JPH08216462A - Printer and its control - Google Patents

Abstract

PURPOSE: To restrain the capacity of a memory occupied by bit-mapped information by providing a comparison process for comparing compression efficiency by the first compression process and compression efficiency by the second compression process. CONSTITUTION: Bit-mapped data are inputted from an external device and developed to a bit-map (S101). The data developed to the bit-map are read from a RAM part, and the bit-mapped data read with an image data converting circuit are compressed (S102). The data compressed once are stored in the RAM part again to send the attribute information of the compressed data to the comparison circuit. The data stored once are read from the RAM part and compressed, and the attribute information of the data compressed twice are sent to the comparison circuit (S102, S103). Based on the attribute which the comparison circuit receives, the comparison of compression ratio to an original image is carried out (S104).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus for receiving print information and printing, and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, as a device for receiving code data from an external device and developing the data in a memory according to the code data, a scalable font is previously developed in the memory in order to increase the printing speed of a printer. The information is stored as a bitmap font in and can be used as a font cache.

[0003]

However, in such a device, since the font information is expanded into the bitmap information, the range of the memory used as the font cache is widened and it is used in other work. In addition to limiting the range of memory to be used, the price of the device itself will be increased by adding more memory.

The present invention has been made in view of the above conventional example, and an object of the present invention is to provide a print control apparatus and method for suppressing the capacity of the memory occupied by the bitmap information and efficiently using the memory. To do.

[0005]

In order to achieve the above object, a printing apparatus and a control method thereof according to the present invention have the following constitution. That is, it is a print control method of storing binary data and printing out based on the binary data. A first compression step of compressing and storing the binary data and a second compression step performed by the first compression step. A second compression step of further compressing the value data, a comparison step of comparing the compression efficiency of the first compression step with the compression efficiency of the second compression step, and the result of the comparison by the comparison step. If the compression efficiency in the second compression step is high, the binary data obtained in the second compression step is stored, and the stored binary data is repeated from the second compression step.

The print control method of the present invention has the following configuration. That is, a printing apparatus that stores binary data and prints out based on the binary data, and includes a first compression unit that compresses and stores the binary data, and a binary value compressed by the first compression unit. A second compression means for further compressing the data, a comparison means for comparing the compression efficiency by the first compression means with the compression efficiency by the second compression means, and a result of the comparison by the comparison means, If the compression efficiency of the second compression means is high, the binary data obtained by the second compression means is stored, and the binary data is further controlled by the first compression means. .

[0007]

With the above structure, the data can be compressed most efficiently by further compressing the compressed data until the compression efficiency is not improved.

[0008]

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

FIG. 3 is a diagram showing a printing system to which the printer of this embodiment is applied.

In the drawing, reference numeral 3 denotes a printer, which inputs data from various external devices such as a host computer and executes recording on a recording medium.

In this embodiment, a laser beam printer is used as the printer 3. The configuration of the laser beam printer to which this embodiment is applied will be described below with reference to FIG.

FIG. 3 is a sectional view showing the internal structure of the printer 3 of this embodiment. The printer 3 can register a character pattern from a data source (not shown).

In FIG. 3, 3 is a printer main body,
Input and store print information (character code etc.) and form information or macro command etc. supplied from the externally connected host computer, and create corresponding character patterns and form patterns according to those information, An image is formed on a recording paper which is a recording medium.

Reference numeral 300 is a switch for various operations and L
An operation panel 301 provided with an ED display and the like is a printer control unit 301 for performing overall control of the printer 3 and analyzing character information supplied from a host computer or the like.

The printer control unit 301 mainly converts character information into a video signal of a corresponding character pattern and outputs it to the laser driver 302.

The laser driver 302 is a semiconductor laser 30.
3 is a circuit for driving the laser beam 3, and the laser beam 3 emitted from the semiconductor laser 303 in accordance with the input video signal.
Switch 04 on / off.

The laser beam 304 is deflected in the left-right direction by the rotary polygon mirror 305, and an electrostatic latent image of a character pattern is formed on the electrostatic drum 306. The latent image is formed on the developing unit 307 arranged around the electrostatic drum 306.
After development by, use a cut sheet for recording paper,
The cut sheet recording paper is stored in the paper cassette 308 attached to the LBP 3, and the paper feed roller 309 and the transport roller 3
It is taken into the apparatus by 10 and 311 and supplied to the electrostatic drum 306.

FIG. 1 is a block diagram showing the detailed arrangement of the printer control unit 301 in the printer 3 described above. In the figure, 101 is an interface unit (I /
F), in which code data and image data are input from an external device (host computer 102, image scanner, etc.). A CPU 102 controls the entire printer. An interface unit (I / F unit) 103 communicates with the recording unit 110. A page buffer memory 104 stores print data for one page sent from the host computer.

Reference numeral 105 denotes a work buffer memory, which is C
It provides a work area required when the PU 102 executes various controls. A frame buffer memory 106 stores image data obtained by expanding the code data included in the print data, image data input from the image scanner, and the like. Reference numeral 112 is a memory area for the font cache. The page buffer memory 104, the work buffer memory 105, the frame buffer memory 106, and the font cache memory 112 are each composed of RAM.

Reference numeral 107 denotes a firmware memory, which is the CPU 1
02 stores various control programs (firmware) executed. Reference numeral 108 denotes a font memory, which stores various font data for developing an image of code data. The firmware memory 107 and the font memory 108 are each composed of a ROM.

A memory control unit 109 transfers image data obtained by expanding the code data and image data input from the image scanner to the frame buffer memory 106 for storage and stores the image data as a video signal. In order to output, the reading control is performed rather than the frame buffer memory 106. A recording unit 110 forms an image on a recording sheet according to the video signal input through the I / F unit 103 by the above laser beam method.

Next, the operation of this embodiment will be described with reference to the flowchart 1 of FIG.

First, in step S101, bitmap data is input from an external device or font information is read from the font memory 108 and developed into a bitmap.

In step S102, the data expanded in the bit map is read from the RAM section, the read bit map data is compressed using the image data conversion circuit 111 of FIG. # 1)
Is stored again in the RAM section and attribute information including the size or compression rate of the compressed data is sent to the comparison circuit 202.

Next, in step S103, step S
The data # 1 once stored at 102 is read from the RAM section and further compressed, and the data compressed twice (data # 1
2) is created and the attribute information is sent to the comparison circuit 202.

In step S104, the comparison circuit 2
02 compares the compression rate (called compression efficiency) with respect to the original image based on the attribute information received in steps S102 and S103. If the compression efficiency of the compressed data # 2 is high, the compressed circuit 201 rewrites the compressed data # 1 stored in the RAM section into the compressed data # 2 from step S106, and the process returns to step S103 again. When the data is stored in the RAM unit in step S106, information indicating how many times the data has been compressed is also stored.

From step S103, the original data is replaced with the data # 1 and the data # 1 is replaced with the data # 2, and the above-described processing is performed.

In this way, the compressed data #n is compressed to create the compressed data # (n + 1), the compressed data 1 and the compressed data 2 are compared, and this operation is repeated as long as the compression efficiency is improved. In FIG. 4, the original data is represented as data # 0.

In step S105, the compressed data #n
If the compression efficiency is high, the compressed data #n stored in the RAM section immediately before is stored as the compressed data as it is.

On the contrary, when the compressed data stored in the RAM section is expanded into a bitmap, the expansion circuit 203
As a result, the compressed data is expanded a number of times corresponding to the number of times of compression added to the compressed data and written in the frame memory 106.

In step S105, the compressed data amounts themselves may be compared. <Example of compression procedure> Here, steps S102 and S in FIG.
An example of data compression performed in 103 will be described. FIG. 5 is a diagram showing a compression method.

FIG. 5A is an example of a binary image, in which white squares are white pixels and black squares are black pixels. It is assumed that this black rectangular area continues from the upper area that is not drawn. FIG. 5B is data obtained by compressing the image of FIG. 5A, and includes three types of values A, B, and C that are determined for each line of the original image. Value A
Is a value obtained by comparing the target line with the immediately preceding line and changing the number of edges which are boundaries between pixels of different colors. In Figure 5, the number of edges is 2 for all lines.
Therefore, there is no change and all the values A are 0.
Further, the value B is the amount of movement of the left side edge compared to the immediately preceding line, and the value C is the amount of movement of the right side edge (the number of edges is an even number in terms of its character, and can be defined in this way) . In FIG. 5, since neither edge has moved, both the values B and C are 0. Although not shown here, the leading line can be coded by a method such as showing the position of the edge with a code. Therefore, the data obtained by compressing the image of FIG. 5A includes the code indicating the edge position of the leading line and the data of FIG.
It is a sequence of 0s obtained by encoding the second and subsequent lines as shown in (b).

FIG. 5 (c) shows a part of the data obtained by one compression, which is a rearranged version of FIG. 5 (b). The data obtained as a result of the compression is binary data and can be compressed in the same manner as the bitmap data of the image. In FIG. 5C, if 0 is regarded as a white pixel, the same method as shown in FIGS. 5A and 5B is used.
It can be compressed as in (d). Although not shown in the drawing, as described above, in this case, the leading line indicates the edge position, so that all are not 0.
If (c) is all white pixels and there is no edge, the values B and C indicating the movement of the edge are unnecessary, and the compression efficiency can be further improved. Of course, the data shown in FIG. 5D can be further compressed.

As described above, depending on the compression method and the image data to be compressed, the compression rate for the original image can be increased by repeating the compression. Therefore, it is extremely effective to perform the compression in the procedure of FIG. is there.

As described above, since the image data compressed at a high compression rate is stored in the RAM section, the memory can be used more effectively than when the bitmap data is stored as it is.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0037]

As described above, the printing apparatus and the control method thereof according to the present invention have the effects of increasing the data compression efficiency and effectively using the internal memory.

[0038]

[Brief description of drawings]

FIG. 1 is a block diagram of a printer of this embodiment.

FIG. 2 is a block diagram of an image data conversion circuit in the printer of this embodiment.

FIG. 3 is a cross-sectional view showing the internal structure of the printer of this embodiment.

FIG. 4 is a flowchart of a bitmap data storage procedure by the printer of this embodiment.

FIG. 5 is a diagram showing a difference in compression rate due to double compression.

[Explanation of symbols]

 101 I / F section 102 CPU 103 I / F section 104 Page buffer 105 Work buffer 106 Frame memory 107 Firmware memory 108 Font memory 109 Control section 110 Recording section 111 Image data conversion circuit 112 Font cache memory

Claims (4)

[Claims] 1. A print control method for storing binary data and printing out based on the binary data, comprising a first compression step of compressing and storing the binary data, and compression by the first compression step. A second compression step of further compressing the binary data obtained, and a comparison step of comparing the compression efficiency of the first compression step with the compression efficiency of the second compression step. As a result of the comparison, if the compression efficiency in the second compression step is high, the binary data obtained in the second compression step is stored, and the stored binary data is repeated from the second compression step. A printing control method characterized by the above. 2. The first and second compression steps divide the binary data into a predetermined size and perform compression based on a difference between data in adjacent divisions. The print control method described. 3. A printing apparatus which stores binary data and prints out based on the binary data, comprising first compression means for compressing and storing the binary data, and compression by the first compression means. Second compression means for further compressing the binary data, comparison means for comparing the compression efficiency by the first compression means with the compression efficiency by the second compression means, and the result of the comparison by the comparison means. If the compression efficiency of the second compression means is high, the control means for storing the binary data obtained by the second compression means and controlling the binary data to be repeated from the first compression means. A printing device comprising: 4. The first and second compression means divides binary data into a predetermined size, and performs compression based on a difference between data in adjacent divisions. The printing device described.