JPH0537901A - Image recorder - Google Patents

Abstract

PURPOSE:To highly efficiently record image data by means of the minimum quantity of data without deteriorating image quality by applying optimum compression processing to each area out of plural ones constituting a screen. CONSTITUTION:After converting a subject image into a digital signal by prescribed processing through a CCD 2, an image pickup process 38 and an ADC 4, a lens/AF control circuit 18 finds out contrast information to execute the AF control of a lens 1. On the other hand, a screen is divided into plural areas and recorded in a RAM 6. A compressing/extending unit 8 executes the coding processing of data read out from the RAM 6. A system control circuit 12 selects and sets up an optimum Q table in each divided area based upon the contrast information of each area read out from the circuit 18 to control compressing processing through a coding control circuit 13. Consequently image data can be efficiently recorded by means of the small quantity of data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording device,
In particular, the present invention relates to an image recording apparatus that compresses and records image data with high efficiency while minimizing deterioration of image quality with a minimum amount of data.

[0002]

2. Description of the Related Art When digital image data is recorded in a memory, since the amount of recorded image data is enormous, not only is the load on the hardware to store the image data in the memory and transfer the image data, Transfer time becomes long. Therefore, normally, the image data is compressed, and the compressed image data is recorded and transferred to the memory. Such an image compression method has recently been adopted in an IC card camera which records an optical image of a subject in an IC card memory instead of a silver salt film. IC
In a card camera, after converting an optical image into an electric signal and a digital signal, orthogonal transformation processing such as discrete cosine transformation is performed to perform data compression, and the obtained transformation coefficient is recorded in an IC card memory. In the data compression in the conventional image recording device such as an IC card camera, a predetermined compression process is performed on the entire image to be recorded, and the amount of compressed data is kept below a certain amount.

[0003]

As described above, the conventional image recording apparatus performs a predetermined compression process on the entire image to be recorded. The image quality deteriorates as the compression rate for compressing image data is increased. On the other hand, the recording target (for example,
The fineness of the subject image is very different, and when the original image (subject image) contains detailed information, increasing the compression rate causes remarkable deterioration of the image quality, which may make it unusable. On the other hand, when the original image includes only coarse information (that is, in the case of a picture with a relatively small change in a plane), the original image information can be reproduced to a satisfactory degree even at a low compression rate. However, the conventional image recording apparatus performs a predetermined orthogonal transformation process regardless of whether the original image is fine or rough, and repeats the process until the amount of data after compression becomes a predetermined value or less. By the way, if the whole original picture contains only detailed information,
It rarely contains only coarse information, and usually one original picture often contains fine information and coarse information. In such a case, since the constant compression processing is performed as in the conventional image recording apparatus, if the optimal compression processing for the fine information is performed on the coarse information, the coarse information is unnecessary from the viewpoint of image quality. Compression processing is applied. On the contrary, if the optimum compression processing for coarse information is performed on fine information, there is a problem that the deterioration of image quality becomes large.

Therefore, an object of the present invention is to display one screen (original image).
An object of the present invention is to provide an image recording apparatus capable of recording image data with high efficiency by performing an optimum compression process for each of a plurality of areas constituting the above and minimizing deterioration of image quality with a minimum data amount. Another object of the present invention is to provide an image recording apparatus which enables highly efficient compression processing in a minimum time.

[0005]

In order to solve the above-mentioned problems, an image recording apparatus according to the present invention uses a contrast signal representing the sharpness of an image corresponding to each section when one image is divided into a plurality of sections. In order to correspond to the output of the contrast signal forming means and the output of the contrast signal forming means corresponding to each section of the image, when the contrast signal indicates a state of relatively high sharpness, relatively low compression is performed. Ratio, the contrast signal indicates a state where the sharpness is relatively low, a quantization table having a relatively high compression rate is selectively applied to perform compression processing of the image signal corresponding to each of the sections. And a signal compression unit for outputting as a recorded image signal.

[0006]

According to the present invention, as described above, one image is divided into a plurality of sections (areas), contrast information representing the sharpness of the image for each divided area is obtained, and based on the obtained contrast information. By setting a quantization table having an appropriate compression ratio in the divided area, optimum compression processing is performed for each divided area of one screen, and reproduction of good image quality is possible with a minimum amount of data.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing an operation processing procedure in an embodiment of an image recording apparatus according to the present invention, showing an application example to an IC card camera. In this embodiment, when recording a digital image signal obtained from the image pickup system, one screen is divided into a plurality of areas, and the sharpness of the image obtained for each area by the imager AF (autofocus) operation is determined. A quantization table (hereinafter referred to as a Q table) indicating a compression degree and a mode for performing compression processing for each divided area is set to an optimum table based on the represented contrast data, and the compression processing is performed. While minimizing the total data volume, deterioration of the overall image quality is minimized. Further, in the imager AF processing process, the contrast value representing the fineness of the original image is calculated for each AF area. Therefore, the compression rate of each area is set by this calculated value, and the compression is performed individually to reduce the image quality. It enables efficient compression while suppressing the decrease.

Referring to FIG. 2, as shown in FIG. 2A, one screen of a subject is divided into 9 areas to, and when the AF operation is completed, as shown in FIG. The contrast values AFD to AFD for each area are recorded on the memory. Based on these contrast values AFD to AFD, the CPU selects the optimum Q table (Q-T) for each contrast value for each area.
ABLE) to Q tables are selected and transferred to the compression processing circuit. FIG. 3A shows an arrangement example of each divided area and the Q table set in each divided area. Although the division mode of each divided area of (A) is shown in (B), the division of the area can be defined as in (C), and the division state is arbitrary.

Now, the operation of the present embodiment will be described with reference to FIG. 1. First, in the photographing standby state, wait until the depression of the trigger 1 (TRG1) button becomes "ON" (step S1). When turned on, the imager AF operation is started (step S2), and the contrast value for each AF area is detected (step S3). After that, it is judged whether or not the focus is OK (step S4), and
If not K, operate the AF motor (step S
5) and returns to the process of step S3. If the focus is OK in step S4, an appropriate Q table is calculated based on the contrast value of the AF selection area (step S4).
6), the divided area number n is set to "1" (step S7). Next, after calculating the Q table of the AFn (n = 1) area (step S8) and setting the obtained Q table in the compression circuit (step S9), whether n matches the total number N of divided areas or not. Is judged. If they do not match, n = n + 1 is set to set the proper Q table for the next area (step S11), and the process returns to step S8. In step S10, n = N
If it is determined that, it is determined that the setting of the appropriate Q table is completed for all the divided areas in one screen,
It is determined whether or not the next trigger 2 (TRG2) is "ON" (step S12). The determination in step S12 is "ON" while waiting for the trigger 2 to be "ON".
Then, compression and recording operations are performed (step S13).

FIG. 4 is a block diagram of the entire camera when the present invention is applied to an IC card camera. In FIG. 4, a subject image formed on the CCD 2 via the lens 1 is converted into an electric signal, and then is converted by the imaging process circuit 3 by γ.
Predetermined processing such as correction is applied to the A / D converter (AD
C) Converted to a digital signal in 4. Signal generator (SS
G) The circuit 17 is a circuit that generates a signal for controlling the CCD 2, the imaging process circuit 3, and the A / D converter 4. The video signal from the imaging process circuit 3 is the lens AF.
It is supplied to the control circuit 18 to obtain contrast information. The obtained contrast information is used by the system control circuit 12
Is supplied to. Further, based on this contrast information, the lens drive circuit 19 performs AF control to focus the lens 1. The selector 5 sets a path for recording the digital image data from the A / D converter 4 in the RAM 6 during recording. The block data read from the RAM 6 (data for each divided block when one screen is divided into a plurality of blocks) is supplied to the compression / expansion unit 8 via the selector 7. Compression / expansion unit 8
The DCT / IDCT circuit 81 is a discrete cosine transform / inverse discrete cosine transform circuit, and performs orthogonal transform processing on block data. The transform coefficient obtained by the orthogonal transform is quantized by the quantization / inverse quantization circuit 82, and then encoded by the encoding / decoding circuit 83.

Processing such as encoding in the compression / expansion unit 8 is controlled by the encoding control circuit 13 based on an instruction from the system control circuit 12. That is, the system control circuit 12 is based on the contrast information for each divided area supplied from the lens / AF control circuit 18.
Selects and sets an appropriate Q table for the divided area as described above, and controls the compression process in the compression / expansion unit 8 via the encoding control circuit 13. In this way, the image data compressed and encoded by the compression / expansion unit 8 is supplied to the card interface (I / F) 10 via the selector 9 and recorded in the IC card 11. The system control circuit 12 includes a RAM 6, a selector 7,
9, which controls the operations of the compression / expansion unit 8 and the card I / F 10, and receives various signals from the operation unit 14 to perform various controls of the entire camera.

FIG. 5 shows contrast information detection and A
A configuration block diagram of the F control system is shown. The video signal from the imaging process circuit 3 is supplied to the output terminal section connected to the A / D converter 4, and the lens / AF
Bandpass filter (BPF) circuit 18 of control circuit 18
1 is supplied. In the BPF circuit 181, a predetermined band signal of the video signal is taken out, the brightness information is converted into a digital signal by the A / D converter 182, and then the arithmetic processing circuit 183.
Is output to. The arithmetic processing circuit 183 obtains the contrast information from the digital signal, and the system control circuit 12
To the motor drive circuit 192 that constitutes the lens drive circuit 19. The motor drive circuit 192 drives the motor 191 to control the lens 1 to perform AF control based on this contrast information,
AF operation is performed.

In the above-described embodiment, an example in which one screen is divided into a plurality of areas has been described. However, in a normal compression, the compression process is performed by an 8 × 8 block of pixels. Since this is performed, if the AF division area is also configured by an integral multiple unit of 8 × 8 blocks, the compression process can be facilitated. This is because the processing at the boundary between areas becomes complicated unless it is set to an integer multiple, so the boundary is set in accordance with the compression processing to facilitate processing. Further, as shown in FIG. 6, it is also possible to compress each block of 8 × 8 pixels in the horizontal direction. The present invention is not limited to a digital camera such as the IC card camera described above. When the video signal of the original image is compressed and recorded, the original image is divided into a plurality of areas, and the contrast value is obtained for each divided area. Of course, it can be applied to other various image recording apparatuses.

[0014]

As described above, the image recording apparatus according to the present invention divides one image into a plurality of sections (areas) and appropriately compresses the divided areas based on the contrast information of each divided area. Set the rate quantization table,
That is, when the contrast information has a relatively high sharpness, a relatively low compression rate is set, and when the contrast information has a relatively low sharpness, a relatively high compression rate is set. Optimal compression processing is performed for each divided area, and good image quality can be maintained with the minimum amount of data as a whole.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation processing procedure of an embodiment of an image recording apparatus according to the present invention, and a diagram showing an application example to an IC card camera.

FIG. 2 is a diagram showing a relationship between divided area contrast information and a corresponding Q table in the embodiment of the image recording apparatus according to the present invention.

FIG. 3 is a diagram showing a relationship between a divided area and a Q table and a division mode in the embodiment of the image recording apparatus according to the present invention.

FIG. 4 is an overall configuration block diagram of an IC card camera to which the present invention has been applied.

FIG. 5 is a block diagram showing a configuration of a contrast information extraction and AF control unit in the embodiment of the present invention.

FIG. 6 is a diagram showing another division mode in the embodiment of the image recording apparatus according to the present invention.

[Explanation of symbols]

1 lens 2 CC
D 3 Imaging process circuit 4 A /
D converter 5, 7, 9 selector switch 6 RA
M 8 compression / expansion unit 10 card interface circuit 11 IC card memory 12 system control circuit 13 encoding control circuit 14 operation unit 15 reproduction process circuit 16 D /
A converter 17 signal generation circuit 18 lens / AF control circuit 19 lens drive circuit

Claims (2)

[Claims] 1. A contrast signal forming means for obtaining a contrast signal representing the sharpness of an image corresponding to each section when one image is divided into a plurality of sections, and a contrast signal forming corresponding to each section of the image. Corresponding to the output of the means, when the contrast signal indicates a relatively sharp state, the compression ratio is relatively low; and when the contrast signal indicates a relatively sharp state. A signal compression means for selectively applying a quantization table having a relatively high compression rate to perform compression processing of the image signal corresponding to each of the sections and output as a recorded image signal. Characteristic image recording device. 2. The image recording apparatus according to claim 1, wherein each of the sections is set to an integral multiple of a pixel block which is a unit of image signal compression processing.