JPH10313411A - Image processor and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs of image memory and also to prevent image deterioration from being conspicuous when image compression is performed by changing compression ratio in accordance with a variable power rate in image size transformation and resolution conversion. SOLUTION: This device performs switching of compression/non-compression according to modes. A controller 10 compares a variable power rate Rs which is preliminarily set by a user of a copier with a memory-effective variable power rate Rm1 which effectively uses a memory space of a buffer memory 4. When a comparison result is Rs<Rm1, compression ratio Rc is set to two, that is, image data capacity is compressed by 1/2 in order to store an entire image within the memory. On the other hand, when a comparison result is Rs>Rm1, the compression ratio Rc is set to one, that is, image data capacity is stored in the memory 4 without compressing it. Specially, when image compression is performed through a fixed length non-reciprocal compression method, it is possible to reduce costs of image memory and also to make a high image quality that prevents image deterioration from being conspicuous.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method suitable for a copying apparatus having a storage medium for image data.

[0002]

2. Description of the Related Art In recent years, in an apparatus which treats an image as digital data, a buffer memory having a huge capacity capable of storing one page or a plurality of pages of image data in order to perform editing processing such as synthesis and processing of image data. Devices equipped with are increasing. In addition, the resolution for reading image data is in the direction of higher resolution, and the memory capacity for storing image data is increasing more and more. For this reason, image compression is becoming an indispensable technology from the viewpoint of cost reduction of memory usage.

[0003] Image compression methods are roughly classified into two types: fixed-length lossy compression method and variable-length lossless compression method. When it is necessary to perform rotation processing or mirror image processing on image data in real time, the fixed-length irreversible compression method, which performs compression operation in block units, is often far more expensive than the variable-length lossless compression method. Easy to perform and highly feasible. However, in the case of the fixed-length irreversible compression method, the restoration of the compressed image data is irreversible as the name implies, and is slightly different from the original data. That is, the fixed-length irreversible compression method has a problem that image deterioration (image distortion for each block) occurs.

[0004]

However, the above-mentioned prior art has the following problems. That is, in the fixed-length irreversible compression method, several factors are involved in the degree of image degradation recognition. A major factor is a compression ratio and image data processing performed before and after the compression processing. In the image data processing, the image distortion of each block becomes very noticeable when the image data after compression and expansion is enlarged. Therefore, there is a problem that it is necessary to find a direction in which the deterioration of the image quality is not noticeable while reducing the cost of the memory for storing the image data by using the fixed-length irreversible compression method.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an image processing apparatus and an image processing apparatus which realize high image quality while reducing the cost of an image memory when compressing an image and which does not make image deterioration noticeable. It is an object to provide a processing method.

[0006]

According to one aspect of the present invention, there is provided an image processing apparatus for compressing and processing image data, comprising: a compression function for compressing a data capacity of the image data; Storage means having an expansion function for expanding image data, scaling means for performing image size conversion and resolution conversion of the image data stored in the storage means, and control for changing the compression ratio according to the scaling ratio in the scaling means Means.

In order to achieve the above object, a second aspect of the present invention is characterized in that the control means changes the compression ratio based on a result of comparison between the scaling factor in the scaling means and a set scaling factor. I do.

In order to achieve the above object, a third aspect of the present invention is characterized in that the compression rate includes a compression rate of 1.

In order to achieve the above object, a fourth aspect of the present invention has a copying function for forming image data as an image on a recording medium.

According to a fifth aspect of the present invention, there is provided an image processing method for compressing and processing image data, comprising a compression function for compressing a data volume of the image data and an expansion function for expanding the compressed image data. Having a storage step, a scaling step for performing image size conversion and resolution conversion of the image data stored in the storage step, and a control step for changing a compression ratio according to the scaling ratio in the scaling step. Features.

In order to achieve the above object, the invention according to claim 6 is characterized in that in the control step, the compression ratio is changed based on a comparison result between the scaling ratio in the scaling step and a set scaling ratio. I do.

In order to achieve the above object, a seventh aspect of the present invention is characterized in that the compression rate includes a compression rate of 1.

[0013] In order to achieve the above object, the invention according to claim 8 is characterized in that it has a copying step of forming image data as an image on a recording medium.

[0014]

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

In the embodiment of the present invention, the following method is adopted in order to minimize the deterioration of the image and to make full use of the fixed-length irreversible compression method as the image compression method. In other words, the image degradation is characterized in that (1) the degradation of the image increases as the compression rate increases, and (2) the image distortion of each block of the image data becomes noticeable according to the enlargement rate. As for (1), there is a feature that (1) image enlargement is performed at a later stage of the buffer memory, and (2) the maximum image size for outputting an image is fixed but the image enlargement ratio is arbitrary.

Therefore, from the above characteristics, it is most effective to lower the compression ratio as the enlargement ratio of the image data is increased. As one specific example, when the input document size is the same as the output paper size, when the compression ratio is 4 at 100% (meaning that the image data capacity is compressed to 1/4), 141
At the time of% enlargement, the compression ratio is 2 (meaning that the image data capacity is reduced to 1/2) because the input image data may be half the size.
To fully use the buffer memory to store the image data. Similarly, at the time of 200% enlargement, the input image data may be half the size, so that the compression ratio is set to 1 and the buffer memory is fully used to store the image data.

In the embodiment of the present invention, by effectively using the buffer memory as described above, the compression ratio at a high enlargement ratio at which image degradation is conspicuous is reduced, and high image quality is obtained. Hereinafter, the first and second embodiments will be described in detail.

[1] First Embodiment First, the overall configuration of a copying apparatus according to a first embodiment will be described with reference to the block diagram of FIG. The copying apparatus includes a CCD linear sensor 1, a preprocessing unit 2, a selector 3, a buffer memory 4, a scaling unit 5, a filter processing unit 7, a gamma conversion unit 8, a halftone processing unit 9, , A controller 10, and a printer unit 20.

The structure of each part of the copying apparatus will be described in detail.
The linear sensor 1 is a sensor that reads a document image on paper, receives light reflected from the document by a lamp, and replaces the light with an electric signal by photoelectric conversion. The pre-processing unit 2 amplifies analog image data output from the CCD linear sensor 1, converts analog image data into digital image data, performs analog / digital conversion, and performs black correction /
Image data normalization such as white correction is performed. The selector 3 selects one of a path for passing the read image data as it is to the subsequent stage and a signal path for storing the image data read from the buffer memory 4 at the subsequent stage in the buffer memory 4 again.

The image data is re-stored in the buffer memory 4 by Move processing for moving a part of an image or Cut processing for bringing a part of another image to a designated position in the image.
& Paste processing is required. The buffer memory 4 has a capacity for storing image data for one surface,
The configuration is extensible for the editing process. Magnification processing unit 5
Performs enlargement / reduction or resolution conversion by performing an interpolation operation from image data stored in the buffer memory 4. The filter processing unit 7 performs frequency calculations such as edge enhancement and smoothing on the target pixel with reference to the peripheral pixels.

The gamma conversion section 8 performs a look-up table. Here, the printer unit 20
An action of canceling the density characteristic at the time of forming an image,
It is an object of the present invention to enhance the two effects of adjusting the density of the entire image for printing out at a density desired by the user of the copying apparatus. The halftone processing unit 9 creates halftone image data by error diffusion processing. The printer unit 20 forms the image data as an image on paper. The controller 10 controls the above-described units in accordance with the control signals 101 to 108 and performs a control process as shown in flowcharts of FIGS. 3 and 5 described below.

Next, the configuration of the buffer memory 4 of the copying apparatus according to the first embodiment is divided into (1) image data writing and (2) image data reading, and refer to the block diagram of FIG. I will explain.

(1) Image data writing The serial / parallel (SP) converter 402
Of the input image data 401 is subjected to serial-parallel processing for outputting a block of 8 × 8 pixels as image data 403 of 512 bits at a time. The image data compression unit 404 uses JPEG (Joint Photographic Exposure)
rt Group: a color still image compression method), and compresses the compression rate Rc to 2, that is, the data amount to 、, thereby converting the image data 405 to 256b.
Compress it to The top 25 uncompressed image data 403
6-bit image data 403a and lower 256 bits
And image data 403b, and are input to separate selectors 440 and 441, respectively. The image data 405a and the image data 405b remain the same signal as the compressed image data 405 and remain at 256 bits.

The image data 403 is selected by the selector 440.
a or 405a is selected, and the image data 420
Is stored in the DRAM 430. Similarly, the image data 421 is stored in the DRAM 431. The separation between the uncompressed image data 403 and the compressed image data 405 will be described later. Write / read control of the DRAMs 430, 431 is performed by the address controller 422. DRAMs 430, 43 by the address controller 422
At the time of writing and reading to 1, the image rotation processing and the mirror image processing are performed.

(2) Image Data Reading Image data 4 read from the DRAMs 430 and 431
The configuration of 21 differs depending on which is selected by the selectors 440 and 441. When the uncompressed image data 403 is selected, the image data 412a is the upper 256 bits of the image data 412,
12b is the lower 256 bits of the image data 412. When the compressed image data 405 is selected, both the image data 412a and the image data 412b are 256 bits of the image data 412, and the DRAM 43
Data is read from only one of 0 and 431. The image data decompression unit 406 decompresses and decompresses the compression-encoded image data.

The input image data 412
Are 256 bits of image data 40 of 512 bits.
7 is restored. The selector 408 switches in synchronization with the write data selectors 440 and 441. When the image data 403 is selected, the image data 412 is output as it is. When the image data 405 is selected, the image data 407 is selected. The 512-bit image data 409 is rearranged again by the parallel-serial (PS) conversion unit 410 as block image data 411 of 8 × 8 pixels.

Next, control of switching between compression and non-compression of image data in the copying apparatus according to the first embodiment configured as described above will be described with reference to the flowchart of FIG.

In the image storage control (3000), A
In order to effectively utilize the buffer memory 4 capable of storing up to three sizes and further improve image quality, compression / non-compression switching is performed depending on the mode. The control method will be described below. When a copy operation start command is issued, the controller 10 compares the set scaling ratio Rs set in advance by the user of the copying apparatus with the memory effective scaling ratio Rml for effectively using the memory space of the buffer memory 4. . Normally, the memory effective scaling ratio Rml is 141 (300
4).

If the result of the comparison is Rs <Rml, the image data capacity is reduced to 1/2 in order to set the compression ratio Rc to 2, that is, to store the entire image in the memory (3006). The image data path selectors 440, 441 of the buffer memory 4
The controller 10 sets the selection setting of 408 to perform compression / decompression (3010). DRAM 430, 431
The data bit width of each is fixed at 256 bits and is modularized. When Rc = 2, the entire image is divided into two parts, and the whole image is divided into two parts, and the DRAM 430 and the DRA are divided into two parts.
M431. The address control setting for that is performed (3014). FIG. 4 shows a conceptual diagram thereof.

FIG. 4 is a conceptual diagram showing the state of image data stored in the buffer memory 4. 2001 indicates a document image, and the various settings 3006 described above in the buffer memory 4;
After the steps 3010 and 3014 are performed, the read image is compressed, divided as shown in 2002 and 2003, and stored in the DRAMs 430 and 431 of the buffer memory 4, respectively. In this manner, the buffer memory 4 can store up to the maximum image size of A3 size. The image data expanded again is output as shown in 2005.

On the other hand, if the comparison result is Rs> = Rml, the compression ratio Rc is set to 1, that is, stored in the buffer memory 4 without compressing the image data capacity (3008). Image data path selectors 440, 441, 40 of buffer memory 4
The controller 10 sets the selection setting of No. 8 for non-compression / non-decompression (3012). DRAM 430, 431
The address control setting for rotating and storing only the necessary image area with a data bit width of 512 bits is performed (3016).

For example, when the image data is enlarged by 141%, the original image size required for outputting on A3 paper can be output only up to A4 size, so the memory size only needs to be A4. That is, the normal image data amount is 1 /
Uncompressed image data can be stored up to A4, which is half of A3, in the buffer memory 4 which can be compressed to 2 and store up to A3 size. FIG. 4 shows a conceptual diagram thereof.

In FIG. 4, reference numeral 2001 denotes an original image, and the read image is compressed and rotated, divided as shown in 2010 and 2011, and stored in the DRAMs 430 and 431 of the buffer memory 4, respectively. . The image enlarged to 141% after decompression is 2012
Is output as shown.

In the first embodiment, an example has been described in which the image data compression ratio is switched between 1 and 2 at a predetermined enlargement ratio. Similarly, the compression ratio is changed to 2 and 4 at a 141% enlargement ratio.
You may switch to the two. Also, the same effect can be achieved by switching the image data compression ratio between 1 and 4 at a 200% enlargement ratio.

As described above, according to the first embodiment, the copying apparatus includes the buffer memory 4 having the compression function of compressing the data capacity of the image data and the decompression function of decompressing the compressed image data; A scaling unit 5 for performing image size conversion and resolution conversion of the image data stored in the storage unit 4, a memory effective scaling ratio Rml for effectively using the memory space of the buffer memory 4, and a scaling ratio Rs preset by a user. In particular, when image compression is performed by the fixed-length irreversible compression method, the controller 10 changes the compression ratio based on the comparison result with the controller 10. Image quality can be realized.

[2] Second Embodiment A copying apparatus according to a second embodiment includes a CCD linear sensor 1 and a pre-processing unit 2 as in the first embodiment.
, Selector 3, buffer memory 4, scaling unit 5
, A filter processing unit 7, a gamma conversion unit 8, a halftone processing unit 9, a controller 10, and a printer unit 20 (see FIG. 1 described above). The configuration of the buffer memory 4 is also the same as that of the first embodiment (see FIG. 2). Since these details have been described in detail in the first embodiment, description thereof will be omitted.

Next, a method of changing the compression ratio in a plurality of stages when the compression ratio is changed in accordance with the scaling ratio of the image in the copying apparatus according to the second embodiment will be described with reference to the flowchart of FIG. I do.

In the image storage control (5000), when a copy operation start command is issued and the input document size and the output paper size are the same, the controller 10 sets the set scaling ratio Rs set in advance by the user of the copying apparatus. And the memory effective scaling factors Rml1 and Rml2 for effectively using the memory space of the buffer memory 4. The effective memory magnification Rml is 141% (5004). If the comparison result is Rs <Rml1, the compression ratio Rc is set to 4 (meaning that the image data capacity is compressed to 1/4) (500
6). As a result, a one-sided document image is stored in the buffer memory 4 (5012, 5018, 5024).

On the other hand, if the comparison result is Rs> = Rml1, since the input image data can be half the size at 141% enlargement, the compression ratio Rc is set to 2 (the image data capacity is reduced by 1 /
2 (meaning compression to 2) (5008), and image data is stored using the buffer memory 4 fully (5014, 514).
020, 5024). Similarly, the comparison result is Rs> = Rm
In the case of l2 (Rml2 = 200%), when the image data is enlarged by 200%, since the input image data may be 1/4 size, the compression ratio Rc is set to 1 (5010), and the buffer memory 4 is fully used in a plurality of stages. To store the image data (5016,
5022, 5024).

As described above, according to the second embodiment, the copying apparatus includes the buffer memory 4 having the compression function of compressing the data capacity of the image data and the decompression function of decompressing the compressed image data; A scaling unit 5 that performs image size conversion and resolution conversion of the image data stored in the storage unit 4, and memory effective scaling ratios Rml 1 and Rml 2 for effectively using the memory space of the buffer memory 4. Since the controller 10 changes the compression ratio based on the result of comparison with the magnification Rs, especially when performing image compression by the fixed-length irreversible compression method, the image memory is made more cost-effective and the image deterioration is made more conspicuous. No high image quality can be realized.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device. A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and a computer (or CPU or MPU) of the system or the apparatus executes the program code stored in the storage medium. Needless to say, this can also be achieved by executing the reading.

In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS or the like running on the computer is actually executed based on the instructions of the program code. It goes without saying that a part or all of the above-described processing is performed, and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU provided in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0046]

As described above, according to the first aspect of the present invention, in an image processing apparatus for compressing and processing image data, a compression function for compressing the data capacity of image data and a decompression of the compressed image data are provided. Storage means having a decompression function, scaling means for performing image size conversion and resolution conversion of image data stored in the storage means, and control means for changing a compression ratio according to a scaling factor in the scaling means. In particular, when performing image compression by the fixed-length irreversible compression method, it is possible to reduce the cost of the image memory (storage means) and to realize high image quality with no noticeable image deterioration.

According to the second aspect of the present invention, the control means changes the compression ratio based on the result of comparison between the scaling factor set by the scaling means and the set scaling factor. Similarly, it is possible to reduce the cost of the image memory (storage means) and to realize high image quality with no noticeable image deterioration.

According to the third aspect of the present invention, since the compression ratio includes the compression ratio of 1, the compression ratio is suitable for obtaining a high image quality by reducing the compression ratio at a high magnification ratio at which image degradation is conspicuous.

According to the fourth aspect of the present invention, since a copying function for forming image data as an image on a recording medium is provided,
In particular, the present invention is suitable for a copying apparatus in which high image quality is realized while reducing image memory cost and reducing image degradation.

According to a fifth aspect of the present invention, in the image processing method for compressing and processing image data, a storage step having a compression function for compressing the data capacity of the image data and an expansion function for expanding the compressed image data; Since there is a scaling step for performing image size conversion and resolution conversion of the image data stored in the storage step, and a control step for changing the compression ratio according to the scaling factor in the scaling step,
Similarly to the first aspect of the present invention, it is possible to realize a high image quality while reducing the cost of the image memory and not conspicuous image deterioration.

According to a sixth aspect of the present invention, in the control step, the compression ratio is changed based on a result of comparison between the scaling ratio in the scaling step and the set scaling ratio. A similar effect is achieved.

According to the seventh aspect of the present invention, since the compression rate includes a compression rate of 1, the compression rate at a high magnification rate at which image degradation is conspicuous is reduced to achieve high image quality, as in the third aspect of the invention. It is suitable for obtaining.

According to the eighth aspect of the present invention, since there is a copying step of forming image data as an image on a recording medium, the cost of an image memory can be reduced particularly in a copying apparatus as in the fourth aspect of the present invention. It is suitable for realizing high image quality while making the image degradation inconspicuous while trying.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a copying apparatus according to first and second embodiments of the present invention.

FIG. 2 is a block diagram showing a configuration of a buffer memory of the copying apparatus according to the first and second embodiments of the present invention.

FIG. 3 is a flowchart illustrating read image data compression / non-compression switching control processing in the copying apparatus according to the first embodiment of the present invention.

FIG. 4 is a conceptual diagram showing a state of image data stored in a buffer memory of the copying apparatus according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a multi-stage compression ratio changing process in a copying apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CCD linear sensor 2 Preprocessing part 3 Selector 4 Buffer memory 5 Magnification processing part 7 Filter processing part 8 Gamma conversion part 9 Halftone processing part 10 Controller 20 Printer part

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuhiro Takiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyoshi Yoshida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Katsuya Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tadashi 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (8)

[Claims] 1. An image processing apparatus for compressing and processing image data, comprising: storage means having a compression function for compressing the data capacity of the image data and an expansion function for expanding the compressed image data; An image processing apparatus comprising: a scaling unit that performs image size conversion and resolution conversion of image data; and a control unit that changes a compression ratio according to a scaling ratio in the scaling unit. 2. The image processing apparatus according to claim 1, wherein the control unit changes the compression ratio based on a result of comparison between the scaling ratio in the scaling unit and a set scaling ratio. 3. The image processing apparatus according to claim 1, wherein the compression rate includes a compression rate of 1. 4. The image processing apparatus according to claim 1, further comprising a copying function for forming image data as an image on a recording medium. 5. An image processing method for compressing and processing image data, comprising: a storage step having a compression function for compressing the data capacity of image data and an expansion function for expanding compressed image data; An image processing method, comprising: a scaling step of performing image size conversion and resolution conversion of image data; and a control step of changing a compression ratio according to a scaling factor in the scaling step. 6. The image processing method according to claim 5, wherein in the control step, the compression ratio is changed based on a comparison result between the scaling ratio in the scaling step and a set scaling ratio. 7. The image processing method according to claim 5, wherein the compression rate includes a compression rate of 1. 8. The method according to claim 5, further comprising a copying step of forming the image data as an image on a recording medium.
8. The image processing method according to any one of claims 1 to 7.