JP2007228451A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which ensures a proper tone property according to a dodging property without lowering a contrast in a high brightness area through tone conversion and ensures a proper sharpness according to a dodging property without producing a factitious image with high frequency components stressed for dodging. <P>SOLUTION: A tone property setting means (or a sharpness offset setting means) determines a tone conversion property (or a sharpness offset) based on a dodging parameter specified in a dodging parameter setting means and a tone conversion means (tone converter 62)(or a sharpness correction module 63) performs tone conversion (or sharpness correction) based on the tone conversion property determined by the tone property setting means (or sharpness offset setting means). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a digital camera, and more particularly to an imaging apparatus having a dynamic range compression function.

  2. Description of the Related Art In recent years, in an imaging apparatus such as a digital camera, with the demand for higher image quality, it has become a major theme to expand the luminance range of a subject that can be handled by an imaging sensor, that is, the dynamic range (DR). . Regarding the expansion of the dynamic range, for example, an imaging sensor whose output characteristic on the high luminance side is a characteristic in which an electrical signal is logarithmically converted according to the amount of incident light, that is, imaging having a photoelectric conversion characteristic composed of a linear characteristic region and a logarithmic characteristic region Sensors (called linear log sensors) are known. Since the linear log sensor obtains an output that is naturally logarithmically converted with respect to the amount of incident light in this way, a wider dynamic range is secured as compared with an imaging sensor having photoelectric conversion characteristics only in the linear characteristic region. .

  While the wide dynamic range of the imaging system is increasing like the above linear log sensor, at present, the wide dynamic range of the display system such as a monitor is not progressing as much as the imaging system, and even if the input image has a wide dynamic range. Even if it is, the effect cannot be sufficiently exhibited in the display system. Therefore, it is necessary to compress the dynamic range of the input image so that the input image with a wide dynamic range falls within the dynamic range of the display system.

The above-mentioned “dynamic range compression” mainly includes the meaning of adjusting the brightness and darkness of the image locally by compressing the illumination component of the image and literally the band while maintaining the relationship between the brightness and darkness of the entire image. There are two meanings of compressing (dynamic range) (regardless of the meaning of performing local contrast adjustment). In order to distinguish these, the former is “dodging” and the latter is simply “DR”. It shall be referred to as “compression”. In the dodging process, specifically, an illumination component is extracted from the image (at this time, a reflectance component is also extracted), DR compression is performed on the illumination component, and an illumination component (low frequency component) after DR compression is performed. And a reflectance component (high-frequency component), a new image in which the brightness of the image is locally adjusted is generated (see, for example, Non-Patent Document 1). With regard to such dodging processing, for example, Patent Document 1 introduces a predetermined compression start point in DR compression so that the luminance and contrast in the main subject region (low luminance portion) are appropriately ensured during the DR compression. Techniques to do this are disclosed.
Japanese Patent Application No. 2005-235987 Image Dynamic Range Compression Technology Image Lab (2004. 4) 24-28

  However, although the above-mentioned Patent Document 1 discloses a dodging process (DR compression) method, for example, gradation conversion (contrast correction) performed as a process after the dodging process is performed separately from the dodging process. No method is disclosed. As the gradation conversion, normally, conversion processing using gamma (gradation conversion characteristic; γ) is performed. In this case, the contrast of the low-luminance portion is high so that the contrast of the main subject portion is suitable. If the gamma is changed as described above, the gradation of the high luminance part is lost, and the contrast of the high luminance part is lowered. In addition to the technique disclosed in Patent Document 1, the dodging process compresses an illumination component containing a large amount of low frequency components, so that the high frequency components (edges) are relatively emphasized, so-called sharpness. Becomes unnatural images (images with unnatural resolution).

  The present invention has been made in view of the above circumstances, and it is possible to obtain a suitable gradation characteristic according to the dodging characteristic without incurring a decrease in contrast of the high luminance portion by gradation conversion. An object of the present invention is to provide an imaging apparatus capable of obtaining a suitable sharpness characteristic according to the dodging characteristic without generating an unnatural image in which high-frequency components are emphasized by the baking process.

  The imaging apparatus according to the present invention includes an image acquisition unit that acquires an image, a dodging processing unit that performs a dodging process on the image, a dodging parameter setting unit that sets a dodging parameter related to the dodging process, Gradation conversion means for performing gradation conversion processing on an image; and gradation characteristic setting means for setting gradation conversion characteristics relating to the gradation conversion processing; wherein the gradation characteristic setting means includes the dodging parameter setting means The gradation conversion characteristic is determined based on the dodging parameter set in the gradation conversion unit, and the gradation conversion unit performs a gradation conversion process based on the gradation conversion characteristic determined by the gradation characteristic setting unit. It is characterized by.

  According to the above configuration, the image is acquired by the image acquisition unit, the dodging process is performed on the image by the dodging processing unit, the dodging parameter related to the dodging process is set by the dodging parameter setting unit, and the gradation conversion unit Thus, gradation conversion processing is performed on the image, and gradation conversion characteristics relating to the gradation conversion processing are set by the gradation characteristic setting means. Then, the gradation characteristic setting means determines the gradation conversion characteristic based on the dodging parameter set in the dodging parameter setting means, and the gradation conversion means determines the gradation conversion determined by the gradation characteristic setting means. A gradation conversion process is performed based on the characteristics.

  In the above configuration, the dodging process is a process of compressing the illumination component extracted from the image and generating a new image from the compressed illumination component and the reflectance component extracted from the image. The gradation characteristic setting means may determine the gradation conversion characteristic based on a parameter representing a degree of compression in a luminance region where the illumination component is compressed.

  According to this, the dodging process is a process of compressing the illumination component extracted from the image and generating a new image from the compressed illumination component and the reflectance component extracted from the image, The gradation setting characteristic is determined by the characteristic setting unit based on a parameter representing the degree of compression in the luminance region where the illumination component is compressed.

  Further, in the above configuration, the gradation characteristic setting means includes a first luminance level that is a predetermined compression start level in the luminance range of the illumination component as the dodging parameter and a second luminance level that is greater than the compression start level. The gradation conversion characteristics may be determined based on the above information.

  According to this, information on the first luminance level that is the predetermined compression start level in the luminance range of the illumination component and the second luminance level that is larger than the compression start level as the dodging parameter is obtained by the gradation characteristic setting means. Based on this, the tone conversion characteristics are determined.

  In the above configuration, the first luminance level is a luminance level equal to or higher than a main subject luminance which is a predetermined luminance value of the main subject, and the gradation characteristic setting unit converts the first luminance level into a gradation conversion input value. The gradation conversion output value with respect to the gradation conversion input value is small when the compression degree of the illumination component is large, and large when the compression degree of the illumination component is small. The characteristics may be determined.

  According to this, when the first luminance level is set to a luminance level equal to or higher than the main subject luminance which is the predetermined luminance value of the main subject, and the first luminance level is set as the gradation conversion input value by the gradation characteristic setting unit. The gradation conversion characteristics are determined so that the gradation conversion output value with respect to the gradation conversion input value is small when the compression degree of the illumination component is large and becomes large when the compression degree of the illumination component is small.

  Further, in the above configuration, when the appropriate gradation conversion output value of the main subject is set to I0 ′, the gradation characteristic setting means sets I0 as the gradation conversion input value of the main subject luminance is I0. The gradation conversion characteristics that can be converted to I0 ′ may be determined.

  According to this, the gradation characteristic setting means determines the gradation conversion characteristic that can convert the gradation conversion input value I0 of the main subject luminance into the appropriate gradation conversion output value I0 'of the main subject.

  Further, an imaging apparatus according to the present invention includes an image acquisition unit that acquires an image, a dodging processing unit that performs a dodging process on the image, and a dodging parameter setting unit that sets a dodging parameter related to the dodging process. A sharpness correction unit that performs a sharpness correction process on the image, and a sharpness correction amount setting unit that sets a sharpness correction amount related to the sharpness correction process. The sharpness correction amount setting unit is set in the dodging parameter setting unit. The sharpness correction amount is determined based on the dodging parameter, and the sharpness correction unit performs a sharpness correction process based on the sharpness correction amount determined by the sharpness correction amount setting unit.

  According to the above configuration, the image is acquired by the image acquisition unit, the dodging process is performed on the image by the dodging processing unit, the dodging parameter related to the dodging processing is set by the dodging parameter setting unit, and the sharpness correction unit is set. Sharpness correction processing is performed on the image, and the sharpness correction amount related to the sharpness correction processing is set by the sharpness correction amount setting means. The sharpness correction amount setting means determines the sharpness correction amount based on the dodging parameter set in the dodging parameter setting means, and the sharpness correction means determines the sharpness correction amount based on the sharpness correction amount determined by the sharpness correction amount setting means. The sharpness correction process is performed.

  Further, in the above configuration, the dodging process is realized by locally performing processing on a plurality of regions obtained by dividing the image, and the dodging parameter is set for each of the local processing targets. You may make it be the size of an area | region.

  According to this, the dodging process is realized by locally processing each of the plurality of areas obtained by dividing the image, and the dodging parameter is set to the size (area of each area to be locally processed). Size).

  In the above configuration, the dodging process is a process of compressing the illumination component extracted from the image and generating a new image from the compressed illumination component and the reflectance component extracted from the image. The dodging parameter may be a size of a filter for extracting an illumination component from the image, and the sharpness correction amount setting means may determine the sharpness correction amount based on the size of the filter.

  According to this, in the dodging process, the illumination component extracted from the image is compressed, and a new image is generated from the compressed illumination component and the reflectance component extracted from the image. Also, the dodging parameter is the size of the filter that extracts the illumination component from the image, and the sharpness correction amount setting means determines the sharpness correction amount based on the filter size.

  Further, in the above configuration, the dodging process is realized by performing local contrast correction on each of a plurality of regions obtained by dividing the image, and the dodging parameter is a target of the local contrast correction. You may make it be the size of each area | region.

  According to this, the dodging process is realized by performing local contrast correction on each of the plurality of areas obtained by dividing the image, and the dodging parameter is set to the size of each area to be subjected to local contrast correction ( Area size).

  Further, in the above configuration, the sharpness correction amount setting means changes an edge extraction frequency characteristic of the sharpness correction means according to a sharpness correction amount determined based on a size of each region to be subjected to the local processing. You may do it.

  According to this, the edge extraction frequency characteristic of the sharpness correction means is changed by the sharpness correction amount setting means in accordance with the sharpness correction amount determined based on the size of each region to be locally processed.

  In the above configuration, the sharpness correction amount setting means changes the edge enhancement amount of the sharpness correction means according to the sharpness correction amount determined based on the size of each region to be subjected to the local processing. It may be.

  According to this, the edge enhancement amount of the sharpness correction means is changed (changed) by the sharpness correction amount setting means in accordance with the sharpness correction amount determined based on the size of each region to be locally processed.

  Further, in the above configuration, the image acquisition unit outputs a linear characteristic in which an electrical signal is linearly converted with respect to an incident light amount and is output logarithmically with respect to an incident light amount and is output. You may make it be an imaging sensor which has the photoelectric conversion characteristic which consists of a logarithmic characteristic.

  According to this, the image acquisition means has a linear characteristic in which an electric signal is linearly converted with respect to the incident light quantity and is output, and a logarithmic characteristic in which the electric signal is converted logarithmically with respect to the incident light quantity and output. An imaging sensor having photoelectric conversion characteristics consisting of

  According to the imaging apparatus of the first aspect, the gradation conversion characteristic is determined based on the dodging parameter, and the gradation conversion process is performed based on the determined gradation conversion characteristic. A suitable gradation characteristic according to the dodging characteristic can be obtained without causing a decrease in contrast of the high luminance part by the conversion.

  According to the imaging device of the second aspect, since the gradation conversion characteristic is determined based on the parameter representing the degree of compression in the luminance region where the illumination component is compressed, the gradation in which the dodging characteristic is appropriately reflected Characteristics can be determined.

  According to the imaging apparatus of the third aspect, the gradation conversion characteristics are determined based on information on the first luminance level that is the compression start level in the luminance range of the illumination component and the second luminance level that is greater than the compression start level. Therefore, a first luminance level that can be representative of a certain dodging characteristic, for example, set as a level value at which the main subject can obtain appropriate brightness (or contrast), and a luminance level from the first luminance level. Using the information on the second luminance level having a large value, the gradation characteristic in which the dodging characteristic is appropriately reflected can be easily determined.

  According to the imaging device of claim 4, when the first luminance level is the gradation conversion input value, the gradation conversion output value for the gradation conversion input value is small when the compression degree of the illumination component is large, Since the gradation conversion characteristic is determined so that it becomes a large value when the degree of compression of the illumination component is small, when the degree of compression of the illumination component is large, that is, the compression luminance range (dynamic range) in the dodging process is wide. In this case, the gradation conversion output level is set low so that the gradation conversion output can be suppressed in the middle or high luminance portion, and when the compression level of the illumination component is small, that is, the compressed luminance range is If it is narrow, the gradation conversion output level can be set high so that a higher gradation conversion output can be obtained in the middle luminance or high luminance part, and suitable gradation conversion according to the dodging characteristics can be performed. Do Theft is possible.

  According to the imaging apparatus of the fifth aspect, the gradation conversion characteristic that can convert the gradation conversion input value I0 of the main subject luminance into the appropriate gradation conversion output value I0 ′ of the main subject is determined. The conversion prevents the main subject image from becoming dark, and more suitable gradation conversion can be performed.

  According to the imaging apparatus of the sixth aspect, the sharpness correction amount is determined based on the dodging parameter, and the sharpness correction process is performed based on the determined sharpness correction amount. A sharpness characteristic suitable for the dodging characteristic can be obtained without generating an unnatural image with emphasized components.

  According to the imaging device according to claim 7, since the area size in the local processing of the image is treated as a dodging parameter, the filter size when filtering the image, or the divided block size when dividing the image into areas It is possible to use various parameters such as these as dodging parameters, and it is possible to obtain suitable sharpness characteristics according to the dodging parameters reflecting these parameters.

  According to the imaging apparatus of the eighth aspect, since the sharpness correction amount is determined based on the size of the illumination component extraction filter, the sharpness correction amount of the dodging parameter in the sharpness correction processing according to the dodging characteristics. Can be easily reflected.

  According to the image pickup apparatus of the ninth aspect, since the region size in the local contrast correction process of the image is handled as the dodging parameter, a suitable sharpness characteristic is obtained according to the dodging parameter in which the contrast correction process is reflected. It becomes possible.

  According to the imaging device of the tenth aspect, the edge extraction frequency characteristic in the sharpness correction means is changed according to the sharpness correction amount determined based on the region size (the edge extraction frequency characteristic corresponding to the sharpness correction amount is changed). Therefore, sharpness correction based on edge extraction can be performed more appropriately according to the dodging characteristics.

  According to the imaging device of the eleventh aspect, the edge enhancement amount in the sharpness correction means is changed according to the sharpness correction amount determined based on the region size (the edge enhancement amount according to the sharpness correction amount is used). Therefore, it is possible to perform sharpness correction based on edge enhancement that is more appropriate for the dodging characteristics.

  According to the imaging apparatus of the twelfth aspect, since the image acquisition means is an imaging sensor having a photoelectric conversion characteristic composed of a linear characteristic and a logarithmic characteristic, a wide dynamic range image can be easily obtained by photographing using the imaging sensor. In the gradation conversion process based on the dodging parameter, an image in which the brightness and contrast of the main subject (low luminance part) are ensured and the high luminance part is suitably adjusted can be easily obtained from the wide dynamic range image. Can be obtained.

(Embodiment 1)
FIG. 1 shows a digital camera which is an example of an imaging apparatus according to the first embodiment, and a schematic block configuration diagram mainly relating to imaging processing of the digital camera. As shown in FIG. 1, the digital camera 1 includes an image input unit 2, a control unit 3, an image memory 4, a user I / F unit 5, and an image processing unit 6.

  The image input unit 2 inputs an image to the digital camera 1, and includes a lens unit 21, an image sensor 22, an amplifier 23, an A / D conversion unit 24, and the like. The lens unit 21 functions as a lens window that captures a subject light image, and an optical system for guiding the subject light to the imaging sensor 22 (for example, a zoom lens or the like arranged in series along the optical axis L of the subject light) Focus lens, and other fixed lens blocks). The lens unit 21 includes a diaphragm (not shown) and a shutter (not shown) for adjusting the amount of light transmitted through the lens, and the control unit 3 controls the driving of the diaphragm and the shutter. .

  The imaging sensor 22 captures a subject light image, and photoelectrically converts it into image signals of R, G, and B components according to the amount of light of the subject light image formed by the lens unit 21, and an amplifier 23 at the subsequent stage. Output to. In the present embodiment, as the imaging sensor 22, a linear characteristic region in which an output pixel signal (an output electrical signal generated by photoelectric conversion) is linearly converted and output when the sensor incident luminance is low (in the dark), and the sensor A photoelectric conversion characteristic composed of a logarithmic characteristic region that is output logarithmically when the output pixel signal is logarithmically converted when the incident luminance is high (during light), in other words, a plurality of different low-linearity is linear and the high-luminance side is logarithmic. An image sensor having photoelectric conversion characteristics (hereinafter, appropriately expressed as a linear log sensor) is used. By capturing with this linear log sensor, a wide DR image having a wide dynamic range (DR) can be acquired. Thus, by obtaining a wide DR image by the imaging sensor 22, it is possible to easily obtain the illumination compression characteristic as shown in FIG.

  In the linear log sensor, for example, a logarithmic conversion circuit including a P-type or N-type MOSFET is added to a solid-state image pickup element in which photoelectric conversion elements such as photodiodes are arranged in a matrix, and the A so-called CMOS image sensor in which an electrical signal is logarithmically converted with respect to an incident light amount by using a threshold characteristic is employed. However, it is not limited to a CMOS image sensor, and may be a VMIS image sensor, a CCD image sensor, or the like.

  An image having a linear characteristic region and a logarithmic characteristic region obtained from the linear log sensor is appropriately expressed as a linear / logarithmic image. In addition, the switching point (hereinafter referred to as an inflection point) between the linear characteristic region and the logarithmic characteristic region in the photoelectric conversion characteristic can be arbitrarily controlled by a predetermined control signal for each pixel circuit of the image sensor 22. . The imaging sensor 22 is not limited to the linear log sensor, and may be any image sensor as long as a wide DR image can be obtained, such as a linear sensor having a plurality of linear regions with different inclinations. Incidentally, the wide DR image may be a wide DR image created from a plurality of images obtained by photographing with different shutter speeds and aperture values by a general linear sensor, for example, or subjected to knee processing. It may be a wide DR image created from the image.

  The amplifier 23 amplifies the image signal output from the imaging sensor 22 and includes, for example, an AGC (auto gain control) circuit, and adjusts the gain (amplification factor) of the output signal. The A / D converter 24 converts the analog image signal (analog signal) amplified by the amplifier 23 into a digital image signal (digital signal), and the light is received by each pixel of the image sensor 22. Each pixel signal obtained in this way is converted into, for example, 12-bit pixel data.

  The control unit 3 includes a ROM that stores various control programs, a RAM that temporarily stores data, and a central processing unit (CPU) that reads and executes control programs from the ROM. It governs control. The control unit 3 calculates control parameters and the like required by each unit of the device based on various signals from each unit of the device such as the image sensor 22, and controls the operation of each unit of the device such as the dodging processing unit 61 based on this.

  The image memory 4 includes a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The image data input by the image input unit 2 or the image data subjected to predetermined image processing by the image processing unit 6. Etc. are stored.

  The user I / F (interface) unit 5 functions as an input key for inputting various operation instructions (commands) from the user, or displays predetermined information. The monitor unit 51 and the operation unit 52 It has. The monitor unit 51 monitors and displays an image input by the image input unit 2, an image stored in the image memory 4, or predetermined operation information or setting information, for example, a liquid crystal display composed of a color liquid crystal display element. It consists of a display (LCD; Liquid Crystal Display). The operation unit 52 is used to input operation instructions to the digital camera 1 by a user, and includes various switch groups (button groups) such as a release switch, a shooting mode setting switch, and a menu selection switch. For example, when the release switch is pressed (turned on), subject light is imaged by the imaging sensor 22, and after the required image processing is performed on the captured image obtained by this imaging, the image data is stored in the image memory. A series of shooting operations such as recording in 4 is executed.

  By the way, the user I / F unit 5 sets parameters (referred to as image processing parameters) relating to image processing such as contrast correction amount, saturation correction amount, and sharpness correction amount as shown in the rear view of the digital camera 1 shown in FIG. It can be set (input). Each image processing parameter can be adjusted in five stages, for example, -2 to +2. As an actual input operation, for example, the selection frame 511 is moved to the position of the required image processing parameter on the monitor screen by a button operation by the operation unit 52, and the image processing parameter to be corrected is selected (activated). ) After (sharpness is selected in FIG. 9), the pointer 512 is moved from the default position (in this case, zero) to a required level position in a range from −2 which is a low luminance priority side to +2 which is a high luminance priority side. By moving, the correction amount of each image processing parameter is set (in FIG. 9, the sharpness correction amount is set to a level of “+1”).

  The image processing unit 6 performs various types of image processing on the captured image data (digital image signal obtained by the A / D conversion unit 24) input by the image input unit 2, and includes a dodging processing unit 61, a gradation A conversion unit 62 and a sharpness correction unit 63 are provided. The dodging processing unit 61 performs a dodging process on the image. This dodging process will be described in detail later. The gradation conversion unit 62 uses the table information for gradation conversion given from the control unit 3 (gradation conversion characteristic calculation unit 32 described later), and R, G, and B pixel data of the input image (captured image). The tone conversion is performed by performing the data conversion for. The sharpness correction unit 63 performs sharpness correction of the input image by performing a filter operation using information on a predetermined filter coefficient for sharpness correction given from the control unit 3. In addition to the above functional units, the image processing unit 6 includes a color interpolation processing unit, a color correction processing unit, a white balance (WB) correction unit, or a fixed pattern noise (FPN) of the image signal. An FPN correction unit that removes the black level, a black reference correction unit that corrects the black level of the image to a reference value, and the like (both not shown) may be provided.

  In the first embodiment, a gradation conversion process is performed by determining a parameter (referred to as a gradation conversion parameter) relating to gradation conversion processing in accordance with each parameter relating to the dodging process (referred to as dodging parameter). The main characteristic point is that the gradation conversion process is controlled according to the parameters. With regard to this, the dodging processing unit 61 and the functional units of the control unit 3 will be described.

The dodging processing unit 61 performs the dodging processing on the image input from the image input unit 2, that is, the image obtained by the imaging sensor 22 (linear / logarithmic image, wide DR image); Is to do. According to the so-called Retinex theory, the base image I has an illumination component (mainly composed of low frequency components) in the base image I as an illumination component L and a reflectance component (mainly composed of high frequency components) as a reflectance component R. Then, it is expressed by the following equation (1).
I = L * R (1)
However, the symbol “*” indicates multiplication (the same applies hereinafter).

  The dodging processing unit 61 extracts the illumination component L by applying a so-called edge maintenance filter (nonlinear filter; illumination extraction filter) such as a median filter or an epsilon (ε) filter to the base image I (illumination component). The remaining components are extracted as the reflectance component R by extracting L). Information on the filter size (referred to as filter size Sf) of this edge maintaining filter is given from the control unit 3. However, this filter size corresponds to an image size composed of a plurality of pixels related to the number of pixels to be averaged during image filtering, for example, the filter size is 10 Pixels, 20 pixels, etc. Also from this, it can be said that the dodging process is a process in which an image is divided into a plurality of regions and a different process (local process) is performed for each region. Here, the filter size of the edge preserving filter is used to represent the size of each region (region size). However, the present invention is not limited to this, and for example, a block size of region division may be used. Accordingly, it can be said that this “region size” information including the filter size and the block size of the region division is a dodging parameter. The local process may be, for example, a contrast correction process, that is, the dodging process may be a process for performing different contrast correction (local contrast correction) for each region. Is a dodging parameter for local contrast correction.

Next, the dodging processor 61 converts the extracted illumination component L into a region (L> Ls) where the illumination component L is equal to or higher than a predetermined compression start level Ls according to the following equation (2) ( DR compression). For a region where the illumination component L is smaller than the compression start level Ls (L ≦ Ls), conversion according to the following equation (3) (this conversion is also included in DR compression) is performed.
L ′ = exp (log (L) * c) * n (2)
However, “c” is a compression rate and “n” is a normalization term.
L ′ = L (3)

  L ′ according to the above equations (2) and (3) is represented by illumination compression characteristics 210 and 220 denoted by reference numerals 210 and 220, respectively, as shown in FIG. The illumination compression characteristic 210 corresponds to a predetermined compression start level Ls of the illumination component L, a point A (Ls, Os) indicated by a reference numeral 211 of the compression start level Os as an output value at this Ls, and an upper limit value Lmax of the illumination component L. A point B (Lmax) indicated by reference numeral 212 in which the output is an output maximum value Omax (for example, when the output image from the image sensor 22 is an 8-bit image having 0 to 255 gradations, an output value of 255 gradations; gradation value). , Omax). Therefore, the compression ratio c and the normalization term n, which are unknown numbers in the above equation (2), are calculated from simultaneous equations obtained by substituting these two coordinate values. The information on Ls and Lmax is given from the control unit 3.

After the above-described processes are performed, the dodging processing unit 61 further generates an image I ′ from the DR-compressed illumination component L ′ and reflectance component R using the following equation (4) ( Output).
I '= L' * R (4)
The above equation (4) may be considered as I ′ = L ′ / L * I. The symbol “/” indicates division (the same applies hereinafter). Further, for a region where the illumination component L is smaller than the compression start level Ls (L ≦ Ls), I ′ = I may be considered instead of I ′ = L ′ / L * I.

  As shown in FIG. 2, the control unit 3 includes a dodging parameter calculation unit 31 and a gradation conversion characteristic calculation unit 32. The dodging parameter calculation unit 31 calculates (acquires) the dodging parameter such as Ls, Lmax, or filter size Sf in the dodging process. Ls is given as a value about twice the main subject luminance (value I0 shown in FIG. 4 to be described later) that provides appropriate brightness when gamma is applied in the gradation conversion unit 62 (gradation conversion processing using gamma is performed). . However, the value of Ls may be a value (fixed value) obtained in advance for each subject, such as a person or a landscape, or a value specified (instructed by the user I / F unit 5) each time by the user. But you can.

  Lmax is given as a predetermined upper limit value for determining to what brightness the dodging process is performed, that is, how far the illumination component L to be compressed is included. Normally, the maximum luminance values of R, G, and B of the base image I (wide DR image) are used as this Lmax, but not limited to this, the maximum value of the illumination component L or Y% of this maximum value (contrast Lmax may be set to a value smaller than the maximum value of the illumination component in order to increase it), and the X% value of the R, G, B luminance maximum value may be used. The value of Lmax may be calculated each time, may be a value obtained in advance (fixed value), or may be a value specified by the user each time an instruction is input from the user I / F unit 5 or the like. Good. The filter size Sf is given as a predetermined value or a value depending on the image (for example, a Z% value of the image size or a value depending on the spatial frequency of the image). The dodging parameter calculation unit 31 transmits the information of Ls, Lmax, and Sf to the dodging processing unit 61 and sets the information in the dodging processing unit 61. Note that the information such as the value obtained in advance may be stored in, for example, a parameter storage unit (not shown) in the control unit 3.

  The gradation conversion characteristic calculation unit 32 calculates the gradation conversion characteristic used in the gradation conversion processing in the gradation conversion unit 62 based on each dodging parameter obtained by the dodging parameter calculation unit 31, and A conversion table (for example, LUT; look-up table) in which tone conversion characteristics are described, that is, tone conversion by tone conversion characteristics is reflected is created. The gradation conversion characteristic calculation unit 32 transmits information of the created conversion table to the gradation conversion unit 62 and sets the information in the gradation conversion unit 62. The gradation conversion characteristics calculated by the gradation conversion characteristic calculation unit 32 are, for example, gradation conversion characteristics 310 and 320 shown in FIGS. In each figure, the horizontal axis indicates the gradation conversion input, and the vertical axis indicates the gradation conversion output. Each gradation conversion characteristic 310, 320 passes through two points (0, 0) and (Omax, Omax) indicated by reference numerals 311 and 312, and also includes a point C (I0, I0 ′) and reference numeral 314 indicated by reference numeral 313. (In FIG. 5, the direction is indicated by reference numeral 315). This is represented by a curve passing through two points D (Ls, Ls ′). In particular, the gradation conversion characteristics 310 and 320 are controlled by changing the positions of two points C and D (in this sense, the points C and D are expressed as first and second control points, respectively). ).

  The first control point C (I0, I0 ') is a point indicating a predetermined level at which appropriate brightness is obtained when gamma is applied. The input value I0 at the first control point C is, for example, a value corresponding to the luminance of the main subject (for example, a human face) (referred to as main subject luminance I0), and the output value I0 ′ is, for example, an 8-bit image. The output value is about 128 gradations.

  The second control point D (Ls, Ls ′) is the slope of the illumination compression characteristics 210 and 220 shown in FIG. 3 (the slope of the characteristic graph), in particular, the illumination compression characteristic 210 (compression region) expressed by the above equation (2). , Compression characteristic), that is, the compression start level set in accordance with the illumination compression characteristic “parameter indicating the slope”. The parameter representing the slope of the illumination compression characteristic corresponds to a parameter in dodging processing for compressing the illumination component using the illumination compression characteristic of FIG.

  By the way, the fact that the slope of the compression region is small means that the input range is larger than the output range when the horizontal axis in FIG. 3 is input and the vertical axis is output. In this case, it can be said that the degree of compression (compression rate) is large. Conversely, when the slope of the compression region is large, it can be said that the degree of compression is small. The inclination of the compression region is determined by two points, the point A (Ls, Os) and another point, that is, a point E (Le, Oe) indicated by reference numeral 213.

  The second control point D (Ls, Ls ′) is determined according to the parameter representing the inclination of the compression region as described above. Specifically, the information on the two points as the parameter representing the inclination is used. To determine. In the present embodiment, instead of the point E, when the point E is the point B (or the point E is at the position of the point B), the point B and the point A are 2 The second control point D is determined using the point information. In other words, the information of point A and point B is used here, but the present invention is not limited to this. In short, the level of points A and A that can determine the inclination of the compression region is higher than point A. The use of at least two points with another large arbitrary point. However, the information of the points A and B are specifically Ls and Lmax (the above-mentioned dodging parameters Ls and Lmax) which are values of the illumination components on the horizontal axis in FIG. The second control point D is determined according to the value of Lmax.

  That is, the input value Ls at the second control point D (Ls, Ls ′) corresponds to the compression start level Ls (the dodging parameter Ls) of the illumination component L shown in FIG. On the other hand, the output value Ls ′ is set according to the magnitude of the upper limit value Lmax of the illumination component L shown in FIG. 3, that is, Ls ′ depends on Lmax, and is a value given by Ls ′ = f (Lmax). Yes ("f" indicates a monotonically decreasing function. However, "monotonic decreasing" indicates that it is not necessary to increase linearly and it is not necessary to increase). Therefore, FIG. 4 shows a case where Lmax is small, and FIG. 5 shows a case where Lmax is large. That is, when Lmax is small, that is, when the DR (compression luminance range) in the dodging process is narrow (in this case, the slope of the compression region is large), the output level of Ls ′ is set high as shown in FIG. A higher gradation conversion output can be obtained in a medium luminance or high luminance portion above the point C level. When Lmax is large, that is, when DR in the dodging process is wide (in this case, the slope of the compression region is small), the output level of Ls ′ is set low as shown in FIG. The gradation conversion output is suppressed in the part. As described above, the gradation conversion characteristics are determined based on the information (the dodging parameter) of the compression start level Ls in the dodging process and the luminance level (Le; Lmax in this case) greater than the compression start level Ls.

  The second control point D (Ls, Ls ′), the gradation conversion characteristic based on the second control point D (Ls, Ls ′), or the conversion table corresponds to the gradation conversion parameter. A characteristic curve 330 shown in FIGS. 4 and 5 shows a normal gamma characteristic (gamma characteristic 330), and the first and second control points C and D do not increase beyond the level of each part of the gamma characteristic 330. Controlled (set). Further, in the present embodiment, from the viewpoint of setting the gradation conversion parameter according to the dodging parameter, the control of the gradation conversion characteristic by the second control point D is essential, but the control by the first control point C is not performed. It can be said that it is preferable to be carried out in order to obtain a more suitable image.

  FIG. 6 is a flowchart illustrating an example of an operation related to the gradation conversion process according to the dodging parameter according to the first embodiment. First, a photographed image is acquired by the image sensor 22 by pressing the release switch or the like, and this photographed image data is input to the control unit 3 (for example, stored in the image memory 4) (step S1). Next, the dodging parameter calculation unit 31 of the control unit 3 transmits the dodging parameters, that is, information on the compression start level Ls and the upper limit Lmax (see FIG. 3) and information on the filter size Sf to the dodging processing unit 61. Is set (step S2). Then, the dodging processing unit 61 performs dodging processing (extracts the illumination component L from the base image I and performs DR compression on the dodging processing based on the set dodging parameter, and the illumination component L ′ and the reflectance component. A process of generating a new image I ′ from R) is performed (step S3). On the other hand, the gradation conversion characteristic calculation unit 32 of the control unit 3 calculates the gradation by calculating the second control point D (Ls, Ls ′) or the like based on each dodging parameter obtained by the dodging parameter calculation unit 31. Conversion characteristics (see FIGS. 4 and 5) are calculated, a conversion table (LUT) for the gradation conversion characteristics is created, and the created conversion table information is transmitted to the gradation conversion unit 62 and set (step). S4). Then, the gradation conversion unit 62 performs gradation conversion processing based on the conversion table (step S5), and the image data obtained by the gradation conversion processing is stored in the image memory 4 (step S6). .

(Embodiment 2)
In the first embodiment, the gradation conversion process is controlled according to the dodging parameter. However, in the second embodiment, a parameter related to sharpness correction (referred to as a sharpness parameter) according to the dodging parameter, For example, a case where the sharpness correction amount is determined and the sharpness correction processing is performed, that is, the sharpness correction processing is controlled according to the dodging parameter will be described. The block configuration of the digital camera in this embodiment is the same as that in FIG. However, as shown in FIG. 7, the control unit 3 ′ (corresponding to the control unit 3 in FIG. 1) is further provided with a sharpness parameter calculation unit 33.

  The sharpness parameter calculation unit 33 calculates the sharpness parameter according to the “region size” when performing the local processing for each region described in the first embodiment (including the case where local contrast correction is performed as the local processing). Is. Similarly in the case of the present embodiment, this area size indicates a filter size or a block size of area division. Here, the former filter size is used as information on the area size. The sharpness parameter calculation unit 33 calculates the sharpness parameter according to the filter size Sf of the illumination component extraction filter calculated by the dodging parameter calculation unit 31. Specifically, as shown in FIG. 9, the sharpness parameter calculation unit 33 corrects the predetermined sharpness correction level (referred to as the sharpness correction amount Sh) input from the user I / F unit 5 according to the filter size Sf. Then, the sharpness correction filter is switched (selected) in accordance with the sharpness correction amount obtained by this correction.

The sharpness correction amount Sh is corrected according to the filter size Sf by the following equation (5).
Sh ′ = Sh + ΔSh (5)
However, Sh ′ is a value after correction of Sh, and ΔSh is a negative monotonous decrease with respect to an increase in the filter size Sf as shown in FIG. This is a value (correction amount) given by the relationship. That is, as the Sf value increases from zero, the value of ΔSh decreases from zero.

  The sharpness parameter calculation unit 33 uses, for example, sharpness correction for increasing sharpness in proportion to Sh ′ when Sh ′ is a positive value based on the Sh information obtained from Equation (5). When a high-pass filter is selected and Sh ′ has a negative value, for example, a low-pass filter for sharpness correction that increases smoothness inversely proportional to Sh ′ is selected. In other words, the sharpness parameter calculation unit 33 performs the edge in the sharpness correction processing in the sharpness correction unit 63 according to the sharpness correction amount Sh determined based on the filter size Sf, that is, the region size to be locally processed. It can be said that the extraction frequency characteristic is changed.

  When the value of Sh ′ is zero in the above equation (5), the sharpness correction filter processing is not performed (no filter is selected). Information on these high-pass filters and low-pass filters may be stored in advance in the sharpness parameter calculation unit 33 or the like. The sharpness parameter calculation unit 33 transmits information on the selected filter to the sharpness correction unit 63 and sets the information in the sharpness correction unit 63. The sharpness correction unit 63 performs sharpness correction processing based on the set filter information (one of the high-pass filter and the low-pass filter). Further, the sharpness correction amount Sh ′ and a filter selected based on the sharpness correction amount Sh ′ correspond to the sharpness parameter here.

  FIG. 10 is a flowchart illustrating an example of an operation related to the sharpness correction process according to the dodging parameter in the second embodiment. First, the information on the sharpness correction amount Sh input from the user I / F unit 5 is set in the sharpness parameter calculation unit 33 (step S11). Next, a photographed image is acquired by the imaging sensor 22 by pressing the release switch or the like, and this photographed image data is input to the control unit 3 '(for example, stored in the image memory 4) (step S12). Next, the dodging parameter calculation unit 31 of the control unit 3 ′ transmits the dodging parameters, that is, information on the compression start level Ls and the upper limit Lmax (see FIG. 3) and information on the filter size Sf to the dodging processing unit 61. Is set (step S13). Then, the dodging processing unit 61 performs dodging processing (extracts the illumination component L from the base image I and performs DR compression on the dodging processing based on the set dodging parameter, and the illumination component L ′ and the reflectance component. A process of generating a new image I ′ from R) is performed (step S14).

  On the other hand, the gradation conversion characteristic calculation unit 32 of the control unit 3 ′ calculates the second control point D (Ls, Ls ′) based on the respective dodging parameters obtained by the dodging parameter calculation unit 31. A tone conversion characteristic (see FIGS. 4 and 5) is calculated, and a conversion table (LUT) of the gradation conversion characteristic is created. Then, the created conversion table information is transmitted and set to the gradation conversion unit 62 (step S15), and gradation conversion processing is performed by the gradation conversion unit 62 based on the conversion table (step S16). . Next, the sharpness correction amount Sh input in step S1 is corrected by the sharpness parameter calculation unit 33 of the control unit 3 ′ according to the filter size Sf obtained by the dodging parameter calculation unit 31 ((5 ) See formula). Then, a sharpness correction filter is selected according to the corrected sharpness correction amount Sh ′, and the selected filter is set in the sharpness correction unit 63 (step S17), and sharpness correction is performed based on the set filter. Sharpness correction processing is performed by the unit 63 (step S18). The image data obtained by this sharpness correction process is stored in the image memory 4 (step S19). Note that the gradation conversion process in steps S15 and S16 does not necessarily have to be performed according to the dodging parameter as described above, and may be a gradation conversion process using normal gamma, or the gradation conversion process. A configuration in which the conversion process itself is not performed (a configuration in which step S14 is followed by step S17) may be employed. Note that the order of steps S15 and S16 and steps S17 and S18 is not limited to that described above, and may be changed, for example, in the order of steps S17 and S18 → steps S15 and S16.

  As described above, according to the imaging apparatus (digital camera 1) according to the first embodiment, an image is acquired by the image input unit 2 (or the imaging sensor 22) (image acquisition unit), and the dodging processing unit 61 ( A dodging process is performed on the image by the dodging processing unit), a dodging parameter relating to the dodging process is set by the dodging parameter calculation unit 31 (dodging parameter setting unit), and a gradation converting unit 62 (gradation converting unit). ), Gradation conversion processing is performed on the image, and gradation conversion characteristics relating to the gradation conversion processing are set by the gradation conversion characteristic calculator 32 (tone characteristic setting means). Then, the gradation conversion characteristic calculation unit 32 determines the gradation conversion characteristic based on the dodging parameter set in the dodging parameter calculation unit 31, and the gradation conversion unit 62 determines the gradation conversion characteristic. A gradation conversion process is performed based on the determined gradation conversion characteristic.

  According to this, the gradation conversion characteristic is determined based on the dodging parameter, and the gradation conversion process is performed based on the determined gradation conversion characteristic. A suitable gradation characteristic according to the dodging characteristic can be obtained without causing a decrease in contrast.

  Further, the dodging process compresses the illumination component L extracted from the base image I, and generates a new image I ′ from the compressed illumination component L ′ and the reflectance component R extracted from the image. Then, the gradation conversion characteristic calculation unit 32 determines the gradation conversion characteristic 310 (320) based on a parameter indicating the degree of compression in the luminance region where the illumination component L is compressed.

  According to this, since the gradation conversion characteristic is determined based on the parameter representing the degree of compression in the luminance region where the illumination component L is compressed, the gradation conversion characteristic 310 (320) appropriately reflecting the dodging characteristic. ) Can be determined.

  In addition, the gradation conversion characteristic calculation unit 32 generates a first luminance level that is a predetermined compression start level Ls in the luminance range of the illumination component L as a dodging parameter and a second luminance level that is greater than the compression start level Ls. The gradation conversion characteristic 310 (320) is determined based on the information.

  According to this, the gradation conversion characteristic is determined based on the information of the first luminance level that is the compression start level Ls in the luminance range of the illumination component and the second luminance level that is greater than the compression start level. A first luminance level that can be representative of dodging characteristics, for example, a level value that allows the main subject to obtain appropriate brightness (or contrast), and a second luminance that has a luminance level greater than the first luminance level. Using the level information, it is possible to easily determine the gradation characteristic 310 (320) in which the dodging characteristic is appropriately reflected.

  The first luminance level is set to a luminance level equal to or higher than the main subject luminance (the gradation conversion input value I0 shown in FIGS. 4 and 5), which is a predetermined luminance value of the main subject. The gradation conversion output value Ls ′ corresponding to the gradation conversion input value Ls when the luminance level is the gradation conversion input value Ls is small when the compression degree of the illumination component L is large, and the compression degree of the illumination component L is small. The gradation conversion characteristic 310 (320) is determined so as to be a large value.

  According to this, the gradation conversion output value Ls ′ relative to the gradation conversion input value Ls when the first luminance level is the gradation conversion input value Ls is small when the degree of compression of the illumination component is large, and the illumination component Since the gradation conversion characteristic 310 (320) is determined so as to be a large value when the compression level of the illumination component L is small, when the compression level of the illumination component L is large, that is, the compression luminance range (DR) in the dodging process. Is wide, the gradation conversion output level is set low so that the gradation conversion output can be suppressed in the middle or high luminance portion (as shown in FIG. 5), and the degree of compression of the illumination component L is small. In this case, that is, when the compressed luminance range is narrow, the gradation conversion output level is set high so that a higher gradation conversion output can be obtained in the middle luminance or high luminance portion (in the case shown in FIG. 4). Can be overturned It is possible to perform suitable gradation conversion in accordance with the baked characteristics.

  Further, the gradation conversion characteristic calculation unit 32 can convert the gradation conversion input value I0 of the main subject luminance into an appropriate gradation conversion output value I0 ′ that is an output level at which the required brightness of the main subject can be obtained. Since the tone conversion characteristic 310 (320) is determined, it is possible to prevent the main subject image from being darkened by the tone conversion, and to perform more preferable tone conversion.

  Furthermore, in the imaging apparatus (digital camera 1) according to the second embodiment, an image is acquired by the image input unit 2 (or the imaging sensor 22) (image acquisition unit), and the dodging processing unit 61 (dodging processing unit). The dodging process is performed on the image, the dodging parameter calculation unit 31 (dodging parameter setting unit) sets the dodging parameter related to the dodging process, and the sharpness correcting unit 63 (sharpness correcting unit) performs the sharpness correcting process on the image. The sharpness correction amount Sh related to the sharpness correction processing is set by the sharpness parameter calculation unit 33 (sharpness correction amount setting means). Then, the sharpness parameter calculation unit 33 determines the sharpness correction amount Sh based on the dodging parameter set in the dodging parameter calculation unit 31, and the sharpness correction unit 63 determines the sharpness correction determined by the sharpness parameter calculation unit 33. Sharpness correction processing is performed based on the amount Sh.

  According to this, the sharpness correction amount Sh is determined based on the dodging parameter, and the sharpness correction processing is performed based on the determined sharpness correction amount Sh. Therefore, the high frequency component is emphasized by the dodging processing. A sharpness characteristic suitable for the dodging characteristic can be obtained without generating an unnatural image.

  Also, the dodging process is realized by locally processing each of a plurality of areas obtained by dividing the image (base image I), and the dodging parameter is the size of each area to be locally processed. (Region size). According to this, since the area size in the local processing of the image is treated as a dodging parameter, various parameters such as a filter size when filtering the image and a divided block size when the image is divided into regions are set. It is possible to use as dodging parameters, and it is possible to obtain a suitable sharpness characteristic according to the dodging parameters reflecting these parameters.

  Also, the dodging parameter is the size (filter size Sf) of the filter (edge maintaining filter) that extracts the illumination component L from the image, and the sharpness parameter calculation unit 33 determines the sharpness correction amount Sh based on the filter size Sf. Is determined (see equation (5)). According to this, since the sharpness correction amount is determined based on the filter size Sf, the dodging parameter can be easily reflected in the sharpness correction amount in the sharpness correction processing according to the dodging characteristics.

  Also, the dodging process is realized by performing local contrast correction on each of the plurality of areas obtained by dividing the image (base image I), and the dodging parameter is set for each area to be subjected to local contrast correction. Size (area size). According to this, since the area size in the local contrast correction process of the image is handled as the dodging parameter, it is possible to obtain a suitable sharpness characteristic according to the dodging parameter reflecting the contrast correction process.

  In addition, the edge extraction frequency characteristic of the sharpness correction unit 63 is changed by the sharpness parameter calculation unit 33 in accordance with the sharpness correction amount determined based on the size of each region to be locally processed. According to this, the edge extraction frequency characteristic in the sharpness correction unit 63 is changed according to the sharpness correction amount determined based on the region size (the edge extraction frequency characteristic corresponding to the sharpness correction amount is used). Sharpness correction based on edge extraction can be performed more appropriately according to the dodging characteristics.

  In addition, the sharpness parameter calculation unit 33 changes (changes) the edge enhancement amount of the sharpness correction unit 63 according to the sharpness correction amount determined based on the size of each region to be locally processed. According to this, since the edge enhancement amount in the sharpness correction unit 63 is changed according to the sharpness correction amount determined based on the region size (the edge enhancement amount according to the sharpness correction amount is used). Sharpness correction based on edge enhancement that is more appropriate for the characteristics can be performed.

  Further, the image acquisition means includes a linear characteristic in which an electric signal is linearly converted with respect to the incident light amount and output, and a logarithmic characteristic in which the electric signal is logarithmically converted with respect to the incident light amount and output. The imaging sensor 22 (linear log sensor) has photoelectric conversion characteristics. According to this, a wide DR image can be easily obtained by photographing with the image sensor 22, and in the gradation conversion processing based on the dodging parameter, the brightness of the main subject (low luminance part) or the like can be obtained from the wide DR image. It is possible to easily obtain an image in which the contrast is ensured and the high luminance part is suitably adjusted.

  In the first embodiment, the gradation conversion characteristic is determined based on the dodging parameter and the gradation conversion process is performed based on the determined gradation conversion characteristic, and the dodging parameter in the second embodiment. It can be said that the configuration in which the sharpness correction amount is determined based on the above and the sharpness correction processing is performed based on the determined sharpness correction amount is realized by the following image processing method or image processing program.

  That is, a dodging process stage for performing dodging processing on image data, a dodging parameter setting stage for setting dodging parameters related to the dodging process, and gradation conversion characteristics based on the set dodging parameters An image processing method comprising: a gradation conversion characteristic determination step for determining the gradation conversion step; and a gradation conversion processing step for performing gradation conversion processing based on the determined gradation conversion characteristic.

  A computer executes a first procedure for setting a dodging parameter relating to dodging processing for image data and a second procedure for determining gradation conversion characteristics based on the dodging parameter set in the first procedure. An image processing program characterized in that

  By using such an image processing method or image processing program, gradation conversion characteristics are determined based on the dodging parameter, and gradation conversion processing is performed based on the determined gradation conversion characteristics. A suitable gradation characteristic according to the dodging characteristic can be obtained without causing a contrast reduction of the high luminance part by the tone conversion.

  In other words, a dodging process stage for performing dodging processing on image data, a dodging parameter setting stage for setting dodging parameters related to the dodging process, and sharpness correction based on the set dodging parameters An image processing method comprising: a sharpness correction amount determining step for determining an amount; and a sharpness correction processing step for performing a sharpness correction process based on the determined sharpness correction amount.

  Causing the computer to execute a first procedure for setting a dodging parameter for dodging processing for image data and a second procedure for determining a sharpness correction amount based on the dodging parameter set in the first procedure. An image processing program characterized by that.

  By using such an image processing method or image processing program, the sharpness correction amount is determined based on the dodging parameter, and the sharpness correction processing is performed based on the determined sharpness correction amount. A sharpness characteristic suitable for the dodging characteristic can be obtained without generating an unnatural image in which high-frequency components are emphasized.

In addition, this invention can take the following deformation | transformation aspects.
(A) In the first and second embodiments, gradation conversion processing and sharpness correction processing corresponding to the dodging parameter are performed in the digital camera 1 (the control unit 3 and the dodging processing unit 61). However, the present invention is not limited to this, and a configuration may be employed in which a predetermined processing unit outside the digital camera 1 executes. Specifically, for example, a user interface configured to be directly connected (wired) to the digital camera 1 using a USB or the like, or connected to a network by a wireless LAN or the like, or to be able to transmit information using a storage medium such as a memory card. In a predetermined host (for example, a computer built-in device such as a PC (Personal Computer) or a PDA (Personal Digital Assistant)), the computer in the host may execute the process.

  (B) In the second embodiment, in the sharpness correction, the sharpness parameter is calculated by correcting the sharpness correction amount Sh according to the filter size Sf (region size) of the illumination component extraction filter. For example, the edge enhancement amount (edge enhancement amount) for the image obtained by the coring process may be changed according to the filter size Sf (region size). Specifically, the sharpness correction unit 63 includes, for example, a filter processing unit 641, an addition unit 642, a coring processing unit 643, an outline enhancement amount setting unit 644, a multiplication unit 645, an addition unit 646, and the like as shown in FIG. A contour enhancement processing unit 64 is provided, and a coring result (edge image 654 described later) by the coring processing unit 643 is multiplied by a gain (contour enhancement amount) set by the contour enhancement amount setting unit 644 according to the filter size Sf. The edge enhancement is performed by multiplication by the unit 645. However, here, the contour enhancement amount is set to a value proportional to the filter size Sf.

  Note that the filter processing unit 641 performs, for example, a two-dimensional LPF (low-pass filter) process using a symmetric filter of M × N, for example, a size of 5 × 5, on the input image 651 (original image), to thereby generate a low-frequency component. The LPF image 652 is output. The adder 642 calculates a difference between the input image 651 and the LPF image 652 and extracts a high-frequency component (difference image 653) in which an edge component and a noise component are mixed. The coring processing unit 643 performs coring processing, that is, noise component removal, on the difference image 653 using a coring coefficient (coefficient that removes only the noise component of the image signal and extracts the edge component) to obtain the edge image. 654 is output. The contour enhancement amount setting unit 644 sets the contour enhancement amount according to the filter size Sf calculated by the dodging parameter calculation unit 31. The multiplying unit 645 multiplies the edge image 654 by the edge enhancement amount set in the edge enhancement amount setting unit 644 (here, the enhancement amount is about 6 times), thereby outputting an edge enhanced image 655. The adder 646 multiplies (synthesizes) the edge enhanced image 655 and the LPF image 652 from the filter processor 641 and outputs an output image 656. In this way, the contour enhancement processing unit 64 obtains an output image 656 from which the input image 651 is denoised and edge-enhanced.

1 is a schematic block configuration diagram mainly relating to imaging processing of a digital camera which is an example of an imaging apparatus according to a first embodiment. FIG. It is a functional block diagram of the control part of the digital camera. It is a graph which shows an example of the compression characteristic of the illumination component in a dodging process. It is a graph which shows an example of the gradation conversion characteristic in a gradation conversion process. It is a graph which shows an example of the gradation conversion characteristic in a gradation conversion process. It is a flowchart which shows an example of the operation | movement regarding the gradation conversion process according to the dodging parameter in 1st Embodiment. It is a functional block diagram of the control part of the digital camera which concerns on 2nd Embodiment. It is a graph which shows the relationship between filter size Sf and correction amount (DELTA) Sh. It is a rear view which shows the user I / F part of the said digital camera, (a) is a figure which shows the state by which sharpness was selected, (b) is a figure which shows the state by which the pointer was moved to the level position of +1. It is. It is a flowchart which shows an example of the operation | movement regarding the sharpness correction process according to the dodging parameter in 2nd Embodiment. It is a functional block diagram of the outline emphasis processing part in a sharpness correction part for demonstrating an example of the deformation | transformation aspect of the sharpness correction | amendment according to the dodging parameter in 2nd Embodiment.

Explanation of symbols

1 Digital camera (imaging device)
2 Image input unit (image acquisition means)
22 Imaging sensor (image acquisition means)
3, 3 'control unit 31 dodging parameter calculation unit (dodging parameter setting means)
32 Gradation conversion characteristic calculation unit (gradation characteristic setting means)
33 Sharpness parameter calculation unit (sharpness correction amount setting means)
5 User I / F unit 6 Image processing unit 61 Dodging processing unit (Dodging processing means)
62 Gradation conversion unit (gradation conversion means)
63 Sharpness correction unit (sharpness correction means)
310, 320 gradation conversion characteristics (gradation conversion characteristics according to claims 2 and 3)

Claims (12)

Image acquisition means for acquiring images;
Dodging processing means for performing dodging processing on the image;
Dodging parameter setting means for setting dodging parameters relating to the dodging process;
Gradation conversion means for performing gradation conversion processing on the image;
Gradation characteristic setting means for setting gradation conversion characteristics relating to the gradation conversion processing,
The gradation characteristic setting means determines the gradation conversion characteristic based on the dodging parameter set in the dodging parameter setting means;
The imaging apparatus according to claim 1, wherein the gradation conversion means performs gradation conversion processing based on the gradation conversion characteristics determined by the gradation characteristic setting means. The dodging process is a process of compressing the illumination component extracted from the image and generating a new image from the compressed illumination component and the reflectance component extracted from the image,
The imaging apparatus according to claim 1, wherein the gradation characteristic setting unit determines the gradation conversion characteristic based on a parameter representing a degree of compression in a luminance region where the illumination component is compressed.   The gradation characteristic setting means is based on information on a first luminance level that is a predetermined compression start level in a luminance range of the illumination component and a second luminance level that is greater than the compression start level, as the dodging parameter. The imaging apparatus according to claim 2, wherein the gradation conversion characteristic is determined. The first luminance level is a luminance level equal to or higher than a main subject luminance which is a predetermined luminance value of the main subject,
The gradation characteristic setting means has a gradation conversion output value corresponding to the gradation conversion input value when the first luminance level is a gradation conversion input value, and is small when the degree of compression of the illumination component is large, The imaging apparatus according to claim 3, wherein the gradation conversion characteristic is determined so as to be a large value when the degree of compression of the illumination component is small. In the case where the appropriate gradation conversion output value of the main subject is defined as I0 ′,
The gradation characteristic setting means determines the gradation conversion characteristic that can convert I0 to I0 'when the gradation conversion input value of main subject luminance is I0. 5. The imaging device according to any one of 4. Image acquisition means for acquiring images;
Dodging processing means for performing dodging processing on the image;
Dodging parameter setting means for setting dodging parameters relating to the dodging process;
Sharpness correction means for performing a sharpness correction process on the image;
Sharpness correction amount setting means for setting a sharpness correction amount related to the sharpness correction processing,
The sharpness correction amount setting means determines the sharpness correction amount based on the dodging parameter set in the dodging parameter setting means,
The imaging apparatus according to claim 1, wherein the sharpness correction unit performs a sharpness correction process based on the sharpness correction amount determined by the sharpness correction amount setting unit.   The dodging process is realized by locally performing processing on a plurality of areas obtained by dividing the image, and the dodging parameter is a size of each area to be subjected to the local processing. The imaging device according to claim 6. The dodging process is a process of compressing the illumination component extracted from the image and generating a new image from the compressed illumination component and the reflectance component extracted from the image,
The dodging parameter is a size of a filter that extracts an illumination component from the image;
The imaging apparatus according to claim 6, wherein the sharpness correction amount setting unit determines the sharpness correction amount based on a size of the filter.   The dodging process is realized by performing local contrast correction on each of a plurality of areas obtained by dividing the image, and the dodging parameter is a size of each area to be subjected to the local contrast correction. The imaging apparatus according to claim 6.   The sharpness correction amount setting means changes an edge extraction frequency characteristic of the sharpness correction means according to a sharpness correction amount determined based on a size of each region to be subjected to the local processing. Item 8. The imaging device according to Item 7.   The sharpness correction amount setting unit changes an edge enhancement amount of the sharpness correction unit according to a sharpness correction amount determined based on a size of each region to be subjected to the local processing. 8. The imaging device according to 7.   The image acquisition means is a photoelectric sensor having a linear characteristic in which an electric signal is linearly converted with respect to an incident light amount and output, and a logarithmic characteristic in which an electric signal is logarithmically converted with respect to the incident light amount. The imaging device according to claim 1, wherein the imaging device has a conversion characteristic.

Images