JPH0546148A - Image output device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an image output device in which the amount of memory used for outline font data is reduced. [Structure] Control for compressing outline font data and storing the compressed font memory 206 in the compressed font memory 206, and restoring the compressed data stored in the compressed font memory 206 using an encoding method for output. The section 200 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output device, and more particularly to an image output device having a reduced amount of memory for storing outline font data.

[0002]

2. Description of the Related Art With respect to data compression in the image field, standardization of the ADCT method and the like is in progress. However, regarding outline fonts, there is a method to reduce the memory capacity by limiting the control points at the stage of creating the character itself, but it is not possible to compress the existing font data and effectively use the memory. Not done. Meanwhile, Japanese desktop publishing (DTP)
-There are some problems to be solved in constructing the system, one of which is the font capacity. In desktop publishing, it is essential to be able to handle many typefaces and fonts of character size. A font that satisfies this condition is an outline font, and the features of this outline font are as follows. When paying attention to the character size, the data capacity is smaller than that of bitmap fonts. You can perform scaling, rotation, etc. while maintaining the character quality.

[0003]

However, although the outline font has a small data capacity as described above, it is about 8 in the JIS 1st and 2nd level of Japanese 1 typeface.
The data of 000 characters becomes enormous. For example, when the font is composed of Beze curves, as shown in FIG. 8, a start point S, an end point E,
One curve is generated with a total of four control points C1 and C2 (hereinafter, these four points are simply referred to as control points). Therefore, in complicated kanji, these points cause an increase in capacity, and one typeface requires about 7 Mbytes. Since it is not easy to store all the font data in the memory in this way, when considering a system, a number of typefaces are built in via ROM, and the other means are held by a hard disk drive or the like. ..

Therefore, an object of the present invention is to provide an image output apparatus in which the capacity of outline font data is reduced by compressing the existing outline font data in advance and the load on the system is reduced. The purpose is to

[0005]

According to a first aspect of the present invention, outline font data is compressed and stored in a compressed font memory, and the compressed data stored in the compressed font memory is encoded. It is configured to include a control unit that controls to restore and output by using.

[0006]

According to the image output device of the present invention, the outline font data is compressed, for example, by calculating the difference between the coordinates of the outline font data and the preceding control point in character units, and the compressed data is stored in the compressed font memory. To do. Then, in the case of restoration, the original font is restored by using the encoding method and output from the printer.

[0007]

Embodiments of the image output apparatus of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows a system block diagram of an embodiment of the present invention. As shown in FIG. 1, a CPU 200 that controls the system is connected to a system bus 201. System bus 20
A ROM 202 in which a program is stored and a RAM 203 for temporarily storing processing data are connected to 1.
Further, the system bus 201 reads data from an interface 204 for connecting to a personal computer or the like and a compressed font memory 206 for storing compressed font data (data created externally in advance) and compresses the data. A restore circuit 205 for restoring the created data, a font cache 207 for efficiently reusing the once output data, and a page memory 208 for storing the expanded image for output to the printer 209. Are connected. If the restoration speed is not high, the restoration circuit 205 may have a RAM as a buffer.

Next, the outline of the processing of the system will be described. This system is usually used with an external personal computer. Send characters and commands that you want to output from the personal computer to this system. The sent data is received by the CPU 200 via the interface 204, and the ROM 20
The received data is translated by the program stored in 2. The font cache 207 is first accessed based on the translated data. So far, it is searched whether the same data as the output data exists in the font cache 207, and if it exists, the restoration circuit 205.
The data is directly sent to the page memory 208 without passing through. If it does not exist, a restore command is issued to the restore circuit 205. After that, the decompression circuit 205 causes the compressed font memory 2 to
Access 06 to execute restoration. The restored data is raster-converted from outline font data as in a general PDL printer, and is sequentially calculated into scanline-processable data.

Since the page memory 208 has a memory capacity depending on the printer performance (resolution), it must be finally converted into a bitmap image. However, even if a character up to a certain size is held in a bitmap, the memory will not be tight, but if it exceeds a certain threshold, it will be held in the state data of the previous stage of the bitmap image. Alternatively, it is more efficient not to cache. However, since the cache memory is finite, the amount of information to be stored is naturally limited.
Therefore, it is necessary to delete old data when it is cacheable. Thus, by using the font cache 207, high-speed expansion is possible. Then, the data is written to the page memory 208 and overwritten until a page break command arrives,
It is output by the printer 209 in response to a page break command.

Next, an example of control points is shown in FIG. In this figure, a part of the data of hiragana "tsu" is extracted (originally, it is a closed curve, but it is omitted for clarity. The illustrated example is regarded as one letter "tsu"). ● in the figure indicates the start point or end point,
The circles represent control points and consist of three types of Beze curves. An approximate value I0 in the section of the symbols S0 to E0 is obtained from the following equation (1). I0 (x, y) = S0 (x, y) (1-t) 3 + 3C10 (x, y) (1-t) 2 t + 3C2 0 (x, y) (1-t) t 2 + E0 (x, y ) t ³ (1) However, 0 ≦ t ≦ 1.

[1] Method for holding difference data of previous control point Method using one character as a reference From FIG. 2 (A), the point S0 is considered as the base point, and the coordinate of the next point C10 is the difference from the base point. This is the method of taking the data and then taking the difference from the coordinates of the previous point. This is done for each character. D0 = C10 (x, y) -S0 (x, y) (2) D1 = C20 (x, y) -C10 (x, y) ..Dn = E3 (x, y) -C23 (x, y) )

A flow chart of this compression process is shown in FIG. In this flowchart, the end of the control point is determined using the character code. Here, the character code is an index assigned to each character. For example, in the font dictionary, a structure such as Mincho type index-character index Gothic type index-character index is used. First, an index indicating which font is used is searched, and then there is desired character data. You can use this code to go through the steps of finding a place. Further, for example, when data representing the data length is stored in the character code part, the final control point may be determined based on the data. The table below the flow chart represents one example of a compressed font data format.

Further, the differential data obtained by the above-mentioned flow chart is compressed using an encoding method capable of restoring, for example, Huffman code. Here, as a range handled by the Huffman coding, coding is performed over a wide range such as one font unit in addition to each character as shown in the figure, or coding within a range grouped in one font. Conceivable. When restoring the above-mentioned compressed data, reverse processing of each compression process may be performed. For example, in the case shown in FIG. 3, “previous coordinate + difference” can be sequentially and repeatedly obtained.

Method based on multi-points of one character This is a method of taking the difference from the coordinates of the previous point by regarding the start point as the base point and the end point as one block in one character. This is done for each character. D0 = C10 (x, y) -S0 (x, y) (3) D1 = C20 (x, y) -C10 (x, y) D2 = E0 (x, y) -C20 (x, y) A flow chart in that case is shown in FIG. In the case of complicated Kanji characters, there is also a method of expanding the block and dividing one character into blocks as shown in FIG.

[2] Averaging Offset Method The font data has coordinates of outline data defined within its frame with a fixed vertical and horizontal size as a reference so that it can be easily handled by the PDL source program. Based on the data in this frame, it is possible to perform transformation by performing matrix calculation such as scaling for each coordinate. Therefore, since the default frame size is known, it is divided into vertical and horizontal M × N. In this example, it is 11 × 11. Although not shown in FIG. 5 (A), there are many control points forming “A” in the frame. Therefore, in the case of vertical Y × horizontal X = 11 × 11, statistics of which block the control point belongs to are taken for each XY direction. As a result, the deviation of the coordinate distribution can be known.

Now, assume that the coordinate distribution of all 11 blocks in the X direction is as shown in FIG. 5 (B). Here, as shown in FIG. 5A, the representative coordinates of each block are 1 point.
(Corresponding to the center of the block in this example). Therefore, the average coordinates are calculated from the representative coordinates of each block and their frequencies. The representative coordinates of the block located at the i-th row and the j-th column are xi, y
When j and the frequencies are pi and pj, the average coordinates of X and Y can be obtained by the following equations (4) and (5). xi = (Σxi p i) / Σ p i (4) yj = (Σ yj pj) / Σp j (5) However, the addition range by Σ in the formula (4) is from i = 1 to N, and in the formula (5) The addition range by Ote Σ is j
= 1 to M. The difference between this average coordinate and each control point is taken. A flowchart in this case is shown in FIG. An example of the compressed font data format is the same as in the case of FIG.

[3] Maximum frequency offset method This method is similar to the case of the averaging offset method of [2] above, and is a method of obtaining the difference between the coordinate having the maximum frequency in the i-th row and the j-th column and each control point. A flow chart in this case is shown in FIG. An example of the compressed font data format is the same as in the case of FIG. According to the method described above, data can be compressed and stored, and the stored data can be restored and output.

In FIG. 1, if the reference numeral 207 is replaced with a cache, the reference numeral 208 is replaced with a video RAM, and the reference numeral 209 is replaced with a display, a general computer configuration can be obtained, and it can be understood that it can be used on a CRT. Code 2
The decompression circuit 05 may be composed of dedicated hardware or may be replaced by application software of a computer.

[0019]

As described above, according to the present invention, outline font data is compressed and stored, and the stored data is restored using the encoding method.
It is possible to increase the amount of fonts installed in the limited memory. Therefore, the required fonts can be provided in a small memory space, which enables cost reduction and system miniaturization.

[Brief description of drawings]

FIG. 1 is a system block diagram to which the present invention is applied.

2A is a diagram showing an example of control points used in the present invention, FIG.
(B) is a diagram showing an example of block division when the present invention is applied to Chinese characters.

FIG. 3 is a flowchart of a method for holding difference data of previous control points according to the embodiment of this invention.

FIG. 4 is a flowchart of another method for holding difference data of previous control points according to the embodiment of this invention.

5A is a diagram showing an example of an averaging offset method according to an embodiment of the present invention, and FIG. 5B is a diagram showing an example of blocks and frequencies of the averaging offset method.

FIG. 6 is a flowchart of the averaging offset method.

FIG. 7 is a flowchart of the maximum frequency offset method according to the embodiment of this invention.

FIG. 8 is a diagram illustrating an example of conventional control points.

[Explanation of symbols]

 200 CPU (control unit) 205 Decompression circuit 206 Compressed font memory 207 Font cache 209 Printer

Claims (4)

[Claims] 1. A control for controlling outline font data to be compressed and stored in a compressed font memory, and the compressed data stored in the compressed font memory being decompressed and output using an encoding method. An image output device comprising a section. 2. The method for compressing the outline font data is characterized in that the difference in coordinates from the previous control point is calculated in units of one character or by dividing one character. Image output device. 3. A method of compressing outline font data, wherein unit coordinates forming an outline font are vertically and horizontally divided by M × N, and the frequency of control points within the divided range is calculated, The average value is calculated from the coordinates representing the.
The image output device described. 4. A method of compressing the outline font data, wherein unit coordinates forming an outline font are vertically and horizontally divided by M × N, and the frequency of control points within the divided range and the range are represented. The image output apparatus according to claim 1, wherein the coordinate to be obtained is calculated and the range having the maximum frequency is calculated.