JP3151244B2 - Image recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus,
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 data amount.

[0002]

2. Description of the Related Art When image information is recorded as digital data in a memory, the amount of digital image data becomes enormous, so that a large-capacity memory is required. Not only does this burden the hardware, it also increases the transfer time.
Therefore, usually, compression processing is performed on the image data, and the compressed image data is recorded and transferred to a memory. Such an image compression technique has recently been adopted, for example, in an IC card camera that converts an optical image of a subject into digital data and records the digital data in an IC card memory. IC
In a card camera, after an optical image is converted into an electric signal or a digital signal, orthogonal transformation processing such as discrete cosine transformation or the like is performed to perform data compression, and the obtained conversion coefficient is recorded in an IC card memory. In the data compression in the image recording apparatus, a predetermined compression process is performed on the entire image to be recorded, and the amount of compressed data is set to a certain value or less.

By the way, as the compression ratio for compressing image data increases, the image quality deteriorates. On the other hand, the fineness of the recording target (for example, the subject image) varies widely, and when the original image (subject image) contains fine information, the image quality deteriorates significantly when the compression ratio is increased, and it is not practical. It may be gone. On the other hand, when the original image contains only coarse information (that is, in the case of a picture having a relatively flat change), the original image information can be reproduced to a satisfactory degree even at a low compression ratio. However, there are few cases where the entire original image contains only fine information or only coarse information.
Fine information and coarse information are often mixed in a single original image. In such a case, if a fixed compression process is performed as in a conventional image recording apparatus, an optimal compression process for fine information is performed on coarse information, and coarse information is unnecessary from the viewpoint of image quality. On the other hand, if the optimal compression processing for coarse information is performed on fine information, there is a problem that image quality is greatly deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image recording apparatus capable of recording image data with a minimum amount of data and minimizing deterioration in image quality and recording image data with high efficiency.

[0005]

In order to solve the above-mentioned problems, an image recording apparatus according to the present invention is provided with an image recording apparatus provided with a compression ratio corresponding to information representing the sharpness of an image contained in an supplied image signal. An image recording apparatus configured to obtain a recorded image signal by performing a quantization process on an image signal, wherein each area set to divide an area in an image frame related to the image into a plurality of areas is provided. The information representing the sharpness of the image is obtained, and based on the correlation between the information representing the sharpness of the image for each region between adjacent regions, the region is optimally divided while resetting the region as necessary. And performs quantization processing at a compression ratio corresponding to information representing the sharpness of the image of each area in each of the divided areas in the optimal division mode, and performs recording from the supplied image signal. Means for obtaining image signal , Together with the recorded image signal obtained by the above-described means, an image recording apparatus characterized by comprising recording means for recording the screen configuration information related to the selected divided form, the. The image recording apparatus further includes a unit for performing an autofocus operation, and the information indicating the sharpness of the image included in the supplied image signal includes information at the time when the autofocus operation is completed. An image recording apparatus according to another aspect of the present invention performs a quantization process on the supplied image signal at a compression rate according to information representing the sharpness of an image included in the supplied image signal, and performs a quantization process on the recorded image signal. In the image recording apparatus, a plurality of division modes for dividing the inside of the image frame related to the image into a plurality of regions are set in advance, and within the image frame for each of the respective division modes. Based on the distribution state of the information indicating the sharpness of the image corresponding to each of the divided areas, an optimal divided form is selected from the plurality of divided forms, and the optimal divided form is selected for each divided area in the optimal divided form. It is provided with means for performing a quantization process at a compression rate corresponding to the information representing the sharpness of the image of each area to obtain a recorded image signal from the supplied image signal.

[0006]

According to the present invention, as described above, one image is divided into a plurality of areas, a contrast value for each divided area is obtained, and a correlation between adjacent divided areas is obtained using the obtained contrast value. The division mode is changed based on the correlation information obtained in this way, and an optimal division mode that specifies high-efficiency image compression with a minimum amount of data while suppressing image quality degradation is determined. Compression and recording processing are performed based on the Q table corresponding to the contrast value of each divided area according to this optimal division mode.

[0007]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an operation processing procedure in an embodiment of an image recording apparatus according to the present invention, and shows an application example to an IC card camera. In the present embodiment, when recording a digital image signal obtained from an imaging system, one screen (image) is divided into a plurality of areas, and based on a contrast value representing sharpness obtained for each area. Change the area division form. In this way, an optimal division mode that enables compression with minimum deterioration of image quality is determined,
The image is compressed and recorded by this division mode. This optimal division mode is performed by dividing the area further finely or expanding the area into a larger area on the basis of the correlation between the contrast values between adjacent divided areas.

In the IC card camera, when the auto focus (AF) operation is completed, each divided area is stored in the memory of the CPU which is built in the camera body and controls the entire camera operation as shown in FIG. The contrast values AFD to AFD corresponding to are stored as shown in FIG. The contrast value is read from the memory, and the state of the original image (image) is estimated from the correlation for each divided area. For example, when the level difference between the contrast values of the adjacent areas is large, the area is divided more finely, and when there is almost no level difference, the area is divided largely. In this manner, an area including a fine image portion is optimally divided into areas, and a Q table that sets a low compression ratio is set in the area portion. Set the table and optimize the compression.

FIG. 3 shows that when one original image (A) is divided into nine parts like a portrait, the contrast value of each divided area is generally an area including a person as shown in FIG. It is high, small in the background part ~, and has an intermediate value in the lower left and lower right.

For example, when a person's face is included in the area, the contrast value greatly changes from the area (FIG. 4A). In such a case, as shown in FIG. The area is further finely divided into A and B, and A and B, and the correlation value is calculated again by obtaining the contrast value again. In the case of FIG. 4, if the contrast value of the area is approximately the same as that of AFD / 2 and the respective contrast values of the areas A and B, it can be determined that there is no overlapping portion of the image at the boundary with the area. This area does not need to be divided to change the compression ratio.

On the other hand, FIG. 5 shows a case where a face portion of a person is included in both areas, and the contrast values of the subdivided areas are as follows: A is small, B is medium, A is high, and B is high. Get higher. AFD / 2 is larger than the contrast value of area A and smaller than the contrast value of area B with respect to the contrast value of the area.
If / 2 is greater than the contrast value of area B and greater than the contrast value of area A, it can be determined that the subject overlaps the boundary between area B and area A. A and B
Change with and record. The above-described processing is performed in the vertical and horizontal directions between the areas where the contrast value is changed, and the area having the high contrast value is separated from the area having the low contrast value. The more areas you can increase the compression ratio, the more
The data weight after compression is reduced.

FIG. 6 shows an example of an optimal division of an original image for a portrait subject. The original image of (A), in which only a person is a fine image, is divided as shown in (B), and the compression ratio of only the hatched area is reduced, and the compression ratio of the other areas is increased. Compression and recording become possible. Thus, the obtained compression ratio for each divided area is converted into a Q table value and sent to the compression circuit. The compression circuit performs compression recording based on the Q table value corresponding to each divided area, thereby increasing the overall compression ratio without deteriorating image quality. At the time of this recording, the image is recorded including screen configuration information such as the division form of one screen of the original image.

Now, the operation of the IC card camera of the present embodiment will be described with reference to the flowchart of FIG. 1. In the photographing standby state, it waits until the trigger 1 (TRG1) button is pressed "ON" (step). S1),
When "ON", the imager AF operation is started and a contrast value for each AF area is detected (step S2). Thereafter, it is determined whether or not the focus is OK (step S3). If not, the AF motor is operated (step S4), and the process returns to step S2. If the in-focus state is OK in step S3, a predetermined calculation process for dividing one screen into a plurality of areas is performed (step S3).
5). The calculation process here is a process for determining the optimal divided area by performing the correlation process based on the contrast value for each divided area as described above. After the area division calculation processing is performed in this way, it is determined in step S6 whether or not the area division is OK based on a criterion such as whether or not the data amount after compression has become a predetermined value or less. If it is determined that the area division is not OK, the area division is changed based on a predetermined division form (step S7), and again
A contrast value for each divided area is detected (step S8). Next, based on the thus obtained contrast value for each area, an area division calculation process in step S5 is performed. In step S6, area division is OK.
Is determined, a Q table for each divided area is obtained based on the contrast value for each divided area (step S9). Then, it waits until the trigger 2 (TRG2) button is turned “ON” (step S10),
When it is turned "ON", compression and recording operations to the memory are performed (step S11).

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

Processing such as encoding in the compression / decompression unit 8 is controlled by an encoding control circuit 13 based on an instruction from a system control circuit 12. That is, based on the contrast information supplied from the lens / AF control circuit 18, the system control circuit 12 performs the operations and processes shown in the flowchart of FIG. 1, sets an appropriate Q table for each divided area, and performs compression. Control the compression processing in the expansion unit 8. The system control circuit 12 performs various operations from the operation unit 14 and processes based on instruction information. The image data compression-encoded by the compression / decompression unit 8 is supplied to the card interface (I / F) 10 via the selector 9 and recorded on the IC card 11. The system control circuit 12 includes a RAM 6, selectors 7, 9, a compression / expansion unit 8, and a card I / F1.
0 controls the operation of the camera and receives various signals from the operation unit 14 to perform various controls of the entire camera.

FIG. 8 shows contrast information detection and A
The block diagram of the configuration of the F control system is shown. The video signal from the imaging process circuit 3 is supplied to an output terminal connected to the A / D converter 4 and the lens / AF
Bandpass filter (BPF) circuit 18 of control circuit 18
1 is supplied. The BPF circuit 181 extracts a predetermined band signal of the video signal, converts the luminance information into a digital signal by the A / D converter 182, and converts the luminance information into a digital signal.
Is output to The arithmetic processing circuit 183 obtains contrast information for each of the divided areas from the digital signal, sends it to the system control circuit 12, and sends it to the motor drive circuit 192 constituting the lens drive circuit 19.
The motor drive circuit 192 drives the motor 191 to move the lens 1 to perform AF control based on the contrast information. The data for each divided area obtained by the arithmetic processing circuit 183 is also sent to the band-pass filter circuit 181 and the A / D converter 182, and responds to the instruction signal from the system control circuit 12 for determining the optimum divided form again. Then, an operation is performed on the next divided area.

FIG. 9 shows the relationship between the image and the contrast. In the figure, hatched portions indicate dark portions. The change in the luminance signal of the image (A1) with little change is as shown in (A2). When this luminance signal is passed through a band-pass filter, it becomes a signal as shown in (A3). This is double-wave rectified to obtain a signal (A4) and then integrated to obtain a DC level signal as shown in (A5). For an image with little change, such as the image (A1), the level difference from the reference level (dotted level) is small. On the other hand, the luminance change for an image having a large change like (B1) is as shown in (B2), and the signal of (B3) is obtained by passing through a band-pass filter. After performing the both-wave rectification to obtain the signal (B4), the signal is integrated to obtain the signal (B5). The difference from the reference level at this time is large.

As described above, an image having a small final contrast value level is an image with little change, and the data amount after compression is small. An image having a large contrast value level is an image having a large change, and the data amount after compression becomes large. Therefore, when the contrast level is low, the data amount can be reduced by using the value of the Q table having a high compression ratio. In this embodiment,
The contrast value is determined based on the level of the integrated value, but may be determined based on the pulse height or the number of pulses of the luminance signal. In addition, the present invention is not limited to the IC card camera, but can be applied to other recording apparatuses that perform image compression processing.

Another example of the area division of the original image in the present invention is shown in FIGS. In the present embodiment, a plurality of types of division forms (patterns) are prepared in advance (for example, on a ROM of a CPU or on an arithmetic processing circuit for obtaining contrast), and an operation in each division form is performed to obtain an optimal division form. To determine. (A) shows a four-part mode,
(B) shows a 9-split mode, and (C) shows a 16-split mode. In (A), since the subject image (mountain) is included in each of the four divided areas, (4 /
4) Processing must be performed at a low compression ratio, and the amount of compressed data increases. In the case of (C),
The subject image is included in eight of the 16 divided areas, and it is necessary to perform processing at a low compression ratio on the 8/16 area. On the other hand, in the case of (B), 4 out of 9 divided areas are used.
The area may include the subject image, and the 4/9 area may be processed at a low compression ratio. Therefore, 9 as in (B)
According to the division mode, the area of the area where recording can be performed at a high compression ratio is increased, and the data amount is reduced as a whole, which indicates that the division mode is optimal.

In the above embodiment, when the area division mode is changed, the contrast value is calculated again from the image data. However, the contrast value and the position information in the detailed block area for one screen are stored in the buffer memory. In this case, high-speed processing can be performed by performing the processing while storing the information in the memory. The compression processing is usually performed on a pixel unit block such as an 8 × 8 pixel block. The compression processing is facilitated by setting the divided area as an integral multiple of the compression processing block unit. Furthermore,
The present invention is naturally applicable not only to a digital camera such as the above-mentioned IC card camera but also to any image signal.

[0021]

As described above, the image recording apparatus according to the present invention divides an image into a plurality of areas, obtains a correlation between the divided areas using a contrast value between adjacent divided areas, and obtains the obtained correlation. By changing the division mode on the basis of, and determining the optimal division mode, it is possible to compress and record an image with a minimum amount of data while suppressing deterioration in image quality.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation processing procedure showing an embodiment of an image recording apparatus according to the present invention.

FIG. 2 shows a divided area of an image according to the embodiment of the present invention;
FIG. 6 is a diagram illustrating a manner of storing contrast values of respective divided areas in a memory.

FIG. 3 is a diagram illustrating a relationship between a division mode of an original image and a contrast value of each divided area according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a division form of an original image according to the embodiment of the present invention.

FIG. 5 is a diagram for explaining a division mode of an original image according to the embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the original image division mode and the compression ratio in the embodiment of the present invention.

FIG. 7 is an overall configuration block diagram of an IC card camera to which the present invention is applied.

FIG. 8 is a configuration block diagram of a contrast information extraction and AF control unit according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating a change in contrast information for an image having a small change and an image having a large change.

FIG. 10 is a diagram showing another division mode of the original image in 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 / decompression 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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1 / 41-1 / 419 H04N 7/30

Claims (3)

(57) [Claims] 1. A sharp image included in a supplied image signal.
The supplied image signal at a compression ratio corresponding to the information representing the degree
Performs quantization processing on the signal to obtain a recorded image signal
An image recording apparatus configured as described above, wherein an area in an image frame related to the image is divided into a plurality of areas.
Indicating the sharpness of the image for each area set
And the adjacent information of the sharpness of the image for each region
Division of the above areas as necessary based on the correlation between the areas
While resetting the state, select the optimal division form,
For each divided area in this optimal division mode, the image of each area
Processing at a compression ratio corresponding to the information representing the sharpness of the image
From the supplied image signal to the recorded image signal
Means to obtainAlong with the recorded image signal obtained by the above means,
Recording means for recording screen configuration information according to the divided division mode
When,  An image recording apparatus comprising: (2)Further equipped with means for performing autofocus operation
And Represents the sharpness of the image contained in the supplied image signal
Information at the time when the above-mentioned auto focus operation ends.
2. The image recording apparatus according to claim 1, comprising information.
Recording device. (3)Sharpness of the image contained in the supplied image signal
The supplied image signal at a compression ratio corresponding to the information representing the degree
Performs quantization processing on the signal to obtain a recorded image signal
An image recording apparatus configured as described above, About dividing the inside of the image frame related to the image into a plurality of regions
A plurality of division forms are set in advance, and each of these division forms
The sharpness of the image corresponding to each divided area within the above-mentioned image frame
Based on the distribution state of the information to represent
Select the optimal division form from the
Represents the sharpness of the image in each of the divided areas in the state
Performs quantization at a compression ratio corresponding to the information and
Means for obtaining a recorded image signal from the supplied image signal
Image recording device characterized by Place.