JPH08275150A - Image processing unit - Google Patents

Abstract

PURPOSE: To keep image quality after decoding nearly constant by providing a frame memory and a setting means selecting any of compression parameters and compressing image data in the frame memory based on the compression parameter set by the setting means. CONSTITUTION: A compression means 17 reads and compresses a digital image in an image frame memory 16 to obtain compressed data, which are stored in a storage device 19. When the means 17 compresses the image data, the means 17 selects a compression/expansion parameter in a parameter storage means 20 and receives it. Three kinds of compression/expansion parameters a, b, c are stored in the means 20 and a compression/expansion parameter from which a compression rate closest to a prescribed predetermined compression rate is selected among them. Then the means 17 uses the selected compression/expansion parameter to compress digital image data. In this case, any of the compression/expansion parameters is selected by operating a changeover switch 21. The processing above is applied similarly to the case with the expansion.

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 or expanding a digital image.

[0002]

2. Description of the Related Art Conventionally, various methods for compressing / expanding digital images have been proposed, but the "JPEG" method, which is an international standard, is currently widely used.

[0003]

The "JPEG" method is
By arbitrarily changing the quantized data and the Huffman code that are compression / expansion parameters based on the DCT operation, it is possible to compress the digital image data into a small amount of data, although it is irreversible. When compressing a plurality of digital images, if the digital images are substantially similar images, the size of the compressed data obtained by compression is almost constant. In this case, even when these compressed data are decompressed, they can be restored as images having substantially the same image quality.

However, when a plurality of digital images have different tendencies, the size of the compressed data obtained by compression is different. That is, the compression rate differs depending on the original image. As a result, when the image is expanded, the image quality of the expanded image also becomes different. That is, the image quality after compression / expansion will not be uniform.

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an image processing apparatus which can make the compression rate of image data uniform.

[0006]

[Means for Solving the Problems] In order to solve the above problems,
The present invention provides an input means for inputting an analog image signal, an A / D converter for converting the analog signal into a digital signal, a frame memory for storing the image data converted into the digital signal by the A / D converter, A plurality of compression parameters for performing the compression are provided, and a setting means for switching the compression parameters and a compression means for compressing the digital image data in the frame memory with the compression parameters set by the setting means are provided. It was configured.

Further, the present invention stores input means for inputting an analog image signal, an A / D converter for converting the analog signal into a digital signal, and image data converted into a digital signal by the A / D converter. Memory, and a plurality of compression / expansion parameters for performing the compression and expansion, and a setting means for switching the parameters and the digital image data in the frame memory is compressed by the parameters set by the setting means. Configuration comprising compression means, storage means for storing the compressed digital image data, and decompression means for decompressing the compressed data with the parameters set by the setting means to restore as digital image data And

[0008]

According to the present invention, a plurality of quantized data serving as compression / expansion parameters are provided, and these can be selected and used.

[0009]

1 is a block diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention. The image processing device 1 includes a compression / expansion control device 10 and an analog / digital converter (A
/ D converter) 13, digital / analog converter (D
/ A converter) 15 and an image frame memory 16. A camera 11, a camera control unit (CCU) 12, and a monitor device 14 are connected to the image processing device 1.

In FIG. 1, an image of an object is taken by a camera 11. The CCU 12 controls the camera 11, converts the image information from the camera 11 into an analog image signal, and outputs it. The analog image signal output from the CCU 12 is input to the A / D converter 13 and converted into digital image data. This digital image data is stored in the image frame memory 16.

The digital image data stored in the image frame memory 16 is compressed and expanded by the compression / expansion control device 10. The compression operation is performed as follows. The compression means 17 reads the digital image data in the image frame memory 16 and compresses it to obtain compressed data.
The compressed data is stored in the storage device (semiconductor memory, magnetic disk, etc.) 19.

The compression means 17 compresses the digital image data from the parameter storage means 20 to the desired compression / compression.
Select and enter the decompression parameter. In this embodiment,
Three types of compression / expansion parameters a, b, and c can be selected. From these, a compression / expansion parameter that gives the closest compression rate to the predetermined compression rate is selected. Then, the compression means 17 compresses the digital image data with the selected compression / expansion parameter. The compression / expansion parameter at this time is selected by operating the changeover switch 21.

The expansion operation is performed as follows. First, the changeover switch 21 selects the compression / expansion parameter 20 selected at the time of compression. The expansion means 18 is the storage device 1.
The compressed data is read out from No. 9 and decompressed to restore the digital image data. Then, the restored digital image data is stored in the image frame memory 16. The decompression unit 18 inputs the compression / decompression parameter from the parameter storage unit 20 when decompressing the compressed data. In this case, as the compression / expansion parameter, the same parameter as the parameter selected at the time of compression is selected.

The compression / expansion parameter at this time is selected by operating the changeover switch 21. Changeover switch 2
When 1a is closed (the other two are open), the compression / expansion parameter a is used. Similarly, the changeover switch 21
When only b is closed, the compression / expansion parameter b is used, and when only the changeover switch 21c is closed, the compression / expansion parameter c is used.

The digital image data in the image frame memory 16 is converted into an analog image signal by the D / A converter 15. The analog image signal is input to the monitor device 14 and an image is displayed.

[0016]

As described above, according to the present invention, compression is performed by changing the compression / expansion parameter depending on the input image, so that the compression is almost equal to the predetermined compression rate regardless of the difference of the images. It becomes possible to obtain data.
Furthermore, the image quality after restoration can be kept almost constant.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Image processing device, 10; Compression / expansion control device, 11; Camera, 12; Camera control unit (CCU), 13; Analog / digital converter (A / D converter), 14; Monitor device, 15; Digital / Analog converter (D / A converter), 16; Image frame memory, 17; Compression means, 18; Decompression means, 19; Compressed data storage device, 20; Compression / expansion parameter storage means, 21; Compression / expansion parameter switching switch.

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Claims (2)

[Claims] 1. An input unit for inputting an analog image signal, an A / D converter for converting the analog signal into a digital signal, and a frame memory for storing the image data converted into the digital signal by the A / D converter. A compression unit for compressing the digital image data in the frame memory according to the compression parameter set by the setting unit. An image processing device characterized by the above. 2. Input means for inputting an analog image signal, an A / D converter for converting the analog signal into a digital signal, and a memory for storing image data converted into a digital signal by the A / D converter. A setting unit that has a plurality of compression / expansion parameters for performing the compression and expansion, and that switches the parameters; a compression unit that compresses the digital image data in the frame memory with the parameters set by the setting unit; It is characterized by further comprising storage means for storing the compressed digital image data, and decompression means for decompressing the compressed data with the parameters set by the setting means and restoring as digital image data. Image processing device.