JP2002132243A - Image processor and method as well as recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the arbitrary luminance of position in images in converting the wide dynamic range image to the narrow dynamic range image. SOLUTION: A high-area function determination section forms a high-area logarithmic function corresponding to a straight line C passing two points (logM, Mm) and (logH, Hm). The low-area function determination section forms a low-area logarithmic function corresponding to a straight line B passing two points (logL, Lm) and (logM, Mm). A function synthesis section forms mapping functions in smooth connection to the high-area function and the low-area function. More specifically, this section divides input luminance Y, i.e., the luminance Y of the wide dynamic range image to a region smaller than the minimum luminance L, a region above the minimum luminance L and smaller than the minimum luminance CL, a region above CH and smaller than the maximum luminance H or a region above the maximum luminance H and forms the mapping functions f(Y) corresponding to the respective regions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method, and a recording medium, and more particularly, to an image processing apparatus and method suitable for changing the dynamic range of luminance of an image signal, and a recording medium. .

[0002]

2. Description of the Related Art CCD (Charge Coupled Device) image sensor and CMOS (Complementary Mental-Oxide Semiconducto)
r) A solid-state image sensor such as an image sensor is used for an imaging device such as a video camera or a digital still
ry Automation)
It is widely used in optical measurement devices such as electronic endoscopes in the field of E (Medical Electronics).

In recent years, many technologies have been developed which can obtain image signals having a dynamic range comparable to that of optical film photography using these solid-state imaging devices.

On the other hand, conventional devices such as a display device such as a CRT (Cathode Ray tube) for displaying a captured moving image or a still image, a printer for printing, and a projector for projecting the image are presently capable of expressing brightness. There are restrictions on gradation. That is, the dynamic range of an image that can be expressed is narrow. Therefore, even if an image signal of an image having a dynamic range comparable to that of an optical film photograph (hereinafter, referred to as a wide dynamic range image) can be obtained, it cannot be expressed (displayed, printed, etc.). There's a problem.

Accordingly, dynamic range compression for compressing the luminance gradation of a wide dynamic range image to narrow the dynamic range and converting the image into an image that can be expressed by a conventional device such as a display device (hereinafter referred to as a narrow dynamic range image). Processing technology is needed.

Hereinafter, four dynamic range compression techniques proposed in the prior art will be described.

As a first technique, there is a method of scaling the luminance by adjusting the gain and offset of the luminance of the image signal. This first technique is extremely simple and can be easily applied. However, since the luminance gradation is not compressed, all luminance values exceeding the dynamic range of the display device or the like are clipped, and the information of the original wide dynamic range image cannot be fully utilized.

As a second technique, there is a technique of compressing a dynamic range by using a gamma correction process originally performed to correct a gamma characteristic of a display device or the like. Since the gamma correction curve used for the gamma correction process is a function of the power, the correction characteristics can be easily adjusted by changing the exponent which is the gamma value.
However, diversion to dynamic range compression may affect the original gamma correction processing, resulting in a loss of color balance and deterioration of contrast.

As a third technique, there is a histogram equalization method using a cumulative histogram curve of an image as a gradation correction curve. In the histogram equalization method, gradation conversion is performed so as to give more gradations to luminance occupying a larger area in an image in accordance with a luminance distribution (histogram). Therefore, the entire image acts in the direction of enhancing the contrast, and even in a narrow dynamic range, it is possible to obtain an image in which the details are clarified and the visibility is high. However, an image obtained as a result of the gradation conversion is greatly influenced by the luminance distribution of the original wide dynamic range image, and thus a desired image may not be obtained.

[0010] As a fourth technique, there is a technique of emphasizing details using a local operator. In the fourth technology,
The images are separated for each spatial frequency band by the local operator, and after adjusting the gain for each of the separated spatial frequency bands, they are integrated again. When adjusting the gain, by attenuating the low frequency band,
The gradation can be compressed, and the attenuation of the high frequency band can be reduced, so that the contrast of the details can be kept from being lost.

Therefore, even in the case of a conventional device such as a display device having a small number of gradations, it is possible to express an image with high visibility of details. However, as a result of the change in the balance of each band, gradation inversion occurs in a high-contrast region such as an edge portion in an image, and that portion is sometimes recognized as a very obtrusive artifact. Sometimes.

[0012]

As described above,
In the conventional dynamic range compression technique, the obtained narrow dynamic range image may not be a result reflecting the user's intention. Specifically, when converting a wide dynamic range image into a narrow dynamic range image, there is a problem that, for example, it is difficult to express a region occupied by a subject in the image with optimal brightness.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to optimize the brightness of an arbitrary area in an image when converting a wide dynamic range image into a narrow dynamic range image. Aim.

[0014]

An image processing apparatus according to the present invention comprises a setting means for setting a second luminance value in a second dynamic range, and a setting means for setting a second luminance value in the first dynamic range corresponding to the second luminance value. 1 for calculating a luminance value, a mapping function generating means for generating a mapping function based on a luminance pair composed of a first luminance value and a second luminance value, and a mapping function generated by the mapping function generating means. And a conversion means for converting the first image signal into the second image signal by using

[0015] The mapping function generating means may include a luminance value in a second dynamic range corresponding to a luminance value smaller than the first luminance value in the first dynamic range passing through a point corresponding to the luminance pair. A first function generating means for generating a first function shown in the first dynamic range, and a second dynamic range passing through a point corresponding to the luminance pair and corresponding to a luminance value equal to or greater than the first luminance value in the first dynamic range. Generating a second function indicating the luminance value at
And a third function generating means for generating a third function that smoothly connects the first and second functions in the vicinity of the point indicated by the luminance pair. .

The third function generating means includes two points defined by three points: a predetermined point indicated by the first function, a point indicated by the luminance pair, and a predetermined point indicated by the second function. The hyperbolic function may be generated as a third function.

An image processing apparatus according to the present invention comprises a calculating means for calculating correction information for correcting the color balance of the three primary color signals constituting the second image signal based on a mapping function, Correction means for correcting the three primary color signals constituting the two image signals.

According to the image processing method of the present invention, a setting step of setting a second luminance value in a second dynamic range, and calculating a first luminance value in the first dynamic range corresponding to the second luminance value. Using a mapping function generated in the processing of the mapping function generation step of generating a mapping function based on a luminance pair composed of the first luminance value and the second luminance value. Converting a first image signal into a second image signal.

[0019] The program of the recording medium according to the present invention comprises a setting step of setting a second luminance value in a second dynamic range, and a first luminance value in the first dynamic range corresponding to the second luminance value. An operation step of calculating, a mapping function generating step of generating a mapping function based on a luminance pair including the first luminance value and the second luminance value, and a mapping function generated in the processing of the mapping function generating step. And converting the first image signal into a second image signal.

According to the image processing apparatus and method of the present invention, and a program for a recording medium, a second luminance value in a second dynamic range is set, and a second luminance value in a first dynamic range corresponding to the second luminance value is set. A luminance value of 1 is calculated. Further, a mapping function is generated based on the luminance pair consisting of the first luminance value and the second luminance value, and the first image signal is converted into a second image signal using the generated mapping function. You.

[0021]

FIG. 1 shows a configuration example of an image processing system to which the present invention is applied. The image processing system includes an imaging device 1 including a digital camera or the like that captures a subject as a wide dynamic range image signal, and a personal computer that converts a wide dynamic range image signal supplied from the imaging device 1 into a narrow dynamic range image signal. And the like.

The image processing apparatus 2 includes an image processing unit 11 for processing an image signal, an operation input unit 12 for receiving an operation command or the like from a user, and notifying the image processing unit 11 of information on the operation command. Corresponds to part 12
It comprises a GUI (Graphical User Interface) and a display unit 13 for displaying the processing results of the image processing unit 11. The image processing unit 11 of the image processing device 2 outputs a narrow dynamic range image signal, which is a processing result, to the outside of the image processing device 2 as appropriate.

FIG. 2 shows an example of the configuration of the image pickup apparatus 1. An imaging device 1 includes a lens 2 for condensing a light image of a subject.
1. A stop 22, which adjusts the amount of transmitted light, a lens 21, a CCD image sensor 23 which converts an optical image input through the stop 22 into an electric signal, a correlated double sampling circuit, a gamma correction circuit, a knee characteristic circuit, and the like. And a video encoder 25 that encodes an electric signal input from the preamplifier 24 into a wide dynamic range image signal, and an output unit 26 that outputs the wide dynamic range image signal to the image processing device 2. .

The CCD image sensor 23 and the preamplifier 24, which are components of the imaging apparatus 1, will be described. FIG. 3 shows a configuration example of the CCD image sensor 23. C
The CD image sensor 23 has the same configuration as an interline CCD that performs interlace scanning. That is, photodiodes (PDs) 31 that accumulate charges according to the amount of incident light are two-dimensionally arranged, and a vertical register (V register) 3 is arranged between each column of the photodiodes 31.
2, a horizontal register (H register) 33 is provided at the end of the vertical register 32 (the lower end in FIG. 3).

It should be noted that the second i (i
= 0, 1, 2,...) Line, a high-sensitivity photodiode 31H is used.
Is used.

The sensitivity characteristics of the photodiodes 31H and 31L will be described with reference to FIG. In FIG.
The horizontal axis Ei indicates the intensity of light input to the photodiodes 31H and 31L, and the vertical axis Eo indicates the amount of charge stored in the photodiodes 31H and 31L.

The low-sensitivity photodiode 31L is shown in FIG.
Has a sensitivity characteristic indicated by a straight line A. That is, electric charges proportional to the intensity of the incident light are accumulated over the entire range of the intensity of the input light. The high sensitivity photodiode 31H is shown in FIG.
Has a sensitivity characteristic indicated by a straight line B. That is, it corresponds to light having a low intensity, and accumulates more charges in proportion to the intensity of the incident light than the photodiode 31L of low sensitivity.

Referring back to FIG. Photodiodes 31H, 3
The electric charge accumulated in 1L is read out to the corresponding vertical register 32 at every predetermined timing,
3 is transferred. The horizontal register 33 sequentially outputs the charges transferred from the vertical register 32 for one horizontal line.

The timing at which the charges stored in the photodiodes 31H and 31L are read will be described. CCD
The image sensor 23 performs an interlaced scan, but at the time of reading the charge, the charge corresponds to one pixel.
The charges of the photodiodes 31H and 31L vertically adjacent to each other are read and added.

For example, as the electric charge of the 2i-th line of the even field, the photodiode 31H of the 2i-th line is used.
And the charge stored in the photodiode 31L of the (2i + 1) th line is read out and added. As the charge of the 2i + 1 line of the odd field, the charge stored in the photodiode 31L of the 2i + 1 line and the charge stored in the photodiode 31H of the second (i + 1) line are read out and added.

Therefore, the CCD image sensor 23
As an electrical signal corresponding to each pixel, the sum of the charge stored in the low-sensitivity photodiode 31L and the charge stored in the high-sensitivity photodiode 31H is output. Accordingly, the CCD image sensor 23 has a straight line A (corresponding to the photodiode 31L) and a straight line B in FIG.
Line C to which (corresponding to photodiode 31H) is added
Has the sensitivity characteristics shown in FIG. That is, in the CCD image sensor 23, the high-sensitivity photodiode 31H accumulates electric charge in the region where the light intensity is low, and the low-sensitivity photodiode 31L in the region where the light intensity is high.
Accumulates electric charges, it is possible to obtain an electric signal having a wide dynamic range with less noise and saturation.

The preamplifier 24 has a function shown in FIG.
Is applied to the wide dynamic range electric signal Eo output from the CCD image sensor 23 to obtain an estimated value Ei ′ of the intensity of the original optical signal.

Next, FIG. 6 shows an example of the configuration of a personal computer which operates as the image processing apparatus 2 by executing an application program for image processing. This personal computer has a CPU (Central Pr
ocessing Unit) 41. An input / output interface 45 is connected to the CPU 41 via a bus 44.

The input / output interface 45 includes an input unit 46 including an input device such as a keyboard and a mouse corresponding to the operation input unit 12, a display control unit 47 for outputting a GUI and an image signal as a processing result to the display unit 13, Imaging device 1
A video decoder 48 that decodes a wide dynamic range image signal input from the microcomputer, an A / D converter 49 that quantizes a voltage corresponding to the luminance of each pixel and converts it into a digital image signal, a hard disk, a frame memory, and the like. Storage unit 50 for storing programs for use, digital image signals and the like, and magnetic disk 52
(Including floppy disk), optical disk 53 (CD-ROM
(Compact Disc-Read Only Memory), DVD (Digital Versa
tile Disc), magneto-optical disc 54 (MD (Mini
Disc) and a drive 51 that reads and writes data from and to a recording medium such as a semiconductor memory 55.

The bus 44 has an input / output interface 45
ROM (Read Only Memory) 42 and RAM (Random Ac
cess Memory) 43 is connected.

An image processing program for causing the personal computer to execute the operation as the image processing apparatus 2 is supplied to the personal computer in a state where it is stored in the magnetic disk 52 to the semiconductor memory 55, read by the drive 51, and It is installed in a hard disk drive built in the storage unit 50. The image processing program installed in the storage unit 50 is transmitted from the storage unit 50 to the RAM 43 by a command from the CPU 41 corresponding to a command from the user input to the input unit 46.
Is loaded and executed.

Next, the operation of the image processing system will be described with reference to the flowchart of FIG. In step S <b> 1, the imaging device 1 captures an optical image of a subject and outputs an obtained wide dynamic range image signal to the image processing device 2.

In step S2, the image processing section 11 of the image processing apparatus 2 sets the optimum exposure information in response to the user's selection operation. A first operation example for setting the optimum exposure information will be described with reference to the flowchart in FIG.

In step S11, the image processing device 2
The image processing unit 11 simply generates a predetermined number of narrow dynamic range image signals from the wide dynamic range image signals input from the imaging device 1. The process of simply generating a narrow dynamic range image signal will be described with reference to the flowchart in FIG. Hereinafter, it is assumed that the image signal to be processed is a luminance signal.

In step S21, the image processing unit 11
Stores the image signal Y (x, y) of each pixel of the wide dynamic range image input and stored from the imaging device 1 and one of a plurality of exposure ratios r prepared in advance in the storage unit. Read from 50. Here, x and y are the vertical and horizontal coordinate values of the image, respectively.

In step S22, the image processing unit 11
Generates the converted image signal Yn (x, y) by multiplying the image signal Y (x, y) of all pixels by the exposure ratio r. Step S2
3, the image processing unit 11 converts the converted image signal Yn (x,
y) is compared with predetermined threshold values Ynmax, Ynmin,
Conversion image signal Yn (x, y) larger than threshold value Ynmax
Is replaced with a threshold Ynmax, and the converted image signal Yn (x, y) smaller than the threshold Ynmin is replaced with the threshold Ynmin.
Replace with The converted image signal Yn (x, y) generated in this manner is a simply generated narrow dynamic range image signal.

The processes of steps S21 to S23 described above are repeatedly executed by the same number as the number of types of the exposure ratio r prepared in advance.

The process returns to step S12 in FIG. In step S12, the image processing unit 11
The display unit 13 displays the narrow dynamic range image signal easily generated in the processing of Step 11 on the display unit 13 and displays a GUI for allowing the user to select one of the plurality of displayed narrow dynamic range images on the display unit 13. Display.

FIG. 10 shows a display example of the display unit 13 for displaying a simply generated narrow dynamic range image. In this display example, the image display area 61 of the display unit 13
In addition, nine (= 3 × 3) simply generated narrow dynamic range images 62 can be displayed, and four simply generated narrow dynamic range images 62 are displayed. A frame 63 is provided around the displayed narrow dynamic range image 62.

FIG. 11 shows a display example of a GUI operated when the user selects a plurality of simply generated narrow dynamic range images 62 displayed on the display unit 13. G
An image selection button panel 71 as a UI has a left shift button 72 that is clicked when specifying an image on the left of the currently specified image, and a click that is specified when specifying an image on the right of the currently specified image. Right button 73,
Further, a select button 74 which is clicked when selecting a designated image is provided.

The frame 63 displayed in the image display area 61 of the display unit 13 is provided, for example, so that the user can recognize the corresponding image when the corresponding image is specified by the user.
It is highlighted. In the case of the display example of FIG. 10, 3 × 3
Of the upper left image is designated, and its frame 6
3 is highlighted.

The user operates the image display area 61 of the display unit 13.
Is selected using the image selection button panel 71, from among the plurality of images displayed in the image, the image in which the gradation of the subject in the image is most appropriately displayed.

Returning to FIG. 8, in step S13, the image processing section 11 waits until the user selects one of the simply generated narrow dynamic range images displayed in the image display area 61 of the display section 13. If it is determined that one of the simply generated narrow dynamic range images has been selected by the user, the process proceeds to step S14. In step S14, the image processing unit 11 sets the exposure ratio r corresponding to the image selected by the user as the optimal exposure information. The process returns to step S3 in FIG.

In step S3, the image processing unit 11
Converts the wide dynamic range image signal input from the imaging device 1 into a narrow dynamic range image signal according to the optimal exposure information set in step S2 and outputs the converted signal to the display unit 13.

The process of converting a wide dynamic range image signal into a narrow dynamic range image signal according to the optimum exposure information will be described in detail.

FIG. 12 shows an image processing unit 1 related to the processing.
1 shows a first configuration example. The luminance pair detection unit 81
Based on the wide dynamic range image signal and the optimum exposure information, a target luminance / optimal target luminance pair (M, Mm) is detected and output to the mapping function generator 82. The mapping function generation unit 82 generates a mapping function based on the wide dynamic range image signal and the target luminance / optimal target luminance pair (M, Mm) from the luminance pair detection unit 81, and outputs the generated mapping function to the mapping unit 83. The mapping unit 83 converts the wide dynamic range image signal into a mapping function generation unit 82
To generate a narrow dynamic range image signal.

The process of detecting the target luminance / optimal target luminance pair (M, Mm) by the luminance pair detecting section 81 will be described with reference to the flowchart of FIG. 13 and FIG. FIG.
Is a diagram for explaining the relationship between the dynamic range of the luminance of the wide dynamic range image and the dynamic range of the luminance of the simply generated narrow dynamic range image, and the horizontal axis of FIG. The logarithmic value logY of the brightness Y of the image is shown, and the vertical axis is the logarithmic value logY of the brightness Yn of the simply generated narrow dynamic range image.
n.

In step S31, the luminance pair detecting unit 8
Reference numeral 1 denotes a preset saturation luminance Ys of a wide dynamic range image and a preset saturation luminance Y of a narrow dynamic range image.
ns, and the intermediate luminance Yn of the narrow dynamic range image
m is obtained from the storage unit 50. Here, the intermediate luminance Ynm of the narrow dynamic range image is calculated in advance using the saturation luminance Yns and the noise level luminance Ynn of a predetermined narrow dynamic range image, for example, as shown in the following equation (1). And Intermediate luminance Ynm = (Yns + Ynn) / 2 (1)

In step S32, the luminance pair detecting unit 8
1 acquires the optimal exposure information (exposure ratio r) set in step S14 of FIG. In step S33,
The luminance pair detection unit 81 calculates the luminance of the wide dynamic range image corresponding to the intermediate luminance Ynm of the narrow dynamic range image using the following equation (2). This luminance is referred to as the luminance
Set to. Attention brightness M = r · Ys (Ynm / Yns) (2)

In step S34, the luminance pair detecting section 8
1 sets the intermediate luminance Ynm of the narrow dynamic range image to the optimum target luminance Mm. In step S35,
The luminance pair detection unit 81 outputs the target luminance / optimal target luminance pair (M,
Mm) is output to the mapping function generator 82.

FIG. 15 shows the mapping function generator 8.
2 shows a detailed configuration example. The mapping function generation unit 82 obtains the maximum luminance H and the minimum luminance L of the wide dynamic range image, the maximum / minimum luminance acquisition unit 91, and the maximum luminance H and the minimum luminance of the wide dynamic range image from the maximum / minimum luminance acquisition unit 91. L, a high-frequency function determination unit 92 that generates a high-frequency logarithmic function based on the luminance of interest / optimal luminance pair (M, Mm) from the luminance pair detection unit 81, and a wide dynamic range from the maximum / minimum luminance acquisition unit 91. A low-frequency function determination unit 93 that generates a low-frequency logarithmic function based on the maximum luminance H and the minimum luminance L of the range image and the luminance / optimal luminance pair (M, Mm) from the luminance pair detection unit 81; It comprises a function synthesis unit 94 that synthesizes a high-frequency logarithmic function generated by the high-frequency function determination unit 92 and a low-frequency logarithmic function generated by the low-frequency function determination unit 93 to generate a mapping function.

The process in which the mapping function generator 82 generates a mapping function will be described with reference to the flowchart in FIG.

In step S41, the maximum / minimum luminance acquisition section 91 generates a histogram of the luminance signal Y of a wide dynamic range image as shown in FIG. In step S42, the maximum / minimum luminance acquisition unit 91 considers noise included in the luminance signal Y and sets the maximum luminance H to a value smaller by a predetermined ratio (for example, 1%) than the maximum value of luminance having frequency. And a value larger by a predetermined ratio (for example, 1%) than the minimum value of the frequency having the frequency is determined as the minimum luminance L of the luminance. The signal is output to the low-frequency function determination unit 93 and the function synthesis unit 94.

In step S43, the function synthesizing section 94
Are the two points (logL, Lm), (logH, H
A logarithmic function Ym (Y) corresponding to a straight line A passing through m) is generated. Ym (Y) = αlogY + β (3)

(Equation 1)

FIG. 18 is a diagram for explaining the relationship between the luminance dynamic range of a wide dynamic range image and the luminance dynamic range of a converted narrow dynamic range image. The horizontal axis of FIG. The logarithmic value logY of the luminance Y of the input wide dynamic range image is shown,
The vertical axis indicates the luminance Ym of the converted narrow dynamic range image. 19 to 21 are the same. Also, H
m and Lm represent the maximum luminance or the minimum luminance of a narrow dynamic range, respectively, and are preset values.

In step S44, the high-frequency function determination section 92 determines the two points (logM, Mm), (logH,
Hm) A high-frequency logarithmic function YmH corresponding to a straight line C passing through Hm)
(Y) is generated and output to the function synthesizing unit 94. YmH (Y) = αHlogY + βH (4)

(Equation 2)

In step S45, the low-frequency function determination unit 93 determines the two points (logL, Lm), (logM,
Mm) The low-frequency logarithmic function YmL corresponding to the straight line B passing through
(Y) is generated and output to the function synthesizing unit 94. YmL (Y) = αLlogY + βL (5)

(Equation 3)

The order of the processes in steps S43, S44, and S45 may be changed as appropriate, or may be performed simultaneously in parallel.

In step S46, function synthesizing section 94
Is obtained by substituting the target luminance M into Y of a logarithmic function Ym (Y) corresponding to the straight line A in FIG. 18, comparing the obtained Ym (M) with the optimum target luminance Mm, and based on the comparison result, The point (logM, Mm) corresponding to the luminance / optimal luminance pair is
It is determined whether it is located above the straight line A, below the straight line A, or coincides with the straight line A.

When the comparison result indicates that Mm is larger than Ym (M), the point (logM, Mm) corresponding to the target luminance / optimal target luminance pair is located above the straight line A as shown in FIG. If it is determined that it is located, the process proceeds to step S47. In step S47, the function synthesizing unit 94 executes the processing in FIG.
As shown in Fig. 9, an upward convex mapping function
The parameters CL and CH on the horizontal axis in FIG. 19 are set as in the following equation (6).

(Equation 4) ... (6)

In step S50, function synthesizing section 94
Are the high-frequency logarithmic function YmH (Y) and the low-frequency logarithmic function YmL
(Y) is smoothly connected to generate a mapping function.
More specifically, the input luminance Y, that is, the luminance Y of the wide dynamic range image is set to a region smaller than the minimum luminance L, a region larger than the minimum luminance L and smaller than CL, and a region larger than CL and smaller than CH. Maximum brightness H above the area, CH
The area is divided into smaller areas or areas having a maximum luminance H or more, and a mapping function f (Y) corresponding to each area is generated (the details will be described later with reference to FIG. 22).

The comparison result in step S46 indicates that Mm is Y
If it is equal to m (M), it is determined that the point (logM, Mm) corresponding to the target luminance / optimal target luminance pair matches the straight line A, and the process proceeds to step S48. In step S48, the function synthesizing unit 94 sets the parameters CL and CH of the mapping function as in the following equation (7). CL = L CH = H (7)

The comparison result in step S46 indicates that Mm is Y
When the distance is smaller than m (M), as shown in FIG.
Points corresponding to the target luminance / optimal target luminance pair (logM, M
m) is determined to be below line A, and the process proceeds to step S49. In step S49, the function synthesizing unit 94 sets the parameters CL and CH as in the following equation (8) so as to be a downwardly convex mapping function as shown in FIG.

(Equation 5) ... (8)

Details of the processing of the function synthesizing section 94 in step S50 will be described with reference to the flowchart in FIG. Steps S61, S63, S65, S72
The mapping function f (Y)
Is classified into any one of the five regions.

After the processing of step S61, the minimum luminance L
For an input luminance Y classified into a smaller area than
In step S62, a mapping function f (Y) is defined as shown in the following equation (9). f (Y) = Lm Y <L (9)

After the processing of steps S61 and S63, the input luminance Y classified into an area that is not less than the minimum luminance L and smaller than CL is determined in step S64 by the following equation (10). The mapping function f (Y) is defined by a low-frequency logarithmic function YmL (Y). f (Y) = YmL (Y) = αLlogY + βL L ≦ Y <L (10)

After the processing in steps S61, S63, and S65, if the area is classified into an area not less than CL and smaller than CH, the processing proceeds to step S66.

In step S66, CL-2M + C
It is determined whether H is greater than zero. CL-2M +
If it is determined that CH is greater than 0, the process proceeds to step S67. In step S67, the parameter t
Is defined by the following equation (11).

(Equation 6) ... (11)

In step S68, the mapping function f is calculated for the input luminance Y as shown in the following equation (12).
(Y) is defined.

(Equation 7) CL ≦ Y <CH (12)

In step S66, CL-2M + C
If it is determined that H is not larger than 0, the process proceeds to step S69. In step S69, CL-2
It is determined whether M + CH is smaller than 0. CL-
If it is determined that 2M + CH is smaller than 0, the process proceeds to step S70. In step S70, the parameter t is defined by the following equation (13).

(Equation 8) ... (13)

In step S69, CL-2M + C
H is not less than 0, ie CL-2M + CH
If it is determined that = 0, the process proceeds to step S71. In step S71, the parameter t is calculated by the following equation (1).
4). t = (Y-CL) / 2 (M-CL) (14)

Steps S61, S63, S65, S72
After the processing of the above, for the input luminance Y classified into an area that is equal to or more than CH and smaller than the maximum luminance H, the step S
At 73, the mapping function f (Y) is defined by the high-frequency logarithmic function YmH (Y) as shown in the following equation (15). f (Y) = YmH (Y) = αHlogY + βH CH ≦ Y <H (15)

Steps S61, S63, S65, S72
In step S74, the mapping function f (Y) is changed to the high-frequency logarithmic function YmH for the input luminance Y classified into the area having the maximum luminance H or more through the processing of step S74. (Y). f (Y) = Lm H <Y (16)

As described above, the mapping function f (Y)
Is generated.

Next, the generated mapping function f (Y)
The processing performed by the mapping unit 83 for generating a narrow dynamic range image signal by applying a wide dynamic range image signal to the image data will be described with reference to the flowchart in FIG.

In step S81, the mapping unit 8
3 acquires a wide dynamic range image signal from the storage unit 50. Further, the mapping unit 83 acquires the mapping function f (Y) from the mapping function generation unit 82.

In step S82, the mapping unit 8
Reference numeral 3 generates a narrow dynamic range image signal by sequentially substituting the luminance signals Y (x, y) of all pixels of the wide dynamic range image into a mapping function f (Y).

As described above, according to the series of processes of the image processing section 11, a plurality of images having a narrow dynamic range generated simply are presented to the user, and the gradation of the subject among them is most appropriately displayed. The selected image is selected by the user, and a target luminance / optimal target luminance pair (M, Mm) is derived based on the selected image. Further, a mapping function f (Y) is generated based on the target luminance / optimal target luminance pair (M, Mm), and the wide dynamic range image signal is converted into a narrow dynamic range image signal by the mapping function f (Y). Therefore, it is possible to obtain an image with a narrow dynamic range in which the subject in the image is expressed with an appropriate gradation.

In the above description, only one target luminance / optimal target luminance pair (M, Mm) is determined, and the subsequent processing is executed. The target luminance pair may be determined to generate a mapping function.

Next, a second operation example in which the image processing section 11 sets the optimum exposure information will be described with reference to FIGS. 24 and 25. In the first operation example described above with reference to FIGS. 8 to 11, the user is caused to select one of the plurality of simply generated narrow dynamic range images, but in the second operation example, Only one narrow dynamic range image generated simply by applying the predetermined exposure ratio r is displayed, and the user is allowed to specify a range to be noted (for example, a range in which the subject is displayed) in the image. And the mask 10 in the specified range (FIG. 24B).
The information indicating 3) is set as the optimal exposure information and supplied to the luminance pair detecting unit 81.

FIG. 24 shows a display example of the display unit 13 for displaying one narrow dynamic range image simply generated. As shown in FIG. 2A, only one narrow dynamic range image 102 generated simply is displayed in the image display / designated range drawing area 101 of the display unit 13. A narrow dynamic range image 102 displayed in the image display / designated range drawing area 101 has a mask 103 representing a range designated by the user as shown in FIG.
Are displayed in a superimposed manner.

FIG. 25 shows a narrow dynamic range image 10.
2 shows a display example of a GUI operated when a user sets a mask 103 displayed to be superimposed on 2. A pen button 112 that is clicked when setting of the mask 103 is started, an eraser button 113 for canceling the set mask 103,
And a complete button 1 for fixing the set mask 103
14 are provided.

After the user clicks the pen button 112, the user draws the range of the mask 103 using an input device such as a mouse, and clicks the completion button 114 to determine the range of the drawn mask 103. Correspondingly, information indicating the determined range of the mask 103 is supplied to the luminance pair detection unit 81 as optimal exposure information.

In the second operation example, the luminance pair detecting section 81
Is set as the optimum target luminance Mm in the above-described step S31.
Similarly to the processing of FIG. 13, the preset intermediate luminance Ynm of the narrow dynamic range image is obtained from the image processing application location program stored in the storage unit 50.

In order to obtain one target luminance M, the luminance pair detecting section 81 obtains luminance signals of the pixels included in the range of the mask 103 in the wide dynamic range image and sets them as a pixel set G1. Of these, pixels having a luminance higher than a predetermined saturation level and pixels having a luminance lower than a predetermined noise level are excluded to form a pixel set G2. further,
The luminance pair detection unit 81 generates a luminance histogram of the pixel set G2, and sets the most frequent luminance as the target luminance M.

The target luminance / optimal target luminance pair (M, Mm) set in this way is calculated by the mapping function generator 82.
And is processed in the same manner as the above-described series of processing.

As described above, according to the second operation example of setting the optimum exposure information, a desired narrow dynamic range can be obtained by an intuitive operation in which the user specifies the range of the subject to be displayed with the optimum brightness. A range image can be created.

Next, a configuration example of the image processing unit 11 corresponding to a case where a color wide dynamic range image signal (three primary color signals R, G, B) is supplied from the imaging device 1 to the image processing device 2. (Hereinafter, this will be described as a second configuration example of the image processing unit 11) and the operation will be described with reference to FIG. In the second configuration example of the image processing unit 11, gradation conversion is performed so that the color balance of a color image is not impaired.

FIG. 26 shows a second example of the configuration of the image processing section 11. The luminance signal generation unit 121 calculates the following equation (17).
, A luminance Y is generated using the three primary color signals R, G, and B of each pixel of the input wide dynamic range image, and a luminance pair detection unit 122, a color correction function generation unit 123, a mapping unit 124, Output to the function generation unit 125, the mapping unit 126, and the exponentiation operation unit 127. Brightness Y = kr · R + kg · G + kb · B (17)

Here, kr, kg, and kb are constants,
For example, kr = 0.3, kg = 0.6, and kb = 0.1.

The luminance-pair detecting section 121 includes the luminance signal generating section 1
21, the luminance Y of each pixel of the wide dynamic range image, and the first or second image processing unit 11 described above.
Based on the optimum exposure information acquired in the operation example of (1), the target luminance / optimal target luminance pair (M, Mm) is detected and output to the color correction function generation unit 123 and the mapping function generation unit 82.

The color correction function generating section 123 outputs the luminance Y of each pixel of the wide dynamic range image from the luminance signal generating section 121 and the target luminance / optimal target luminance pair (M, Mm) from the luminance pair detecting section 81. , A color correction function fC (Y) indicating the color correction amount γ corresponding to the luminance Y is generated and output to the mapping unit 124.

The color correction function generator 123 generates the color correction function fC
The process of generating (Y) will be described in more detail.
The color correction function generation processing is substantially the same as the mapping function generation processing of the mapping function generation unit 82 described above with reference to FIGS. 16 to 22, and the processing in step S50 (FIG. 16) described with reference to FIG. Only slightly different. Therefore, of the color correction function generation processing, only processing corresponding to the processing in step S50 of the mapping function generation processing will be described with reference to FIG.

The color correction function generator 123 determines in step S9
The input luminance Y, which is a variable of the color correction function fC (Y), is classified into any of the five regions based on the magnitude comparison determination in 1, S93, S95, and S102.

After the processing in step S91, the minimum luminance L
For an input luminance Y classified into a smaller area than
In step S92, a color correction function fC (Y) is defined as shown in the following equation (17). fC (Y) = αL
Y <L (1
7)

After the processing of steps S91 and S93, for the input luminance Y classified into an area not less than the minimum luminance L and smaller than CL, in step S94, as shown in the following equation (18), A color correction function fC (Y) is defined. fC (Y) = αL L ≦ Y <L (18)

If the area is classified into an area that is equal to or larger than CL and smaller than CH through the processing of steps S91, S93, and S95, the processing proceeds to step S96.

In step S96, CL-2M + C
It is determined whether H is greater than zero. CL-2M +
If it is determined that CH is greater than 0, the process proceeds to step S97. In step S97, the parameter t
Is defined by equation (11).

In step S98, a color correction function fC (Y) is calculated for the input luminance Y as shown in the following equation (19).
Is defined. fC (Y) = (1−t) αL + tαH CL ≦ Y <CH (19)

In step S96, CL-2M + C
If it is determined that H is not larger than 0, the process proceeds to step S99. In step S99, CL-2
It is determined whether M + CH is smaller than 0. CL-
If it is determined that 2M + CH is smaller than 0, the process proceeds to step S100. In step S100,
The parameter t is defined by equation (13).

In step S99, CL-2M + C
H is not less than 0, ie CL-2M + CH
If it is determined that = 0, the process proceeds to step S101.
Proceed to. In step S101, the parameter t is defined by Expression (14).

Steps S91, S93, S95, S10
In step S103, for the input luminance Y classified into an area equal to or higher than CH and smaller than the maximum luminance H after the processing of step 2, the color correction function fC (Y ) Is defined. fC (Y) = αH CH ≦ Y <H (20)

Steps S91, S93, S95, S10
In step S104, for the input luminance Y classified into the area having the maximum luminance H or more after the processing of step 2,
As shown in the following equation (21), a color correction function fC (Y) is defined. fC (Y) = αH H <Y (21)

The color correction function generator 12 as described above
By the process of 3, the color correction function fC (Y) is generated.

The mapping section 124 is provided with a luminance signal generating section 1
The luminance Y of each pixel from the pixel 21 is applied to a color correction function fC (Y) to calculate a color correction amount γ.
28R, 128G and 128B.

Similar to the mapping function generator 82 described above, the mapping function generator 125 calculates the mapping function f based on the luminance Y of each pixel of the wide dynamic range image and the target luminance / optimal target luminance pair (M, Mm). (Y) is generated and output to the mapping unit 126. The mapping unit 126 calculates the luminance Y of each pixel of the wide dynamic range image.
Is applied to the mapping function f (Y) from the mapping function generation unit 125 to generate the luminance Ym of each pixel of the narrow dynamic range image, and the scaling units 129R and 129
G, 129B.

The exponentiation operation unit 127 raises the luminance Y of each pixel of the wide dynamic range image to the power of γ, and obtains the corrected luminance Yγ obtained by scaling units 129R, 129G, 129B.
Output to The exponentiation operation unit 128R raises the red signal R of each pixel of the wide dynamic range image to the power of γ, and outputs the obtained corrected red signal Rγ to the scaling unit 129R. The exponentiation operation unit 128G raises the green signal G of each pixel of the wide dynamic range image to the power of γ, and outputs the obtained corrected green signal Gγ to the scaling unit 129G. The exponentiation operation unit 128B raises the blue signal B of each pixel of the wide dynamic range image to the power of γ and outputs the obtained corrected blue signal Bγ to the scaling unit 129B.

The scaling units 129R to 129B
Using the following equations (22) to (24), respectively, the red signal Rm and the green signal G of each pixel of the narrow dynamic range image
m or the blue signal Bm. Rm = Rγ · Ym / Yγ (22) Gm = Gγ · Ym / Yγ (23) Bm = Bγ · Ym / Yγ (24)

As described above, according to the second configuration example of the image processing section 11, the dynamic range of the three primary color signals R, G, and B of the input wide dynamic range image is compressed according to the degree of compression. Since the correction is performed so as to obtain a natural color balance, it is possible to convert a color image having a wide dynamic range into a color image having a narrow dynamic range in which the color balance is not unnatural.

Next, FIG. 28 shows a configuration example of a digital camera to which the present invention is applied. This digital camera 140 is, so to speak, an image processing system shown in FIG. 1 housed in a single housing. The digital camera 140 captures a subject as a wide dynamic range image signal, and converts it into a narrow dynamic range image signal as appropriate. The data is recorded in the built-in memory 148.

The digital camera 140 includes a lens 141 for condensing a light image of a subject, an aperture 142 for adjusting the light amount of the light image, and a CCD for photoelectrically converting the condensed light image to convert it into a wide dynamic range electric signal. Image sensor 1
43, CDS (Core) that reduces noise by sampling electrical signals from the CCD image sensor 143
related Double Sampling) 144, an A / D converter 145 for digitizing an analog electric signal, an image signal processor and an image for converting a digitized electric signal into an image signal or compressing a dynamic range. DSP (Digital Signal Proces)
sor) 146.

The digital camera 140 has a DSP 1
The image signal processed by 46 is compression-encoded and stored in a memory 148.
, And CODEC (Compression / Decompression) 147, DSP1
The D / A converter 149 converts the processed image signal into an analog signal, the video encoder 150 encodes the analogized image signal into a video signal in a format suitable for the display unit 151 at the subsequent stage, and an image corresponding to the video signal. LC that functions as a finder by displaying
The display unit 151 includes a D (Liquid Crystal Display) or the like.

Further, the digital camera 140 controls the drive 153 to read a control program stored in the magnetic disk 154, the optical disk 155, the magneto-optical disk 156, or the semiconductor memory 157, and reads the read control program. A control unit 152 including a CPU for controlling the entire digital camera 140 based on a command from the user input from the operation unit 158, an operation unit 158 for the user to input a shutter timing and other commands, and It comprises a timing generator 159 for controlling the operation timing of the CCD image sensors 143 to DSP 146.

In the digital camera 140, the DSP
146 is the image processing unit 11 of the image processing system described above.
And performs a process of converting a wide dynamic range image signal into a narrow dynamic range image signal.

The operation unit 158 and the display unit 151 of the digital camera 140 are connected to the operation input unit 12 and the display unit 13 of the image processing apparatus 2 (comprising a personal computer) of the image processing system of FIG. In comparison, since a small one is used, it is necessary to allow the user to execute various operation inputs more easily.

Therefore, in the digital camera 140, the overall processing sequence is different from the processing sequence of the image processing system of FIG. 1 described with reference to the flowchart of FIG.
Prior to acquiring a wide dynamic range image signal, optimal exposure information is set.

A first operation example of the digital camera 140 will be described with reference to a flowchart of FIG.
In step S111, the composition of the image to be captured is selected by the user. The composition of the selected image (corresponding to a guide 172 described later) is set as the optimal exposure information.

The process of setting the optimum exposure information will be described with reference to FIGS. FIG.
9 shows a display example of an image display area 171 of a display unit 151 functioning as a finder. As shown in the figure, in the image display area 171, a guide 172 indicated by a thick line or the like and an auxiliary line indicated by a broken line are displayed so as to be superimposed on the image of the subject. A plurality of patterns are prepared for the shape of the guide 172, and a guide selection panel 181 (see FIG. 3) provided on the operation unit 158.
Each time 2) is operated by the user, the shape is switched.

FIGS. 31A to 31Q show examples of the shape of the guide 172 prepared in advance. Guide 1
A predetermined index is given to each of the shapes 72. The shape of the guide 172 may be, for example, a circle or a polygon other than the rectangle as shown in FIG.

FIG. 32 shows a guide selection panel 181 provided on the operation unit 158. Guide switching button 1
The button 82 is pressed to switch the shape of the guide 172 to the one corresponding to the previous index. The switch button 183 is pressed when switching the shape of the guide 172 to the one corresponding to the next index. The selection button 184 is pressed when the shape of the displayed guide 172 is determined.

For example, FIG. 30 shows a state in which the shape of the guide 172 is switched to the example of FIG. 31 (J). In this state, when the switch button 182 is pressed, Is switched to the example of FIG. 11I, and when the switch button 183 is pressed, the shape of the guide 172 is switched to the example of FIG.

The user looks at the display unit 151 functioning as a finder and moves the subject (for example, a person) to the guide 1.
After switching the guides 172 by operating the switch buttons 182 and 183 of the guide selection panel 181 so that the guides 172 fall within the 72, the selection button 184 is pressed down to determine the shape of the guides 172. When the selection button 184 is pressed, an index corresponding to the shape of the currently displayed guide 172 is set as optimal exposure information.

Returning to FIG. In step S112, when the user operates the shutter provided on the operation unit 158, a wide dynamic range image signal is acquired correspondingly and stored in the image RAM incorporated in the DSP 146.

In step S113, step S1
A wide dynamic range image signal is converted into a narrow dynamic range image signal based on the optimal exposure information (index indicating the shape of the guide 172) set in 11.

More specifically, for the target luminance / optimal target luminance pair, an image signal of an area inside the guide 172 is obtained based on the optimum exposure information (index indicating the shape of the guide 172), and a histogram of the luminance is obtained. The luminance that is generated and has the highest frequency is set as the target luminance M. An intermediate luminance of a preset narrow dynamic range is set as the optimum noticeable luminance Mm. The subsequent processing is the same as the second operation example when the image processing unit 11 of the image processing system sets the optimum exposure information described above with reference to FIGS.

The converted narrow dynamic range image signal is stored in the memory 148.

The DSP 14 of the digital camera 140
In the sixth example, as in the second configuration example of the image processing unit 11 of the image processing system shown in FIG. 26, a color wide dynamic range image is converted into a color narrow dynamic range image without impairing the color balance. May be executed.

Next, a second operation example of the digital camera 140 will be described with reference to the flowchart in FIG. In step S121, the composition of the image to be captured is selected by the user. The composition of the selected image (corresponding to the guide 172) is set as the first optimum exposure information.

The processing for setting the first optimum exposure information is the same as the processing for setting the optimum exposure information in the first operation example described above with reference to FIGS.

In step S122, when the user operates the shutter provided on the operation unit 158, a wide dynamic range image signal is acquired correspondingly.
The image is stored in the image RAM incorporated in the DSP 146.

In step S123, an exposure ratio r is set as second optimal exposure information in response to a user operation. The process of setting the exposure ratio r as the second optimum exposure information will be described with reference to FIGS.

FIG. 34 shows a display example of the image display area 171 of the display unit 151 in step S123. In this case, the wide dynamic range image acquired in step S122 is displayed in the image display area 171, and the guide 172 and the auxiliary line (dashed line) set in step S121 are displayed so as to be superimposed thereon. However, a brightness correction panel 191 (FIG. 3) provided on the operation unit 158 is provided in an area inside the guide 172 of the image display area 171.
A narrow dynamic range image simply generated using the exposure ratio r changed in response to the user operation for 5) is displayed.

FIG. 35 shows a luminance correction panel 191 provided on the operation unit 158. The brightness correction (BRIGHTER) button 192 is pressed to increase the brightness of the narrow dynamic range image displayed in the internal area of the guide 172 by one step from the current level (increase the brightness). Dark correction (D
The ARKER) button 193 is pressed to lower the brightness of the narrow dynamic range image displayed in the inner area of the guide 172 by one level (reduce the brightness) from the current level.
The OK button 194 is pressed to determine the current brightness.

For example, when the lightness correction button 192 is pressed, the exposure ratio r used for simple generation of a narrow dynamic range image is increased by a predetermined value. Therefore, the brightness of the narrow dynamic range image in the inner area of the guide 172 is displayed with increased brightness. Conversely, when the darkness correction button 193 is pressed, the exposure ratio r used for simple generation of a narrow dynamic range image is reduced by a predetermined value. Therefore, the brightness of the narrow dynamic range image in the area inside the guide 172 is reduced and displayed. When the OK button 194 is pressed, the current exposure ratio r is set as the second optimum exposure information.

Returning to FIG. In step S124, based on the first optimal exposure information (index indicating the shape of the guide 172) set in step S121 and the second optimal exposure information set in step S123, the wide dynamic range image signal is converted into a narrow dynamic range image signal. It is converted to a range image signal.

More specifically, for the target luminance / optimal target luminance pair, the luminance of the wide dynamic range image in the area inside the guide 172 is obtained based on the first optimum exposure information (index indicating the shape of the guide 172). Then, a histogram of the luminance is generated, and the luminance indicating the highest frequency is set as the target luminance M.

As the optimum noticeable brightness Mm, a narrow dynamic range image is easily generated by multiplying the brightness of the wide dynamic range image by the exposure ratio r as the second optimum exposure information, and the brightness of the internal area of the guide 172 is obtained. Is extracted, a histogram is generated, and the luminance indicating the highest frequency is set as the optimum luminance of interest Mm. The subsequent processing is the same as the second operation example when the image processing unit 11 of the image processing system sets the optimum exposure information described above with reference to FIGS.

The converted narrow dynamic range image signal is stored in the memory 148.

As described above, the digital camera 1
According to the second operation example of 40, a simple operation on the operation unit 158 is used to guide the user to the area of interest.
2 and the desired brightness can be specified for the internal region of the guide 172, so that the gradation of the obtained narrow dynamic range image is closer to the result desired by the user.

The DSP 14 of the digital camera 140
6 may execute the same processing as that performed by the image processing unit 11 of the image processing system described above. Conversely, the digital camera 1 is provided in the image processing unit 11 of the image processing system.
The same processing as the DSP 146 of 40 may be executed.

By the way, the present invention can be applied to the case where the luminance is changed without changing the dynamic range of the image.

The present invention can be applied not only to an image conversion system and a digital camera as in the present embodiment, but also to electronic equipment for processing image signals, such as a scanner, a facsimile, and a copier. is there.

[0148] In this specification, the steps for describing the program recorded on the recording medium are not limited to the processing performed in chronological order according to the described order, but are not necessarily performed in chronological order. Alternatively, it also includes individually executed processing.

In this specification, a system is
It represents the entire device composed of a plurality of devices.

[0150]

As described above, according to the image processing apparatus and method of the present invention and the program of the recording medium, the second
A second brightness value in the dynamic range of
A first luminance value in a first dynamic range corresponding to the second luminance value is calculated, and a mapping function is generated based on a luminance pair including the first luminance value and the second luminance value. Therefore, when converting a wide dynamic range image into a narrow dynamic range image, it is possible to optimize the luminance at an arbitrary position in the image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an image processing system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of the imaging apparatus 1 of FIG.

FIG. 3 is a block diagram illustrating a configuration example of a CCD image sensor 23 in FIG. 2;

FIG. 4 is a diagram for explaining a sensitivity characteristic of the CCD image sensor 23;

FIG. 5 is a diagram for explaining processing of a preamplifier 24;

FIG. 6 is a block diagram illustrating a configuration example of a personal computer that implements the image processing apparatus 2 of FIG.

FIG. 7 is a flowchart illustrating an operation of the image processing system.

FIG. 8 is a flowchart illustrating an optimal exposure information setting process of the image processing apparatus 2.

FIG. 9 is a flowchart illustrating a process in which the image processing apparatus 2 simply generates a narrow dynamic range image.

FIG. 10 is a diagram illustrating a display example of a display unit for explaining a first operation example of setting optimum exposure information.

FIG. 11 is a diagram illustrating a display example of a GUI in a first operation example for setting optimal exposure information.

FIG. 12 is a block diagram illustrating a first configuration example of an image processing unit 11;

FIG. 13 is a flowchart illustrating processing of a luminance pair detection unit 81 in FIG. 12;

FIG. 14 is a diagram for explaining processing of a luminance pair detection unit 81;

15 is a block diagram illustrating a configuration example of a mapping function generation unit 82 in FIG.

FIG. 16 is a flowchart illustrating processing of a mapping function generation unit 82;

FIG. 17 is a diagram for explaining processing of a maximum / minimum luminance acquisition unit 91 in FIG. 15;

FIG. 18 is a diagram for explaining processing of a mapping function generation unit 82;

FIG. 19 is a diagram for explaining processing of a mapping function generation unit 82;

FIG. 20 is a diagram for explaining processing of a mapping function generation unit 82;

FIG. 21 is a diagram for explaining processing of a mapping function generation unit 82;

FIG. 22 is a flowchart illustrating details of a process in step S50 in FIG. 16;

FIG. 23 is a flowchart illustrating a process of a mapping unit 83 of FIG. 12;

FIG. 24 is a diagram illustrating a display example of the display unit for explaining a second operation example of setting the optimum exposure information.

FIG. 25 is a diagram illustrating a display example of a GUI in a second operation example for setting optimal exposure information.

FIG. 26 is a block diagram illustrating a second configuration example of the image processing unit 11;

FIG. 27 is a flowchart illustrating processing of the second configuration example of the image processing unit 11;

FIG. 28 is a block diagram illustrating a configuration example of a digital camera 140 according to an embodiment of the present invention.

FIG. 29 is a flowchart illustrating a first operation example of the digital camera 140.

30 is a diagram illustrating a display example of a display unit for explaining a process of setting optimal exposure information in the first operation example of the digital camera. FIG.

FIG. 31 is a diagram showing types of shapes of a guide 172 displayed on a display unit 151.

FIG. 32 is a view showing a guide selection panel 181 provided on the operation unit 158 of the digital camera 140.

FIG. 33 is a flowchart illustrating a second operation example of the digital camera 140.

FIG. 34 is a diagram illustrating a display example of the display unit 151 for describing a process of setting optimal exposure information in the first operation example of the digital camera 140.

FIG. 35 is a diagram showing a luminance correction panel 191 provided in the operation unit 158 of the digital camera 140.

[Explanation of symbols]

1 imaging device, 2 image processing device, 11 image processing unit, 12 operation input unit, 13 display unit, 41 CP
U, 52 magnetic disk, 53 optical disk, 5
4 magneto-optical disk, 55 semiconductor memory, 71 image selection button panel, 81 luminance pair detection unit, 82
Mapping function generation unit, 83 mapping unit, 91
Maximum / minimum luminance acquisition unit, 92 high-frequency function determination unit,
93 Low-frequency function determination unit, 94 Function synthesis unit, 111
Range designation panel, 121 Luminance signal generator, 12
2 luminance pair detector, 123 color correction function generator, 1
24 mapping section, 125 mapping function generation section, 126 mapping section, 127, 128 exponentiation operation section, 129 scaling section, 140 digital camera, 146 DSP, 152 control section,
154 magnetic disk, 155 optical disk, 15
6 magneto-optical disk, 157 semiconductor memory, 15
8 operation section, 172 guide, 181 guide selection panel, 191 brightness correction panel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/46 H04N 1/40 D 5C082 5/20 101E 9/73 1/46 Z F term (Reference) 5B057 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE11 CE16 CH08 DC23 5C021 PA78 PA80 PA85 PA86 RB03 RB09 XA02 XA35 5C066 AA03 AA05 AA11 CA17 EA13 EC01 GA05 KE09 KE19 KE20 KF05 P15P07P15PPK15PPK JA23 LA23 LA26 LB02 MA11 NA01 5C082 AA03 AA27 CA11 CA84 CB01 MM10

Claims (6)

[Claims] 1. An image processing apparatus for converting a first image signal having a first dynamic range into a second image signal having a second dynamic range with respect to a luminance value, wherein: Setting means for setting a second brightness value; calculating means for calculating a first brightness value in the first dynamic range corresponding to the second brightness value; and a first brightness value and a second brightness value Mapping function generating means for generating a mapping function based on a luminance pair consisting of the luminance values of: the first image signal is converted to the second image signal using the mapping function generated by the mapping function generating means An image processing apparatus comprising: a conversion unit configured to perform conversion. 2. The method according to claim 1, wherein the mapping function generation unit is configured to: pass the point corresponding to the luminance pair and correspond to a luminance value smaller than the first luminance value in the first dynamic range. First function generating means for generating a first function indicating a luminance value in a range; and a luminance value passing through a point corresponding to the luminance pair and being equal to or greater than the first luminance value in the first dynamic range. A second function generating means for generating a second function indicating a luminance value in the second dynamic range corresponding to the following; and smoothing the first and second functions near a point indicated by the luminance pair. Third to generate a third function to connect
The image processing apparatus according to claim 1, further comprising: a function generating unit. 3. The third function generating means includes: a predetermined point indicated by the first function, a point indicated by the luminance pair, and a predetermined point indicated by the second function. The image processing apparatus according to claim 2, wherein a defined quadratic curve function is generated as the third function. 4. A calculating means for calculating correction information for correcting a color balance of three primary color signals constituting the second image signal based on the mapping function, and using the correction information, 2. The image processing apparatus according to claim 1, further comprising: a correction unit configured to correct the three primary color signals constituting the two image signals. 5. An image processing method of an image processing device for converting a first image signal having a first dynamic range into a second image signal having a second dynamic range with respect to a luminance value, wherein A setting step of setting a second luminance value in a dynamic range of; a calculating step of calculating a first luminance value in the first dynamic range corresponding to the second luminance value; and the first luminance value And a mapping function generating step of generating a mapping function based on a luminance pair composed of the second luminance value, and the first image signal using the mapping function generated in the processing of the mapping function generating step. Converting the image data into the second image signal. 6. An image processing program for converting a first image signal having a first dynamic range into a second image signal having a second dynamic range with respect to a luminance value, the program comprising: A setting step of setting a second luminance value in a dynamic range of; a calculating step of calculating a first luminance value in the first dynamic range corresponding to the second luminance value; and the first luminance value And a mapping function generating step of generating a mapping function based on a luminance pair consisting of the second luminance value, and the first image signal using the mapping function generated in the processing of the mapping function generating step. And a conversion step of converting the image data into the second image signal. In which the recording medium.