JPH09247462A - Reversible compression processing method in page printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the compression processing efficiency by considerably reducing the memory capacity in a page printer. SOLUTION: A page buffer is divided in the unit consisting of a prescribed number of blocks in a prescribed dot, drawn data are checked for each unit and when not all are at a white level, a compression processing result for each block is stored in a compression data table(CDT) designated by a white map table(WMT). When the compression processing is disable, image data are stored in an uncompression data record(UCDR) area as they are designated by the CDT. To which unit and to which block of a unit an image to be drawn belongs is calculated, Data drawn precedingly are decoded and replaced with new drawn data and compressed and drawn in the block of the page buffer. In a block with the 1st UCDR, data drawn newly are compressed and when compression is disable again by picture drawing and new 2nd UCDR is generated, then flag information is stored in the 1st UCDR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention draws binary or multi-valued image data to be printed in a page printer (including a printer section of a digital copying machine) such as a black-and-white or color laser printer or LED printer. The present invention relates to a lossless compression processing method of image data for reducing the memory capacity of a frame buffer.

[0002]

2. Description of the Related Art In recent years, the resolution of page printers such as laser printers has become higher and higher, and recently 600 DPI.
Has become mainstream. 800DPI and 1200D in the future
Printers with PI will appear, and multi-resolution printers, that is, printers in which the resolution of the engine changes according to emulation will increase.

However, the memory capacity of the frame buffer (page memory) in the page printer is A4,600D.
It is about 4MB for PI and about 8MB for A3,600DPI. Such an increase in the memory capacity of the frame buffer greatly affects the product price. On the other hand, since the price of the page printer has been changing to a low price, it is necessary to suppress the price increase accompanying the high resolution by some means.

For this purpose, lossless compression techniques for binary image data include MH (Huffman coding: a standard G3 facsimile coding method using a one-dimensional compression method) and MR (G3 using a two-dimensional compression method) used in facsimile and the like. Optional coding method for facsimile), MMR (standard coding method for G4 facsimile, which is a modification of MR coding method)
For example, there is LZ compression used for text files and binary files handled by a computer.
Recently, JB using the international standard arithmetic coding
There is also an IG method.

[0005]

However, in these binary image data compression techniques, since an encoding process is performed sequentially from the head of an image or a file, only a desired arbitrary block cannot be restored in real time. . With a page printer, the document information to be printed comes in the order in which it was actually created on the CRT of the computer.
The compression process must be performed in block units of a certain size. Therefore, the above compression technique cannot be used as it is.

The present invention has been made in view of the above circumstances, and it is possible to provide a low-cost high-resolution page printer by reducing the memory capacity of the page memory in the page printer by compressing image data to be drawn. The purpose is to In addition, it is possible to perform lossless compression of a binary image in block units, further improve the compression efficiency of each block and unit that is the basic unit of compression, and a memory area that is no longer used due to repeated compression processing. It also aims to make effective use of.

Further, in a page printer which prints not only a binary image of black and white but also a multi-valued image such as a grayscale printer or a color printer, the drawing data can be reversibly compressed block by block, and the memory capacity of the page buffer is reduced. Another purpose is to be able to significantly reduce.

[0008]

In order to achieve these objects, the present invention is based on the following points for a lossless compression processing method for binary image data. In a page printer, two basic units are set for a binary image data to be drawn: a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction.

Then, the page buffer required for drawing (rasterizing) the image data to be printed to a predetermined resolution is divided into the above-mentioned unit units. As a step of compression processing, a step of checking whether or not the drawing data is all white for each unit and saving the result in a white map table (WMT) of a collection of m-bit unit records, If the drawing data of is not all white, prepare a compressed data table (CDT) in which u blocks of n-bit compressed data records (CDR) are collected in the address area specified by the white map table, and the unit is stored therein. Storing a compression processing result for each of u blocks constituting
A step of preparing a t-bit uncompressed data record (UCDR) in the address area specified by the compressed data table and storing the image data of the block as it is when the compression processing for each block is impossible. Have.

Then, it is calculated which block of which unit the image data to be drawn corresponds to,
Variable-length lossless compression that restores the data previously drawn in the block, rewrites it to new drawing data, compresses the drawing data by the processing of each step, and draws in the block in the page buffer. Processing is performed for each block.

Therefore, in the first invention, in the block having the first uncompressed data record, the data to be drawn in the block can be compressed by a new drawing, and cannot be recompressed by the further drawing and is newly added. If such a second uncompressed data record occurs, the flag information is stored in the first first uncompressed data record. As a result, since the uncompressed data record itself that is wastefully generated has information, it is possible to reduce the memory capacity without requiring another new area.

The second invention is an uncompressed data record (U
In a block having a CDR, if the data to be drawn in the block can be compressed by new drawing, the count value of the readable / writable count register is increased.
Further, in a block having an uncompressed data record (UCDR), the data drawn in the block can be compressed by new drawing, and the data drawn in the block cannot be compressed again by further drawing, and a new non-compressed data can be created. When a compressed data record occurs, the count value of the count register is decremented.

Alternatively, the uncompressed data record (U
If the data to be drawn in the block becomes incompressible due to new drawing,
The count value of a count register other than the above count register is increased. In this way, by managing the uncompressed data record (UCDR) by the count register, the garbage collection function can be achieved, the memory capacity can be used more efficiently, and the memory capacity can be further reduced.

According to a third aspect of the invention, in a block having the first uncompressed data record (UCDR), data to be drawn in the block can be compressed by new drawing, and cannot be compressed again by further drawing. While a new second uncompressed data record is generated, in a block having a third uncompressed data record (UCDR), the data to be drawn in the block can be compressed by new drawing, and can be uncompressed again by further drawing. If enabled and a new fourth uncompressed data record occurs and the first and third uncompressed data records are contiguous addresses, contiguous flag information is stored in the first uncompressed data record. . In this way, by having continuous information in the non-compressed data record, it has a garbage collection function, and it is possible to reduce the memory capacity with a small number of steps.

According to a fourth aspect of the invention, in a block having the first uncompressed data record (UCDR), data to be drawn in the block can be compressed by new drawing, and cannot be compressed again by further drawing. When a new second uncompressed data record occurs, the address information of the first uncompressed data record is stored in the writable address register. This makes it possible to directly refer to the address information of the address register and has a garbage collection function. Furthermore, when a third uncompressed data record (UCDR) occurs, it is preferable to store the third uncompressed data record in the first uncompressed data record which is the address indicated by the address register.

The third uncompressed data record (UC
DR) In a block, if new drawing makes the data drawn in the block compressible, and further drawing makes it uncompressible again and a new fourth uncompressed data record occurs, The address of the first uncompressed data record may be stored in the uncompressed data record, the address of the third uncompressed data record may be stored in the address register, and the termination information may be stored in the first UCDR. With these, all useless UCDR
Can be referred to, and it can be reused collectively at any number and at any timing.

In the fifth aspect of the invention, when the capacity of the page buffer is insufficient during the variable length compression process, the unit is switched to the fixed length compression process. Alternatively, which of the variable-length reversible compression process and the fixed-length compression process is suitable is discriminated on a unit-by-unit basis, and the compression process may be switched on a unit-by-unit basis based on the discrimination result.
Depending on the type of image (image, character, line drawing, etc.), the variable length lossless compression process may not be suitable, so there is a possibility that compression will be possible by switching to the fixed length compression process. Thus, the compression method can be optimized.

According to a sixth aspect of the present invention, when the compression process is switched, garbage collection is performed to make unused compressed data records and non-compressed data records usable in the fixed length compression process. As a result, the area used by the compression method before switching can be reused, and the compression efficiency can be improved.

A seventh aspect of the invention is to carry out uncompressed data record (UCD) in a unit during the variable length lossless compression process.
If the number of R) becomes more than half of the number of blocks in the compressed data table (CDT), all blocks in the unit are converted into uncompressed data records and the compressed data table corresponding to the unit is deleted. Then, the flag information is stored in the record of the corresponding unit in the white map table (WMT). In this case, not compressing does not consume the compression memory.

An eighth aspect of the present invention is such that, when all of the units in which a compressed data record (CDR) has been generated during the compression process become white data, the compressed data table corresponding to that unit is deleted and a white map is created. Initialize the corresponding unit record in the table. In addition, when all the black data is generated in the unit in which the compressed data record (CDR) is generated during the compression processing, the compressed data table corresponding to the unit is deleted,
All black information is stored in the corresponding unit record in the white map table. By this, when the inside of the unit is changed to the state of all white or all black data, the CDT and CDR can be deleted, so that the memory can be efficiently used.

A ninth aspect of the invention is to delete the compressed data table corresponding to the unit when a compressed data record (CDR) is generated in the unit during the compression process and all have a bit pattern of p bits. Then, the pattern flag information, the number of pattern bits, and the pattern information are stored in the corresponding unit record in the white map table. As a result, when the fill pattern is repeated in the unit, the CDT and CDR can be deleted, so that the memory can be used efficiently.

A tenth aspect of the present invention prepares a plurality of fill patterns corresponding to the above-mentioned blocks in advance, and refers to the patterns when the compression processing for each block cannot be performed. Alternatively, when the compression process for each block cannot be performed, the dot pattern of the block is stored, and if the same pattern appears during the subsequent compression process, refer to the address where the dot pattern is stored. By doing so, compression processing may be performed.

Further, when the above block-by-block compression processing cannot be performed, a certain kind of logical operation is performed on the dot pattern of that block, and if the result can be compressed, it is converted into a compression code and is expanded. May perform a logical operation process that is the reverse of the above logical operation. With these, the compression efficiency can be increased.

The eleventh invention provides the following lossless compression processing method of image data in order to enable lossless compression processing of multi-valued image data in block units. In a page printer, a block composed of t dots in the main scanning direction and b bits corresponding to a bit plane of the multivalued data for multi-valued image data to be drawn, and u blocks in the main scanning direction or the sub-scanning direction. Set the two basic units of the unit.

Then, the page buffer required for drawing the image data to be printed at a predetermined resolution is divided into the unit units. As a step of compression processing, a step of checking whether or not the drawing data is all white for each unit and saving the result in a white map table (WMT) of a collection of m-bit unit records, When the drawing data of is not all white, a compressed data table (CDT) is prepared in which u × b blocks of n-bit compressed data records (CDR) are collected in the address area specified by the white map table. A step of storing the compression processing result for each block of u × b constituting the unit, and t bit uncompressed data in the address area specified in the compressed data table when the compression processing for each block is impossible. A step of preparing a record (UCDR) and storing the image data of the block therein as it is.

Then, it is calculated which block of which unit the image data to be drawn corresponds to,
Restore the image data previously drawn in that block,
It is rewritten into new drawing data, and the drawing data is compressed by the processing of each step described above, and variable length lossless compression processing for drawing in the block in the page buffer is performed for each block.

A twelfth aspect of the present invention is a compressed data table (CDT) which is no longer used due to repeated variable length lossless compression processing in the above-described method for lossless compression processing of image data.
And a free list of memory areas for uncompressed data records (UCDR) and compressed data tables (CD
T) and an uncompressed data record (UCDR) are searched on the free list, and if there is a memory area in the free list, it is allocated and reused. If it does not exist, a new memory area is secured. As a result, it is possible to reduce the wasteful memory area generated in the drawing process and to efficiently allocate the memory area.

[0028]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a diagram showing an example of the configuration of an image forming system using a page printer provided with the image data compression processing apparatus according to the present invention.
Is a personal computer, and 200 is a page printer. Normally, a user creates a document by using a CRT screen of the personal computer 100, a keyboard and a DTP (Desktop Publishing) application,
Page printer 200 through printer driver 101
Transfer to and print.

The printer driver 101 converts the content of a document to be normally printed into a printer language supported by the page printer 200, such as PCL of Hewlett-Packard (HP) or Postscript language of Adobe. The printer connected to the former is generally connected to a PC.
The L emulation printer and the printer connected to the L emulation printer are called PostScript printers. There is also a printer called a dumb printer which simply prints a bit image which is entirely rasterized on the personal computer 100 side.

The page printer 200 may be a laser printer, an ink jet printer, a thermal printer, or the like, but the laser printer is superior in high speed printing. Recently, a color laser printer has begun to appear on the market, and it is also possible to use it. Further, while the resolution is increasing year by year, 600 DPI is currently the standard. In the following embodiments, the page printer 200 will be described as a 600 DPI black and white PostScript laser printer (hereinafter simply referred to as “page printer”), but the present invention is not limited to this.

FIG. 3 is an external view of the page printer, and FIG. 4 is a vertical sectional view showing the outline of the internal mechanism.
The page printer 200 has a paper feed tray 2 detachably provided, a first paper output stacker 3 provided at an upper portion, and a second paper output stacker 3 provided at a rear portion.
A discharge stacker 4 is provided. 2 paper output stackers 3,
4 can be switched by the switching claw 5. Normally, the first discharge stacker 3 is selected as the discharge stacker. However, the second discharge stacker 4 is selected in a special case such as when using easily curlable paper such as an envelope or a postcard.

Further, inside thereof, a photosensitive drum 10, a charging section 11, an optical writing section 12, a developing section 13, a transfer section 14, a fixing section 15, which constitute an image forming section of a printer engine, a paper feed roller 16 and A paper feed section using a pair of registration rollers 17, etc.,
Paper discharge transport unit 1 composed of transport rollers and paper guide plates
8 and a controller board 19 constituting a printer controller for controlling the entire page printer, an engine driver board 20 constituting a sequence controller of the printer engine, and the like.

When the print sequence is started by the sequence controller of the printer engine,
Paper is fed from the paper feed tray 2 by the paper feed roller 16,
The sheet is temporarily stopped in a state where the leading end of the sheet abuts against the pair of registration rollers 17. On the other hand, the photosensitive drum 10 rotates in the direction of arrow A in FIG. 4, and the surface charged by the charging unit 11 is
A laser beam modulated by the optical writing unit 12 according to the image data from the printer controller is irradiated while performing main scanning in the drum axis direction to be exposed, and the photosensitive drum 10 is exposed.
To form an electrostatic latent image on the surface of.

The developing unit 13 develops it with toner, and the registration roller pair 17 transfers it to a sheet fed at a predetermined timing by the transfer unit 14, and the fixing unit 1
The print paper heated and fixed in step 5 is sent to the second discharge stacker 4 or is conveyed to the first discharge stacker 3 above through the discharge conveyance section 18.

FIG. 5 is an internal block diagram of the controller board 19. This controller board 19 has a CPU 20.
1, NVRAM 203, program ROM 204, font ROM 205, RAM 206, and four interfaces (hereinafter abbreviated as “I / F”) 207, 209,
211 and 213 and a bus line 215 connecting them
It is constituted by.

The CPU 201 has a program ROM 204.
The controller is controlled by a program stored in the controller, a mode instruction from the operation panel 210, a command from a personal computer (personal computer) 100 as a host device, and the like. In addition, the inserted IC card 2
From 02, font data and programs can be imported. Further, it also carries out processing relating to drawing and compression of binary image data to be printed in a page memory, which will be described later. The NVRAM 203 is a non-volatile memory that stores the content of a mode instruction from the operation panel 210 and the like.

The program ROM 204 is a read-only memory that stores a control program for this controller. The font ROM 205 stores character font pattern data and the like. RAM206 is CPU2
The random access memory is used as a work memory 01, an input buffer for input data, a page memory (frame buffer) for print data, a memory for download fonts, and the like.

The engine I / F 207 is an interface that is connected to a printer engine 208 that actually performs printing and that communicates commands, statuses, and print data. A panel I / F 209 is an interface that is connected to the operation panel 210 and communicates commands and status. The operation panel 210 displays and informs the user of the current status of the printer, and allows the user to specify the mode. Panel device.

The host I / F 211 is an interface for communicating with the personal computer 100 which is a host device, and is usually a Centronics I / F or RS23.
Use 2C. The disk I / F 213 is a disk interface for communicating with the disk device 214. The disk device 214 is an external storage device for storing various data such as font data, programs, and print data, and is a floppy disk device, a hard disk device, or the like.

The page printing operation of the page printer 200 will be described with reference to FIGS. 6 and 1. FIG. 6 is an operation flow diagram when the page printer 200 prints one page, and FIG. 1 is a block diagram showing a functional configuration related to the processing. Therefore, along with the flow of FIG. 6, the operation of page printing will be described with reference to FIG. The printer driver 101 in the personal computer 100 shown in FIG. 2 converts the document data to be printed page by page into a Postscript (hereinafter referred to as PS) file and sends it to the page printer 200.

Then, the page printer 200 uses the PS
When the file is received, the PS interpreter 21 shown in FIG. 1 rasterizes (draws) in fixed block units of 600 DPI which is the first resolution, and the compression unit 2
2 tries variable length lossless compression processing in the block unit, and if the compression is successful, the resulting compression code is stored in the compression memory (300
It is stored in page memory 23 having a capacity of one page by DPI) 23, and if it cannot be compressed, it is rasterized 60
The data of 0DPI is stored in the uncompressed memory 24. In practice, the non-compressed memory 24 can also be used as the compressed memory 23. Therefore, the R shown in FIG.
There is no need to increase the memory capacity of the AM 206.

When the processing for one page is completed, the compressed image stored in the compression memory 23 is decompressed in the decompression unit 25 in order from the upper left of the page, and the 600 DPI image data is sent to the printer engine 208 of 600 DPI to print the result. To get 600 DPI stored in uncompressed memory 24
The non-compressed image data of is sent to the printer engine 208 of 600 DPI as it is.

In these cases, the binary / multi-value conversion processing unit 26 shown in FIG. 1 uses the image data of 600 DPI obtained by expanding the compressed image from the expansion unit 25, or the uncompressed memory 24.
The non-compressed image data of 600 DPI is sent to the printer engine 208 as it is, and the binary multi-value conversion process is not performed.

If the processing for one page is finished,
When the data of (compressed memory + non-compressed memory) exceeds a certain capacity, the PS interpreter 21 changes the resolution to the second resolution of 300 DPI and the compressed memory 23.
When rasterization (drawing) is performed again and the processing for one page is completed, the uncompressed image data of 300 DPI is sequentially sent to the binary multi-value conversion processing unit 26 without performing any processing in the expansion unit 25, and resolution conversion is performed there. The binary multi-value conversion process including the conversion is performed, and the data whose resolution is converted to 600 DPI is sent to the printer engine 208 and printed.

<Description of Block-by-Block Compression Processing> Next,
Details of the compression processing in block units described above will be described with reference to FIGS. 7 to 16. In this page printer, two basic units are set for the binary image data to be drawn: a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction. are doing.

Then, as shown in FIG. 7, the compression memory 2
Frame 23 for one page which is a page buffer in 3
a is divided into a number of units. In this example, as shown in an enlarged view in FIG. 8, a block word (Brock Word: hereinafter abbreviated as “BW”) of 64 dots (t = 64) in the main scanning direction has 16 lines in the sub scanning direction, that is, 16 lines. A block (u = 16) constitutes one unit.

Further, as shown in FIG. 9, the compression memory 23 stores one page of virtual frames (virtual flam).
e) is also prepared, and a white map table (hereinafter abbreviated as “WMT”) of a collection of m-bit (32-bit in this example) unit records is provided for each unit. And check whether all drawing data is white for each unit,
If all white, the unit record corresponding to this unit of this WMT is set to NULL (0xffffffff).

If there is more than one black dot,
In this 32-bit unit record, as shown in FIG. 10, a compression data table (Compression Data Table:
Hereinafter, the real address (CDT address) of "CDT" is stored. The CDT consists of 16 32-bit compressed data records (Comp
ression Data Record: Abbreviated as "CDR" below) C
It is composed of DR-0 to CDR-15.

The details of the 32-bit CDR are shown in FIG. For each WB that makes up the unit, try variable length lossless compression of drawing data, and if compression is possible, bit 3
1 is set to "0", and the compressed code (according to the Huffman code shown in FIG. 12) is stored in bits 29 to 0.
If the data cannot be compressed, the bit 31 is set to "1", and the uncompressed data record (Uncomp.
ression Data Record: hereinafter abbreviated as "UCDR")
Uncompressed data table address (Unco
mpression DataTable Address: Stored below is abbreviated as “UDT address”.

The image data compression method according to this embodiment includes the following two steps. First of all, the target BW data is all white (all white) or all black (all black).
Find out what. If all white or all black, then B
The CDT corresponding to W is 0x00000000 or 0x7ff, respectively.
fffff. If not, depending on whether the first dot is a white dot or a black dot (see the CD shown in FIG. 11).
(Specified by bit 30 of R), the rung of white dots or black dots is described by the Huffman code shown in FIG.

For example, the BW shown in FIG. 14 (a) is converted into the compressed code shown in FIG. 14 (b). The last white dot (run length = 10) is not included in the compressed code, but restoration is possible because the black dots (run length = 19) are all white dots.
Also, 1 is written in the surplus area of the CDT. Here, in a block that could not be compressed to 29 bits, the bit 31 of CDR is set to 1, the address of the corresponding UCDR is stored, and B before compression is stored in UCDR.
The W image data is stored as it is.

FIG. 16 shows an example of a concrete image, and FIG. 16 shows the contents of the buffer in the RAM as the compression memory when the image data is drawn. When the graphic figure shown in FIG. 15 is drawn in the order of elliptical, triangular, and rectangular figures, the elliptical figure is first compressed.

When all the blocks corresponding to (A) in the WMT of FIG. 16 corresponding to the (A) part in the ellipse of FIG. 15 can be compressed, data such as CDT-A is created.
Next, in the WMT of FIG. 16 corresponding to the drawing of the triangle,
As an example when a block corresponding to (B) is drawn, the (B) part of FIG. 15 is overwritten on the previously drawn elliptical figure. In this example, since the block corresponding to CDRb1 could not be compressed, the record UCDRb1 is generated.

Furthermore, when a rectangle is drawn, CDT-C
For example, when the ellipse is drawn, CDRc1
After creating the UCDR without being able to compress 5, the unused recording (Unused Record) occurs when CDRc15 can be compressed by drawing the triangle (C) part. If the data cannot be compressed due to the data when drawing a new rectangle, the CD in another area
Creates Rc15. Since most of the drawing forms are such overwriting, the capacity of unused recording becomes so large that it cannot be ignored.

<Method for Reusing Unused Recording Area> This invention is designed to eliminate this unnecessary unused recording area (U
In order to make the CDR) reusable, the following methods are proposed. This will be described by taking a certain CDT as an example.

FIG. 17 is a diagram for explaining the first method. In FIG. 17A, when the drawing data is newly stored in the CDR15 in the state of the CDT in which the CDR15 cannot be compressed and has the UCDRc15, If new data can be compressed, the UCDRc15 becomes unnecessary and becomes an unused record as shown in b). Therefore, in order to execute the garbage collection for reusing this unused UCDR area, this unused record (64
In the bit UCDR), flag information as shown by "XX ......... XXX1X" is provided. In this way, by having flag information in the UCDR itself that is no longer used, garbage collection can be executed without needing another new area.

FIG. 18 is a diagram for explaining the second method. In FIG. 18A, the CDR 15 is also incompressible and the UCDR is the same.
When drawing data is newly stored in CDR15 in the state of CDT having c15, UCDRc15 becomes unnecessary if the new data can be compressed, and as shown in b) Unused Record become. Therefore, in order to execute the garbage collection for reusing the unused UCDR area, when the unused recording occurs, the count value (X) of the count register provided in another area is increased ( X + 1). This allows for bulk processing rather than a single garbage collection.

FIG. 19 is a diagram for explaining the third method. In FIG. 19A, the CDR 15 is also incompressible and the UCDR is the same.
When drawing data is newly stored in CDR15 in the state of CDT having c15, UCDRc15 becomes unnecessary if the new data can be compressed, and as shown in b) Unused Record become. At this time, the count value (X) of the count register provided in another area is increased (set to X + 1).

Further, when new drawing data is written in the CDR 15 and the UCDRc15 is created at the same location as the old UCDRc15 as shown in c) (the UCDR created once may not be compressed thereafter. ), The value (X) of the count register is reduced (set to X-1). As a result, it is possible to calculate at the time of drawing the number of records that have become unused records and that have been reused. Therefore, there is no need for calculation when executing garbage collection.

FIG. 20 is a diagram for explaining the fourth method. In FIG. 20A, the CDR 15 is also incompressible and the UCDR is the same.
When drawing data is newly stored in CDR15 in the state of CDT having c15, UCDRc15 becomes unnecessary if the new data can be compressed, and as shown in b) Unused Record become. In this case, the first and second count registers are provided in another example area,
The first count register value when the state of b) is entered
Increase (X) (set to X + 1).

Further, when new drawing data is written in the CDR15 and the UCDRc15 is created at the same location as the old UCDRc15 as shown in c) (a UCDR created once does not have a compression method thereafter). Yes, the value (Y) of the second count register is increased (to Y + 1).
This allows the garbage collection function to be divided, since the number of data that can be compressed in the UCDR is known by the second register.

FIG. 21 is a diagram for explaining the fifth method. In FIG. 21A, the CDR 15 is also incompressible and the UCDR is the same.
When drawing data is newly stored in CDR15 in the state of CDT having c15, UCDRc15 becomes unnecessary if the new data can be compressed, and as shown in b) Unused Record become. After that, when incompressible data is drawn, UCDRc1 is created as shown in b), compressible data is drawn in CDR0, and unused recording becomes continuous as shown in c), The flag information indicating that they are continuous is provided so that garbage collection can be continuously executed.

FIG. 22 is a diagram for explaining the sixth method. In FIG. 22A, the CDR 15 is also incompressible and the UCDR is the same.
When drawing data is newly stored in CDR15 in the state of CDT having c15, UCDRc15 becomes unnecessary if the new data can be compressed, and as shown in b) Unused Record become. In this example, an address register is provided in another area, and the UCD that has not been used for recording
The R address pointer is stored in the address register. This allows simple garbage collection by directly referencing the address pointed to by this address register.

FIG. 23 is a diagram for explaining the seventh method. In FIG. 23A, the CDR 15 is also incompressible and the UCDR is the same.
When drawing data is newly stored in CDR15 in the state of CDT having c15, UCDRc15 becomes unnecessary if the new data can be compressed, and as shown in b) Unused Record become. In this example as well, an UCD that has not been used for recording has an address register in another area.
The R address pointer is stored in the address register. After that, when another UCDR is further generated, the UCDR is stored at the address indicated by this address register. As a result, even if an arbitrary CDT next generates a UCDR, the UCDR can be stored in the location of the address register, so that real-time garbage collection can be performed while compressing.

24 and 25 are diagrams for explaining the eighth method. First, when the first unused record occurs, the address of the first unused record is stored in the address register. When the second unused recording occurs, the end information such as NULL data is stored in the first one pointed by the address register, the contents of the address register is stored in the second one, and the second address is set. Store in another address register. At the time of the third address, the contents of the address register are stored in the third address, and the third address is stored in another address register. This is repeated sequentially.

FIG. 24 shows a state where there is an unused record up to AI in the scratch pad memory of the RAM, and FIG. 25 shows a state where the unused record J is increased by one. There is. By doing so, since the UCDRs of all unused records can be traced at any time, garbage collection can be performed at any number and at any timing.

<Structure of Compression Unit and Compression Processing> Here, FIG. 26 shows an example of the hardware structure of the compression unit 22 shown in FIG. The compression unit 22 includes a lead block 22.
It is composed of a 64-bit buffer 222, a modify block 223, and a compression block 224, each of which has a capacity for storing data of 1 and 1 block word BW.

Then, the PS interpreter of FIG. 1 having the function of the CPU 201 shown in FIG. 5 performs variable length lossless compression on the data drawn at a resolution of 600 DPI in block word BW units, and the page memory using the RAM 206 of FIG. Compressed memory (WMT, CDT, UD
23) (with each area of T) storing the compressed code.

The read block 221 uses the unit number to be drawn and the position information of the block word BW calculated by the CPU 201 to determine the corresponding white map table WMT, compressed data table CDT,
And a block for reading the compressed data of the non-compressed data table UDT from the compression memory 23 and restoring the uncompressed block word BW to the 64-bit buffer 222.

The modify block 223 is C
The data (Write Data) of the block word BW newly designated by the PU 201 to be drawn is stored in the buffer 2
22 is a block for performing read / modify / write (read / modify / write).

Then, the compression block 224 reads
A block for recompressing the data in the buffer 222 that has been subjected to the modify write processing, and the result is stored in the compression memory 23.
Write to the BW position of the unit number read earlier.
That is, the compression memory 23 is first drawn (rasterized).
The compressed data that has been created is sequentially rewritten for each block word into the compressed data of an image to be newly drawn.

FIG. 27 is a flow chart of a processing routine relating to drawing of image data by the CPU 201 shown in FIG. The CPU 201 first checks whether the hardware shown in FIG. 26 is operable after the previous drawing operation is completed, and if it is operable, calculates the unit number of the data to be drawn and the position of the BW. Then, it is set in the read block 221 and the compression block 224.

Then, in the modify block 223,
Data to be newly drawn in the block word BW (Wri
te Data) is set, the hardware operates in the order of the read block 221, the modify block 223, and the compression block 224 to execute the compression drawing of the 1-word block BW in the compression memory 23 which is the page memory, and
The above process is repeated until drawing of the page is completed.

If the system in which the CPU is in the idle state in many cases until the operation of the hardware shown in FIG. 26 ends, the unit number, the position of the BW, and the data of the BW to be newly drawn are temporarily stored. To store C
A FIFO (First In First Out) memory 225 is provided between the PU and each block of the compression unit 22 as indicated by a virtual line in FIG.
~ 227 may be provided. When the remaining capacity of each of the FIFO memories 225 to 227 becomes a certain size,
If it is designed to notify the CPU by an interrupt, the CPU
The drawing operation can be executed without worrying about the hardware state of the compression unit 22.

<Description of Switching of Compression Method> The variable length reversible compression method described above (“CDT compression method” in the following description).
8) shows the breakdown of the memory used.
The system area used in this system is always fixed, and the areas used in the CDT compression method are the white map table (WMT) area and the CDT and UCDT areas. The WMT size is fixed because it is determined when the paper size is determined (before the compression process is started). Therefore, when the CDT and UCDT areas reach the RAM end, it means that the compression memory is full.

In the embodiment described here, it is also possible to decompress the portion where the CDT and UCDT are formed in the unit into a picture image and perform the compression processing by the fixed length compression method. Then, as shown in FIG. 29, the WMT is used so that the unit can determine whether the compression processing of the drawing data is performed by the CDT compression method or the fixed length compression method.
A compression processing method determination flag is provided in the 32 bits of the above.

Further, it is possible to determine whether the CDT compression method or the fixed length compression method is suitable for each unit.
It can be judged when the CDR exceeds a certain number. C
When the number of CUDRs of a unit exceeds a certain number during the DT compression process, the fixed length compression method is switched to.
The certain number is determined by the average size required for fixed length compression of one unit and the sizes of CDR (32 bits × 16) and UCDR (64 bits) used in the CDT compression method. Also, when switching between CDT compression processing and fixed-length compression processing, decompressed CDR and UCDR, and CD
It is possible to execute a garbage collection that enables fixed length compression of the garbage (unused record) generated during the T compression processing.

According to these embodiments, it is possible to perform compression by a compression processing method suitable for the type of image (image, character, line drawing, etc.), and the probability of compression becomes high. By determining whether the compression processing method is suitable for the image for each unit, the compression method can be optimized in small units. When switching the compression processing method, the area used by the compression method before the switching can be reused, so that the compression rate can be improved.

<Management of whether or not to perform CDT compression> When the image is drawn in a certain unit, the address of the CDT is stored in WMT, and when the CDR in the CDT cannot be compressed, UCDR
Create In the example shown in (a) of FIG. 30, when the number of UCDRs exceeds 8, the compressed CDR expands, and as shown in (b), a 64 × 16 UCDR is created and the WMT is created. Stores the address of the UCDR. In other words, if nine UCDRs occur, the CDRs are (32 × 1
6 bits) and UCDR (64 x 9 bits) for a total of 1
Since 088 bits are required, more memory is used than when one unit is expanded to UCDR (64 × 16 = 1024 bits).

Therefore, in the present invention, when (u / 2) or more UCDRs are generated, one unit is converted into UCDRs and the CDTs are deleted. With this compression method, if there are (u / 2) or more uncompressible blocks in one unit, there is a disadvantage that compression memory is not consumed if not compressed. In that case, switch to the fixed length compression method. It is possible to reduce the consumption of memory capacity.

<Deletion of CDT and UCDR> In the CDT compression method according to the present invention, in the initial state of the WMT, all 32 bits are "1" as shown in FIG. 31 (a). Draw once from this state and CDT
When occurs, the CDT address is stored in the WMT as shown in (b). After that, by further drawing, when the unit is all white data, WMT (a)
Then, the previously generated CDT and UCDR are deleted. As a result, when the inside of the unit is changed to the all-white data state, the CDT and UCDR can be deleted, so that the memory can be reduced.

Further, when all black data is written to a certain unit, or when all black data is newly written to a unit which has been drawn once and CDT has occurred, (c) in FIG. All black information is stored in the WMT as shown in, and if CDT or UCDR has previously occurred, they are deleted. As a result, when all black data is written in the unit, the CDT and UCDR can be deleted, so that the memory can be reduced.

Further, when the WMT is in the initial state shown in (a) of FIG. 31 or in the once drawn state shown in (b) of FIG. ), The pattern storage flag information, the pattern bit number information method, and the pattern data information are stored, and if CDT or UCDR has previously occurred, they are deleted. In this example, the WMT state is shown when one unit is completely filled with a 16-bit '1001110010011000' pattern. As a result, when the fill pattern is repeated in the unit, the CDT and UCDR can be deleted, so that the memory can be reduced.

<Method of Increasing Compression Rate> Here, a method of increasing the compression rate of drawing data will be described. The first method is to prepare several kinds of fill patterns in advance, refer to this fill pattern table when compression cannot be performed by the above-mentioned CDT compression method, and if they match, the WM
Bit 30 of T is set to 1 and the table code is stored below bit 30. FIG. 32 shows a flowchart of this process.

The second method reserves an area in the memory in which several types of frequently appearing patterns can be stored in the BW that cannot be compressed by the CDT compression method described above, and this area is stored when an uncompressable BW appears. Refer to and match B
If W is present, set bit31 = 1 of WMT and set bit3
Below 0, only the address where the BW is stored is set.

In the third method, a certain fixed dot pattern is prepared, and if the CDT compression method cannot be used for compression, the BW and the dot pattern prepared in advance are subjected to, for example, exclusive OR. Such a logical operation is performed, and if a pattern that can be compressed by the CDT compression method is obtained as a result, compression processing is performed and the compression code is stored.
The original pattern can be restored by performing the reverse operation during expansion. A flowchart of this processing is shown in FIG.

The compression rate can be increased by any of these methods. If compression is not possible even using these means, set bit31 = 1 of WMT and set
The address UDT address for storing BW is set in t30 to bit0. The other processing is the same as described above, and thus the description thereof is omitted.

<Application to Multi-Valued Printer> The image data compression / decompression method described so far is intended for printing a binary black and white image, such as a gray scale printer or a color printer. It did not explain the use for multi-valued printers. Therefore,
An embodiment of the present invention, which is developed by expanding the above-described image data compression / decompression method and can be applied to a multi-value printer such as a grayscale printer or a color printer,
This will be described below with reference to FIGS. 34 to 36.

The hardware configuration of the multi-value page printer in this embodiment is the same as that described with reference to FIGS.
Since they are basically common, the description thereof is omitted. In this embodiment, as shown in FIG. 34 or FIG. 35, the shape of the unit is one block word (BW) and t dot (dot).
Xb bits, and this BW is u blocks in the main scanning direction (FIG. 34) or u blocks (lines) in the sub scanning direction.
Then, change to configure one unit. Therefore, 1 unit = t dot × b bit (bi
t) × u. Here, b corresponds to the number of bit planes of multi-valued or color image data. For example, since 256 bit planes require 8 bit planes, b
= 8.

An example of compression processing for multi-valued data will be described with reference to FIG. FIG. 3A is a 32 (bit) white map table (WMT) for the above-mentioned unit. If one unit is all white,
WMT is set to NULL (0xffffffff), and if there is one or more black dots, the 32-bit compressed data table (CDT) real address (CDT address) shown in FIG. 3B is stored. The length of the record indicated by the CDT address is b × u × CDT.

The CDT corresponds to the BW of the width t (dot) of the bit plane of u (line) × b (bit), and the run-length compression is attempted in the same manner as in the above-mentioned embodiment, and the compression is possible. If so, the compressed code is stored in bits 29 to 0. If it is compressible, bit31 =
1 and the uncompressed data table address (UD) for storing BW in bits 30 to 0 as shown in (c) of FIG. 36.
Taddress) is stored.

As described above, by simply changing the block (BW), which is the basic unit of data compression according to the present invention, and the shape of the unit, it becomes possible to perform random accessible compression processing on a multi-valued image, and a multi-valued printer. Can be applied to.

<Formation of Flaist> In such a compression method of image data for a multi-valued printer as well,
CDT that is no longer used when the drawing of compressed data in units of BW to each unit in the compression memory is repeated
And UDT or UCDR occurs, and it increases gradually, but it is not reused and becomes a useless memory area in the drawing process, which cannot be ignored.

Therefore, in order to reduce the useless memory area generated in such a drawing process and enable efficient memory area allocation, a free list is formed as shown in FIG. That is, the areas of the CDT and UDT (or UCDR) that are no longer used due to the repetition of the drawing process are set as free CDT and free UDT.
As a free CDT address or free UD
The T addresses are linked in a chain (the positions on the memory may be separated), and the last address is set to NULL.

Then, C is newly added in the drawing process during the compression process.
When the DT and UDT are needed, the free list is searched, and if the free list has a memory area, it is allocated and reused. If not, a new memory area is secured. By doing so, more efficient memory area allocation can be performed during compression processing, and the memory capacity can be further reduced even in a multi-valued printer.

[0096]

As described above, according to the present invention, the memory capacity of the page memory in the page printer can be reduced by compressing the image data, and a low-cost high-resolution page printer can be provided. In addition, it is possible to perform lossless compression of a binary image in block units, further improve the compression efficiency of each block and unit that is the basic unit of compression, and a memory area that is no longer used due to repeated compression processing. You can also make effective use of.

Further, in a page printer that prints not only a binary image of black and white but also a multi-valued image such as a grayscale printer or a color printer, the drawing data can be reversibly compressed in block units, and the memory capacity of the page buffer is increased. Can be significantly reduced, and the price can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a functional configuration of a portion related to a process for printing document data of a PS file in page printer 200 shown in FIGS. 2 to 4.

FIG. 2 is a diagram showing a configuration example of an image forming system using a page printer to which the present invention is applied.

FIG. 3 is an external view showing an example of the page printer in FIG.

FIG. 4 is a longitudinal sectional view showing the outline of the internal mechanism of the same.

5 is a block diagram showing a configuration of a controller board 19 in FIG.

6 is an operation flow chart when printing one page by each unit shown in FIG. 1. FIG.

7 is a diagram showing a frame for one page in the compression memory 23 of FIG. 1 and a division state of the unit.

FIG. 8 is a block word (B
It is explanatory drawing of W group.

9 is an explanatory diagram of a white map table (WMT) including a virtual frame for one page in the compression memory 23 of FIG. 1 and unit records corresponding to respective units provided therein.

FIG. 10 is a diagram showing the structure of one unit record and a compressed data table (CDT) in which addresses are stored.

FIG. 11: One compressed data record (CD
It is a figure which shows the structure of R).

FIG. 12 is an explanatory diagram of a Huffman code that describes the run length of white dots or black dots.

FIG. 13 is an explanatory diagram of an uncompressed data record (UCDR) that stores uncompressed data.

FIG. 14 is a diagram showing a conversion example of a compressed code.

FIG. 15 is a diagram showing an example of actual drawing of an image.

16 is an explanatory diagram showing the contents of a buffer in a RAM serving as a compression memory when the image data of FIG. 15 is drawn.

FIG. 17 is a CD for explaining a first method for enabling reuse of an unused unused recording area.
It is a figure which shows the change of T.

FIG. 18 is a CD for explaining a second method for enabling reuse of an unused unused recording area.
It is a figure which shows the change of T with the count register provided in another area | region.

FIG. 19 is a CD for explaining a third method for enabling reuse of an unused unused recording area.
It is a figure which shows the change of T with the count register provided in another area | region.

FIG. 20 is a CD for explaining a fourth method for making it possible to reuse an unused unused recording area.
It is a figure which shows the change of T with the 1st, 2nd count register provided in another area | region.

FIG. 21 is a CD for explaining a fifth method for making it possible to reuse an unused unused recording area.
It is a figure which shows the change of T.

FIG. 22 is a CD for explaining a sixth method for enabling reuse of an unused unused recording area.
It is a figure which shows the change of T with the address register provided in another area | region.

FIG. 23 is a CD for explaining a seventh method for enabling reuse of an unused unused recording area.
It is a figure which shows the change of T with the address register provided in another area | region.

FIG. 24 is a diagram showing a state of an unused recording area in a scratch pad memory for explaining an eighth method for enabling reuse of an unnecessary unused recording area.

25 is a diagram showing a state in which the number of unused records J is increased by one from the state of FIG. 24.

FIG. 26 is a block diagram showing a hardware configuration example of a compression unit 22 shown in FIG.

27 is a flowchart of a processing routine relating to drawing of image data by the CPU 201 shown in FIG.

28 is an explanatory diagram showing a breakdown of a memory used in the variable-length lossless compression method by the compression unit 22. FIG.

FIG. 29 is an explanatory diagram of a WMT having a compression processing method determination flag.

FIG. 30 is an explanatory diagram of management of whether or not to perform CDT compression according to the present invention.

FIG. 31 is a WMT involved in drawing compressed data according to the present invention.
It is explanatory drawing which shows the example of the content change of.

FIG. 32 is a flowchart showing an example of compression processing of drawing data with a high compression rate.

FIG. 33 is a flowchart showing another example of compression processing of drawing data with a high compression rate.

FIG. 34 is a diagram showing a shape example of a block word (BW) and a unit when the present invention is applied to a multi-valued printer or a color printer.

FIG. 35 is a diagram similarly showing another example of the configuration of the unit.

FIG. 36 is a diagram for explaining the compression process of the drawing data.

FIG. 37: CDT table and U that are no longer used
It is a figure which shows the example of formation of the free list of a DT table.

[Explanation of symbols]

 10: Photoconductor drum 11: Charging part 12: Optical writing part 13: Developing part 14: Transfer part 15: Fixing part 19: Controller board 20: Engine driver board 21: Host script (PS) interpreter 22: Compressing part 23: Compressed memory 24: Non-compressed memory 25: Decompression unit 26: Binary / multi-value conversion processing unit 100: Personal computer 101: Printer driver 200: Page printer 201: CPU 206: RAM 208: Printer engine

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mutsuo Shiomae 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Makoto Onozuka 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Inventor Akira Ohori 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd.

Claims (20)

[Claims] 1. In a page printer, two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction for binary image data to be drawn. , The page buffer necessary for drawing the image data to be printed at a predetermined resolution is divided into the above-mentioned units, and it is checked whether or not the drawing data is all white for each unit. Storing in a white map table (WMT) of a collection of bit unit records, and when the drawing data of the unit is not all white, an n-bit compressed data record (CDR ), A compressed data table (CDT) in which u blocks are collected, and the unit is configured there Storing a compression processing result for each of u blocks, and t-bit uncompressed data record (UCDR) in the address area specified in the compressed data table when the compression processing for each block is impossible. ) Is prepared, and the image data of the block is stored as it is, the image data to be drawn corresponds to which block of the divided unit, and the image data previously drawn in the block is calculated. Variable length reversible compression processing for reconstructing the reconstructed data, rewriting it to new drawing data, compressing the drawing data by the processing of each step described above, and drawing in the block in the page buffer for each block. And in the block with the first uncompressed data record,
If the new drawing allows the data to be drawn in the block to be compressed, and further drawing makes the data incompressible again and a new second uncompressed data record is generated, the first first uncompressed data record is written. A lossless compression processing method of image data, characterized by storing flag information. 2. In a page printer, two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction for binary image data to be drawn. , The page buffer necessary for drawing the image data to be printed at a predetermined resolution is divided into the above-mentioned units, and it is checked whether or not the drawing data is all white for each unit. A step of storing in a white map table (WMT) of a collection of bit unit records, and an n-bit compressed data record (CDR) in an address area specified by the white map table when the drawing data of the unit is not all white ), A compressed data table (CDT) in which u blocks are collected, and the unit is configured there Storing a compression processing result for each of u blocks, and t-bit uncompressed data record (UCDR) in the address area specified in the compressed data table when the compression processing for each block is impossible. ) Is prepared, and the image data of the block is stored as it is, the image data to be drawn corresponds to which block of the divided unit, and the image data previously drawn in the block is calculated. The variable-length lossless compression process of restoring the image data that has been restored, rewriting it to new drawing data, compressing the drawing data by the processing of each step described above, and drawing in the block in the page buffer for each block. In a block with uncompressed data record (UCDR), the data to be drawn in the block is compressed by new drawing. If enabled, lossless compression image data processing method, characterized in that to increase the count value of the read-write count register. 3. The lossless compression processing method for image data according to claim 2, wherein in a block having an uncompressed data record (UCDR), data to be drawn in the block can be compressed by new drawing, and further drawing can be performed. A reversible compression processing method for image data, comprising reducing the count value of the count register when the data to be drawn in the block becomes incompressible again and a new non-compressed data record occurs. 4. The lossless compression processing method for image data according to claim 2, wherein the uncompressed data record (UCD).
R) In a certain block, if the data to be drawn in the block becomes incompressible due to new drawing, the count value of a count register different from the count register is increased, and reversible compression of image data. Processing method. 5. In a page printer, two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction for binary image data to be drawn. , The page buffer necessary for drawing the image data to be printed at a predetermined resolution is divided into the above-mentioned units, and it is checked whether or not the drawing data is all white for each unit. A step of storing in a white map table (WMT) of a collection of bit unit records, and an n-bit compressed data record (CDR) in an address area specified by the white map table when the drawing data of the unit is not all white ), A compressed data table (CDT) in which u blocks are collected, and the unit is configured there Storing a compression processing result for each of u blocks, and t-bit uncompressed data record (UCDR) in the address area specified in the compressed data table when the compression processing for each block is impossible. ) Is prepared, and the image data of the block is stored as it is, the image data to be drawn corresponds to which block of the divided unit, and the image data previously drawn in the block is calculated. The variable-length lossless compression process of restoring the image data that has been restored, rewriting it to new drawing data, compressing the drawing data by the processing of each step described above, and drawing in the block in the page buffer for each block. In the block having the first uncompressed data record (UCDR), the data to be drawn in the block is newly drawn. Becomes uncompressible by further drawing and a new second uncompressed data record is generated, while a new drawing is performed in the block having the third uncompressed data record (UCDR). When the data to be drawn in the block can be compressed and cannot be compressed again due to further drawing, and a new fourth uncompressed data record is generated, and the first and third uncompressed data records have consecutive addresses. A lossless compression processing method for image data, characterized in that consecutive flag information is stored in the first uncompressed data record. 6. In a page printer, two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction for binary image data to be drawn. , The page buffer necessary for drawing the image data to be printed at a predetermined resolution is divided into the above-mentioned units, and it is checked whether or not the drawing data is all white for each unit. Storing in a white map table (WMT) of a collection of bit unit records, and when the drawing data of the unit is not all white, an n-bit compressed data record (CDR ), A compressed data table (CDT) in which u blocks are collected, and the unit is configured there Storing a compression processing result for each of u blocks, and t-bit uncompressed data record (UCDR) in the address area specified in the compressed data table when the compression processing for each block is impossible. ) Is prepared, and the image data of the block is stored as it is, the image data to be drawn corresponds to which block of the divided unit, and the image data previously drawn in the block is calculated. The variable-length lossless compression process of restoring the image data that has been restored, rewriting it to new drawing data, compressing the drawing data by the processing of each step described above, and drawing in the block in the page buffer for each block. In the block having the first uncompressed data record (UCDR), the data to be drawn in the block is newly drawn. Becomes compressible and becomes incompressible again by further drawing and a new second uncompressed data record is generated, the address information of the first uncompressed data record is stored in the writable address register. A lossless compression processing method for image data, comprising: 7. The lossless compression processing method for image data according to claim 6, wherein a third uncompressed data record (UCD) is used.
R), the third uncompressed data record is stored in the first uncompressed data record which is the address pointed to by the address register. 8. The method of lossless compression processing of image data according to claim 6, wherein a third uncompressed data record (UCD) is used.
R) In a block, if data to be drawn in the block can be compressed by new drawing and becomes incompressible again by further drawing and a new fourth uncompressed data record occurs, the third Stores the address of the first uncompressed data record in the uncompressed data record, stores the address of the third uncompressed data record in the address register, and stores termination information in the first UCDR. A lossless compression processing method of image data, characterized by the above. 9. In a page printer, two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction for binary image data to be drawn. , The page buffer necessary for drawing the image data to be printed at a predetermined resolution is divided into the above-mentioned units, and it is checked whether or not the drawing data is all white for each unit. Storing in a white map table (WMT) of a collection of bit unit records, and when the drawing data of the unit is not all white, an n-bit compressed data record (CDR ), A compressed data table (CDT) in which u blocks are collected, and the unit is configured there Storing a compression processing result for each of u blocks, and t-bit uncompressed data record (UCDR) in the address area specified in the compressed data table when the compression processing for each block is impossible. ) Is prepared, and the image data of the block is stored as it is, the image data to be drawn corresponds to which block of the divided unit, and the image data previously drawn in the block is calculated. The variable-length lossless compression process of restoring the image data that has been restored, rewriting it to new drawing data, compressing the drawing data by the processing of each step described above, and drawing in the block in the page buffer for each block. When the capacity of the page buffer becomes insufficient during the variable length compression process, switch to fixed length compression process for each unit. Lossless compression method of the image data, characterized in that. 10. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. The variable length reversible compression process or the fixed length compression process is suitable, in which each block is subjected to the process of drawing the drawing data and compressing the drawing data by the process of each step and drawing the block in the block in the page buffer. Whether or not the compression process is performed for each unit, and the compression process is switched for each unit based on the determination result. Lossless compression method that the image data. 11. The variable-length lossless compression processing method for image data according to claim 9 or 10, wherein compressed data records and non-compressed data records that are no longer used are used in the fixed-length compression processing when switching compression processing. A lossless compression processing method of image data, characterized by executing a garbage collection that enables it. 12. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. , The drawing data is compressed by the processing of each step and the variable length lossless compression processing of drawing the block in the page buffer is performed for each block, and a unit during the variable length lossless compression processing is performed. If the number of uncompressed data records (UCDR) in the compressed data table (CDT) is more than half the number of blocks in the compressed data table (CDT), Converting all blocks in a unit to uncompressed data records, deleting the compressed data table corresponding to that unit, and storing the flag information in the record of the corresponding unit in the white map table (WMT). A method for lossless compression processing of characteristic image data. . 13. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. , The drawing data is compressed by the processing of each step described above, and variable length lossless compression processing of drawing in the block in the page buffer is performed for each block, and a compressed data record (CDR) is generated during the compression processing. When all the white data is generated in the unit where
A lossless compression processing method for image data, characterized in that the compressed data table corresponding to the unit is deleted and the corresponding unit record in the white map table is initialized. 14. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. , The drawing data is compressed by the processing of each step described above, and variable length lossless compression processing of drawing in the block in the page buffer is performed for each block, and a compressed data record (CDR) is generated during the compression processing. In the unit where is generated, if all become black data,
A lossless compression processing method for image data, characterized in that the compressed data table corresponding to the unit is deleted and all black information is stored in the corresponding unit record in the white map table. 15. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. , The drawing data is compressed by the processing of each step described above, and variable length lossless compression processing of drawing in the block in the page buffer is performed for each block, and a compressed data record (CDR) is generated during the compression processing. In the unit where is generated, if all have a p-bit bit pattern, the compressed data corresponding to that unit A lossless compression processing method of image data, characterized in that the pattern table is deleted and the pattern flag information and the number of pattern bits and the pattern information are stored in a corresponding unit record in the white map table. 16. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. , The drawing data is compressed by the processing of each step described above, and the variable-length lossless compression processing of drawing in the block in the page buffer is performed for each block, and a plurality of fill patterns corresponding to the blocks are previously stored. The feature is that if the compression processing for each block cannot be performed, the pattern is referred to in advance. A method for lossless compression processing of image data. 17. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. If the variable length reversible compression processing is performed for each block and the drawing data is compressed by the processing of each step described above and is drawn in the block in the page buffer, the compression processing for each block cannot be performed. , The dot pattern of that block is stored, and if the same pattern appears during the subsequent compression processing, The image compression method according to claim 1, wherein the compression processing is performed by referring to an address in which the input pattern is stored. 18. A page printer for drawing 2
Two basic units of a block composed of t dots in the main scanning direction and a unit composed of u blocks in the main scanning direction or the sub scanning direction are set for the value image data, and the image data to be printed has a predetermined resolution. The page buffer necessary for drawing is divided into units, and it is checked whether the drawing data is all white for each unit. The result is a white map table (WMT) of a collection of m-bit unit records. ), When the drawing data of the unit is not all white, a compressed data table (CDT) is created by collecting n blocks of compressed data records (CDR) in the address area specified by the white map table for u blocks. ) Is prepared, and the compression processing result for each of u blocks constituting the unit is stored therein. Step, and when the compression processing for each block is impossible, a t-bit uncompressed data record (UCDR) is prepared in the address area specified by the compressed data table, and the image data of the block is directly stored therein. Storing the image data to be drawn, calculating which block of which unit the divided image data corresponds to, restoring the image data previously drawn in that block, and using it as new drawing data. If the variable length reversible compression processing is performed for each block and the drawing data is compressed by the processing of each step described above and is drawn in the block in the page buffer, the compression processing for each block cannot be performed. , If a certain kind of logical operation is applied to the dot pattern of the block and the result can be compressed, A reversible compression processing method for image data, which comprises performing a logical operation process that is the reverse of the above-described logical operation upon conversion and decompression. 19. In a page printer, a block composed of t dots in the main scanning direction and b bits corresponding to a bit plane of the multivalued data and u in the main scanning direction or sub-scanning direction for the multivalued image data to be drawn. Set the two basic units of the unit composed of blocks, divide the page buffer required for drawing the image data to be printed at a predetermined resolution into the above-mentioned units, and draw the drawing data in all white. Checking whether there is any, and saving the result in a white map table (WMT) of a collection of m-bit unit records; A compressed data record in which n × compressed data records (CDRs) of u × b blocks are collected in the address area (CDT) is prepared, and the compression processing result for each of the u × b blocks forming the unit is stored therein; and when the compression processing for each block is impossible, the compressed data table Prepare a t-bit uncompressed data record (UCDR) in the address area specified by, and store the image data of the block as it is, in which unit the image data to be drawn is divided. Calculates which block it corresponds to, restores the image data previously drawn in that block, rewrites it with new drawing data, compresses the drawing data by the processing of each of the above steps, and compresses it in the page buffer. A lossless compression processing method for image data, in which variable length lossless compression processing is performed for each block in each block. 20. The lossless compression processing method for image data according to claim 19, wherein a compressed data table (CD which is no longer used due to the repetition of the variable length lossless compression processing).
T) and the uncompressed data record (UCDR) memory area free list is formed and the compressed data table (C
DT) and uncompressed data record (UCDR) are searched on the free list, and if there is a memory area in the free list, it is allocated and reused. A method for lossless compression processing of image data, characterized by newly allocating a memory area when there is no such data.