JP3463643B2 - Compression device, compression method, recording medium recording compression method, printer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer having a function of compressing image data for each band.

[0002]

2. Description of the Related Art In recent years, electrophotographic printers have been increasing in resolution in order to make printed output look beautiful. Currently, the resolution is normally 600 dpi 600 dots / inch, and high image quality is 1200.
A resolution of 2400 dpi is required for the dpi.
Therefore, a large memory space is required for the image expansion processing. However, the price of the electrophotographic printer has been reduced, and a large amount of expensive memory cannot be installed. Therefore, there is a situation where the memory capacity must be reduced by some compression technique.

If the compression technique used in the printer is binary data, MH, MR, JBIG, etc., and JPEG, etc. are used for multi-valued data. It may also be performed by an original algorithm. However, since most compression techniques depend on the compression ratio image characteristics, after performing compression processing for each band, the size of code data is confirmed or predicted, and if the memory space is likely to run short, the user is informed. Must request memory expansion, use a compression algorithm with a good compression rate but poor recoverability, or reduce the resolution.

FIG. 13 is a flowchart showing the operation of the compression method in the "image forming apparatus" of Japanese Patent Laid-Open No. 09-093425. In the "image forming apparatus", the original image is compressed, and when the code data exceeds a predetermined size, the compressed data is once (temporarily) discarded, the resolution of the original image is reduced, and the thinning is performed. The memory capacity is saved by processing, redrawing, and compressing.

[0005]

Since most compression techniques depend on the image characteristics of the compression ratio, if the compression process is performed for each band and the code data length is confirmed and judged, the code data length is expected in one page. There is a possibility that a band that becomes larger than the data size that you were
There is a problem.

Further, when it is judged that the memory space is likely to be over with the compression ratio as it is at the time of compressing a page halfway, the data compressed up to now is compared with the data size expected by the code data length. There is a problem that it is necessary to perform (temporary) expansion or redrawing including the small band to restore the original image data, perform resolution conversion thinning, and then perform compression processing again.

FIG. 14 is a diagram showing the processing time of the compression method in the "image forming apparatus" of Japanese Patent Laid-Open No. 09-093425. If the expected compression ratio is not obtained, there is a problem in that the speed performance of the device is reduced because the compression process occurs once (once) after decompression or redrawing.

A main object of the present invention is to shorten the time required for the thinning process performed when the data size after compression becomes larger than the expected data size.

[0009]

The first compression device of the present invention.
Is used in printers to compress image data and expand it during printing.
The image data to be compressed in a compression device that performs compression
Input FIFO for input and thinning processing for image data
Divide the image data into odd dots and even dots.
And the image data of the odd-numbered dots
The first compression processing unit for compression and the odd-numbered dot code data
First output FIFO for temporarily storing data
A second compression processing unit for compressing the image data of
The second output that temporarily stores the code data of even-numbered dots
Force FIFO and the sign of the odd dots when decompressing
A first input FIFO for temporarily storing data and the odd number
First decompression process for decompressing the code data for dots
Part and the second data for temporarily storing the code data of the even dots
Input FIFO and the extension of the code data for the even dots.
The second extension processing unit that performs the
A data synthesizing unit for synthesizing the result of the expansion of the even dot
And temporarily store the expanded and combined image data.
Power FIFO.

[0010]

[0011]

[0012]

[0013]

The printer of the present invention has an interface section for controlling connection with a host device, a print engine for executing printing, and the first compression apparatus of the present invention.

The compression method of the present invention is a compression method used in a printer for compressing image data and decompressing it at the time of printing, and the first step of drawing the image data on the memory and the drawing on the memory. A second step of dividing the image data into odd dot components and even dot components,
The compressed code data is stored in different areas for the odd dot component and the even dot component respectively.
When the processing of the band is completed, a fourth step of releasing the memory space of the first band, which has been expanded in the image data storage area, and a fifth step of allowing the next drawing expansion to be performed in that area , Check the code data storage area,
A sixth step of confirming whether there is a free space for continuing the compression process as it is, and a seventh step of compressing the second and subsequent bands in the same manner as the first band,
When checking the free memory space for storing the code data for each band, if it is determined that the memory space may be over, discard the code data of the even dot components It is composed of a step, a ninth step of drawing the original image and performing compression processing of the odd dot lines again, and a tenth step of performing the first to ninth steps over one page.

The computer-readable recording medium of the present invention has recorded therein a program for causing a control microprocessor to execute the first to tenth steps of the compression method of the present invention.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION To clarify the above and other objects, features and advantages of the present invention, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the structure of a compression apparatus according to the first embodiment of the present invention. The compression device includes an input FIFO 101 for inputting image data to be compressed, a thinning processing unit 102 that performs thinning processing on the image data and divides the image data into odd dots and even dots, and a compression processing unit 103 that compresses the odd dot image data. , An output FIFO 104 for temporarily storing code data of odd dots, a compression processing unit 105 for compressing image data of even dots, an output FIFO 106 for temporarily storing code data of even dots,
At the time of decompression, an input FIFO 107 for temporarily storing code data of odd dots, a decompression processing unit 108 for decompressing code data of odd dots, an input FIFO 109 for temporarily storing code data of even dots, and a code data of even dots. A decompression processing unit 110 for decompressing, a data synthesizing unit 11 for synthesizing a decompression result of odd dots and a decompression result of even dots.
1 and an output FIFO 112 for temporarily storing the expanded and combined image data.

Besides, an input / output data bus control unit, an interrupt control unit, an internal timing control unit, and a DMA controller or the like are required when the input / output data transfer is performed by DMA, but these are simplified in the drawing and description. Therefore, it is omitted here. The compression algorithm adopted here is not specified. However, the compression rate varies depending on the characteristics of the image data to be compressed, that is, the compression algorithm is not a fixed code length, and includes not only the binary compression algorithm but also the multi-value compression algorithm.

Next, the operation of this embodiment will be described.

First, the operation at the time of compression will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation of the compression method according to the first embodiment of the present invention. FIG. 3 is a diagram showing a data flow of image data and a code data storage unit at the time of compression according to the first embodiment of the present invention.

The image data is drawn on the memory (step A-1). The image data drawn on the memory is divided into an odd dot component and an even dot component by the thinning processing unit 102, the odd dot component is sent to the compression processing unit 103, and the even dot component is sent to the compression processing unit 105, respectively compressed in parallel. It is processed (steps A-2 and A-3). The compressed code data is stored in different areas for the odd dot components and the even dot components (step B-1). When the processing of the first band is completed, the memory space of the first band that has been expanded in the image data storage area is released so that the next drawing expansion can be performed in that area (step A-
4). Further, the code data storage area is confirmed, and it is confirmed whether or not there is a free space enough to continue the compression process (step A-5). After the second band, compression is performed in the same manner as the first band (steps B-2 and B-3). When the empty memory space for storing the code data is confirmed for each band, if it is determined that the memory space may be exceeded, the code data of the even dot component is discarded (step A- 6) Then, the original image is drawn (step A-7), and the odd dot line compression processing is performed again (step A-8). The above processing is performed over one page (steps A-9 and A-10), whereby the memory space is secured. At this time, since the code data of the odd-numbered dot component remains, it coincides with the data obtained by thinning and compressing the original image (step B-4).

FIG. 4 is a diagram showing the processing time of the compression method according to the first embodiment of the present invention. The processing when the memory space is exceeded can be performed faster than the processing time of the conventional technique shown in FIG.

Next, the operation at the time of expansion will be described. Figure 5
FIG. 6 is a diagram showing a flow of image data and a data in a code data storage unit when a memory overflow does not occur at the time of decompression according to the first embodiment of the present invention. The decompression processing unit 108 decompresses the code data of the odd dot components in the code data storage area, and decompresses the code data.
At 0, the code data of the even dot component is expanded. The results of expansion performed by the expansion processing units 108 and 110 are combined by the data combining unit 111, and the results are stored in the image data storage area (steps C-1 to C-4).

FIG. 6 is a diagram showing the flow of image data and the data in the code data storage unit when a memory overflow occurs during decompression according to the first embodiment of the present invention. The coded data of the odd-numbered component is transferred to the expansion processing unit 108 and expanded (steps D-1 to D-4). The data decompressed by the decompression processing unit has a resolution half that of the original image and is transferred to the image data storage area as it is.

As described above, when the memory space is insufficient by the above method, the decompression can be performed at half the resolution, and when the memory is sufficient, the decompression can be performed at the resolution of the original image. Also,
In a device that does not have enough main memory capacity, when it is determined that the memory space for storing the code data is not able to obtain the expected image compression rate at the time when the compression process for a band of one page is completed, By only discarding one of the compressed code data, the thinning process can be simplified and the device processing speed performance does not have to be reduced.

Next, a compression device according to a second embodiment of the present invention will be described. FIG. 7 is a block diagram showing the configuration of the compression device according to the second embodiment of the present invention. The second compression device 1b compresses image data, an image data input FIFO 201 for inputting image data, a thinning process for the image data, a thinning processing unit 202 for dividing the image data into odd dots and even dots, and image data. Compression processing unit 203,
Code data output FIFO 20 for temporarily storing code data
4, a code data input FIFO 205 for temporarily storing code data when decompressing, and a thinned image input FIFO 2
08, a decompression processing unit 206 for decompressing code data, a data synthesizing unit 207 for synthesizing a result of decompressing odd dots and a result of decompressing even dots, and an image data output FIFO 209 for temporarily storing the decompressed and combined image data. It consists of.

In the second embodiment, the basic configuration is as described above, but it is also possible to reduce the number of compression processing units and the number of expansion processing units by one as shown in FIG. In this case, when the data synthesizing unit 207 expands,
Although it is necessary to combine the output of the decompression processing unit 206 with the data in the image data storage area, the other components are the same as those of the compression device according to the first embodiment.

FIG. 9 shows the operation of the compression apparatus of the second embodiment during compression. First, the image data is taken out from the image data storage area, only the odd dot components are extracted by the thinning processing unit 202, compressed by the compression processing unit 203, and the code data of the odd dot components is stored in the code data storage area (step E). -1). Next, regarding the same band, the image data is extracted from the image data storage area, and the thinning processing unit 202 extracts only the even dot components, and the compression processing unit 2
After being compressed in 03, the code data of the even dot component is stored in the code data storage area (steps E-2 and E-
3). If it is predicted that the memory space will be over, as described above, the code data of the even dot components are discarded (step E-4).

FIG. 8 is a diagram showing the processing time of the compression method according to the second embodiment of the present invention.

Next, the operation at the time of expansion will be described. When memory space over occurs during decompression, the same operation as described in the first embodiment is performed.

FIG. 10 is a diagram showing the flow of image data and the data in the code data storage unit when a memory overflow does not occur during decompression according to the second embodiment of the present invention. In this case, the odd-numbered dot component is first expanded, and every other dot is stored in the image data storage area only in the odd-numbered dot. Next, when the extension of the odd-numbered dot component is completed, the extension of the even-numbered dot component of the same band is performed (step F-
1). At this time, the image data synthesizing unit 207 synthesizes the expansion result of the even dot component and the odd dot image in the image data storage area, and stores the result in the same area (step F).
-2, 3, 4).

The compression and decompression steps described above can be executed as a program in combination with computer instructions. FIG. 11 is a diagram showing a recording medium 61 and a printer 60 in which a program for causing the control microprocessor 601 to execute the compression method according to the embodiment of the present invention is recorded. The printer 60 has a control microprocessor 601 built therein.

FIG. 12 is a diagram showing a printer according to the embodiment of the present invention. The printer of the present invention comprises the above-described compression device 1, a printer engine 2 for executing printing, and an interface unit 3 for interfacing with a higher-level device.

[0035]

As described above, according to the present invention, the image data is compressed in order to reduce the memory capacity used in the device having the insufficient main memory capacity, and the compression processing of the band having one page is performed. When it is determined that the memory space for storing code data at the time of completion is likely to be over because the expected image compression rate cannot be obtained, by discarding the code data compressed for every even dot or even line, The thinning process when the memory space is exceeded can be simplified. Therefore, it is possible to obtain the effect that the device processing speed performance is not degraded even when the memory space is overrun.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the compression method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a data flow of image data and a code data storage unit at the time of compression according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a processing time of the compression method according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a flow of image data and a data in a code data storage unit when a memory overflow does not occur during decompression according to the first embodiment of this invention.

FIG. 6 is a diagram showing a flow of image data and data in a code data storage unit when a memory overflow occurs during decompression according to the first embodiment of this invention.

FIG. 7 is a block diagram showing a configuration of a compression device according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a processing time of the compression method according to the second embodiment of the present invention.

FIG. 9 is a diagram showing a data flow of image data and a code data storage unit at the time of compression according to the second embodiment of the present invention.

FIG. 10 is a diagram showing a flow of image data and data in a code data storage unit when a memory overflow does not occur during decompression according to the second embodiment of the present invention.

FIG. 11 is a diagram showing a control medium 601 and a recording medium recording a program for causing the control microprocessor to execute the compression method according to the embodiment of the present invention.

FIG. 12 is a diagram showing a printer according to an embodiment of the present invention.

FIG. 13 is a flowchart showing an operation of a compression method in Japanese Patent Application Laid-Open No. 09-093425 “image forming apparatus”.

FIG. 14 is a diagram showing a processing time of a compression method in Japanese Patent Laid-Open No. 09-093425, “Image forming apparatus”.

[Explanation of symbols]

1 Compressor 1b Second compression device 2 Printer engine 3 Interface section 60 printer 61 recording medium 101 Input FIFO 102 thinning processing unit 103 compression processing unit 104 output FIFO 105 compression processing unit 106 output FIFO 107 input FIFO 108 Decompression processing unit 109 input FIFO 110 Decompression processing unit 111 Data synthesizer 112 output FIFO 201 Image data input FIFO 202 Thinning processing unit 203 compression processing unit 204 code data output FIFO 205 code data input FIFO 206 Decompression processing unit 208 Thinned-out image input FIFO 207 Data synthesizer 209 Image data output FIFO 601 Control microprocessor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI H04N 1/411 H04N 1/411 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/38-1/393 H04N 1/41-1/419

Claims (4)

(57) [Claims] 1. A compression device used in a printer for compressing image data and decompressing at the time of printing, wherein an input FIFO for inputting the image data to be compressed and a thinning process are performed on the image data to obtain odd dots and even dots. A thinning-out processing unit that divides the image data, a first compression processing unit that compresses the image data of the odd-numbered dots, a first output FIFO that temporarily stores code data of the odd-numbered dots, the even-numbered dots A second compression processing unit that compresses image data, a second output FIFO that temporarily stores the code data of the even dots, and a first input that temporarily stores the code data of the odd dots when decompressing. A FIFO, a first decompression processing unit that decompresses the code data for the odd dots, and a second input that temporarily stores the code data for the even dots. IFO, a second decompression processing unit for decompressing the code data for the even dots, a data synthesizing unit for synthesizing the expansion result for the odd dots and the expansion result for the even dots, and the image synthesized by decompression A compression device comprising an output FIFO for temporarily storing data. 2. A printer comprising an interface unit for controlling connection with a higher-level device, a print engine for executing printing, and the compression device according to claim 1. 3. A compression method used in a printer for compressing image data and decompressing at the time of printing, the first step of drawing the image data on a memory, and the image data drawn on the memory with an odd number of dots. The second step of dividing into the component and the even dot component, the third step of storing the compressed code data in different areas of the odd dot component and the even dot component respectively, and when the processing of the first band ends, Check the fourth step of releasing the memory space of the first band that was expanded in the image data storage area, the fifth step that allows the next drawing expansion in that area, and the code data storage area. , The 6th step to check if there is enough free space to continue the compression process and the second and subsequent bands,
In the seventh step of compression similar to the first band, and when checking the free memory space for storing the code data for each band, it was judged that there is a possibility that the memory space may be exceeded. In this case, the eighth step of discarding the code data of the even dot components, the ninth step of drawing the original image and performing the compression processing of the odd number of dot lines again, and the first to ninth steps on one page A compression method comprising a tenth step carried out across. 4. A co which records a program for executing the first to tenth steps in control microprocessor
Computer-readable recording medium.