JP2002354394A - Digital still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly convenient digital still camera, capable of storing additional files by continuing photographing, without having to erase stored files or exchanging a storage medium, even when the storable capacity of a storage medium is running out during photographing. SOLUTION: This digital still camera is provided with a photographing optical system, an imaging means for obtaining image data by imaging an optical image photograph formed by the photographing optical system, an image processing means for generating the image compression file of a JPEG 2000 file format, based on the image data fetched by the imaging means, a storage means for storing the image compression file generated by the image processing means, and a storage capacity detecting means for detecting the storable capacity of the storage means. The image processing means is provided with a re- quantizing means for generating the storable capacity of a new image compression file in the storage means by re-quantizing the image compression file, which has already been stored in the storage means, and reducing the file size, according to the detected result of the storable capacity of the storage means from the storage capacity detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital still camera, and more particularly to a digital still camera in which a generated compressed image file is stored in a storage medium.

[0002]

2. Description of the Related Art C incorporated in a digital still camera
Since multi-valued image data captured and generated by an image sensor such as a CD contains a great deal of information, it is stored in a storage medium, for example, an internal storage medium such as a built-in memory provided in the camera body, or the like. When stored in an external storage medium such as a memory card detachably provided in the camera body or transmitted to a peripheral device, for example, a computer terminal, a printer, a mobile terminal, or the like, the data amount becomes enormous, and the processing time becomes extremely long I will. In recent years, the number of pixels of an image sensor has been increasing and the image quality has tended to be higher, and even a single image may have a considerable data amount. Therefore, in general, in order to reduce the data storage amount and speed up the transmission time,
By encoding the obtained multi-valued image data and performing a compression process, a process of greatly reducing the data amount is performed.

As a compression processing technique for image data, a JPEG method for encoding image data using discrete cosine transform (DCT) is known. In a digital still camera, a standard compression processing of a multi-valued still image is performed. Spread as technology. Also, as a multi-valued still image compression technique in which the compression ratio and functionality are further greatly improved, the JPEG2000 system, which was internationally standardized at the end of 2000, is known.

In the JPEG2000 system, discrete wavelet transform is used in encoding image data instead of DCT as in the JPEG system, and its widespread use has attracted attention because of its high compression ratio and high functionality.

[0005]

By the way, in a digital still camera, an image compression file is generated by compressing image data obtained by photographing as described above. Since the generated image compression file is temporarily stored in a storage medium such as an internal storage medium in the camera body or an external storage medium detachable from the camera body, the number of images that can be shot generally depends on the storage capacity of the storage medium. I do. For this reason, if the storage capacity of the storage medium runs out during shooting, the next shooting cannot be performed. In this case, the file already stored in the storage medium is deleted and a new one is taken. The only option was to create a storable capacity or replace it with a new storage medium.

Accordingly, the present invention provides a method for continuing to capture an additional file without erasing the stored file or replacing the storage medium even if the storage capacity of the storage medium is exhausted during the capturing. It is an object to provide a user-friendly digital still camera capable of storing information.

[0007]

According to a first aspect of the present invention, there is provided a photographing optical system, and an image pickup means for photographing an optical image formed by the photographing optical system to obtain image data. Image processing means for generating a compressed image file in the JPEG2000 file format based on the image data captured by the imaging means, storage means for storing the compressed image file generated by the image processing means, and storage means Storage capacity detection means for detecting the storage capacity of the storage means, and the image processing means has already stored in the storage means in accordance with the result of detecting the storage capacity of the storage means by the storage capacity detection means. Creates a new storage capacity for the new compressed image file in the storage unit by requantizing the compressed image file to reduce the file size A digital still camera, characterized in that it comprises a re-quantization means to ability.

According to a second aspect of the present invention, after the image compression file is newly generated, the storage capacity detection means detects the storage capacity of the storage means, and as a result, the storage capacity is newly generated. A first selection unit for allowing a user to select whether or not to execute requantization by the requantization unit when the file size is smaller than the file size of the compressed image file. 2. The requantization by said requantization means is performed after requantization is selected by said selection means.
It is a digital still camera of the description.

According to a third aspect of the present invention, as a result of detecting the storable capacity of the storage means by the storage capacity detection means, it is determined whether or not to change the file size of the compressed image file already stored in the storage means. 2. The image processing device according to claim 1, further comprising a second selecting unit for performing a requantization by the requantizing unit after a change is selected by the second selecting unit. It is a digital still camera of the description.

According to a fourth aspect of the present invention, the image processing means includes a count means for counting the number of times requantization has been performed by the requantization means, and the count by the count means has reached a predetermined number. 4. The digital still camera according to claim 1, wherein the requantization by the requantization means is disabled when the digital camera is turned on.

[0011]

Embodiments of the present invention will be described below.

FIG. 1 is a block diagram showing the overall schematic configuration of a digital still camera according to the present invention.
Is a control unit, 2 is a switch input unit, 3 is a photographing optical system, 4 is an image sensor, 5 is an A / D converter, 6 is a signal processing unit, 7 is an arithmetic processing unit, 8 is an external storage medium interface unit, 9 Denotes an image display unit, and 10 denotes a data transmission / reception interface unit.

The control unit 1 starts and controls sequences such as photographing / recording, reproduction, data transmission / reception, arithmetic processing, and image display, based on an input signal from a switch input unit 2 including a power switch, various operation switches, and the like.

An optical image obtained by photographing and recording through a photographing optical system 3 including a lens and the like is used as a photographing means for a CC as an imaging means.
An image is formed on the light receiving surface of the image sensor 4 composed of D or the like. The imaging device 4 photoelectrically converts the formed optical image, and sends the converted analog image signal to the A / D converter 5.

The A / D converter 5 converts the analog image signal sent from the image sensor 4 into a digital image signal for each pixel, and sends the digital image signal to the signal processing unit 6. The signal processing unit 6 converts the color components (R, G, B) of the digital image signal for each pixel into luminance / color difference signals (Y, Cb, Cr) and sends them to the arithmetic processing unit 7 as image processing means. The image signal converted into the luminance / color difference signal is subjected to image compression in the arithmetic processing unit 7.

The configuration of the arithmetic processing unit 7 will be described with reference to the block diagram shown in FIG. In the present invention, the arithmetic processing unit 7 employs a JPEG2000 system which is a compression system for encoding an image signal by using a discrete wavelet transform.
An image compression file in the JPEG2000 file format is generated.

The image signal for each pixel, which is converted into a luminance / color difference signal by the signal processing unit 6 and input to the arithmetic processing unit 7,
Discrete wavelet transform is performed in the wavelet transform unit 7a. That is, in the wavelet transform unit 7a, each pixel data of one screen input from the signal processing unit 6 is
A known discrete wavelet transform is performed to decompose the data into a plurality of frequency bands called subbands.

This discrete wavelet transform is shown in FIG.
As shown in FIG. 4, the original image data shown in FIG. 4A is subjected to a low-pass filter (LPF) and a high-pass filter (HPF) in the order of the horizontal direction and the vertical direction, so that the frequency component becomes a low-frequency component (L). High frequency component (H)
And down-sampling the data by 、 to obtain LL, HL, L as shown in FIG.
Subband encoding is performed on a subblock including four components of H and HH.

Next, the same processing as described above is performed on the LL component of the generated four sub-blocks, thereby further dividing the LL component into four sub-blocks.
LLLL, LLHL, LLLH, L as shown in (c)
Sub-band coding is performed on seven sub-blocks of LHH, HL, LH, and HH to generate hierarchical data.

The wavelet transform coefficients generated by the above-described sub-band coding are temporarily stored in a buffer 7b, and then LLLL, LLHL, LLLH, LLHH, H
L, LH, and HH are sent to the quantization unit 7c in this order.

In the case of image data having a large number of pixels, the same processing as described above is performed to further divide the LLLL component into sub-blocks as shown in FIG. It is also possible to have data.

The quantization unit 7c quantizes the wavelet transform coefficients for each sub-band output from the buffer 7b at a quantization step determined for each sub-band.
Assuming that the quantization step in the quantization unit 7c is 1,
Substantially, quantization need not be performed.

After quantizing all wavelet transform coefficients in one sub-band, the quantizing unit 7c outputs the quantized value to the coefficient bit modeling unit 7d.

In the coefficient bit modeling unit 7d, the quantized data of the wavelet transform coefficient quantized by the quantization unit 7c is converted from a high energy MSB (Most Significant Bit) to a low energy LSB (LSB) as shown in FIG. (Least Significant Bit) in order of bit planes BP1, BP2,... BPn.

Next, the quantized data of the wavelet transform coefficients converted into bit planes is output to the encoding unit 7e and encoded.

In the coding section 7e, known arithmetic coding is performed. That is, the quantized wavelet transform coefficients are divided into a plurality of encoded blocks called code blocks for each sub-block. FIG. 6 shows an example in which one sub-block is divided into 16 × 16 encoded blocks. Each bit plane is further divided into stripes, and for each coding block, the inside of the stripe is scanned vertically from the upper left to perform arithmetic coding. The illustrated example shows a case where the stripe width is 4.

The image data encoded by the encoding unit 7e is generated as an image compression file with a necessary header and the like added thereto.

For example, when a resolution progressive file is generated for this image compression file, information such as the number of horizontal and vertical pixels, block arrangement, and supported resolutions is first written in a file header, and then as described above. The encoded data of the code block of the sub-band having the lowest frequency component of the MSB bit plane (for example, the LLLLLL component in FIG. 3D) is written.
Next, encoded data of a code block corresponding to the position of the code block on the plane immediately below the MSB is written. Similar processing is repeatedly performed up to the LSB plane. Further, the position of the code block is moved, and the encoded data from the MSB to the LSB is written in the same manner as described above. After all the sub-bands of one frequency component are encoded in this way, the encoded data of the code block of the sub-band of the high-frequency component is sequentially written.

The generated compressed image file is temporarily stored in the buffer 7f, then output from the encoded data output unit 7g, and is output from the external storage medium interface unit 8 shown in FIG.
Via an external storage medium M such as a memory card as a storage means.

At the time of reproduction, the compressed image file is read from the external storage medium M via the external storage medium interface section 8 and the encoded data input section 7h of the arithmetic processing section 7 is read.
Is output to a decompression processing unit 7i, and decompression processing is performed in the decompression processing unit 7i. The luminance and chrominance signals generated by the expansion processing are output from the expansion data output unit 7j to the signal processing unit 6. Here, after being converted into a signal suitable for display, LC
The image is output to the image display unit 9 including a display device such as D and displayed.

In the present invention, the control unit 1 includes a storage capacity detecting means (not shown) for detecting the storage capacity of the external storage medium M. By accessing, the storable capacity of the external storage medium M can be detected, and the presence or absence of the capacity capable of storing a new compressed image file can be detected.

Further, as shown in FIG. 2, in the present invention, the arithmetic processing section 7 has a requantization section 7k as requantization means. The requantization unit 7k requantizes the compressed image file stored in the external storage medium M according to the result of detecting the storable capacity of the external storage medium M by the storage capacity detection means, and reduces the file size. By reducing the size, a capacity enough to store the newly generated compressed image file can be created in the external storage medium M.

Here, after the stored image compressed file read from the external storage medium M is decoded and the bit-plane data is restored as shown in FIG.
Dequantize each quantized value to restore wavelet coefficients, perform requantization on the coefficient values in a different quantization step than when the image compression file was generated, and encode the requantized data As a result, the stored compressed image file is reduced.

An example of the control relating to the storage capacity detecting means of the control section 1 and the requantization section 7k will be described in more detail with reference to the control flowchart shown in FIG. Here, the control unit 1 detects the storable capacity of the external storage medium M when a new image compression file is generated from the encoding unit 7e of the arithmetic processing unit 7 and stored in the buffer 7f. I have.

First, the control unit 1 confirms that an image compression file is generated from image data by the information output from the encoding unit 7e of the arithmetic processing unit 7 and stored in the buffer 7f (S1). Then, the external storage medium M is accessed via the external storage medium interface unit 8, and the storable capacity of the external storage medium M is detected (S2). At this time, the control unit 1 acquires the information on the file size of the newly generated compressed image file from the encoding unit 7e.

As a result of detecting the storage capacity of the external storage medium M, if it is determined that the storage capacity is sufficient to store the newly generated compressed image file (Yes in S3), The image compression file is output from the buffer 7f to the encoded data output unit 7g (S
4) The writing to the external storage medium M is executed as it is via the external storage medium interface unit 8 (S5).

On the other hand, when the storage capacity of the external storage medium M is detected, and it is determined that there is not enough capacity to store the newly generated compressed image file (No in S3) ), A part or all of the compressed image file already stored in the external storage medium M is read out via the external storage medium interface unit 8 and the coded data is input to the coded data input unit 7h of the arithmetic processing unit 7. (S6).

Next, after temporarily storing the encoded data input to the encoded data input unit 7h in the buffer 71, the requantization unit 7k performs the quantization step in the quantization unit 7c as described above. Re-quantizes in different quantization steps, encodes the obtained re-quantized data, obtains encoded data with a reduced data size, and re-generates an image compression file (S7).

Here, the quantization step for performing re-quantization may be appropriately determined based on the information on the storable capacity of the external storage medium M and the file size of the newly generated compressed image file. preferable. For example, a table in which the relationship between the difference between the detected storage capacity of the external storage medium M and the file size of the new compressed image file and the quantization step is prepared in advance, and when requantization is performed,
The quantization step is automatically determined based on the table, and requantization is performed. In this way, the optimum quantization step can be determined in advance in the table, so that re-quantization does not need to be repeated many times, and the stored compressed image file is excessively reduced. Don't worry.

When the encoded data is requantized and the file size is reduced in this way, the compressed image file is written to the external storage medium M again (S8).

Next, the newly generated image compressed file is output from the buffer 7f to the encoded data output unit 7g (S4), and the writing to the external storage medium M is executed via the external storage medium interface unit 8 (S4). S5).

As described above, according to the detection result of the storage capacity of the external storage medium M by the storage capacity detection means, the re-quantization unit 7k requantizes the image compression file stored in the external storage medium M. By reducing the file size, it is possible to create a storage capacity of a new compressed image file in the external storage medium M. Therefore, a capacity sufficient to store the new compressed image file in the external storage medium M during shooting. Even if there is no more, the photographing can be continued and the newly generated compressed image file can be stored without replacing the external storage medium M or erasing the file already stored therein. become.

It should be noted that repeated compression of image data may cause deterioration of the image quality of the image after the expansion processing. For this reason, the control unit 1 is provided with a selection unit (first selection unit) for allowing the user to select whether or not to re-quantize the image compression file stored in the external storage medium M. When the storable capacity of the external storage medium M is detected as a result of detecting the storable capacity of the external storage medium M after the generation of the compressed file, the user is warned by displaying the lack of capacity on the image display unit 9. As a result, when re-quantization is selected by the user operating the selection means, re-quantization of the image compression file already stored in the external storage medium M may be performed. preferable. This eliminates the risk of inadvertently deteriorating the image quality of an image that has already been captured and stored in the external storage medium M. This is particularly useful when the stored image is an important image that the user wants to save without deteriorating the image quality.

The first selecting means can be operated from the switch input unit 2 as a selection button, a selection switch or the like.

In the requantization control described above, the storage capacity detecting means detects the storable capacity of the external storage medium M when a new compressed image file is generated. An operation switch or the like for detecting the available capacity is provided in the switch input unit 2, and the storage capacity detection unit is activated by a user's arbitrary operation on the switch input unit 2 to reduce the storable capacity of the external storage medium M. In addition to the detection, the control unit 1 includes a selection unit (second selection unit) that allows the user to select whether to execute the requantization of the stored compressed image file according to the detection result. When the execution of the requantization is selected by the selection unit, the requantization of the image compression file stored in the external storage medium M may be performed.

An example of this control will be further described with reference to a control flow chart shown in FIG. 8. For example, prior to photographing or after an image compression file is newly stored in the external storage medium M, the external storage medium When the user operates an operation switch or the like for detecting the storage capacity of M, the storage capacity of the external storage medium M is detected (S10).
Next, the detection result is displayed on the image display unit 9 and the user waits until the user selects whether or not to re-quantize the compressed image file stored in the external storage medium M (S11).

Here, when execution of requantization is selected by the user's operation of the selection means (Yes in S12), the requantization is already stored in the external storage medium M via the external storage medium interface unit 8. Part or all of the image compression file is read, and the encoded data is input to the encoded data input unit 7h of the arithmetic processing unit 7 (S13).

Next, after temporarily storing the encoded data input to the encoded data input section 7h in the buffer 71,
As described above, in the requantization unit 7k, quantization is performed again at a quantization step different from the quantization step in the quantization unit 7c, and the obtained requantized data is encoded to reduce the file size. The compressed data is obtained and the image compression file is generated again (S14). When the encoded data read from the external storage medium M is requantized to reduce the file size, the data is written back to the external storage medium M again (S15).

It is preferable that the quantization step at the time of the requantization is executed by a predetermined quantization step. For example, in the requantization unit 7k, a plurality of quantization steps different from the quantization unit 7c (larger than the quantization step in the quantization unit 7c) are prepared, and the second selection unit is selected. In accordance with the number of times, the quantization steps are sequentially selected from the smaller one.

By reducing the file size by the re-quantization, the capacity that can be stored in the external storage medium M is newly created, and the storage capacity is increased. It can be stored.

On the other hand, if execution of requantization is not selected by the selecting means (No in S12), requantization is not performed.

In the present invention, the arithmetic processing section 7 is provided with a counting means (not shown) for counting the number of requantizations by the requantization section 7k, and the image stored in the external storage medium M is provided. Requantizer 7k for compressed file
It is preferable to count the number of times re-quantization has been performed by, and when the number reaches a predetermined number, disable re-quantization by the re-quantization unit 7k. As a result, excessive requantization can be prevented, and excessive reduction in image quality can be prevented.

In the present invention, when the requantization unit 7k requantizes the encoded data, the requantization is performed in a different quantization step from that of the quantization unit 7c as described above. Alternatively, the following may be performed. That is, first, all the code blocks in the encoded data read from the external storage medium M are decoded, and the M code shown in FIG.
Restore all bit planes from SB to LSB. Next, the LSB bit plane is discarded, and the upper bit plane is bit-shifted. This processing is equivalent to performing the quantization processing on the wavelet transform coefficients. The image compression file is regenerated by encoding the bit plane whose data has been updated. Since the file size of the compressed image file generated in this manner can be adjusted by the bit shift amount, the size of the compressed image file is reduced by repeating the bit shift process and the subsequent steps so that the required data size is obtained. You.

In the above description, an example is described in which an external storage medium M such as a memory card detachably provided in a camera body is used as storage means for storing an image file generated by the image processing means. But
The invention is not limited to this, and an internal storage medium such as a built-in memory built in the camera body may be used.

[0055]

According to the present invention, even if the storage capacity of the storage medium is exhausted during shooting, the shooting can be continued and additional files can be added without replacing the storage medium or erasing the stored files. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a digital still camera.

FIG. 2 is a block diagram illustrating an embodiment of an arithmetic processing unit.

FIGS. 3A to 3D are explanatory diagrams showing a state in which image data is decomposed into a plurality of subbands.

FIG. 4 is an explanatory diagram showing a filter configuration in wavelet transform.

FIG. 5 is an explanatory diagram showing a state in which image data is converted into a bit plane.

FIG. 6 is an explanatory diagram showing an example in which one sub-block is divided into coding blocks.

FIG. 7 is a flowchart illustrating an example of a control flow of requantization in a control unit;

FIG. 8 is a flowchart showing another example of the requantization control flow in the control unit.

[Explanation of symbols]

 1: control unit 2: switch input unit 3: photographing optical system 4: imaging device 5: A / D converter 6: signal processing unit 7: arithmetic processing unit 7a: wavelet conversion unit 7b: buffer 7c: quantization unit 7d: Coefficient bit modeling unit 7e: encoding unit 7f: buffer 7g: encoded data output unit 7h: encoded data input unit 7i: decompression processing unit 7j: decompressed data output unit 7k: requantization unit 71: buffer 8: external storage Medium interface unit 9: Image display unit 10: Data transmission / reception interface unit

Claims (4)

[Claims] 1. An image pickup optical system, image pickup means for picking up an optical image formed by the image pickup optical system to obtain image data, and an image in JPEG2000 file format based on the image data taken in by the image pickup means. Image processing means for generating a compressed file, storage means for storing the image compressed file generated by the image processing means, and storage capacity detection means for detecting the storage capacity of the storage means, The image processing means requantizes the compressed image file stored in the storage means to reduce the file size in accordance with the result of the detection of the storage capacity of the storage means by the storage capacity detection means. Digital still having re-quantization means for creating a storage capacity of a new compressed image file camera. 2. After the image compression file is newly generated, as a result of detecting the storage capacity of the storage means by the storage capacity detection means, the storage capacity becomes the file of the newly generated image compression file. When the size is smaller than the size, the image processing apparatus further includes first selection means for allowing a user to select whether or not to perform requantization by the requantization means. 2. The digital still camera according to claim 1, wherein requantization by said requantization means is executed after the selection of the quantization. 3. A second step for allowing a user to select whether or not to change the file size of an image compression file already stored in the storage means as a result of detecting the storage capacity of the storage means by the storage capacity detection means. 2. The digital still camera according to claim 1, further comprising a selection unit, wherein the image processing unit performs requantization by the requantization unit after a change is selected by the second selection unit. 4. The image processing means includes counting means for counting the number of times requantization has been executed by the requantization means, and when the count number by the counting means reaches a predetermined number, the requantization is performed. 4. The digital still camera according to claim 1, wherein requantization by means is disabled.