JP2001211317A - Device and method for compression, storage medium recorded with compressing method, and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time needed for a thinning-out processing which is carried out when the size of data having been compressed exceeds an expected data size. SOLUTION: The device comprises a thinning-out processing part 102 which divides image data into odd dots and even dots, a compressing processing part 102 which compresses the odd-dot image data, an output FIFO 104 which temporarily stores the code data of the odd dots, a compressing process part 105 which compresses the even-dot image data, an output FIFO 106 which temporarily stores the code data of the even dots, an input FIFO 107 which temporarily stores the code data of the odd dots, an expanding processing part 108 which expands the code data of the odd dots, an input FIFO 109 which temporarily stores the code data of the even dots, an expanding processing part 110 which expands the code data of the odd dots, a data composition part 111 which puts the expansion results of the odd and even dots together, and an output FIFO 112 which temporarily stores the image data obtained by the expansion and composition.

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, the resolution of electrophotographic printers has been increased in order to make print output look beautiful.
A resolution of 2400 dpi is required.
For this reason, a large memory space is required for the image development processing. However, the cost of electrophotographic printers has been reduced and expensive memories cannot be mounted in large quantities. For this reason, 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 multi-value data, JPEG, etc. will be used. In some cases, the algorithm is performed using a unique algorithm. However, most compression technologies depend on the compression ratio image characteristics, so after performing compression processing for each band, check or predict the size of the code data, and if the memory space is likely to be insufficient, the user will be asked It is necessary to perform processing such as requesting memory expansion, using a compression algorithm having a good compression ratio but poor resilience, or lowering the resolution.

FIG. 13 is a flowchart showing the operation of a compression method in Japanese Patent Application Laid-Open No. 09-093425, entitled "Image Forming Apparatus". Japanese Patent Application Laid-Open No. 09-093425 discloses an "image forming apparatus" in which an original image is subjected to a compression process, and when the code data exceeds a predetermined size, the compressed data is temporarily discarded (once), and the resolution of the original image is reduced to thin out. Processing, redrawing, and compression are performed to save memory capacity.

[0005]

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

Further, when it is determined that the memory space is likely to be exceeded at the compression ratio as it is when the data is compressed to the middle of one page, the data which has been compressed so far is compared with the data size whose code data length is expected. There is a problem in that it is necessary to perform expansion or redrawing once (including once for a small band) to return to 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 Japanese Patent Application Laid-Open No. 09-093425 "Image forming apparatus". If the expected compression ratio cannot be obtained, the compression process is performed again after the image is temporarily (temporarily) decompressed or redrawn, so that the speed performance of the device is reduced.

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

[0009]

A first compression apparatus according to the present invention is a compression apparatus used in a printer, which compresses image data and decompresses the image data at the time of printing. Compression
If the available memory capacity exceeds the available memory capacity due to the low compression ratio, the code data compressed for each of the odd or even dots or lines is discarded, and the original image data is thinned.

A second compression device of the present invention is a compression device used in a printer which compresses image data and decompresses the image data at the time of printing. When a high compression ratio is obtained, each code data compressed for each odd-numbered and even-numbered dot or line is used.At the time of decompression, each code data is expanded, and an image divided by odd-numbered and even-numbered dots or lines is synthesized. It has the function to do.

A third compression device according to the present invention is a compression device used in a printer, which compresses image data and decompresses the image data at the time of printing. If the rate exceeds the available memory capacity due to the low rate, the code data compressed for each of the odd or even dots or lines is discarded, and the original image data is thinned to obtain a sufficient compression rate. In this case, each code data is compressed for each odd or even dot or line. At the time of decompression, each code data is decompressed, and an image divided by odd and even dots or lines is synthesized.

A fourth compression device according to the present invention is a compression device which is used in a printer and compresses image data and decompresses the image data at the time of printing. In the compression device, original image data is divided in advance into odd dots and even dots or odd lines and even lines. Then, when it is determined that the memory capacity for storing the code data is likely to exceed when the compression processing of a certain band in one page is completed, the code data compressed for each even dot or even line is discarded. I do.

According to a fifth aspect of the present invention, there is provided a compression apparatus which is used in a printer and which compresses image data and decompresses the image data at the time of printing.
O, a thinning processing unit that performs thinning processing on the image data, and divides the image data into odd and even dots;
A first compression processing unit for compressing the image data of the odd dots, a first output FIFO for temporarily storing code data of the odd dots, and a second compression processing unit for compressing the image data of the even dots A second output FIFO for temporarily storing the code data of the even-numbered dots, a first input FIFO for temporarily storing the code data of the odd-numbered dots when expanded, and the code data for the odd-numbered dots. A first decompression processing unit for decompressing the data, a second input FIFO for temporarily storing the code data of the even-numbered dots,
A second decompression processing unit for decompressing the code data for the even-numbered dots, a data synthesizing unit for synthesizing the expansion results of the odd-numbered dots and the expansion results of the even-numbered dots, and temporarily expanding the image data synthesized by the expansion. It consists of an output FIFO to be stored.

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

The compression method according to the present invention is a compression method for compressing image data used in a printer and decompressing the image data at the time of printing, wherein the first step of drawing the image data on a memory and the step of drawing the image data on the memory A second step of dividing the image data into odd and even dot components,
A third step of storing the compressed code data in different areas of the odd-numbered dot component and the even-numbered dot component respectively;
When the processing of the band is completed, a fourth step of opening the memory space of the first band which has been developed in the image data storage area, and a fifth step of enabling the next drawing development in the area. , Check the code data storage area,
A sixth step of checking whether there is enough free space to continue the compression processing as it is, a seventh step of performing compression in the same manner as the first band for the second and subsequent bands,
When confirming the free memory space for storing the code data for each band, if it is determined that the memory space may be exceeded, the eighth data for discarding the code data of the even-numbered dot component is determined. It comprises a step, a ninth step of drawing the original image and compressing odd-numbered dot lines again, and a tenth step of performing the first to ninth steps over one page.

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

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order 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 configuration of the 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 a thinning process on image data, and divides image data into odd and even dots, and a compression processing unit 103 that compresses odd dot image data. An output FIFO 104 for temporarily storing odd-dot code data, a compression processing unit 105 for compressing even-dot image data, an output FIFO 106 for temporarily storing even-dot code data,
When decompressing, 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 processing of code data for even dots. A decompression processing unit 110 for decompressing, a data synthesizing unit 11 for synthesizing the expansion result of odd-numbered dots and the expansion result of even-numbered dots
1 and an output FIFO 112 for temporarily storing the decompressed and synthesized image data.

In addition, an input / output data bus control unit, an interrupt control unit, an internal timing control unit, and a DMA controller when input / output data transfer is performed by DMA are also required. Therefore, the description is omitted here. The compression algorithm used here is not particularly defined. However, the compression ratio varies depending on the characteristics of image data to be compressed, that is, a compression algorithm having a fixed code length, and includes not only a binary compression algorithm but also a 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 flow of image data and data in the 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-numbered dot component and an even-numbered dot component by the thinning-out unit 102, and the odd-numbered dot component is sent to the compression unit 103, and the even-numbered dot component is sent to the compression unit 105. The processing is performed (steps A-2 and A-3). The compressed code data is stored in separate areas for odd-numbered dot components and even-numbered dot components, respectively (step B-1). When the processing of the first band is completed, the memory space of the first band that has been developed in the image data storage area is released so that the next drawing development can be performed in that area (step A-).
4). Further, the code data storage area is checked, and it is checked whether there is a free space enough to continue the compression processing as it is (step A-5). Compression is performed for the second and subsequent bands in the same manner as for the first band (steps B-2 and B-3). When confirming the free memory space for storing the code data for each band, if it is determined that the memory space may be exceeded, the code data of the even-numbered dot component is discarded (step A-). 6) Then, the original image is drawn (Step A-7), and the odd dot line is compressed again (Step A-8). The above processing is performed over one page (steps A-9 and A-10), thereby securing a memory space. At this time, since the code data of the odd-numbered dot component remains, it matches the original image that has been thinned out and compressed (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 prior art shown in FIG.

Next, the operation at the time of decompression will be described. FIG.
FIG. 7 is a diagram illustrating a flow of image data and a data flow of a code data storage unit when a memory overflow does not occur during decompression according to the first embodiment of this invention. The code data is decompressed by the decompression processing unit 108 into the code data of the odd-numbered dot component in the code data storage area, and the decompression processing unit 11
If 0, the code data of the even dot component is expanded. The results decompressed by the decompression processing units 108 and 110 are synthesized by the data synthesizing 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 data in the code data storage unit when a memory overflow occurs during decompression according to the first embodiment of the present invention. The odd-numbered component code data is transferred to the decompression processing unit 108 and decompressed (steps D-1 to D-4). The data decompressed by the decompression processing section has half the resolution of the original image, and is transferred directly to the image data storage area.

As described above, when the memory space is insufficient by the above-described method, the resolution can be reduced to one half, and when the memory is sufficient, expansion can be performed at the resolution of the original image. Also,
When it is determined that the memory space for storing the code data at the time when the compression processing of a certain band of one page is completed in the device having insufficient main memory capacity is likely to be over because the expected image compression ratio cannot be obtained. By simply discarding one of the compressed code data, the thinning process can be simplified, and the processing speed performance of the apparatus does not need to be reduced.

Next, a compression apparatus according to a second embodiment of the present invention will be described. FIG. 7 is a block diagram illustrating a configuration of a compression device according to the second embodiment of this invention. The second compression device 1b performs an image data input FIFO 201 for inputting image data to be compressed, a thinning processing unit 202 that performs a thinning process on the image data, divides the image data into odd and even dots, and compresses the image data. Compression processing section 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, a thinned image input FIFO 2
08, a decompression processing unit 206 for decompressing code data, a data synthesizing unit 207 for synthesizing an odd dot expansion result and an even dot expansion result, and an image data output FIFO 209 for temporarily storing decompressed and synthesized image data. It consists of.

In the second embodiment, the basic configuration is as described above. However, as shown in FIG. 7, it is also possible to reduce the number of compression processing units and expansion processing units by one. In this case, the data synthesizing unit 207
It is necessary to combine the output of the decompression processing unit 206 with the data in the image data storage area, but the rest is the same as the compression device of the first embodiment.

FIG. 9 shows the operation of the compression device of the second embodiment during compression. First, image data is taken out from the image data storage area, and only the odd-numbered dot component is extracted by the thinning-out processing unit 202 and compressed by the compression processing unit 203, and then the code data of the odd-numbered dot component is stored in the code data storage area (step E). -1). Next, with respect to the same band, image data is extracted from the image data storage area, and only the even-numbered dot components are extracted by the thinning processing unit 202.
03, the code data of the even-numbered dot component is stored in the code data storage area (steps E-2 and E-
3). If the memory space over is predicted, the code data of the even dot component is discarded as described above (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 decompression will be described. When the memory space is exceeded 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 no memory overflow occurs during decompression according to the second embodiment of the present invention. In this case, first, the odd-numbered dot component is expanded, and only the odd-numbered dots are stored in the image data storage area at every other dot. Next, when the expansion of the odd-numbered dot components is completed, the expansion of the even-numbered dot components of the same band is performed (step F-).
1). At this time, the image data combining unit 207 combines the expansion result of the even-numbered dot component with the odd-numbered dot image in the image data storage area, and stores the result in the same area (step F).
-2, 3, 4).

Each of the compression and decompression steps described above can be executed as a program in combination with a computer instruction. FIG. 11 is a diagram showing a recording medium 61 and a printer 60 on 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 includes 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, image data is compressed in order to reduce the memory capacity used in a device having insufficient main memory capacity, and the compression processing of a band of one page is performed. When it is determined that the memory space for storing the code data is likely to exceed the expected image compression ratio at the end of the process, the code data compressed for each even-numbered dot or even-numbered line is discarded. The thinning process when the memory space is over can be simplified. For this reason, even if the memory space is exceeded, the effect that the processing speed performance of the apparatus is not reduced is obtained.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram illustrating a flow of image data and a data flow of a code data storage unit during compression according to the first embodiment of this invention.

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

FIG. 5 is a diagram illustrating a flow of image data and a data flow of 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 illustrating a flow of image data and a data flow of 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 illustrating processing time of a compression method according to the second embodiment of this invention.

FIG. 9 is a diagram illustrating a flow of image data and a data flow of a code data storage unit during compression according to the second embodiment of this invention.

FIG. 10 is a diagram illustrating 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 this invention.

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

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

FIG. 13 is a flowchart illustrating the operation of a compression method in Japanese Patent Application Laid-Open No. 09-093425, “Image Forming Apparatus”.

FIG. 14 is a diagram illustrating processing time of a compression method in Japanese Patent Application Laid-Open No. 09-093425, “Image Forming Apparatus”.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 compression device 1b second compression device 2 printer engine 3 interface unit 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 expansion FIFO unit 109 input FIFO 110 expansion processing section 111 data synthesis section 112 output FIFO 201 image data input FIFO 202 thinning processing section 203 compression processing section 204 code data output FIFO 205 code data input FIFO 206 expansion processing section 208 thinning image input FIFO 207 data synthesis section 209 image Data output FIFO 601 Control microprocessor

Claims (8)

[Claims] 1. A compression device used in a printer, which compresses image data and decompresses it at the time of printing, compresses odd-numbered dots, even-numbered dots or lines in advance when performing compression, and can be used because the compression ratio is low. A compression device for discarding code data compressed for each of the odd or even dots or lines and thinning out the original image data when the memory capacity exceeds the maximum memory capacity. 2. A compression device used in a printer, which compresses image data and decompresses it at the time of printing, performs compression in advance for each odd-numbered dot, even-numbered dot, or line when performing compression, and obtains a sufficient compression ratio. In this case, each code data compressed for each odd or even dot or line is used, and at the time of decompression, each code data is decompressed and then combined with an image divided by odd and even dots or lines. Compression device. 3. A compression device used in a printer, which compresses image data and decompresses it at the time of printing, compresses odd-numbered dots, even-numbered dots, or lines in advance when performing compression, and can be used because the compression ratio is low. If the memory capacity exceeds the maximum memory capacity, the code data compressed for each of the odd or even dots or lines is discarded and the original image data is thinned out. A compression apparatus having a function of using respective code data compressed for each even dot or line, decompressing each code data at the time of decompression, and synthesizing an image divided by odd and even dots or lines. 4. A compression apparatus used in a printer, which compresses image data and decompresses the image data at the time of printing. The compression apparatus divides original image data into odd dots and even dots or odd lines and even lines before compressing. When it is determined that the memory capacity for storing the code data is likely to exceed when the compression processing of a certain band in the page is completed, the code data compressed for each even dot or even line is discarded. apparatus. 5. A compression device used for a printer, which compresses image data and decompresses the image data at the time of printing, wherein the input FIFO for inputting the image data to be compressed and the thinning-out process are performed on the image data to convert the input data into odd and even dots. A thinning-out processing unit for dividing the image data, a first compression processing unit for compressing the image data of the odd-numbered dots, a first output FIFO for temporarily storing code data of the odd-numbered dots, A second compression processing unit for compressing the image data, a second output FIFO for temporarily storing the code data of the even-numbered dots, and a first input for temporarily storing the code data of the odd-numbered dots when decompressing. FIFO, a first decompression processor for decompressing the code data of the odd dots, and a second input for temporarily storing the code data of the even dots. An IFO, a second decompression processing unit for decompressing the code data of the even-numbered dots, a data synthesizing unit for synthesizing the expansion results of the odd-numbered dots and the even-numbered dots, and the expanded and synthesized image A compression device comprising an output FIFO for temporarily storing data. 6. A printer comprising: an interface unit for controlling connection with a host device; a print engine for executing printing; and a compression device according to claim 1. 7. A compression method for compressing image data used in a printer and decompressing at the time of printing, comprising: a first step of drawing image data on a memory; A second step of dividing the data into a component and an even-numbered dot component, a third step of storing the compressed code data in different areas of the odd-numbered dot component and the even-numbered dot component, respectively. A fourth step of opening the memory space of the first band developed in the image data storage area, a fifth step of enabling the next drawing development in the area, and checking the code data storage area In the sixth step of checking whether there is enough free space to continue the compression processing as it is, and for the second and subsequent bands,
When the seventh step of performing compression in the same manner as in the first band and the confirmation of the free memory space for storing the code data for each band, it was determined that there is a possibility that the memory space might be exceeded. In this case, the eighth step of discarding the code data of the even-numbered dot component, the ninth step of drawing the original image and compressing the odd-numbered dot lines again, and the first to ninth steps are performed on one page. 10. A compression method comprising a tenth step performed across. 8. A recording medium recording a program for causing a control microprocessor to execute the first to tenth steps.