WO2001013628A1

WO2001013628A1 - Electronic camera and program for image processing

Info

Publication number: WO2001013628A1
Application number: PCT/JP2000/005469
Authority: WO
Inventors: Hideyasu Kuniba; Sadami Okada; Toshihisa Kuroiwa
Original assignee: Nikon Corporation
Priority date: 1999-08-17
Filing date: 2000-08-15
Publication date: 2001-02-22
Also published as: JP2001054115A; JP4273586B2

Abstract

A compression mode of constant size mode/constant image quality mode is set up. In the constant size mode, image compression is performed by adjusting a compression parameter (an adjustable factor that influences the amount of compression codes in the compression processing) to limit the amount of compression codes of the image data within the range corresponding to the target compression ratio. In the constant image quality mode, image compression is performed while fixing the compression parameter to uniform the image quality after compression of the image data. Furthermore, one of these two modes is selected depending on the amount of information of the image data or on the adjusted value of the compression parameter to automate compression mode selection.

Description

Description Electronic camera and image processing program This application is based on Japanese Patent Application No. 23,092, Heisei 11 (filed on August 17, 2001) And incorporated here. Technical field

The present invention relates to an electronic camera having an image compression function and an image processing program. In particular, the present invention is intended to use an image compression mode (constant image quality mode) that takes into account special image data such as a lack of information amount with other image compression modes (constant size mode). About technology. Background art

Normally, in an electronic camera, the target compression ratio of image data is determined according to the image quality setting (for example, switching between FINE / N0RMAL / BASIC) performed by the photographer. Such an electronic camera gradually adjusts the compression parameters (scale factor, etc.) while repeatedly performing test compression on image data, and compresses the image data, that is, the compressed data size after compression processing, that is, the target compression code amount. The rate is within the range.

By the way, some special image data (for example, a black image or an overexposed image) has significantly different features such as the spatial frequency distribution from general natural images. For this reason, the compression parameter adjustment method as described above cannot be used as it is, and the compression code amount does not easily converge within the target compression ratio range. As a result, for special image data, the number of times of test compression (the number of trials of compression) inevitably increases, resulting in an adverse effect such as a long time for image compression.

In addition, this kind of special image data is often an image partially lacking information. Therefore, when such image data is compressed to the target compression ratio, invalid information unrelated to the image, such as image noise, remains after compression, resulting in poor image quality. In some cases, it did. If the invalid information remains after the compression, adverse effects such as the storage capacity being used unnecessarily occurred.

In addition, appropriate image compression processing has not been performed on images with extremely large amounts of information, such as trees with many twigs. Disclosure of the invention

An object of the present invention is to provide an electronic camera provided with an image compression mode in consideration of special image data.

Another object of the present invention is to provide an image processing program for performing image compression processing in consideration of special image data.

In order to achieve the above object, an electronic camera according to the present invention includes: an image pickup device that picks up an image of a subject; and outputs the imaged subject as image data; and a size that allows a compression code amount of the image data to fall within a target compression ratio. A compression mode setting processing section for setting one of a fixed mode and a fixed image quality mode for equalizing the image quality after compression of the image data; and a compression mode setting processing section. Image compression processing that adjusts compression parameters to compress image data when set to constant size mode, and compresses image data by fixing compression parameters when set to constant image quality mode Unit.

When the mode is set to the fixed image quality mode, the compression parameter adjustment step can be omitted by fixing the compression parameter, and the compression processing time can be reduced. When the fixed size mode is set, the compression code amount can be kept within the target compression ratio, so that the memory capacity can be used systematically when recording the compressed data in a memory or the like. The compression parameter is an adjustable element that affects the amount of compression code during the compression process.

The electronic camera further includes an operation member for setting a compression mode, and the compression mode setting processing section can set the compression mode when the operation member is manually operated.

The electronic camera further sets a determination processing unit that determines whether the information amount of the image data is greater than a predetermined value, and sets a fixed size mode when the determination processing unit makes an affirmative determination; A compression mode control processing unit that controls the compression mode setting processing unit to set the image quality constant mode when the determination processing unit makes a negative determination.

Since the electronic camera sets the compression mode according to the information amount of the image data, the user does not have to set the compression mode. The user can concentrate on shooting.

The electronic camera further sets a determination processing unit that determines whether the compression parameter is within the adjustment range, and sets a fixed size mode when the determination processing unit makes an affirmative determination, and the determination processing unit makes a negative determination. A compression mode control processing unit that controls the compression mode setting processing unit to set the constant image quality mode. In this case, the compression parameter includes a scale factor that changes the amount of compression code, and the adjustment range is preferably a range where the scale factor is equal to or greater than a predetermined value. In addition, the determination processing unit can change the adjustment range in accordance with one or more of the target compression ratio, the strength of edge enhancement or not, the shooting sensitivity setting, and the shooting mode of color Z monochrome.

Since the electronic camera sets the compression mode according to the compression parameter, the user does not have to set the compression mode. The user can concentrate on the shooting act.

The electronic camera including the image compression processing unit further includes a first determination processing unit that determines whether a compression parameter is within an adjustment range, and determines whether the compression parameter is equal to or less than a first predetermined value. A second determination processing unit, an operation member for setting a compression mode, and (1) a constant size mode when both the first determination processing unit and the second determination processing unit make a positive determination. (2) When the first determination processing unit makes a negative determination, sets the constant image quality mode. (3) The first determination processing unit makes a positive determination, and the second determination processing unit makes a negative determination. A compression mode control processing unit that controls the compression mode setting processing unit so that the compression mode is set by the operation member. In this case, the compression parameter includes a scale factor for changing the compression code amount, and the adjustment range is preferably a region where the scale factor is equal to or more than a second predetermined value. In addition, the first determination processing unit can change the adjustment range in accordance with at least one of the target compression ratio, the strength of edge enhancement or not, the shooting sensitivity setting, and the color Z monochrome shooting mode. it can.

The electronic camera sets the compression mode according to the amount of information in the image data, For example, when the information amount of the image data is very large, the user sets the compression mode by using the operation member, so that the user usually does not have to set the compression mode.

The image processing program according to the present invention provides one of a fixed size mode for keeping the compression code amount of image data within a range of a target compression ratio and a fixed image quality mode for uniforming the image quality of image data after compression. The compression mode setting process that sets the compression mode of the image, and when the fixed size mode is set by the compression mode setting process, adjusts the compression parameters to compress the image data, and And an image compression process for compressing image data while fixing the compression parameters when the fixed mode is set. Such an image processing program can be stored in a computer-readable recording medium or transmitted via a communication line such as the Internet. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic block diagram illustrating the configuration of the electronic force mera.

FIG. 2 is a flowchart illustrating an image compression process according to the first embodiment. FIG. 3 is a flowchart illustrating an image compression process according to the second embodiment. FIG. 4 is a flowchart illustrating an image compression process according to the third embodiment. FIG. 5A is a first half flowchart illustrating the image compression processing according to the fourth embodiment.

FIG. 5B is a second half flowchart illustrating the image compression processing according to the fourth embodiment.

FIG. 6A is a first half flowchart illustrating the image compression processing according to the fifth embodiment.

FIG. 6B is a second half flowchart illustrating the image compression processing according to the fifth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1st Embodiment 1 FIG. 1 is a schematic block diagram illustrating the configuration of the electronic force camera 10. In FIG. 1, a photographing lens 11 is attached to the electronic force camera 10. An image sensor 13 is arranged in the image space of the photographing lens 11. The image data generated by the image sensor 13 is subjected to predetermined processing through a signal processing unit 15, an AZD conversion unit 16, and an image processing unit 17 in that order. Entered in 18. The compression processing section 18 performs JPEG compression of the input image data and outputs the result to the recording section 19. The recording unit 19 records the input compressed image data on a recording medium (not shown) such as a memory card.

In addition, the electronic camera 10 is provided with a control unit 21 for system control, an operation button group 24 for performing camera operation and compression mode setting, and the like. Hereinafter, a camera having two compression modes, a fixed image quality mode and a fixed size mode, will be described.

FIG. 2 is a flowchart illustrating the image compression processing performed in the compression processing section 18. Hereinafter, the image compression processing which is a feature of the present invention will be described with reference to FIG. In step S1, the compression processing unit 18 first communicates with the control unit 21 to acquire the compression mode set by the operation button group 24. If the acquired compression mode is the constant image quality mode, the compression processing unit 18 proceeds to step S2. On the other hand, when the obtained compression mode is the fixed size mode, the compression processing unit 18 proceeds to step S4.

In step S2, the compression processing unit 18 selects a scale factor from the scale factors recorded in the nonvolatile memory of the compression processing unit 18 in advance in accordance with the target compression ratio, for the image quality constant mode. Determine the fixed scale factor FSF.

In step S3, the compression processing section 18 first divides the image data into 8 × 8 pixel blocks, and performs DCT (Discrete Cosine Transform) for each pixel block. Next, the compression processing section 18 multiplies the fixed scale factor FSF by all the elements of the reference quantization table recorded in the non-volatile memory in advance to create a quantization table for the constant image quality mode. The compression processing unit 18 quantizes the transform coefficient obtained by DCT using the created quantization table. The compression processing unit 18 sorts the quantized conversion coefficients in the order of zigzag scan, and then performs variable-length coding or the like to perform coding. Compress volume. Through the above procedure, the image compression in the constant image quality mode is completed, and the image compression processing of FIG. 2 is completed.

In step S4, the compression processing unit 18 selects a scale factor for the fixed size mode from the scale factors recorded in the nonvolatile memory of the compression processing unit 18 in advance in accordance with the target compression ratio. Determine the initial scale factor SF 1.

In step S5, the compression processing section 18 performs test compression on the image data using the determined initial scale factor S F1. The compression process is performed through the creation, quantization, and rearrangement of a DCT for each pixel block and a quantization table for a fixed size mode.

In step S6, the compression processing section 18 determines whether or not the compression size S obtained by performing the test compression is within the range of the target compression ratio. The compression size S is the compression code amount after image compression, that is, the compression data size. If a negative determination is made in step S6 that the compression size S is out of the range of the target compression ratio, the compression processing unit 18 proceeds to step S7. On the other hand, if the affirmative determination is made that the compression size S is within the range of the target compression ratio, the compression processing unit 18 determines that the image compression in the fixed size mode has ended, and ends the image compression processing of FIG. I do.

In step S7, the compression processing section 18 increases or decreases the scale factor SF according to the result of the compression size S.

In step S8, the compression processing section 18 compresses the image data again using the adjusted scale factor SF, and returns to step S6 to determine the compressed size again. According to the series of operations described above, in the first embodiment, the compression mode manually set by the operation button group 24, that is, any one of the constant size mode / constant image quality mode It is possible to switch.

To summarize the effects of the first embodiment described above, the electronic camera is provided with two types of image compression modes, a constant image quality mode and a constant size mode. The compression parameters were fixed and the test compression process was omitted. As a result, all or a part of the compression parameter adjustment step is omitted, so that the image compression process can be sped up.

In particular, the constant image quality mode was applied to image data with an extremely small amount of information. In this case, the image data is compressed to a small compression code amount according to the information amount. Therefore, there is little adverse effect such as the fact that invalid information (noise) remains after data compression, and there is no danger of wasting storage capacity.

Since the two types of image compression modes of the electronic camera are switched according to the manual operation of the operation button group 24, it is possible to reliably reflect the user's intention in the image compression process.

If it is possible to set the image quality during plane image compression (for example, switching between FINE / NORMAL / BASIC, etc.), the compression processing unit 18 sets the following parameters for the two types of image compression modes. It is preferable to make changes.

(1) In the constant size mode, the target compression ratio is changed to a low compression ratio (high compression ratio) in response to the image quality setting being set to high image quality setting (low image quality setting).

(2) In the constant image quality mode, the fixed value of the compression parameter is changed to the value on the low compression side (the value on the high compression side) in response to the image quality setting being set to the high image quality setting (low image quality setting). I do.

By changing the parameters as described in ① and ② above, it is possible to accurately reflect the image quality setting at the time of image compression in the two types of image compression modes.

Second Embodiment I

FIG. 3 is a flowchart illustrating the image compression processing according to the second embodiment, which is performed in the compression processing unit 18. In step S11, the compression processing section 18 first determines an initial scale factor SF1 corresponding to the target compression ratio.

In step S12, the compression processing unit 18 performs test compression on the image data using the determined initial scale factor S F1.

In step S13, the compression processing section 18 determines whether or not the compression size S obtained by the test compression is equal to or larger than a threshold. The threshold here is set to a value about the lower limit of the compression size S in general natural images. A natural image is an image of the natural world such as a general landscape-snapshot. When the compression size S is equal to or larger than the threshold, the compression processing unit 18 makes an affirmative determination because the amount of information of the image data is large. In this case, the compression processing unit 18 proceeds to step S16, and performs compression processing in the fixed size mode. On the other hand, if the compression size S is less than the threshold, the compression processing unit 18 determines that the information amount of the image data is The determination is negative because the number is smaller than the typical natural image. In this case, the compression processing unit 18 proceeds to step S14, and performs compression processing in the constant image quality mode.

In step S14, the compression processing section 18 determines a fixed scale factor FSF for the constant image quality mode corresponding to the target compression ratio.

In step S15, the compression processing unit 18 compresses the image data using the determined fixed scale factor FSF. Through the above procedure, the image compression in the constant image quality mode is completed, and the image compression processing in FIG.

In step S16, the compression processing section 18 determines whether or not the compression size S obtained by the test compression is within the target compression ratio. If a negative determination is made that the compression size S is out of the range of the target compression ratio, the compression processing unit 18 proceeds to step S17. On the other hand, when it is determined that the compression size S is within the range of the target compression ratio, the compression processing unit 18 determines that the image compression in the fixed size mode has been completed at the test compression stage, The image compression processing of FIG. 3 ends.

In step S17, the compression processing unit 18 increases or decreases the scale factor SF according to the result of the compression size S.

In step S18, the compression processing section 18 compresses the image data again using the adjusted scale factor SF, and returns to step S16 to determine the compressed size again. According to the series of operations described above, in the second embodiment, the image compression mode is automatically switched according to the information amount of the image data.

To summarize the operation and effect of the second embodiment described above, the electronic camera is provided with two types of image compression modes, a constant image quality mode and a constant size mode, and performs test compression on image data. The fixed size mode is automatically selected when the obtained compressed size S is equal to or greater than the threshold. For image data with a large compression size S, that is, for natural images with an average or relatively large amount of information, the compression size S can be adjusted in a relatively short time by going through the adjustment process of the compression parameters suitable for this Can be kept within the range of the target compression ratio. As a result, high-speed compression processing becomes possible. Furthermore, even when the information amount of the image data is large, such as when the sensitivity of the image sensor is high and there is a lot of noise, the compressed size S can be kept at a substantially constant size. , Preservation, management, etc. can be performed systematically. On the other hand, when the compression size S obtained by test-compressing image data is smaller than the threshold, the constant image quality mode is automatically selected. In the case of image data whose compression size S is not large, that is, image data whose information amount is not large, the process of adjusting compression parameters by repeating image compression is omitted, so that image data can be compressed at high speed. Will be possible. For image data with a small amount of information, the compression size S hardly exceeds the expected or average value corresponding to the target compression ratio even if the compression parameter is fixed. In addition, when the fixed image quality mode is selected, image data having a small amount of information is not forcibly reduced to a fixed size, so that the adverse effect that invalid information (noise) remains after compression is reduced. As a result, it is possible to efficiently record, save, and manage image data with a small compression size.

As described above, the image compression mode of the electronic camera is switched automatically and appropriately according to the amount of information of the image data, so that the user does not have to manually select the image compression mode. It is possible to concentrate on the act of shooting.

In the second embodiment, after the test compression (step S12), the compression in the constant image quality mode (step S15) is executed again. In this case, it is possible to set the fixed scale factor FSF for constant image quality mode and the initial scale factor SF1 for information amount judgment to different values, and select the optimal value for each purpose. There are excellent advantages such as.

However, the initial scale factor SF1 may be equal to the fixed scale factor FSF. In this case, the completion of the test compression may be regarded as the completion of the constant image quality mode, and the operations of steps S14 and S15 shown in FIG. 3 can be omitted.

In the above-described second embodiment, the compression size S after test compression is determined as a method for determining the information amount of image data. In this case, there is an excellent advantage that the amount of information can be determined by effectively utilizing the result of the test compression required for the fixed size mode.

The method for determining the information amount of the image data is not limited to the method described above. For example, a high frequency component of the image data may be extracted using a spatial frequency filter, and the amount of the high frequency component may be determined to determine the information amount of the image data. Also, One or more of the histogram, gradation characteristics, and contrast of the data may be obtained, and the amount of information may be determined from the obtained result.

Third Embodiment I

FIG. 4 is a flowchart illustrating image compression processing according to the third embodiment, which is performed in the compression processing unit 18. In step S21, the compression processing section 18 first determines an initial scale factor SF1 corresponding to the target compression ratio.

In step S22, the compression processing unit 18 determines the lower limit value S F min of the scale factor in consideration of the combination conditions of the following parameters.

-Target compression ratio

-Strength or absence of edge emphasis

-Imaging sensitivity setting

• Color Monochrome Shooting Mode

Specifically, the lower limit value S F min is determined by referring to the corresponding table created through the following preparatory preparations 1 to ような.

① Prepare many general natural images.

(2) Compress the image data of the natural image prepared in (1) to the target compression ratio for each combination of the above parameters, and find the lower limit of the compression scale factor (compression parameter).

(3) A value slightly lower than the lower limit obtained in (1) is defined as the lower limit S F min.

する Record the “correspondence table between the combination conditions of the above parameters and the lower limit value S F min” thus obtained in the non-volatile memory of the compression processing unit 18.

In step S23, the compression processing section 18 performs test compression on the image data using the initial scale factor S F1.

In step S24, the compression processing section 18 determines whether or not the compression size S obtained by the test compression is within the range of the target compression ratio. If a negative determination is made that the compression size S is out of the range of the target compression ratio, the compression processing unit 18 proceeds to step S25. On the other hand, if the affirmative determination is made that the compression size S is within the range of the target compression ratio, the compression processing unit 18 determines that the image compression in the fixed size mode has ended, and performs the image compression processing of FIG. finish. In step S25, the compression processing unit 18 increases or decreases the scale factor SF according to the compression size S.

In step S26, the compression processing unit 18 determines whether or not the adjusted scale factor SF is equal to or larger than the lower limit SFmin. When it is determined that the adjusted scale factor SF is equal to or more than the lower limit value SF min, the compression processing unit 18 proceeds to step S27. On the other hand, when the negative determination that the scale factor S ^Ca? Less than the lower limit value SF min after adjustment, the compression processing unit 1 8, proceeds non Step S 2 8 to switch the image quality constant mode. It is presumed that the image data to be compressed in the case of a negative determination lacks the information amount. Therefore, the compression processing unit 18 proceeds to step S28 to switch to the constant image quality mode.

In step S27, the compression processing unit 18 compresses the image data again using the adjusted scale factor SF, and returns to step S24 to determine the compressed size again.

In step S28, the compression processing section 18 determines a fixed scale factor FSF for the constant image quality mode corresponding to the target compression ratio.

In step S29, the compression processing section 18 compresses the image data using the determined fixed scale factor FSF. Through the above procedure, the image compression in the constant image quality mode is completed, and the image compression processing in FIG.

To summarize the operation and effect of the third embodiment described above, the electronic camera is provided with two types of image compression modes, a constant image quality mode and a constant size mode, and the scale factor SF is equal to or more than the lower limit value SF min In case of, fixed size mode is automatically selected. When the scale factor SF is greater than or equal to the lower limit value SF min, that is, when the compression parameter is in the adjustment range, the image data is regarded as image data having an average or relatively large amount of information (for example, a general natural image) and It can be judged that the application of the constant size mode is appropriate.

On the other hand, when the scale factor SF is less than the lower limit value SF min, the constant image quality mode is automatically selected. If the scale factor SF is less than the lower limit value SF min, that is, if the compression parameter is out of the adjustment range, it is regarded as an image having a relatively small amount of information (for example, an overexposed image) and the image quality is fixed. Is appropriate Can be determined.

As described above, by automatically switching the compression mode according to the adjustment value of the compression parameter, it is possible to select a suitable compression mode according to the image data. Become. Furthermore, the user does not need to manually select the image compression mode, and can concentrate on the shooting operation.

Information on the target compression ratio, strength of edge enhancement or not, imaging sensitivity setting, and color Z monochromatic shooting mode are all information that affects the final adjustment value of the compression parameter. Therefore, by changing the adjustment range in accordance with one or more of these pieces of information, it becomes possible to make the switching mode switching judgment and the timing thereof more appropriate.

Fourth Embodiment I

FIGS. 5A and 5B are flowcharts illustrating an image compression process according to the fourth embodiment, which is performed in the compression processing unit 18. FIG. In step S41 of FIG. 5A, the compression processing unit 18 first initializes the following parameters corresponding to the target compression ratio.

• Compression size tolerance S span

-Initial scale factor S F 1

• Lower limit of scale factor S F min

-Discontinued scale factor S F 4

In step S42, the compression processing unit 18 performs test compression on the image data using the initial scale factor S F1.

In step S43, the compression processing unit 18 applies the result of one-time compression to the statistical data stored in the memory of the compression processing unit 18 in advance to obtain an appropriate scale for obtaining the target compression ratio. Estimate the factor SF2.

In step S44, the compression processing section 18 limits the estimated scale factor SF2 with a lower limit SFmin.

In step S45, the compression processing section 18 compresses the image data using the scale factor SF2.

In step S46, the compression processing unit 18 determines that the compression size S is within the allowable range S span It is determined whether or not it fits in. If a negative determination is made that the compression size S is out of the allowable range S span, the compression processing unit 18 proceeds to step S47. On the other hand, if the compression processing unit 18 determines that the compression size S is within the allowable range S span, the compression processing unit 18 determines that the image compression in the fixed size mode has ended, and the image compression shown in FIG. Finish the process.

In step S47, the compression processing unit 18 determines whether "the current compression is higher than the target compression ratio" and "the scale factor SF2 is equal to the lower limit SFmin" are satisfied. judge. When all of the above conditions are satisfied, it can be assumed that the image data to be compressed is a special image having an extremely small amount of information. Therefore, the compression processing unit 18 terminates the image compression when making a positive determination, and ends the image compression processing of FIG. 5A. In this case, the image compression in the constant image quality mode by the lower limit value SFmin is consequently executed. On the other hand, if a negative determination is made in step S47, the compression processing unit 18 proceeds to step S48 in FIG. 5B.

In step S48, the compression processing unit 18 applies the results of the two compressions to the statistical data stored in the memory of the compression processing unit 18 in advance to obtain an appropriate scale for obtaining the target compression ratio. Estimate the factor SF3.

In step S49, the compression processing unit 18 limits the estimated scale factor SF3 with the lower limit SFmin.

In step S50, the compression processing unit 18 compresses the image data using the scale factor SF3.

In step S51, the compression processing section 18 determines whether or not the compression size S falls within the allowable range S span. If a negative determination is made that the compression size S is out of the allowable range S span, the compression processing unit 18 proceeds to step S52. On the other hand, when it is determined that the compression size S is within the allowable range S span, the compression processing unit 18 determines that the image compression in the fixed size mode has been completed, and the image compression shown in FIG. Finish the process.

In step S52, the compression processing unit 18 determines whether “the current compression is higher than the target compression ratio” and “the scale factor SF3 is equal to the lower limit SFmin” are satisfied. judge. If all of the above conditions are met, the image In the evening, it can be assumed that the amount of information is extremely small and special. Therefore, the compression processing unit 18 terminates the image compression when making a positive determination, and ends the image compression processing of FIG. 5B. In this case, image compression in the constant image quality mode with the lower limit value SF min is consequently executed. On the other hand, if a negative determination is made in step S52, the compression processing unit 18 proceeds to step S53.

In step S53, the compression processing section 18 compresses the image data using the truncation scale factor SF4.

In step S54, the compression processing unit 18 determines whether or not the compression size S force ⁵ '(upper limit of the allowable range Span) is less than or equal to. If a negative determination is made that the compression size S exceeds (the upper limit of the allowable range S span), the compression processing unit 18 proceeds to step S55. On the other hand, if an affirmative judgment is made while satisfying the loose condition of being within the compression size (the upper limit of the allowable range S span), the compression processing unit 18 determines that the image compression in the fixed size mode has been temporarily completed. Then, the image compression processing of FIG. 5B ends.

In step S55, the compression processing unit 18 determines whether or not the number of compression trials has exceeded the limited number. If it is determined that the number of times exceeds the limit, the compression processing unit 18 terminates the compression processing based on the final compression result, and ends the image compression processing of FIG. 5B. On the other hand, if a negative determination is made that the number of times has not exceeded the limit, the compression processing unit 18 proceeds to step S56.

In step S56, the compression processing section 18 multiplies the set scale factor SF4 by a predetermined number (for example, 1.5 times), and proceeds to step S53 again.

In summary of the operation and effect of the fourth embodiment described above, the constant size mode and the constant image quality mode are appropriately switched flexibly in response to the result of the compression trial. Therefore, it is possible to appropriately avoid adverse effects such as invalidly repeating the image compression processing.

That is, in the case where a negative determination is made in each of step S47 and step S52 described above, that is, when the compression parameter is in the adjustment range, the image data whose information amount is average or relatively large (for example, general It can be judged that the application of the normal constant size mode is appropriate.

On the other hand, in steps S47 and S52 described above, If the compression parameter is out of the adjustment range and the scale factors SF2 and SF3 are less than the lower limit, image data with a relatively small amount of information (for example, an overexposed image) Therefore, it can be judged that the application of the constant image quality mode is appropriate. As described above, by automatically switching the compression mode according to the adjustment value of the compression parameter, it is possible to select a suitable image compression mode according to the image data.

Fifth Embodiment I

FIGS. 6A and 6B are flowcharts illustrating an image compression process performed by the compression processing unit 18 according to the fifth embodiment. In step S61 of FIG. 6A, the compression processing unit 18 first determines an initial scale factor S F1 corresponding to the target compression ratio.

In step S62, the compression processing unit 18 determines the lower limit value SF min and the upper limit value SF max of the scale factor in consideration of the combination conditions of the following parameters. -Target compression ratio

-Strength or absence of edge emphasis

-Imaging sensitivity setting

• Monochrome mouth shooting mode

(1) Prepare a large number of general natural images for the constant size mode.

(2) Compress the image data of the natural image prepared in (1) to the target compression ratio for each combination of the above parameters, and find the lower and upper limits of the scale factor (compression parameter) at the time of compression.

(3) A value slightly lower than the lower limit obtained in (2) is set as the lower limit value SFmin, and a value slightly higher than the upper limit obtained in (2) is set as the upper limit value SFmax.

『The thus obtained“ correspondence table between the combination conditions of the above parameters and the lower limit value SF min and the upper limit value SF max ”is recorded in the non-volatile memory of the compression processing unit 18. In step S63, the compression processing section 18 performs test compression on the image data using the initial scale factor SF1. In step S64, the compression processing section 18 determines whether or not the compression size S obtained by the test compression is within the range of the target compression ratio. If a negative determination is made that the compression size S is out of the range of the target compression ratio, the compression processing unit 18 proceeds to step S65. On the other hand, if the affirmative determination is made that the compression size S is within the range of the target compression ratio, the compression processing unit 18 determines that the image compression in the fixed size mode has been completed, and performs the image compression processing of FIG. finish.

In step S65, the compression processing section 18 increases or decreases the scale factor S F according to the compression size S.

In step S66, the compression processing section 18 determines whether or not the adjusted scale factor SF is equal to or larger than the lower limit SF min (the compression parameter is within the adjustment range). If it is determined that the adjusted scale factor SF is equal to or more than the lower limit SF min, the compression processing unit 18 proceeds to step S69 in FIG. 6B. On the other hand, if it is determined that the adjusted scale factor SF is less than the lower limit value SFmin, the compression processing unit 18 proceeds to step S67 to switch to the constant image quality mode. It is presumed that the image data to be compressed in the case of a negative determination lacks the information amount. Therefore, the compression processing unit 18 proceeds to step 67 to switch to the constant image quality mode.

In step S67, the compression processing unit 18 determines the fixed scale factor FSF in consideration of a combination condition of the following parameters.

-Target compression ratio

-Strength or absence of edge emphasis

-Imaging sensitivity setting

-Color Monochrome shooting mode

In step S68, the compression processing section 18 compresses the image data using the determined fixed scale factor FSF. Through the above procedure, the image compression in the constant image quality mode is completed, and the image compression processing of FIG. 6A is completed.

In step S69 of FIG. 6B, it is determined whether or not the scale factor SF is equal to or smaller than SFmax. If it is determined that the scale factor SF is equal to or smaller than SFmax, the compression processing unit 18 proceeds to step S70. On the other hand, if it is determined that the scale factor SF is not equal to or smaller than SF max (exceeds SF max), the compression processing unit 18 proceeds to step S 7 1 Proceed to.

In step S70, the compression processing section 18 compresses the image data with the scale factor SF adjusted in step S65, and after compression, proceeds to step S64 in FIG. 6A.

In step S71, the compression processing unit 18 issues a warning to the user that the image has an extremely large amount of information, and prompts the user to select one of the fixed file size mode and the fixed image quality mode. . When the user selects the fixed file size mode, the compression processing section 18 proceeds to step S70. When the user selects the constant image quality mode, the compression processing section 18 proceeds to step S72.

In step S72, the compression processing unit 18 determines the fixed scale factor FSF in consideration of the combination condition of the following parameters, and proceeds to step S68 in FIG. 6A.

-Target compression ratio

• The strength of the edge enhancement

-Imaging sensitivity setting

-Color Z Monoc Mouth Shooting Mode

The amount of correction to the file size selected by the user in the trade-off between file size and image quality

To summarize the operation and effect of the fifth embodiment described above, the electronic camera is provided with two types of image compression modes, a constant image quality mode and a constant image size mode, and adjusts the adjustment values of the compression parameters. In addition to automatically switching the image compression mode in response to the image data, if the image data contains extremely large amount of information, a warning is issued to the user, and the user can be switched between the fixed size mode and the fixed quality mode. It was done manually.

In other words, when the determination is affirmative in steps S66 and S69 described above, that is, when the compression parameter is in the adjustment range and the scale factor SF is equal to or less than the upper limit SFmax, the information amount is average. Considering that the image data is targeted or relatively large (for example, general natural images), it can be judged that the application of the normal constant size mode is appropriate. However, if a negative determination is made in step S69, that is, the scale factor SF exceeds the upper limit SF max even if the compression parameter is in the adjustment range. In such a case, the user considers image data with an extremely large amount of information (for example, an image like a tree with many twigs), and allows the user to select the constant image quality mode or constant size mode.

If a negative determination is made in step S66, that is, if the compression parameter is out of the adjustment range, it is regarded as image data having a relatively small amount of information (for example, an overexposed image, etc.) and the image quality constant mode It can be determined that the application is appropriate.

As described above, by interweaving the automatic selection and the manual selection of the image compression mode, a suitable image compression mode can be applied to any image data. The user usually does not need to manually select the image compression mode, and can concentrate on the shooting. In the case of image data with an extremely large amount of information, a warning is issued from the electronic camera, so that the user can make a manual selection. Industrial applicability

Although the embodiment as an electronic camera has been described, the image compression processing represented by any one of the flowcharts in FIGS. 2 to 6 may be described as an image processing program, and this image processing program may be stored in a recording medium. Good. By executing such an image processing program on a computer, it is possible to obtain the same functions and effects as those of the above-described embodiment.

Further, by transmitting the image processing program to a computer using a communication line and executing the program on the computer, it is possible to obtain the same operational effects as those of the above-described embodiment.

Claims

The scope of the claims

1. Electronic camera

An image sensor that captures an image of a subject and outputs the captured subject as image data; a fixed size mode that keeps a compression code amount of the image data within a target compression ratio; and an image quality of the image data after compression. A compression mode setting processing section for setting one of the compression modes for the uniform image quality constant mode;

When the compression mode setting processing unit sets the fixed size mode, the compression parameter is adjusted to compress the image data, and when the fixed image quality mode is set. An image compression processing section for fixing the compression parameters and compressing the image data.

2. The electronic camera according to claim 1,

The compression parameter is an adjustable element that affects the compression code amount during the compression process.

3. The electronic camera according to claim 1 is

Further comprising an operation member for setting the compression mode,

The compression mode setting processor sets the compression mode when the operation member is manually operated.

4. The electronic camera according to claim 1

A determination processing unit that determines whether or not the information amount of the image data is greater than a predetermined value; and when the determination processing unit makes an affirmative determination, the size constant mode is set, and the determination processing unit makes a negative determination. At this time, the image processing apparatus further includes a compression mode control processing unit that controls the compression mode setting processing unit so as to set the image quality constant mode.

5. The electronic camera according to claim 1 is

A determination processing unit that determines whether the compression parameter is in an adjustment range;

When the determination processing section makes an affirmative determination, the compression mode setting processing section is controlled to set the fixed size mode, and when the determination processing section makes a negative determination, the compression mode setting processing section is set to set the fixed image quality mode. And a compression mode control processing unit.

6. The electronic camera according to claim 5,

The compression parameter includes a scale factor for changing the compression code amount, The adjustment area is an area where the scale factor is equal to or greater than a predetermined value.

7. The electronic camera according to claim 5,

The determination processing unit,

-Target compression ratio

-Strength or absence of edge emphasis

-Shooting sensitivity setting

-Camera mode

The adjustment range is changed corresponding to one or more of the above.

8. The electronic camera according to claim 1 is

A first determination processing unit that determines whether the compression parameter is in an adjustment range; a second determination processing unit that determines whether the compression parameter is less than or equal to a first predetermined value; An operation member for setting a mode,

(1) When both the first determination processing unit and the second determination processing unit make an affirmative determination, the constant size mode is set, and (2) the first determination processing unit makes a negative determination. (3) When the first determination processing section makes an affirmative determination and the second determination processing section makes a negative determination, the compression mode is set by the operating member. A compression mode control processing unit that controls the compression mode setting processing unit to set a compression mode.

9. The electronic camera according to claim 8,

The compression parameter includes a scale factor for changing the compression code amount, and the adjustment range is a region where the scale factor is equal to or more than a second predetermined value.

10. The electronic camera according to claim 8,

The first determination processing unit includes:

'' Target compression ratio

-Strength or absence of edge emphasis

-Shooting sensitivity setting

• Color / monochrome shooting mode

The adjustment range is changed corresponding to one or more of the above.

1 1. Constant size mode to keep the compression code amount of image data within the range of target compression ratio A compression mode setting process for setting one of the compression modes of a fixed image quality mode for equalizing the image quality of the image data after compression;

When the fixed size mode is set by the compression mode setting processing, the image data is compressed by adjusting the compression parameter, and when the fixed image quality mode is set, An image compression program for compressing the image data while fixing the compression parameter.

12. A recording medium on which the image processing program according to claim 11 is recorded.

13. A signal for transmitting the image processing program according to claim 11 via a communication line.