JPH06276476A - Electronic still camera device - Google Patents

Abstract

PURPOSE:To provide the electronic still camera device able to change a compression ratio as to an area of part of a picked-up picture without changing an existing data format at all. CONSTITUTION:Digital picture data are divided in the unit of blocks each comprising plural picture elements and subject to orthogonal transformation processing to calculate the activity of all the pattern based on an orthogonal transformation output thereby calculating a 1st coefficient corresponding to each block, and quantization processing is applied to the orthogonal transformation output in the unit of blocks based on a quantization table formed by multiplying the 1st coefficient with a reference quantization table 35, and it is discriminated that a block subject to quantization processing is a block corresponding to a pattern area whose compression ratio revision is requested, a predetermined 2nd coefficient corresponding to each block is generated and multiplied with the 1st coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an electronic still camera device for converting an optical image of a photographed object into digital image data, compressing the image, and recording it on a recording medium.

[0002]

2. Description of the Related Art As is well known, in recent years, there has been an electronic photographic system which converts an optical image of a photographed subject into digital image data and causes a television receiver to display an image based on the digital image data. It has been developed and is becoming popular in the market. An example of such an electronic photography system is an electronic still camera device. This electronic still camera device includes a semiconductor memory, a magnetic tape,
A recording medium such as a disc is attached to the camera body, and digital image data obtained by shooting is recorded.After recording, take out the recording medium from the camera body, attach it to the playback device, and connect it to the playback device. A still image is displayed by the television receiver that has been set up.

In such an electronic still camera device, since the amount of digital image data to be handled is enormous, in order to record a large amount of digital image data in a limited recording medium capacity, The digital image data is compressed. The compression method of this digital image data is generally one of the orthogonal transformation methods.
The DCT (discrete cosine transform) method is widely used. In this method, the digital image data obtained by photographing is divided into a plurality of blocks composed of n × m pixels in the horizontal and vertical directions, two-dimensional DCT arithmetic processing is performed, and then quantization and Huffman coding are performed. It was done.

That is, as shown in FIG. 4, the digital image data forming one still image 11 is divided into a plurality of blocks 12 each having 4 × 4 pixels in the horizontal and vertical directions, for example. The value of each pixel of this block 12 represents the brightness level in 256 steps from 0 to 255, and D
By performing the CT calculation processing, it is converted into a two-dimensional spatial frequency component as shown in block 13. Incidentally, in this block 13, the upper left portion represents the DC (direct current) component. Next, each component of the block 13 is multiplied by the reciprocal of each value of the quantization table 15 by the multiplication circuit 14 in order to reduce the code amount. That is, block 13
After dividing each component of (1) by each value of the quantization table 15 to obtain a block 16, the value of each component of this block 16 is Huffman encoded to compress the data amount.

FIG. 5 shows a conventional electronic still camera device having a data compression function by such a DCT method. That is, an optical image of a subject incident through the lens 17 is formed on a CCD (charge coupled device) 18 and converted into an electric image signal. The image signal output from the CCD 18 is supplied to an image pickup signal processing circuit 19 and separated into a luminance signal and a color difference signal, and then an A / D (analog / digital) conversion circuit 2
At 0, it is converted into digital image data and stored in the frame memory 21. Then, the digital image data stored in the frame memory 21 is read out for each block by the memory controller 22, DCT operation processing is performed by the DCT operation circuit 23, and quantization and Huffman encoding processing is performed by the coder circuit 24. Then, the data is recorded on the memory card 26 having a semiconductor memory (not shown) as a recording medium through the card controller 25.

By the way, in the image data compression by the DCT method as described above, the deterioration of the image quality in appearance is considerably small even when the compression rate is 1/8 to 1/16.
Since the high frequency components after calculation disappear due to quantization,
The image tends to be slightly blurred. For this reason, even if the area 28 to be focused is defined in the finder image 27 as shown in FIG. 6, there is a case where the subject does not feel sufficiently focused. In other words, as a photographer, if the quantization table 15 is constant as described above, even if the photographer wants to lower the compression rate of the area where he / she wants to focus tightly and increase the compression rate of the portion that may be slightly blurred Therefore, it is impossible to obtain the image intended by such a photographer.

However, even if the quantization table is changed for each block, it is necessary to record the quantization tables corresponding to all the blocks in the memory card 26, which cannot be ignored as a data amount. At the same time, the inconvenience that the quantization process becomes considerably complicated occurs. In addition, the quantization table may have a format in which one corresponding to the entire screen is written in one memory card, so writing multiple quantization tables in the memory card should be avoided from the viewpoint of compatibility. Is desired.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In a conventional electronic still camera device that performs data compression processing by the method, it is practically impossible to partially change the compression ratio of a captured image without changing the current data format. I have a problem.

Therefore, the present invention has been made in consideration of the above circumstances, and it is extremely preferable that the compression rate can be changed for a partial area of a photographed image without changing the existing data format. An object is to provide an electronic still camera device.

[0010]

SUMMARY OF THE INVENTION An electronic still camera device according to the present invention comprises a conversion means for converting an optical image of a photographed subject into digital image data, and digital image data output from the conversion means into a plurality of pixels. A dividing unit that divides the image into block units, an orthogonal transform unit that performs an orthogonal transform process on the block-by-block digital image data that is divided by the dividing unit, and the activity of the entire screen is calculated based on the output of the orthogonal transform unit Then, the orthogonal transform means uses the calculation means for calculating the predetermined first coefficient corresponding to each block and the quantization table obtained by multiplying the reference quantization table by the first coefficient output from the calculation means. Means for performing quantization processing on the output of each block in a block unit, and the screen for which the block to be quantized by this quantization means is requested to change the compression rate. Determines that a block corresponding to the rear, a generation unit for generating a predetermined second coefficient corresponding to each block, a second output from the generator
And a coefficient control unit that multiplies the first coefficient output from the calculation unit by the coefficient control unit, and is obtained by multiplying the reference quantization table by the multiplication value of the first and second coefficients obtained by the coefficient control unit. In the quantization table, the output of the orthogonal transform means is configured to perform quantization processing in block units.

[0011]

According to the above configuration, the block corresponding to the screen area for which the change of the compression rate is requested is discriminated and the second
Is generated, and for the digital image data of the block, the value obtained by multiplying the normal first coefficient by the generated second coefficient is multiplied by the reference quantization table to obtain the quantization table. Since the output of the orthogonal transform means is quantized in block units, there is no need to provide a quantization table for the total number of blocks as in the prior art, and the current data format is not changed at all, and the captured image is It is possible to change the compression ratio of some areas of the area and that of other areas.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, the digital image data stored in the frame memory 29 is divided into blocks of 8 × 8 pixels in the horizontal and vertical directions by a block division circuit 30 and taken out, and then the DCT arithmetic circuit 3
At 1, DCT calculation processing is performed for each block, and its DC component and AC (alternating current) component are calculated. Of these, the AC component is supplied to the activity calculation circuit 32 and is used for calculation of the activity representing the fineness of the image of each block.

Then, the activity calculation circuit 32
The activity of the entire screen obtained in step 3 is supplied to the coefficient α calculation circuit 33. The coefficient α calculation circuit 33 calculates a coefficient α for multiplying each value of the reference quantization table 35 based on the activity of the entire screen and the set value set by the photographer via the image quality mode setting circuit 35. calculate. This coefficient α is set in the reference quantization table 3 in order to prevent the compression code amount from largely changing due to the difference in the picture.
5 is multiplied by each value, and acts to coarsen the quantization when the pattern is fine and the coefficient α increases, that is, to increase each value of the quantization table 15 shown in FIG. Is.

On the other hand, the photographer sets, via the table writing circuit 36, a screen area whose compression rate is desired to be changed. Then, the block number corresponding to the set screen area is read from the block table 37 and supplied to the block determination circuit 38. This block determination circuit 38
When the number of the block to be encoded output from the block division circuit 30 and the number of the block corresponding to the screen area whose compression rate is to be changed read from the block table 37 match, the coefficient β ≠ 1 is set. When the values do not match, the coefficient β = 1 is output. That is, when lowering the compression rate of the block of the screen area for which the compression rate is desired to be changed, the coefficient β <1.

The coefficient β output from the block determining circuit 38 is multiplied by the coefficient α calculated by the coefficient α calculating circuit 33 by the multiplying circuit 39 to create a coefficient αβ, and this coefficient αβ is multiplied by the multiplying circuit 40. Is multiplied by each value of the reference quantization table 35 to create a quantization table for each block. The quantization table for each block is supplied to the quantization circuit 41 and is used for quantization of each block output from the DCT operation circuit 31. The output of the quantization circuit 41 is Huffman coded by the AC Huffman coding circuit 42.

The DC component of the output of the DCT operation circuit 31 is Huffman-encoded by the DC Huffman encoding circuit 44 after the DPCM circuit 43 takes the difference value from all the blocks. Then, the outputs of the AC Huffman coding circuit 42 and the DC Huffman coding circuit 44 are supplied to the multiplexer 45 to switch the data transmission order to create compressed coded data, and the compressed coded data is generated by the card. The data is recorded on a memory card 47 having a built-in semiconductor memory (not shown) via the controller 46.

Here, as shown in FIG. 2A, the data storage area in the memory card 47 is an area 48a in which card attribute information is recorded, an area 48b in which card header information is recorded, and a packet identification. An area 48c in which information is recorded, an area 48d in which packet directory information is recorded, and a plurality of areas 48e, 48e in packet units in which digital image data is recorded are constructed.

The plurality of areas 48e, 48e, ... In which the digital image data is recorded are shown in FIG.
As shown in (b), the area 49a in which the packet header information, which is the header information of the packet, is recorded, and the quantization table when the digital image data recorded in the packet is quantized (this is the reference quantization). Area 49 where each value of table 35 is multiplied by coefficient α) is recorded
b, an area 49c in which compression encoded data of the luminance signal Y component is recorded, an area 49d in which compression encoded data of the color difference signal Cr component is recorded, and compression encoded data of the color difference signal Cb component are recorded. Area 49e is provided.

Further, in the area 49a in which the packet header information is recorded, as shown in FIG. 2C, the area 50a in which the ID number of the packet is recorded and the digital image data recorded in the packet are recorded. An area 50b in which the encoding method is recorded, an area 50c in which the compression mode is recorded, an area 50d in which the horizontal pixel number of the digital image data recorded in the packet is recorded, and a digital image recorded in the packet. An area 50e in which the number of vertical pixels of data is recorded, an area 50f in which the block number of the screen area whose compression ratio is changed is recorded, an area 50g in which the value of the coefficient β at that time is recorded, and other data are recorded. Area 50h is provided.

Therefore, when the digital image data recorded in the memory card 47 is read out and reproduced, the block numbers and the coefficient β are read out from the areas 50f and 50g and set in the decoder so that each component of the DCT is read. The value of can be restored by changing the quantization table for each block.

Therefore, according to the configuration of the above embodiment, when the photographer sets a screen area whose compression ratio is desired to be changed, the data of the block corresponding to the set screen area is updated to the normal coefficient α. Quantization is performed by a quantization table obtained by multiplying each value of the reference quantization table 35 by a coefficient αβ obtained by multiplying the other coefficient β, and for other data of the block corresponding to the screen area whose compression rate is not changed. Since the coefficient β is set to 1 and substantially only the coefficient α is quantized by the quantization table obtained by multiplying each value of the reference quantization table 35, it is not necessary to provide quantization tables for all blocks. It is possible to change the compression ratio of a part of the captured image with that of the other part without changing the existing data format.

In the above embodiment, the photographer can set the screen area whose compression rate is desired to be changed through the table writing circuit 36. However, the screen area whose compression rate can be changed is set on the camera side. Alternatively, it may be set in advance. That is, as shown in FIG. 3A, it is assumed that the area 52 in which the compression rate can be changed is set at the center of the finder image 51 on the camera side. At this time,
As shown in (b), when two persons are located, even if it is desired to focus on the person on the left side, the compression rate of the area between the two persons is reduced and it is wasted. In this case, focus lock is performed at the angle shown in FIG. 3A, and when the angle is changed as shown in FIG. 3B, control is performed so that the area for reducing the compression rate remains at the person on the left side. Is effective. This control can be realized by providing a means for freely moving the area 52 when using the liquid crystal viewfinder. The present invention is not limited to the above embodiment,
In addition, various modifications can be made without departing from the scope of the invention.

[0023]

As described above in detail, according to the present invention,
It is possible to provide an extremely good electronic still camera device capable of changing the compression ratio for a partial region of a captured image without changing the existing data format.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic still camera device according to the present invention.

FIG. 2 is a diagram for explaining the data storage area of the embodiment.

FIG. 3 is a diagram shown for explaining a modified example of the same embodiment.

FIG. 4 is a diagram shown for explaining a data compression process by the DCT method.

FIG. 5 is a block configuration diagram showing a conventional electronic still camera device.

FIG. 6 is a diagram for explaining a problem of the conventional device.

[Explanation of symbols]

11 ... Still image, 12, 13 ... Block, 14 ... Multiplication circuit, 15 ... Quantization table, 16 ... Block, 17 ... Lens, 18 ... CCD, 19 ... Imaging signal processing circuit, 20 ...
A / D conversion circuit, 21 ... Frame memory, 22 ... Memory controller, 23 ... DCT arithmetic circuit, 24 ... Coder circuit, 25 ... Card controller, 26 ... Memory card,
27 ... Finder image, 28 ... Area, 29 ... Frame memory, 30 ... Block division circuit, 31 ... DCT operation circuit, 32 ... Activity calculation circuit, 33 ... Coefficient α calculation circuit, 34 ... Image quality mode setting circuit, 35 ... Reference quantum Table 36, table writing circuit 37, block table 38, block determination circuit 39, 40, multiplication circuit 41, quantization circuit 42, AC Huffman coding circuit 43, DPCM circuit 44, DC Huffman encoding circuit, 45 ... Multiplexer, 46 ... Card controller, 47 ... Memory card, 48a to 48e ... Area, 4
9a to 49e ... area, 50a to 50h ... area, 51
Viewfinder image, 52 ... area.

Claims (1)

[Claims] 1. A converting means for converting an optical image of a photographed subject into digital image data, a dividing means for dividing the digital image data output from the converting means into a block unit composed of a plurality of pixels, and this dividing means. Orthogonal transformation means for subjecting the digital image data of the block unit divided by to orthogonal transformation processing, and the activity of the entire screen is calculated based on the output of the orthogonal transformation means, and a predetermined first coefficient corresponding to each block. And a quantization table obtained by multiplying the reference quantization table by the first coefficient output from this calculation means. It is determined that the quantization means and the block quantized by the quantization means are the blocks corresponding to the screen area for which the change of the compression rate is requested. Predetermined second corresponding to each block
And a coefficient control means for multiplying the first coefficient output from the calculation means by the second coefficient output from the generation means. A quantization table obtained by multiplying the reference quantization table by the multiplication value of the first and second coefficients, which is configured to perform quantization processing on the output of the orthogonal transform means in block units. Characteristic electronic still camera device.