JP2001268400A - Histogram creation device and histogram creation method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To make it possible to obtain good visibility and accurate reproducibility when displaying a small histogram representing the luminance distribution of an image. SOLUTION: Even-numbered pixel number data L (2), L (4), L (6), ... are thinned out from pixel number data L (1) to L (256) for each luminance level in an image ( b). Remaining pixel number data L (3), L (5), L
(7), ...
An average value of the two pixel number data is calculated, and frequency data D (1) to D (128) are newly created (c). By displaying a histogram based on the frequency data created,
Even if the display area is small, a smooth histogram can be obtained in which a step between data having adjacent luminance values is not emphasized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a histogram creating apparatus and a histogram creating method suitable for use in, for example, an electronic still camera.

[0002]

2. Description of the Related Art Conventionally, in electronic still cameras and the like,
For the purpose of making it easy to confirm the suitability of exposure at the time of imaging, the distribution of the luminance level in a predetermined section of the captured image is calculated, and a histogram of a bar graph or a line graph representing the frequency for each luminance level is used as a liquid crystal. There is known a technique for displaying on a monitor or the like (see Japanese Patent Laid-Open No. 7-38801).

[0003]

However, when the above-mentioned histogram of a captured image or the like is displayed on a small monitor or is displayed in a small area on the screen, that is, the display area of the histogram itself is small. In this case, even if the frequency is represented for every luminance level,
Actually, the frequency of each luminance level cannot be visually recognized, and the useless portion in the histogram display processing increases.
For this reason, as shown in FIG. 8, a method of thinning out and displaying a part of the histogram is conceivable. In this case, a step larger than the actual one occurs between adjacent bar graphs, and the peak of the histogram is rattled. There is a problem that the visibility is deteriorated and the frequency of each luminance level displayed after the thinning is not different from that before the thinning, so that the histogram before the thinning cannot be faithfully reproduced. 8A shows a state in which the frequencies are displayed for all the luminance levels, and FIG. 8B shows a state in which every other luminance level is thinned out.

The present invention has been made in view of such a conventional problem, and has a histogram creating apparatus capable of creating a histogram capable of obtaining good visibility and accurate reproducibility even when it is displayed in a small size. And a histogram creation method.

[0005]

According to a first aspect of the present invention, there is provided a histogram creating apparatus for creating a histogram representing a luminance distribution of an image.
Calculation means for calculating new frequency data using each frequency data corresponding to a plurality of brightness values in the brightness distribution, and a display histogram is created using the plurality of frequency data calculated by the calculation means. And a creation means.

In such a configuration, the creating means creates a display histogram based on a plurality of new frequency data calculated by the calculating means. It is possible to create a smooth histogram in which the difference between them is not emphasized.

Further, in the invention according to claim 2, the calculating means calculates the new plurality of frequency data by using a plurality of frequency data obtained by thinning out frequency data of a predetermined luminance value. It was taken. In such a configuration, it is possible to reduce the load required for calculating a plurality of new frequency data to be calculated.

According to a third aspect of the present invention, the calculating means duplicates at least one of frequency data corresponding to a plurality of luminance values in the luminance distribution to obtain the new frequency data. Data was calculated. In such a configuration, it is possible to create a histogram in which the actual distribution shape is more accurately reflected.

Further, in the invention according to claim 4, the calculating means calculates an average value of frequency data corresponding to a plurality of luminance values in the luminance distribution. Even in such a configuration, it is possible to create a smooth histogram in which the actual distribution shape is more accurately reflected.

According to a fifth aspect of the present invention, the calculating means includes, for each of a plurality of frequency data corresponding to a plurality of luminance values in the luminance distribution, a predetermined frequency data of the plurality of frequency data. , And the new frequency data is calculated. Even in such a configuration, it is possible to create a smooth histogram in which the actual distribution shape is more accurately reflected.

Further, the invention according to claim 6 is characterized in that the calculation means is provided with a display means for displaying a histogram using the new plurality of frequency data calculated. In such a configuration, the histogram representing the luminance distribution of the image can be displayed small on the display means in a smooth state in which the difference between the data having adjacent luminance values is not emphasized.

Further, in the invention according to claim 7, the histogram creating device constitutes an electronic camera device having an image pickup means for picking up an image of a subject and the display means. In such a configuration, a histogram representing a luminance distribution of a subject image or the like captured by the imaging unit is displayed on the display unit in a smooth state in which the difference between data having adjacent luminance values is not emphasized. be able to.

[0013] In the invention according to claim 8, the calculating means uses each frequency data corresponding to a plurality of luminance values in the luminance distribution, and calculates the new frequency having a smaller number than the frequency data. Data was calculated. In such a configuration, it is possible to create a histogram that can be easily displayed in a small size (with a small area) in a smooth state in which the difference between data having adjacent luminance values is not emphasized.

According to a ninth aspect of the present invention, in the histogram creating apparatus for creating a histogram representing a luminance distribution of an image, a thinning means for reducing the number of frequency data corresponding to luminance values in the luminance distribution is provided. Creating means for creating a histogram for display using a plurality of frequency data after the number of frequency data is reduced by the thinning means, wherein the frequency data is reduced in frequency data by the thinning means. It is assumed that the value is a value corresponding to a difference between the number of pieces of frequency data before the reduction and the number of pieces of frequency data after the frequency data is reduced by the thinning-out means. In such a configuration, it is possible to create a histogram in which the actual distribution shape is more accurately reflected.

According to a tenth aspect of the present invention, there is provided a method for creating a histogram representing a luminance distribution of an image, wherein a new frequency is generated by using respective frequency data corresponding to a plurality of luminance values in the luminance distribution. Data was calculated, and a histogram for display was created using the calculation result. In such a method, when displaying the data in a small size, it is possible to create a smooth histogram in which the difference between data having adjacent luminance values is not emphasized.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG.
1 is a block diagram of an electronic still camera 1 according to the present invention.

The electronic still camera 1 has a lens 2
And a diaphragm device 3 for adjusting the amount of light of the subject image incident through the lens 2 and an image pickup device 4 composed of a CCD are sequentially arranged along the optical axis. The aperture device 3 is variably set in the aperture amount and is connected to an aperture control circuit 5, and the solid-state imaging device 4 is connected to a signal processing circuit 6.
Each of these units is connected to the CPU 7 and the CP
U7 includes a ROM 8, a working RAM 9, and a recording memory 1.
0, key input unit 11, external I / F control unit 12, display R
AM 13 and a histogram calculation circuit 14 are connected. The CPU 7 controls each unit by operating as a work RAM 9 work area according to an operation program stored in the ROM 8. For example, automatic exposure control (A
At the time of E control), the CPU 7 determines an aperture value according to the brightness of the subject, drives the aperture device 3 via the aperture control circuit 5 based on the aperture value, adjusts the amount of light incident on the image sensor 4, and The signal charge accumulation time (shutter speed) in the element 4 is controlled.

The signal processing circuit 6 performs gain adjustment of an analog image signal output from the image sensor 4, color signal processing for the signal, and conversion to a digital signal. The image data for one frame converted into a digital signal is sent to the display RAM 13, and the display circuit 15 generates a video signal. As a result, the RE in the imaging standby
When the C through mode is set, the captured subject image is L
When a photographing instruction is displayed on the display element 16 composed of a CD as a through image and the shutter key is pressed in that state, the image data for one frame is stored in the recording memory 10.
Will be recorded. When the PLAY mode is set, the image recorded in the recording memory 10 is read and displayed on the display element 16. The key input unit 11 includes the shutter key, a key for switching between the REC through mode and the PLAY mode, and the like. The external I / F control unit 12 controls input and output of data to and from an external device such as a personal computer connected to the electronic still camera 1. The histogram calculation circuit 14 includes one frame of image data generated by the signal processing circuit 6,
From the luminance data included in the image data read from the recording memory 10, the luminance levels (in the present embodiment, “0” to “25”) for each pixel corresponding to the image size at the time of recording are obtained.
5) (256 steps), the number of pixels at each luminance level is calculated, and the calculation result is sent to the CPU 7.

Next, the operation of displaying an image designated by the user when the PLAY mode is set in the embodiment having the above configuration will be described with reference to the flowchart of FIG.

That is, when any one of the images is selected by the user (step SA1), the CPU 7 reads out the data of the selected image from the recording memory 10 and expands it on the display RAM 13 and the first one. The image data for the frame is sent to the histogram calculation circuit 14 (step SA2). The histogram calculation circuit 14 acquires the luminance data of each pixel from the transmitted image data, counts the number of pixels corresponding to each luminance level, and sends the count result (pixel number data) to the CPU 7 (step SA3). ). On the other hand, the CPU 7 calculates the even-numbered pixel number data L (2), L (4), L from the transmitted pixel number data L (1) to L (256) for each luminance level.
After thinning out (6),... (Step SA4), the remaining pixel number data L (3), L (5), L (7),.
Is used repeatedly, an average value is calculated for each two adjacent (or more than three) pixel number data, and new frequency data D (1) to D (128) are created (step SA).
5).

FIGS. 3A and 3B are diagrams schematically showing data during the processing of the CPU 7. FIG. 3A shows the basic pixel number data, and FIG. 3B shows the half number data at step SA4. The pixel number data (odd-numbered pixel number data) thinned out in FIG. 3C is for display for display obtained in step SA5 in which two adjacent pixel number data in FIG. This is frequency data. Thereafter, the CPU 7 determines the frequency data D (1) to D (12) acquired in step SA5.
The display data of the histogram is generated using step 8) (step SA6), and is displayed in step SA2.
3 (step SA7), the display image A on which the histogram H is superimposed is displayed on the display element 16 as shown in FIG. 4 (step SA8). When the histogram H is combined with the image, a graph display area a is set at the lower part of the center of the image,
A bar graph with the luminance level on the X axis and the frequency on the Y axis is overwritten in that area. The number of dots on the X axis is 128.

Here, in the present embodiment, as described above, as the frequency data for displaying the histogram H, the number of the basic pixel number data is once decimated to 、, and then the two adjacent pixel number data are reduced. Since the average value (number of pixels) of the pixel number data is used, it is compared with a conventional case where the number of base pixel number data is simply thinned out (FIG. 8).
), And the histogram H is smooth without a step between adjacent bar graphs. Therefore, even when the histogram H is displayed small in a part of the display image as shown in FIG. 4, good visibility of the histogram H can be secured. Further, since the average value of the two adjacent pixel number data is used as new frequency data, the displayed histogram H more accurately reflects the actual distribution shape. Further, since the frequency data for display is created (calculated) from the pixel number data after the data number has been thinned to １ ／, the load on the CPU required for the calculation is reduced.

In the present embodiment, when generating the frequency data D (1) to D (128) for display, first, the even-numbered pixel number data is thinned out, and then the pixel number data is repeatedly used. Although the case where the average value is calculated for each of two adjacent pixel number data has been described, the average value is calculated for each of the two adjacent pixel number data of the pixel number data L (1) to L (256) without using them repeatedly. , The frequency data D (1) to D (128) are created (calculated), compared to the case where the number of base pixel number data is simply thinned out as in the conventional case. It is possible to create a smooth histogram H in which the distribution shape of the actual histogram is accurately reflected and in which the steps between the adjacent bar graphs are not emphasized. Also, the description has been given of the case where the average value of the two adjacent pixel number data calculated without using the pixel number data redundantly is used as the value of the frequency data for display.
In addition, for example, when the display area of the histogram H is smaller, an average value of three or more consecutive pixel number data may be calculated and used as the value of the frequency data for display.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. In the present embodiment, a program for creating display data of a histogram different from that of the first embodiment is stored in the ROM 8 of the electronic still camera 1 described above.

The operation of displaying an image designated by the user when the PLAY mode is set in this embodiment will be described below with reference to the flowchart of FIG.

Also in this embodiment, when any image is selected by the user (step SB1), C
The PU 7 reads the data of the selected image from the recording memory 10, expands the data in the display RAM 13, and sends the image data for one frame to the histogram calculation circuit 14 (step SB 2). The histogram calculation circuit 14 obtains luminance data of each pixel from the transmitted image data, counts the number of pixels corresponding to each luminance level, and counts the result (pixel number data).
Is sent to the CPU 7 (step SB3). On the other hand, in the present embodiment, as shown in FIG. 6A, the CPU 7 sends the transmitted pixel number data L (1) to L (1) to L
Regarding (256), while mutually using mutually adjacent pixel number data, the even-numbered pixel data and three adjacent pixel-number data before and after the even-numbered pixel number data are set as one set, and the even-numbered pixel number data is weighted. Calculation for averaging is performed to newly generate frequency data of half the number of pixel data as shown in FIG. 6B (step SB4). In other words, a calculation for correcting each even-numbered pixel number data using the preceding and following odd-numbered pixel number data is performed, and the result is used as new frequency data.

Thereafter, the CPU 7 generates histogram display data using the frequency data D (1) to D (128) obtained in step SB4 (step SB5).
By combining it with the display image developed in the display RAM 13 in step SB2 (step SB6),
As shown in FIG. 7, the display element A on which the histogram H is superimposed is displayed on the display element 16 (step SB7).
FIG. 7 shows a case where a histogram H of the same type as that of the first embodiment is synthesized on the upper left of the image with the number of X-axis dots being about 85 dots.

Also in this embodiment, when the histogram H is displayed in a small size, the level difference between adjacent bar graphs is smooth without being emphasized.
And good visibility can be ensured. As frequency data when displaying the histogram H, three consecutive
By creating (calculating) one new frequency data from one pixel number data, the actual distribution shape is more accurately reflected. Furthermore, when creating new frequency data, specific pixel number data (even number data)
Since the calculation for weighting and averaging is performed, the actual distribution shape is more accurately reflected.

Also in the present embodiment, when generating frequency data D (1) to D (128) for display,
Although the case where the base pixel number data L (1) to L (256) are used repeatedly is shown, the number of base pixel number data is simply thinned out as in the related art even when the base pixel number data L (1) to L (256) is not used. Compared to the case of using a histogram, a smooth histogram H can be created in which a step between adjacent bar graphs is not emphasized. Further, in the present embodiment, one new frequency data is created (calculated) from three consecutive pixel number data, but in addition to this, a new plurality of pixel number data is generated from a plurality of continuous pixel number data. Create a small number of frequency data,
For example, two frequency data may be created from five pixel number data.

In the first and second embodiments described above, the pixel number data L (1)
ＬL (256) to display frequency data D (1) 〜D
After creating (128), the values of the frequency data D (1) to D (128) are further reduced according to the difference between the two data numbers. For example, when the data number is １ ／ as described above, Calculates the value of frequency data D (1) to D (128) by 1 /
It may be reduced to two. In that case, the actual distribution shape of the histogram represented by the pixel number data L (1) to L (256) is more accurately reflected. Further, if the same processing is performed on data in which the number of base pixel number data is simply thinned out, a level difference between adjacent bar graphs is not emphasized in a histogram displayed using the processed data. It becomes something.

In the first and second embodiments described above, the histogram to be displayed is constituted by a bar graph indicating the number of pixels for each luminance level, but the histogram is represented by a line graph. Can also.
Also, a case has been described in which, when an image recorded in the recording memory 10 is read in the PLAY mode, a histogram is always superimposed on the display image, but the through image displayed in the REC through mode is also the same as described above. May be displayed in a superimposed manner. In addition, histogram (frequency data)
May be created, the created data may be stored in association with the image data, and at the time of reproduction, the created data may be read and displayed. Further, regardless of the above-mentioned difference in the mode, display / non-display of the histogram may be selected according to a predetermined operation. In addition, although the histogram is configured to be superimposed on the display image, the histogram H and the display image may be displayed independently, or a configuration may be provided in which a histogram-specific display unit such as an LED is provided.

The case where the present invention is applied to the electronic still camera 1 has been described. However, the present invention is also applicable to a video camera, a personal computer, and a general computer for displaying and processing moving images and still images. The present invention can be applied to a television receiver and the like. For example, it is conceivable to display a histogram when adjusting the brightness of the screen. Further, the present invention can be applied to an apparatus having no means for displaying a histogram created by the user, such as an image scanner. In such a case, it is conceivable to create a histogram relating to the captured image data and send it to a personal computer together with the captured data.

[0033]

As described above, in the present invention,
When it is displayed small, it is possible to create a smooth histogram without emphasizing the difference between data having adjacent luminance values. Therefore, it is possible to create a histogram that provides good visibility for the histogram even when the histogram is displayed small. Further, in the case where the display device is provided, the histogram can be displayed small while ensuring good visibility. In the case of the electronic camera device, the histogram representing the luminance distribution of a captured image or the like can be displayed in a favorable manner. It is possible to display a small image while ensuring excellent visibility.

Further, when calculating new frequency data for displaying a histogram, frequency data having a predetermined luminance value is thinned out from a plurality of base frequency data, so that a plurality of new frequency data to be calculated can be calculated. Can be reduced.

The calculation of a plurality of new frequency data for displaying a histogram may be the calculation of an average value of the frequency data corresponding to each of the plurality of luminance values. At least one of the data
Histograms that more accurately reflect the actual distribution shape can be created by using multiple duplicates or weighting predetermined frequency data out of the multiple frequency data for each of multiple frequency data Becomes That is, accurate reproducibility of the histogram can be ensured. Furthermore, if the value of the new frequency data for displaying the histogram is a value corresponding to the difference between the number of the respective frequency data as the base and the number of the new frequency data whose number is reduced, A histogram in which the actual distribution shape is more accurately reflected can be created.

If the number of new frequency data for displaying a histogram is made smaller than the number of base frequency data, it is possible to create a histogram which can be easily displayed in a small size (with a small area). Becomes

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing an operation in a PLAY mode in the embodiment.

FIG. 3 is a schematic explanatory view showing a procedure for calculating histogram display data in the embodiment.

FIG. 4 is a diagram showing a display example of an image on which a histogram is superimposed in the embodiment.

FIG. 5 is a flowchart showing an operation in a PLAY mode according to the second embodiment of the present invention.

FIG. 6 is a schematic explanatory view showing a procedure for calculating histogram display data in the embodiment.

FIG. 7 is a diagram showing a display example of an image on which a histogram is superimposed in the embodiment.

FIG. 8 is a schematic explanatory diagram showing a histogram in a case where frequency data of a luminance level is simply decimated every other one.

[Explanation of symbols]

 Reference Signs List 4 imaging device 6 signal processing circuit 7 CPU 8 ROM 11 key input unit 14 histogram calculation circuit 16 display device H histogram

Claims (10)

[Claims] 1. A histogram creating apparatus for creating a histogram representing a luminance distribution of an image, comprising: calculating means for calculating new frequency data using each frequency data corresponding to a plurality of luminance values in the luminance distribution; A histogram generating device for generating a histogram for display using a plurality of frequency data calculated by the calculating device. 2. The histogram creating apparatus according to claim 1, wherein said calculating means calculates the new frequency data by using a plurality of frequency data obtained by thinning out frequency data of a predetermined luminance value. apparatus. 3. The new frequency data is calculated by using at least one frequency data among frequency data corresponding to a plurality of luminance values in the luminance distribution in an overlapping manner. Item 3. The histogram creation device according to item 1 or 2. 4. The histogram creation device according to claim 1, wherein said calculation means calculates an average value of each frequency data corresponding to a plurality of brightness values in said brightness distribution. 5. The method according to claim 5, wherein the calculating means weights predetermined frequency data among the plurality of frequency data corresponding to the plurality of luminance values in the luminance distribution and weights the new frequency data. The histogram creation device according to claim 1, wherein data is calculated. 6. The histogram creation device according to claim 1, further comprising a display unit that displays the histogram for display created by the creation unit. 7. The histogram creation device according to claim 6, wherein the histogram creation device constitutes an electronic camera device having an image pickup means for picking up an image of a subject and the display means. 8. The method according to claim 1, wherein the calculating means calculates new frequency data having a smaller number than the frequency data by using frequency data corresponding to a plurality of luminance values in the luminance distribution. Item 1. A histogram creating apparatus according to Item 1. 9. A histogram creating apparatus for creating a histogram representing a luminance distribution of an image, comprising: a thinning unit for reducing the number of frequency data corresponding to a luminance value in the luminance distribution; Creating means for creating a histogram for display using a plurality of frequency data after the reduction, the frequency data, the number of frequency data before the frequency data is reduced by the thinning means, A histogram creating apparatus characterized in that the histogram data is a value corresponding to a difference between the frequency data after the frequency data is reduced by the thinning means. 10. A method for creating a histogram representing a luminance distribution of an image, comprising: calculating new frequency data using respective frequency data corresponding to a plurality of luminance values in the luminance distribution; A histogram for display by using a histogram.