JPH1023270A - Image-processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the transmission efficiency by effectively re-utilizing digital image data. SOLUTION: A coding section 3 applies compression decoding of digital image data, to select the reversible compression coding system or the irreversible compression coding system. Furthermore, the switching is conducted for each transfer destination, reusing digital image data. When a transfer destination reuses the digital image data, the reversible compression coding system with less image quality deterioration is selected and when not in use, the irreversible compression coding system with an excellent transmission efficiency is selected. Thus, the digital image data are reused effectively, and the transmission cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for compressing and restoring digital image data, and more particularly to an image processing apparatus useful for a digital copying machine (particularly, a multifunction peripheral), an electronic file, and a facsimile.

[0002]

2. Description of the Related Art In compressing and restoring digital image data, it is an important theme to achieve both an increase in the compression ratio and a maintenance of image quality. Here, as a compression method of digital image data, there are an irreversible compression coding method and a lossless compression coding method.

Generally, according to the irreversible compression coding method, the amount of digital image data to be compressed is reduced.
Although the data compression ratio can be increased, the quality of the restored image deteriorates in proportion thereto. On the other hand, according to the reversible compression coding method, although the compression ratio is not so high,
The image quality is good. A conventional image processing apparatus for compressing digital image data is disclosed in JP-A-3-12.
The thing described in 3335 gazette etc. are known.

[0004]

However, in the conventional image processing apparatus, when the restored digital image data is stored as an image file and reused repeatedly, an irreversible compression coding method is used. Since the quality of the restored image deteriorates, there is a problem that it is not preferable to reuse the image. Conversely, when digital image data is not reused as in the case of outputting an image, there is a problem that the transmission efficiency is deteriorated if a reversible compression encoding method is used.

Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide an image processing apparatus capable of effectively reusing digital image data and transmitting data efficiently.

[0006]

In order to achieve the above object, an image processing apparatus according to the first aspect of the present invention comprises an irreversible compression / decompression means for irreversibly compressing / decompressing digital image data; And lossless compression / restoration means for compressing and restoring the digital image data, and transfer destination switching means for switching between the irreversible compression / restoration means and the lossless compression / restoration means for each transfer destination of digital image data.

[0007] This is a combination of irreversible compression / restoration means and lossless compression / decompression means, and can be switched for each digital image data transfer destination. In such a configuration, when reusing digital image data, switching to a reversible compression / restoration unit with less deterioration in image quality is performed. Therefore, digital image data can be effectively reused. Conversely, when not reusing, switching to irreversible compression / decompression means with good transmission efficiency is performed. Therefore, transmission costs can be reduced.

Next, in the image processing apparatus according to the second aspect, an irreversible compression / decompression means for irreversibly compressing / decompressing digital image data, a lossless compression / decompression means for reversibly compressing / decompressing digital image data, Request switching means for switching between the irreversible compression / reconstruction means and the reversible compression / reconstruction means in response to a request from the transfer destination of the image data.

This time, the irreversible compression / reconstruction means and the lossless compression / reconstruction means are switched in response to a request from the transfer side of the digital image data. That is, the switching is entrusted to the transfer side. By doing so, the range of selection of external devices that can be connected is widened, and the functionality is improved. Also, it is convenient because it is easy to adjust to the convenience of the user.

Next, in the image processing apparatus according to claim 3, when the transfer destination is an image output unit, the irreversible compression / decompression unit compresses the digital image data.

In an image output means such as a printer or a CRT, there is little need to reuse digital image data. Therefore, digital image data is compressed by an irreversible compression / decompression means. For this reason, the compression ratio can be increased to a visually acceptable level, and transmission can be performed efficiently.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment.

FIG. 1 is a block diagram showing an image processing apparatus according to the present invention. In the image processing apparatus 100, reference numeral 1 denotes a scanner, which outputs a read document as an analog image signal. Reference numeral 2 denotes an image processing unit that performs processing such as shading correction and A / D conversion on the analog image signal, and outputs digital image data.

An encoding unit 3 compresses the digital image data. The encoding unit 3 can switch between a lossy compression encoding method and a lossless compression encoding method. As the irreversible compression coding method, for example, JPEG (Bas
area system). Also,
Examples of the lossless compression encoding method include a JPEG lossless method (Independent Function),
JBIG system, MH system, MR system, MMR system are mentioned.

Reference numeral 5 denotes a decoding unit for restoring the compressed digital image data. The decoding unit 5 can switch between the irreversible compression encoding method and the lossless compression encoding method, similarly to the encoding unit 3.

Reference numeral 6 denotes a printing unit such as a laser printer for printing the restored digital image data.

Reference numeral 7 denotes an encoding control unit. The encoding control unit 7 controls switching between a lossy compression encoding method and a lossless compression encoding method. The switching is determined based on the reuse status of the digital image data, which will be described later in detail.

Reference numeral 8 denotes an operation unit such as an operation panel and a keyboard, which is connected to the control unit 9.

An external interface 11 transfers compressed digital image data to an external device. 12 is
A facsimile unit for transmitting and receiving compressed digital image data.

Next, the operation of the image processing apparatus 100 will be described. An original is read by the scanner 1 and analog image data is output. This analog image data is sent to the image processing unit 2
After the image processing is performed, the image data is sent to the encoding unit 3 as digital image data. Further, the image processing unit 2 determines the type of the document. For example, it is determined whether the original is a photo original or a character original.

The encoding section 3 compresses and encodes the digital image data. In the compression, the switching between the irreversible compression encoding method and the lossless compression encoding method is implemented.

The switching pattern is shown below. When the restored digital image data is printed by the print unit 6, the digital image data is switched to the lossy compression encoding method. Print section 6
This is because digital image data is not reused. In the irreversible compression encoding method, the compression ratio is set to a range in which the image quality of the restored digital image data can be tolerated in accordance with the output characteristics of the printing unit 6.

Next, when the compressed digital image data is reused in an external device, the system is switched to a lossless compression encoding system. This is to prevent the image quality from deteriorating. Digital image data compressed by the reversible compression encoding method is transferred to an external device via the external interface 11.
When the external device is a printing device or the like and requests digital image data compressed by the irreversible compression encoding system, the system switches to the irreversible compression encoding system. Also,
Even if it is not a printing apparatus, it is possible to switch from the lossless compression encoding method to the lossy compression encoding method at any time at the request of the external device. Further, the reverse switching is also possible.

Next, when transmitting / receiving by facsimile, a lossless compression encoding method is selected. This is because it is necessary to reuse digital image data in FAX. Usually G
In the transmission mode of the 3 / G4 protocol, MH, MR, M
A lossless compression encoding method such as the MR or JBIG method is used. Digital image data compressed by the reversible compression encoding method is transferred to the FAX unit 12. On the other hand, in the reception mode, the mode is switched to the lossless compression encoding method as in the transmission mode. The information of the lossless compression encoding method is G3 / G4
Sent by protocol. The decoding unit 5 performs switching according to the transmission information.

Next, in the print mode, switching is performed based on digital image data transferred from the external interface 11. The transferred digital image data is digital image data compressed and encoded by a reversible compression encoding method or a lossy compression encoding method, or digital image data that is not compression encoded.
That is, the switching of the compression encoding method of the encoding unit 5 is performed according to the information of the digital image data transmitted from the outside.

Next, the compressed digital image data is restored. First, the acquired compressed digital image data is sent to the decoding unit 5. The decoding unit 5 switches the compression encoding method according to the information of the digital image data. The decoding unit 5 restores the digital image data by the switched compression encoding method. As described above, when digital image data is not compression-coded, there is no need to restore. Subsequently, the restored digital image data is output by the print unit 6.

The same configuration and operation can be achieved by replacing the printing unit 6 with a display device such as a CRT display.

As described above, according to the image processing apparatus 100 of the present invention, when reusing digital image data, switching to the reversible compression / decompression means with little deterioration in image quality is performed, so that digital image data can be effectively reused. In addition, when not reused, switching to irreversible compression / decompression means with good transmission efficiency can reduce transmission costs. Next, switching between the lossless compression encoding method and the irreversible compression encoding method is performed according to the request of the external device, so that the selection range of the external device that can be connected to the image processing apparatus 100 is widened, and the functionality is increased. Furthermore, it is convenient because it is easy to adjust to the convenience of the user.

[0029]

As described above, according to the image processing apparatus of the present invention (claim 1), the irreversible compression and restoration means and the lossless compression and restoration means are switched for each digital image data transfer destination. That is, when digital image data is reused, switching is performed to a lossless compression / restoring unit that causes less deterioration in image quality. Therefore, digital image data can be effectively reused, and transmission costs can be reduced.

Next, according to the image processing apparatus of the present invention (Claim 2), switching is entrusted to the transfer destination, and the irreversible compression / reconstruction means and the lossless compression / reconstruction means are switched in response to a request from the transfer destination. . For this reason, the range of selection of an external device that can be connected to the image processing apparatus is expanded, and the functionality is increased. Furthermore, it is convenient because it is easy to adjust to the convenience of the user.

Next, according to the image processing apparatus of the present invention (claim 3), when the transfer destination is an image output means such as a printer or a CRT, the lossy compression / decompression means compresses / decompresses the digital image data. I did it. For this reason, the compression ratio can be increased to a visually acceptable level, and transmission can be performed efficiently. In the image output means, since there is little need for reuse, it is not necessary to use the lossless compression / decompression means.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an image processing apparatus according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Image processing apparatus 1 Scanner 2 Image processing unit 3 Encoding unit 4 Image memory 5 Decoding unit 6 Printing unit 7 Encoding control unit 8 Operation unit 9 Control unit 11 External interface 12 FAX unit

Claims (3)

[Claims] An irreversible compression / decompression means for irreversibly compressing / decompressing digital image data; a lossless compression / decompression means for irreversibly compressing / decompressing digital image data; An image processing apparatus comprising: a destination switching unit that switches between a compression decompression unit and a reversible compression and decompression unit. 2. An irreversible compression / decompression means for irreversibly compressing / decompressing digital image data; a lossless compression / decompression means for irreversibly compressing / decompressing digital image data; An image processing apparatus comprising: a request switching unit that switches between irreversible compression / restoration unit and lossless compression / restoration unit. 3. The digital image data is compressed by the irreversible compression / decompression means when the transfer destination is an image output means.
An image processing apparatus according to claim 1.