JPH0486157A - Picture digitizing and compressing device - Google Patents

Abstract

PURPOSE:To simplify the operation to improve the operation efficiency and to prevent misinput by generating a signal indicating whether a smoothing space filter is applied or not and inputting this signal to a compressor and selecting a compression parameter corresponding to this signal. CONSTITUTION:The signal which drives a relay 108 is given from a circuit consisting of a constant voltage source 109, a resistance 110, and a switch 111 and is switched binarizingly by setting of the switch 111. This signal is transmitted to a system bus 210 through a gate 206 provided in a compressor 2. The gate 206 is controlled by the signal from an I/O decoder 207 newly connected to the system bus 210. Thus, the compressor can recognize whether a smoothing filter 106 is applied to a film digitizer 2 or not. That is, a user can select whether the smoothing filter 106 is applied or not by setting of the switch 111.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an image digitization/compression device used to digitize medical X-ray film images and store them in various recording media or transmit them to remote locations. In particular, the present invention relates to an image digitization/compression device using an irreversible data compression method.

[Conventional technology]

In recent years, systems for digitizing medical X-ray film images, storing them in various recording media, and transmitting them to remote locations have come into wide use. When X-ray film images are digitized, the amount of image data is approximately 8 megabytes per image, resulting in enormous recording medium costs and transmission time. Therefore, as an input device for such a system, a digitizing means (hereinafter referred to as a "film digitizer") that digitizes an X-ray film image and a compressed data are created by compressing the digitized uncompressed image data. compression means (in the following,
It is called a "compressor". ) is commonly used as an image digitization/compression device. Compressors in such devices often use lossy data compression methods that provide high compression ratios. There are many types of irreversible image data compression methods, but in general, the compression ratio, which is the ratio of the amount of uncompressed image data to the amount of compressed data, is the ratio of uncompressed image data of reproduced image data reconstructed from compressed data. It includes a parameter (hereinafter referred to as a "compression parameter") that adjusts both the amount of error and the amount of error from. Note that there are many methods for evaluating the amount of error, such as one based on the overall root mean square error, one based on the local mean square error, and one based on the local maximum error. By adjusting the compression parameters,
If the compression ratio is increased to reduce the amount of compressed data, the amount of error increases and the quality of the reproduced image deteriorates.

Conversely, if the compression parameters are adjusted to obtain reproduced image data that is almost the same as uncompressed image data, including components corresponding to noise contained in the original image, the amount of compressed data will increase and the compression ratio will decrease. Therefore, in the image digitization/compression equipment used in such systems, the compression parameters are optimally adjusted so that as much of the useful information contained in the original image is preserved and as much unnecessary information such as noise is removed. ,ing.

FIG. 3 is a block diagram showing an example of a conventional image digitization/compression device. Phil 11 digitizer] has
A film scanning system 1-01 that combines one-dimensional scanning of a laser beam using a rotating mirror and transport of the film to two-dimensionally scan the laser beam on the film surface, and measures the amount of laser light that has been two-dimensionally scanned and transmitted through the film. An optical density detector 102 for converting into an electrical signal corresponding to the local optical density is incorporated, and these convert the image information of the Xg film-1- into a time-series electrical signal. This time-series electrical signal is sequentially converted into digital data by an analog-to-digital converter 103 and stored in a buffer memory ]04. Digital data on the buffer memory +04 is transmitted to the compressor 2 via the interface 105. The compressor 2 converts digital data containing image information input from the film digitizer to the CPU 2.
01 through the interface 202, and the working memory 203 is connected to the system bus 210.
Store in. The CPU 201 performs irreversible image data compression processing on the digital data in the working memory 203-H using the image pig encoding method described in Japanese Patent Laid-Open No. 1-140882. At that time, the parameter d (hereinafter referred to as "allowable distortion") indicating the allowable distortion value used in the determination of Equation 24 of Document L corresponds to the parameter for adjusting the compression ratio and error amount in "-". However, as the value of allowable distortion, a value that has been optimally adjusted is used. After the created compressed data is stored in the working memory 203, the CPU 20
The information is transmitted to various storage devices and transmission lines via the interface 204 under the control of 1.

[Problem to be solved by the invention]

Film digitizers incorporated into image digitization and compression systems often have the ability to apply smoothing spatial filters. Here, the smoothing spatial filter is
This is to remove moiré caused by interference between the striped image created by the fixed X-ray grid used to remove scattered X-rays during film photography and the spatial sampling of the film digitizer. Using this feature changes the local amplitude of the image data. That is, if a smoothing spatial filter is used to limit the spatial frequency distribution of input image information,
Since the alternating current component of the density fluctuation on the image is suppressed, the amplitude of the data value corresponding to a locally constant density amplitude on the original image becomes small. Compression parameters are often defined as quantities related to the amplitude of local data fluctuations in real or frequency space. Therefore, using the above function produces an effect substantially similar to changing the compression parameter, and if left as is, it will greatly affect the compression ratio and image quality. Therefore, in order to maintain the compression ratio and image quality at a constant level, it is necessary to select the optimal compression parameters depending on whether or not a smoothing spatial filter is applied in the film digitizer.

In conventional image digitization and compression equipment, the compressor could not recognize whether a smoothing spatial filter was applied in the film digitizer, so the optimal compression parameters for each case were manually input into the compressor. However, the operation of the equipment was complicated, which worsened operational efficiency. In addition, errors in selection of compression parameters occurred due to input errors.

In the image digitization/compression apparatus shown in FIG.
6 is incorporated, which performs the function of a smoothing spatial filter.

Further, by using a switch 107, it is possible to select whether or not to apply the smoothing filter 106. What is the setting of switch 107?
A user inputs information to the compressor 2 using the console 205. The compressor 2 is set with two types of allowable distortion values that are optimally adjusted depending on whether or not the smoothing filter 106 is applied, and the CPU 201 uses the image data encoding method described in JP-A-1-140882. Switch 1 input from the console 205 when performing irreversible image data compression processing
According to the information regarding the setting of 07, one of two types of allowable distortion values is selected.

[Means to solve the problem]

The image digitizing/compressing device of the present invention generates a signal indicating whether or not a smoothing spatial filter is applied in a film digitizer, inputs the signal from Fukui et al. Select the compression parameters according to the information and execute the compression process.

[Effect]

In the image digitization/compression device configured in this way,
The compressor can recognize whether a smoothing spatial filter is applied in the film digitizer and automatically select the optimal compression parameters depending on these settings.

〔Example〕

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of an image digitization/compression apparatus according to the present invention, which differs from the conventional image digitization/compression apparatus shown in FIG. 3 in the following points. Switch 107 in FIG.
A relay 108 is provided instead. relay 10
The signal driving 8 is a newly provided constant voltage source 10.
9° resistance 110. It is provided by a circuit consisting of a switch 111, and can be switched binary depending on the setting of the switch 111. This signal is transmitted to the system bus 210 via a new gate 206 in the compressor 2. The gate 206 is controlled by a signal from a newly provided ■/○ decoder 207 connected to the system bus 210.

With this configuration, the compressor can recognize whether or not the smoothing filter 106 is applied in the film digitizer 2. That is, the user can select whether or not to apply the smoothing filter 106 by setting the switch 111, and the CPL 12
01 can read the setting of the switch 111 by driving the gate 206 using the I10 decoder 207.

With the image digitization/compression device configured in this way,
The irreversible image data compression process in the compressor 2 is executed according to the flowchart shown in FIG. That is, first, by processing the switching signal reading 301, the gate 206 is driven and the setting of the switch 111 is read. Next, in accordance with the result, in the process of selecting an allowable distortion value 302, one of two types of allowable distortion values that are optimally adjusted depending on whether or not the smoothing filter 106 is applied is selected. Using the allowable distortion values selected in this way, in image data encoding processing 303, irreversible image data compression processing is performed using the image data encoding method described in Japanese Patent Laid-Open No. 1-140882.

It goes without saying that the present invention is not limited to the above-mentioned embodiments and can be modified in various ways. For example, a configuration in which a circuit including a switch 111 that generates a signal for driving the relay 108 is installed on the compressor 2 side is also possible. In that case, it is also possible to perform the settings using the switch 111 by operating the console 205 instead. In addition, the smoothing filter 106
It is also possible to use a digital filter instead of the analog-to-digital converter 103 and place it at a later stage than the analog-to-digital converter 103. In that case, it is also possible for CPU:'01 to act as a digital filter.

Furthermore, in the above embodiment, the allowable distortion is used as a parameter for adjusting the compression ratio and the amount of error, and its value is selected.
Other lossy image data compression methods also include parameters with similar functions. For example, NHK Technology Monthly Report,
Showa 60.5 (1985) pages 164 to 171
In the two-layer encoding discussed in page 16 of the document,
"Mode selection 1" and "Mode selection 2" in Figure 6 on page 8
"Threshold values Tho and Tht used in " are applicable, and these -
One or both values may be selected depending on whether or not a smoothing spatial filter is applied. Also, video information (M) = 18
, (1986), pp. 719 to 724, the threshold value Tb used in "truncation of coefficients" and "
The quantization precision q used in "quantization of coefficients" corresponds to this, and one or both of these values may be selected depending on whether or not a smoothing spatial filter is applied.

〔Effect of the invention〕

With the present invention configured as described above, the optimal compression parameters are automatically selected depending on whether or not a smoothing spatial filter is applied in the film digitizer, thereby simplifying the operation and improving operational efficiency6. Also. Compression parameter selection errors due to input errors do not occur.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the configuration of an image digitization/compression device of the present invention, and Fig. 2 is a block diagram showing the configuration of an image digitization/compression device of the present invention.
FIG. 3 is a flowchart showing the processing procedure of irreversible image data compression processing executed by the compressor 2 in the compression device. FIG. 3 is a block diagram showing the configuration of a conventional image digitization/compression device.

Claims (1)

[Claims] 1. An image digitization/compression device comprising a digitization means for digitizing an image, and a compression means for irreversibly compressing digitized uncompressed image data to create compressed data, in which the digitization means digitizes an image. The compression method used by the compression means includes a parameter that can adjust the amount of error between the reproduced image data reconstructed from the compressed data and the uncompressed image data. An image digitization/compression device comprising: an image digitizing/compressing device, wherein the parameter is automatically selected from a plurality of options depending on whether or not the spatial filter is applied.