JP4844094B2 - Digital still camera - Google Patents

Description

This matter disclosure relates to a digital still camera.

In a digital still camera, a target file size for recording image data is often determined in advance in accordance with image quality settings (for example, FINE: high definition, NORMAL: standard, BASIC: basic) by a user.
In such a digital still camera, the image data obtained by shooting is repeatedly subjected to test compression while changing the compression parameter to search for the optimum compression parameter and recognize the target file size corresponding to the image quality setting. The image data is compressed so as to be within the allowable range.

  This is because, in the JPEG method widely used for still image compression processing in digital still cameras, the size of compressed data obtained after compression varies greatly depending on the characteristics of the captured scene, so image data obtained by capturing various scenes. This is because it is necessary to apply compression to each image data by applying an appropriate quantization parameter in order to keep the size of the compressed data obtained for the above in a predetermined range. For example, for image data obtained by shooting scenes rich in changes with many high-frequency components, the compression rate is increased to reduce the size of the compressed data, while for image data corresponding to scenes with little change, The compression rate is kept small so that the size of the compressed data does not become too small.

Such adjustment of the compression rate is performed by adjusting the quantization parameter used when encoding the image data according to the JPEG method by the scale factor SF, thereby realizing a fixed length of the compressed data. Has been.
In the conventional general fixed length technology, pre-compression is performed a few times while changing the scale factor, and the optimal scale factor is estimated based on the change in the size of the compressed data obtained at this time. The final compressed data is obtained by applying the optimum value of the scale factor.

In addition, a method for obtaining an optimum value of a scale factor based on a single preliminary compression result using a model related to a change in the size of compressed data corresponding to a change in the scale factor has been proposed (Patent Document). 1).
In addition, for a plurality of image data obtained by continuous shooting, using the fact that these image data have similar characteristics, the scale factor obtained for the first frame is also applied to the second and subsequent frames. Thus, there has also been proposed a method for realizing a certain fixed length for compressed data while realizing high-speed processing required for continuous shooting (see Patent Documents 2, 3, and 4).

In this way, by compressing the size of the compressed data to a substantially fixed length, at the stage of recording a compressed image on a medium such as a flash card, the number of images expected to correspond to the image quality is the number of images recorded on the medium. Guaranteed.
JP 2004-56680 A JP 10-117352 A JP-A-3-267877 JP-A-4-170879

As the number of pixels of digital still cameras increases, the user base of digital still cameras has expanded to include semi-professionals and professionals, and at the same time, the quality of recorded images is improved and the processing of captured images is required. There is an increasing demand for shortening the time.
In particular, in order to support fixed-length compression of continuously captured image data, it is apparent that there is a limit to the processing speed in the method of optimizing the scale factor from a few preliminary compressions. This is because if the clock frequency of the image processing LSI is increased to increase the processing speed, the power consumption is increased, the battery is exhausted and sufficient operating time cannot be secured. There is also an upper limit on the clock frequency, and there is a limit to the speedup of the compression process that can be achieved by simply operating the hardware at high speed.

Even if the technique of Patent Document 1 described above is applied, if the shooting interval at the time of continuous shooting is shortened, the fixed length is set according to the time required for performing the pre-compression on all continuously shot images. There is a possibility that the conversion process cannot catch up.
On the other hand, if the scale factor obtained for the first frame of image data is applied to the second and subsequent frames as in the techniques disclosed in Patent Documents 2 to 4, a plurality of image data obtained by continuous shooting can be processed at high speed. It is possible to perform compression processing.

  However, whether or not the compressed data obtained by this method falls within an allowable range related to the target file size depends on the degree of similarity between a plurality of images that are continuously captured. For this reason, there is a case where the fixed length of the compressed data cannot be reliably guaranteed. For example, when a subject that moves greatly in the field is photographed over a relatively long period of time, the characteristics may vary greatly between the first frame image and the last image of continuous shooting. Conceivable. In such a case, if the scale factor of the first frame is simply applied to the compression of the last image as it is, the compressed data corresponding to the first frame and the compressed data corresponding to the last frame are large in size. There will be a gap. In the worst case, compressed data corresponding to a part of a plurality of continuously shot images may not be recorded on the medium.

This matter disclosure is intended to provide a fixed-length compression possible digital still camera image data at high speed and with high accuracy.

The digital still camera according to the present disclosure includes an imaging unit that captures an image of a subject and generates image data, and a compression parameter used when compressing the image data to adjust the first image data generated by the imaging unit. Fixed-length compression means for compressing the first image data so that the data size falls within a predetermined range including the first target data size that is a target when the first image data is compressed; and Based on the first compression parameter used when the first compressed image data compressed and within the predetermined range is obtained, the data size of the first compressed image data, and the first target data size, An initial parameter for calculating an initial parameter of a compression parameter used when compressing the second image data generated after the generation of the first image data. A calculation unit, by using the initial parameter calculated by said initial parameter calculation unit, the second compression means for compressing the image data, and imaging sensitivity of the first image data, the photographic sensitivity of the second image data Determination means for determining that continuous shooting is performed when the difference between the two is equal to or less than a predetermined threshold .

According to the present disclosure, it is possible to provide a digital still camera capable of fixed-length compression of image data at high speed and with high accuracy.

(First embodiment)
Hereinafter, with reference to the accompanying drawings, it will be described in detail embodiments of the digital still camera of the present matter disclosure.
Figure 1 shows a first embodiment of a digital still camera of the present matter disclosure.
In the digital still camera shown in FIG. 1, an image formed on the image sensor 12 by the photographing optical system 11 is converted into an electric signal by the image sensor 12 and processed by the signal processing unit 13 and the A / D conversion unit 14. Thus, it is converted into image data representing a digital still image. The image data obtained in this way is subjected to image quality adjustment processing by the image processing unit 15 and then passed to the compression processing unit 16 via the memory 20, and the compression processing unit 16 corresponds to image quality setting. The data is compressed to a size and recorded on a storage medium such as a memory card via the recording unit 17.

  The control unit 18 illustrated in FIG. 1 controls the operation of each unit described above according to instructions input by the user via the operation panel 19. For example, the control unit 18 is provided in the operation panel 19. The information indicating the image quality (FINE, NORMAL, BASIC, etc.) set by the operation of the button or the like and the information related to the shooting conditions are passed to the compression processing unit 16, and the compression processing unit 16 accordingly receives the received image quality setting. The fixed length compression is performed as described below with reference to a target size determined in advance corresponding to the information.

FIG. 2 shows a detailed configuration of the compression processing unit.
In the compression processing unit 16 shown in FIG. 2, the encoding unit 21 applies the compression parameter received from the compression control unit 23 and encodes the image data stored in the memory 20 according to the JPEG method. Compress. The compression control unit 23 controls the compression parameter estimation operation by the parameter estimation unit 22 based on the comparison result between the compressed data size obtained by the encoding unit 21 and the target size, and sets an appropriate compression parameter. A search is performed to control the size of the image data to converge to the target size.

  In FIG. 2, the image quality setting information input by operating the operation panel 19 is detected by the image quality setting detection unit 31 provided in the control unit 18, and the compression control unit 23 provided in the compression processing unit 16. And the target size is determined accordingly. In the control unit 18 illustrated in FIG. 2, the interval measurement unit 32 collects, for example, information on the time when individual image data is acquired from the signal processing unit 13, and based on this, the image data acquisition interval is collected. And the measurement result is passed to the mode determination unit 24 provided in the compression processing unit 16. On the other hand, for example, the sensitivity information collection unit 33 illustrated in FIG. 2 collects information indicating shooting sensitivity regarding individual shooting from the signal processing unit 13 and passes the collected information to the mode determination unit 24 described above.

  The mode determination unit 24 illustrated in FIG. 2 is an image in which image data newly input can be applied with compression processing in a continuous shooting mode, which will be described later, based on the information regarding the imaging conditions input from the control unit 18 described above. It is determined whether it is data. Also, the compression control unit 23 shown in FIG. 2 uses a standard initial value SF1 appropriately determined in advance as an initial value used for calculating the scale factor SF based on the determination result by the mode determination unit 24, or as will be described later. Then, one of the adjusted initial value SF11 obtained by the parameter estimation unit 22 based on the scale factor of the immediately preceding frame is used for the processing of the encoding unit 21.

FIG. 3 is a flowchart showing an outline of the operation of the compression processing unit.
First, information related to shooting conditions (for example, shooting interval and shooting sensitivity) is received from the control unit 18, and based on this information, whether or not the continuous shooting mode should be applied to image data to be compressed by the mode determination unit 24. Is determined (steps 301 and 302). At this time, the mode determination unit 24 determines, for example, whether or not the shooting interval D is equal to or less than a predetermined threshold Dth as the condition determination regarding the shooting interval D, and the shooting sensitivity of the immediately preceding frame as the condition determination regarding the shooting sensitivity V. It is determined whether or not the difference between V _old and the shooting sensitivity V of the current frame is equal to or less than a predetermined threshold value V _th , and it is determined that the continuous shooting mode should be applied when both conditions are satisfied. Accordingly, the continuous shooting mode can be applied only when high similarity can be expected between the image of the immediately preceding frame and the image of the current frame.

  For example, in the first frame shot after the digital still camera is turned on, neither the above-described shooting interval condition nor shooting sensitivity condition is satisfied, so the mode determination unit 24 does not apply the continuous shooting mode. A determination result to that effect is passed to the compression control unit 23 (No determination in step 302). In response to this, the compression control unit 23 determines that the image data of the current frame should be individually compressed, and in advance compresses each image data independently (hereinafter referred to as individual mode compression). The determined standard scale factor initial value SF1 is subjected to compression processing by the encoding unit 21 (step 303).

In the individual mode compression, the encoding unit 21 performs preliminary compression using the above-described initial value SF1 (step 304), and then the compression control unit 23 performs the compression data size S1 obtained by this preliminary compression. Is determined to be within the allowable range set for the target size Ts corresponding to the image quality setting, it is determined whether or not the fixed length compression has been completed (step 305). At this time, the compression control unit 23 compares the lower limit value S _min and the upper limit value S _max of the size of the compressed data set in advance based on the target size Ts with the size S ₁ of the pre-compressed data. When it is determined that the upper limit value _Smax is exceeded (or less than the lower limit value), it is determined that the fixed length compression has not been completed (No determination in step 305).

In this case, in response to an instruction from the compression control unit 23, the parameter estimation unit 22 sets the initial value of the scale factor applied to the first preliminary compression (SF1 in the case of the individual mode) and the first preliminary compression result. Using the size S ₁ of the obtained compressed data, the target size Ts, and the coefficient a _i adjusted for each estimation number i based on the statistical relationship between the scale factor and the size of the compressed data, 1 ) The i-th scale factor SF _i expressed as follows is estimated (step 306).

SF _i = (S ₁ / Ts) ^{(−1 / ai)} · SF 1 ( 1 )
For details regarding the estimation of the scale factor SF, refer to Japanese Patent Application Laid-Open No. 2003-179926.
Next, as long as the number of preliminary compressions (or the estimated number of scale factors) does not exceed the specified number N, the compression control unit 23 returns to step 304 as a negative determination in step 307 and is estimated as described above. The encoding unit 21 is caused to execute compression processing to which the new scale factor SF _i is applied. At this time, the compression control unit 23 limits the estimated value of the new scale factor SF _i using the upper limit value SF _max and the lower limit value SF _min that are set in advance for the value of the scale factor. The scale factor SF _i is applied to the encoding unit 21.

If the fixed-length compression has not yet been completed even though the number of preliminary compressions exceeds the above-mentioned number of times, the compression control unit 23 determines that a hardware failure has occurred and performs appropriate error processing. To finish the process. Further, after the predetermined number of trials (for example, the fourth time), instead of performing the estimation based on the above-described equation ( 1 ), the cut-off scale factor SF4, the coefficient c (c> 1) and the equation ( 2 ) ) May be used to estimate the scale factor.

SF _i = SF4 · c ^i-1 ( 2 )
When the pre-compression and the estimation of the scale factor described above are repeated, and the compressed data whose size S is not less than the lower limit value S _{min and not} more than the upper limit value S _max is obtained, the compression control unit 23 It is determined that the fixed length compression has been completed (Yes determination at step 305). In response to this, the compressed data finally obtained by the encoding unit 21 is output to the recording unit 17 (step 308), and the last applied scale factor value and the size of the compressed data are the same as the previous frame. The scale factor SF (old) and the size S (old) are stored in the compression control unit 23 (step 309).

In the case where the size S of the compressed data obtained by the encoding unit 21 is less than the lower limit value S _min and the scale factor value applied to the pre-compression is the above-described lower limit value SF _min , It is determined that the current frame image has a characteristic that the code amount is extremely small (for example, there are few components with high spatial frequency like an image showing the sky), and it is determined that the fixed-length compression processing has been completed. . In this case as well, the compressed data is output and the scale factor is stored (steps 308 and 309). In addition, when compression is performed by applying the truncation scale factor SF4 described above, the compression control unit 23 determines that the fixed length compression is completed when the size S of the compressed data is less than the upper limit value _Smax. Only when the size S exceeds the upper limit value _Smax , the estimation of the scale factor using the above-described equation ( 2 ) may be applied.

Thereafter, unless an instruction to end shooting is given through the control unit 18, the compression control unit 23 returns to step 301 as a negative determination in step 310, receives information on the shooting conditions corresponding to the new frame, and The compression process for the frame is started.
Based on the information received corresponding to the new frame, when the mode determination unit 24 obtains a determination result indicating that the continuous shooting mode should be applied (positive determination in step 302), the compression control In response to an instruction from the unit 23, the parameter estimation unit 22 performs an estimation process of the initial value of the scale factor (step 311).

At this time, the parameter estimation unit 22 uses the scale factor SF (old) and size S (old) stored in step 309 of the compression process of the immediately preceding frame, the target size Ts, the appropriately determined coefficient a, and The scale factor SF (new) of the current frame is estimated using Equation (3) shown below.
SF (new) = (S (old) / Ts) ^{(−1 / a)} · SF (old) (3)
Then, the parameter estimation unit 22 returns the value obtained by the estimation using Expression (3) to the compression control unit 23 as the initial value SF11 of the scale factor. Here, the value of the coefficient a described above is based on the relationship obtained for the scale factor and the size of the compressed data by statistically analyzing information accumulated in advance for images having various characteristics, for example, It is determined by calculating an average value of parameters indicating the relationship obtained for each image, and is used for estimation processing of the initial value SF11 of the scale factor.

  Thus, the estimated initial value SF11 of the scale factor reflects the characteristics of the image corresponding to the previous frame, and is adjusted based on the ratio between the compressed data of the previous frame and the target size. ing. Therefore, when the image of the current frame is similar to the image of the immediately preceding frame, the scale factor SF11 estimated as described above is applied to the compression processing in step 304, so that the size is almost certainly allowed. Compressed data that falls within the range can be obtained. Therefore, in this case, the compression result obtained by applying the scale factor SF11 estimated as described above can be used as the main compression result, and the compressed data obtained as the compression result is output to the recording unit. (Step 308) The scale factor SF11 and the size S of the compressed data are stored for the compression process in the next frame (Step 309).

When the continuous shooting mode is to be applied as described above, the similarity between the current frame image and the previous frame image is often high. Therefore, most of the image data to be compressed while the continuous shooting mode is applied is compressed to a fixed length by the compression process using the scale factor estimated as described above.
Here, as described above, instead of using the scale factor of the previous frame as it is, by adjusting based on the ratio between the compressed data of the previous frame and the target size, the scale factor of the current frame is obtained. An error between the size of the compressed data obtained in the previous compression process and the target size can be corrected in the compression process for the current frame. That is, when the size of the compressed data obtained in the previous frame is smaller than the target size Ts, the scale factor of the current frame is adjusted to be slightly smaller than that of the previous frame. If it is larger than the size Ts, the scale factor of the current frame is adjusted to be slightly larger than the previous frame. By performing such correction, when the characteristics of a plurality of continuously shot images are changing little by little, the scale factor value can follow the change. As a result, the size of the compressed data obtained by the compression processing for the current frame can be made closer to the target size Ts, and high-speed and high-precision fixed-length compression can be realized.

  Furthermore, the target value Ts ′ for the size of the compressed data relating to the current frame can be adjusted according to the target size Ts corresponding to the image quality setting and the compressed data size S (old) of the previous frame. For example, if the scale factor is estimated by substituting the target value Ts ′ represented by the equation (4) into the equation (1) instead of the target size Ts corresponding to the image quality setting, the compressed data of the previous frame The size of the compressed data obtained in correspondence with the large number of image data that is the target of compression processing during the period when the continuous shooting mode is applied. Can be converged to the target size with high accuracy.

Ts ′ = 2Ts−S (old) (4)
On the other hand, even when the continuous shooting mode is applied, the characteristics of the image of the previous frame may be greatly different from the characteristics of the image of the current frame. In such a case, as described above. In the estimated scale factor SF11, there is a possibility that a non-negligible error may occur between the compressed data size S and the target size Ts.

  In such a case, step 304 to step 307 are repeated in the same manner as in the individual mode compression processing described above, using the compressed data obtained by the compression processing using the scale factor SF11 estimated in step 303 as a preliminary compression result. The optimum value of the scale factor SF is estimated, and the compressed data obtained by applying the estimated scale factor is output to the recording unit 17 as the main compression result. Fixed length compression can be realized while flexibly responding to large changes. At this time, the parameter estimation unit 22 uses the equation (the following equation (5)) in which the initial value SF1 of the scale factor in equation (2) is replaced with the initial value SF11 of the scale factor estimated in step 311 described above. The i-th estimation parameter estimation process is performed.

SF _i = (S ₁ / Ts) ^{(−1 / ai)} · SF11 (5)
Of course, by repeating the preliminary compression in this way, the time required for the compression processing for the corresponding frame becomes longer than the case where the scale factor estimated in step 311 can be used as it is. However, since the frames that require such processing are only a part of many images that are taken during the period when the continuous shooting mode is applied, the average processing time as a whole is sufficiently high. It is possible to fit within the shooting interval for continuous shooting. Therefore, the advantage of having fixed length compression guaranteed by flexibly responding to changes in image characteristics that may occur during continuous shooting is greater.
(Second Embodiment)
Figure 4 shows another configuration example of the compression processing unit.

In the compression processing unit 16 shown in FIG. 4, the coefficient table 25 includes coefficients used for estimating the scale factor in the continuous shooting mode in addition to the standard coefficient a _i series used for estimating the scale factor in the individual mode. The series of a _i is stored for each of the plurality of sections set for the value obtained as the initial value of the scale factor by the estimation process in step 311 described above.

  From the data accumulated for image data having various characteristics, it is known that there is a relationship as shown in FIG. 5A between the value of the scale factor and the size of the compressed data. As can be seen from FIG. 5A, as the scale factor value increases, the size of the compressed data decreases monotonously, but there are several graphs showing the relationship between the compressed data size and the scale factor. Has an inflection point.

Therefore, for each section obtained by dividing the scale factor at the inflection point described above, an appropriate scale factor can be obtained with higher accuracy by switching the value of the coefficient a indicating the slope of the change in the compressed data size with respect to the change in the scale factor. Can be estimated.
For example, as shown in FIG. 5A, when three inflection points appear in the graph indicating the relationship between the size of the compressed data and the scale factor, the value of the scale factor is changed at these inflection points. For the four sections obtained by partitioning, the slopes in the respective sections of the graph relating to a plurality of images having representative characteristics are stored in the coefficient table 25 as a series of coefficients a _i . That is, in the coefficient table 25, as shown in FIG. 5B, a series of coefficients a corresponding to each of the sections 1 to 4 is stored together with a standard series including the coefficients a _S2 and a _S3. . In FIG. 5B, the coefficients used for estimating the i-th estimated value SFi when the initial value SF11 of the scale factor belongs to the section j are shown with suffixes j and i.

Next, a method for estimating an optimum scale factor using such a coefficient table 25 will be described.
First, the parameter estimation unit 22 determines whether or not the continuous shooting mode is applied (step 312). If the determination is negative, the parameter estimation unit 22 corresponds to the estimated number of times i corresponding to the standard sequence shown in FIG. Then, the coefficient a _Si stored in the coefficient table 25 is selectively read out (step 313), the i-th scale factor is estimated using this coefficient a _Si and the above-described equation (2) (step 314), and compression is performed. The data is supplied to the processing of the encoding unit 21 via the control unit 23.

On the other hand, in the case of an affirmative determination in step 312, the parameter estimation unit 22 corresponds to the estimation number i corresponding to the series corresponding to the section j to which the initial value SF11 of the scale factor estimated in step 311 described above belongs. 25, the coefficient a _ji stored in 25 is selectively read out (step 313), the i-th scale factor is estimated using the coefficient a _Si and the above equation (2) (step 314), and the compression control unit 23 is To the processing of the encoding unit 21. Note that the parameter estimation unit 22 first estimates the scale factor based on the preliminary compression result obtained by applying the initial value of the scale factor, and the initial value SF11 of the scale factor described above and the inflection described above. By comparing with the value of the scale factor corresponding to the point, the section j to which the initial value SF11 belongs can be determined, and this section j can be stored and used for the subsequent estimation processing.

  In this manner, in the estimation process of the scale factor in the continuous shooting mode, by appropriately using the appropriate coefficient series according to the initial value of the scale factor calculated using the scale factor of the previous frame, The estimation accuracy of the scale factor can be improved, and the size of the compressed data can be converged to the target size with higher accuracy.

As described above, the digital still camera of the present matter disclosure eliminated while realizing a high speed operation is required, such as during continuous shooting, the convergence error of the size due to the change in the characteristic of conventional overlooked have image In addition, it is possible to reliably compress the compressed data corresponding to a large number of continuously photographed images. Accordingly, since all of the captured images can be compressed and recorded within a predetermined range including the target size corresponding to the image quality setting, the storage capacity of the storage medium can be used without waste, and various scenes can be captured. Regardless of the nature, it is possible to reliably record the number of images obtained from the storage capacity and the target size of the storage medium on the storage medium. That is, the storage capacity of the storage medium can be utilized to the maximum.

With such a feature, the digital still camera of the present matter disclosure can be recorded to ensure that the storage medium more compressed images at shorter shooting distance, the general user when capturing a hobby Of course, it can fully meet the strict requirements of semi-professional and professional photography.

It is a diagram showing a first embodiment of a digital still camera of the present matter disclosure. It is a figure which shows the detailed structure of a compression process part. It is a flowchart showing the outline of operation | movement of a compression process part. It is a figure which shows another structural example of a compression process part. It is a figure explaining parameter estimation operation. It is a flowchart showing the operation | movement which estimates the optimal value of a scale factor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Imaging optical system, 12 ... Image sensor, 13 ... Signal processing part, 14 ... A / D conversion part, 15 ... Image processing part, 16 ... Compression processing part, 17 ... Recording part, 18 ... Control part, 19 ... Operation Panel, 20 ... Memory, 21 ... Encoding unit, 22 ... Parameter estimation unit, 23 ... Compression control unit, 24 ... Mode determination unit, 25 ... Coefficient table

Claims (5)

Imaging means for imaging a subject and generating image data;
By adjusting a compression parameter used when compressing the image data, the data size of the first image data generated by the imaging unit is set to a target first target data size when the first image data is compressed. Fixed length compression means for compressing the first image data so as to fall within a predetermined range including:
The first compression parameter used when the first compressed image data that is within the predetermined range is obtained by compressing the first image data, the data size of the first compressed image data, and the first target data An initial parameter calculation means for calculating an initial parameter of a compression parameter used when compressing the second image data generated after the generation of the first image data based on the size;
Compression means for compressing the second image data using the initial parameter calculated by the initial parameter calculation means ;
And determining means for determining that continuous shooting is performed when a difference between a shooting sensitivity of the first image data and a shooting sensitivity of the second image data is equal to or less than a predetermined threshold value. Digital still camera. The digital still camera according to claim 1.
The compression means adjusts the compression parameter so that the data size of the second image data falls within a predetermined range including a second target data size that is a target when the second image data is compressed. A digital still camera, wherein the second image data is compressed. The digital still camera according to claim 2.
Determining means for determining whether or not a data size of compressed image data obtained by compressing the second image data using the initial parameter is within a predetermined range including the second target data size;
When the determination unit determines that the data size of the compressed image data obtained by compressing the second image data using the initial parameter does not fall within a predetermined range including the second target data size, the initial parameter and Estimating a compression parameter to be used when compressing the second image data based on the data size of the compressed image data obtained by compressing the second image data using the initial parameter and the second target size And further comprising means,
The digital still camera, wherein the compression unit compresses the second image data with the compression parameter estimated by the estimation unit. In the digital still camera according to claim 2 or 3,
A digital still camera, further comprising an adjusting unit that adjusts the second target data size according to a data size of the first compressed image data and the first target data size. In the digital still camera according to any one of claims 2 to 4,
The initial parameter calculation means includes
The second compression parameter used when the second compressed image data is obtained by compressing the second image data and falling within the predetermined range including the second target data size, and the data of the second compressed image data An initial parameter of the compression parameter used when compressing the third image data generated after the generation of the second image data is calculated based on the size and the second target data size. Digital still camera.

Images