether or not the value of the bit of the coordinate position r matches the value of the bit at the coordinate position r (step 106). Here, as shown in FIG. 3, the bit value of the coordinate position I (0,0) is “0”, the bit value of the coordinate position r (15,0) is “0”, and (Step 106, YES), the process proceeds to the next step 107. If the value of each coordinate position does not match (step, 106, NO), the pattern indicated by this bitmap font is not symmetrical, so the flag is set to a value of "0" (step 102), and the process is terminated. .

Next, it is determined whether or not the value of (x + 1) is equal to ((the value of bitmap font width "16" -1) -x) (step 107). Here, (x
+1) is the value “1”, and ((the value of the bitmap font width “16” −1) −x) is the value “15”, and the values do not match (step 107, NO). 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 step 104 is the coordinate position (1) indicating the second bit from the left of the bit array on the first line in the bitmap font. , 0), and the coordinate position r obtained in step 105 is the coordinate position (1) indicating 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 value of the bit at the coordinate position I (1, 0) matches the value of the bit at the coordinate position r (14, 0) (step 106). Then, it is determined whether or not (x + 1) matches ((the value of the width “16” -1) −x of the bitmap font) (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 processing up to 8 is repeated, a pair of the value of each bit from the left side of the first row and the value of each bit from the right side of the same row in the bitmap font are selected, and one pair of each bit Are checked sequentially. Then, when the value of the last bit on the left side (coordinate position I (7, 0)) of the first row matches the value of the last bit on the right side (coordinate position r (8, 0)) (step 106, YES) ),
(X + 1) = 8 and ((bitmap font width “1
6 "-1) -x) = 8 (step 107, YES), so that the process proceeds to the next step 109. That is, the value of each bit from the left side of the first row and
If it is possible to confirm that each pair of values of each bit from the right side of the same row all match, the next step 1
Go to 09.

It should be noted that the first in the bitmap font
If the value of the bit from the left side of the row and the value of the bit from the right side of the same row do not match even at least one pair (step 10)
6, NO), and set the flag to the value “0” (step 1).
02), the process ends.

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

After the steps 109 and 110, the coordinate position I (the value of x, the value of the height “16” -y of the bitmap font) is changed to the leftmost position in the second line of the bitmap font. (Step 104), the value of the coordinate position r ((the width of the bitmap font "16" -1) -x, the height of the bitmap font "16" -y Value) is set to the rightmost coordinate position (15, 1) in the second row.

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

By repeating the processing from step 104 in this way, a pair of the value of each bit from the left side of the second row and the value of each bit from the right side of the same row in the bitmap font are selected, It is sequentially confirmed that the values of a pair of bits match. If 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
Is equal to 8 (step 107, YES).
), The value of y is updated in the following steps 109 and 110, and after confirming 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 the value of each bit from the left side and the value of each bit from the right side of the same row are selected, and 1 It is sequentially confirmed that the values of each bit of the pair match. here,
The value of the last bit on the left side (coordinate position I (7, 15)) of the 16th row matches the value of the last bit on the right side (coordinate position r (8, 15)) (step 106, YES), ( x +
1) = 8, and (((width of bitmap font “16”) −
1) -x) = 8 (step 107,
YES), the value "0" of y is obtained in the next step 109. If it is determined that the value “0” of y is not a positive integer (step 110, NO), 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 processing is terminated.

As described above, if it can be confirmed that a pair of the value of each bit from the left and the value of each bit from the right coincide with each other in each line in the bitmap font of the bitmap section 73-1. The pattern indicated by this bitmap font is bilaterally symmetric, in which case the flag is set to the value "1".

When the arithmetic unit 3 determines that the pattern indicated by the bitmap font in the bitmap unit 73-1 is symmetric, and sets the flag for this bitmap font to a value "1", the value "1" The flag “1” is written in the metrics information section 72-1 corresponding to the bit map section 73-1.

Similarly, the arithmetic unit 3 sequentially determines whether or not the bitmap fonts of the bitmap units 73-2 to 73-n in the data shown in FIG. 7 are bilaterally symmetric. If the pattern indicated by the bitmap font in the bitmap section is bilaterally symmetric, a flag having a value “1” is written in the metric information section corresponding to the bitmap section, and the pattern indicated by the bitmap font in the bitmap section is changed. If it is not symmetric, the value “0” is stored in the metrics information section corresponding to the bitmap section.
Write the flag. When the calculation unit 3 completes the determination on the bitmap fonts of all the bitmap units, the header unit 71 and each of the metrics information units 72-1 in which the flag of the value “1” or “0” is written, respectively.
To 72-n and each metric information section 72-1 to 72-72
−n bit map units 73-1 to 73-
n is given to the extraction unit 4.

The extraction section 4 includes a header section 71, respective metric information sections 72-1 to 72-n, and a respective bit map section 7.
Given 3-1 to 73-n, the bitmap fonts of these bitmap sections are sequentially arranged to form a bitmap font sequence. When forming this bitmap font string, the extraction unit 4 uses each metric information unit 7
The value of each flag written in 2-1 to 72-n is sequentially checked, and the flag in the metrics information part is set to the value “1”.
If so, the left half bitmap font portion is extracted from the bitmap font of the bitmap portion corresponding to the metrics information portion, and this bitmap font portion is arranged in a bitmap font sequence. If the flag in the metric information section is a value “0”, the entire bitmap font of the bitmap section corresponding to the metric information section is arranged in a bitmap font sequence. For example, if the flag in the metric information section 72-1 is “1”, the bitmap section 7 corresponding to this metric information section
The left half bitmap font portion is extracted from the bitmap font 3-1 and the bitmap font portion is arranged in a bitmap font row. If the flag in the metrics information section 72-2 is “0”, the bitmap section 7 corresponding to this metrics information section
The entire bitmap font of 3-2 is arranged in a bitmap font row. That is, if the pattern indicated by the bitmap font in the bitmap portion is symmetrical, the left half bitmap font portion is extracted from this bitmap font, and this bitmap font portion is arranged in a bitmap font column. . If the pattern indicated by the bitmap font in the bitmap section is not symmetric, the entire bitmap font is arranged in a bitmap font row.

The bitmap font string thus formed is as shown in FIG. 5, for example. In this bitmap font sequence, the left half of the bitmap font portion extracted from the bitmap font indicating the symmetrical character "A" is arranged first, followed by the non-symmetrical character "E". The entire bitmap font is arranged, and subsequently, the left half bitmap font portion extracted from the bitmap font indicating the character “H” that is symmetrical left and right is arranged.
Similarly, for a bitmap font indicating a symmetric pattern, only the left half bitmap font portion extracted from the bitmap font is arranged, and for a bitmap font indicating a non-symmetric pattern, the entire bitmap font is displayed. Are arranged.

The bitmap font string formed in this manner is stored in the header section 71 and each metric information section 72-1.
Are transmitted from the extraction unit 4 to the compression unit 5 together with .about.72-n. The compression unit 5 performs compression processing on the bitmap font sequence, thereby forming compressed data. And
The compression section 5 forms storage data in a format as shown in FIG. 6 comprising compressed data, a header section 71 and each of the metrics information sections 72-1 to 72-n, and stores the storage data in the font storage memory 6. Store.

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

As described above, in this embodiment, for each of a plurality of bitmap fonts, it is determined whether the pattern indicated by the bitmap font is symmetrical, and the bitmap indicating the pattern determined to be symmetrical is determined. Extract the left half bitmap font part from the font,
A bitmap font sequence is formed by sequentially arranging the extracted bitmap font portion of the left half and the entire bitmap font indicating a pattern determined to be not symmetrical, and compression processing is performed on the bitmap font sequence. And stores the resulting compressed data. 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. In addition, comparing the compression of a plurality of bitmap fonts separately with the compression of a bitmap font sequence formed by arranging a plurality of bitmap fonts at one time,
Since the latter can perform compression without waste, it is clear that the amount of compressed data obtained by compressing the bitmap font sequence at one time is small. Therefore, compressing the bitmap font sequence 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 of the conventional example. The capacity of the memory for storage can be reduced.

In the above embodiment, the left half of the bitmap font indicating a symmetric pattern is extracted. However, the present invention is not limited to this, and a bitmap font indicating a vertically symmetric pattern is determined. Either half of the upper and lower sides of the bitmap font may be extracted, and the bitmap font portion may be arranged in a bitmap font row.

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 sequence. ,
The bitmap fonts are reproduced one by one from the beginning of the bitmap font sequence. That is, the metric information section 72-1 at the head of the metric information sections 72-1 to 72-n is selected, a flag indicating whether the metric information section is symmetrical is read from the metric information section, and the flag is set to the value " If it is 1 "and indicates a symmetrical pattern, a bitmap font portion corresponding to the left half of the bitmap font is cut out from the beginning of the bitmap font row, and 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, a flag indicating whether or not the pattern is symmetrical is read from the next metrics information 72-2. If the flag is “0” and indicates that the pattern is not a symmetrical pattern, the entire bitmap font is read. Is extracted from the bitmap font sequence, and the entire bitmap font is reproduced. Similarly, if the flag of value “1” is described in the metrics information section, the bitmap font portion is cut out from the bitmap font sequence, and the entire bitmap font is reproduced based on the cutout bitmap font portion. If the flag of value "0" is described in the metrics information section, the entire bitmap font is cut out from the bitmap font sequence.

[0039]

As described above, according to the present invention, a bitmap font string indicating an unsymmetrical pattern and a bitmap font string formed by arranging portions extracted from the bitmap font indicating a symmetrical pattern are formed. Since the bitmap font string is formed and converted into compressed data, a large number of bitmap fonts can be compressed with good efficiency and converted into compressed data.

[Brief description of the 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 to explain processing by a calculation unit in the embodiment apparatus shown in FIG. 1;

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

FIG. 4 is a view showing a pixel matrix corresponding to the bitmap font shown in FIG. 3;

FIG. 5 is a view exemplifying a bitmap font string formed in the embodiment apparatus shown in FIG. 1;

FIG. 6 is a view showing a format of data stored in a font storage memory in the apparatus of the embodiment shown in FIG. 1;

FIG. 7 is a view exemplifying a format of data including a plurality of bitmap fonts.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input device, 2 ... Read part, 3 ... Operation part, 4 ... Extraction part, 5 ... Compression part, 6 ... Font storage memory.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06T 1/00 G06T 9/00-9/40 H04N 1/411-1/419 G09G 5/24 B41J 2/485

Claims (1)

(57) [Claims] 1. A bitmap font compression apparatus for converting a plurality of bitmap fonts indicating respective patterns into compressed data, wherein it is determined whether or not each pattern indicated by each of the bitmap fonts is symmetric. Judging means, and extracting, from the bitmap font indicating the pattern determined to be symmetric by the judging means, a portion capable of reproducing the pattern based on the symmetry of the pattern, A bitmap font indicating a pattern determined to be not symmetrical, and a bitmap forming a bitmap font sequence formed by arranging the portions extracted from the bitmap font indicating the pattern determined to be symmetrical by the determination means Font string forming means, and the bit Bitmap fonts compression apparatus characterized by comprising a conversion means for converting the Ppufonto column to compressed data.