JP4404011B2 - Image processing apparatus and method - Google Patents

Description

  According to the present invention, a density correction processing unit that performs density correction processing on input original image data based on a predetermined density correction value, and image data that has been subjected to density correction processing by the density correction processing unit. The present invention relates to an image processing apparatus including a contrast correction processing unit that performs a contrast correction process based on the contrast correction value.

  Conventionally, a photographic image processing apparatus has an analog method in which an image recorded on a negative film is directly exposed on a photographic paper, or an image recorded on a negative film is once read by a scanner or the like, and photographic paper is based on the obtained image data. Various digital methods for exposing the light have been proposed.

By the way, the negative film can obtain a very wide range of expression of density values of images recorded on the negative film. In other words, even if the subject is the same, the image may be recorded as a thin overall image by underexposure, while the image may be darkened overall as a result of overexposure. is there. For this reason, in the analog photographic image processing apparatus, when the image recorded on the negative film is exposed on the photographic paper, the exposure on the photographic paper is applied to the image that is recorded thinly as a whole. The time is set to be short, and the exposure time for the photographic paper is set to be long for an image that is darkly recorded as a whole. That is, the exposure processing is performed so that the image is almost the same on the photographic paper regardless of the image recording state on the negative film. Further, in the digital photographic image processing apparatus, the entire frame image data is generally compared with the frame image data once read by a high resolution scanner or the like having a resolution of about 12 bits. Shift processing for evenly shifting the density values of the images. In this case as well, the same concept as that of the analog type photographic image processing apparatus is used so that the image on the photographic paper is almost the same regardless of the recording state of the image on the negative film. It was.
JP 2000-350031 A

  However, in the case of image data taken with a digital still camera, since an 8-bit (256 gradation) image is generally applied, compared to the negative film or frame image data read from the negative film. There is only an overwhelmingly narrow range of expression. For this reason, the image of the portion in which the expression range is inferior to the negative film or the like is a state in which the light and shade information of the image is compressed (saturated), that is, an image having a poor contrast feeling. In the above-described shift processing, there has been a problem that it is impossible to improve the state in which the shade information of the image is compressed (saturated).

  SUMMARY OF THE INVENTION In view of the above-described conventional problems, the present invention provides an image processing apparatus and method capable of making an original image an image in which image density information is compressed.

In order to achieve the above-mentioned object, the first characteristic configuration of the image processing apparatus according to the present invention is that, as described in claim 1 of the document of the claims , original image data photographed by a digital camera is stored in a predetermined manner. A density correction processing unit that performs density correction processing by expanding a density range of pixels included in the original image data to a density range wider than the density range based on an exponential function having a density correction value as an index, and the density correction processing A contrast correction processing unit that performs contrast correction processing on the image data that has undergone density correction processing by a unit based on a predetermined contrast correction value, wherein the contrast correction processing unit converts the original image data into a segmentation unit for segmentation in the dark shadow areas than the predetermined density value and bright highlights region than a predetermined density value, among the original image data A backlight intensity calculation unit that calculates the ratio of the density average value of the surrounding pixel area to the density average value of the pixel area as the backlight intensity, and the density correction value as a variable, and has a maximum value in the setting range of the density correction value The first contrast correction value is calculated based on a predetermined convex quadratic function, and the ratio calculated by the backlight calculation unit is used as a variable. When the ratio is less than the predetermined ratio, a constant backlight correction value is obtained. The backlight intensity correction value is calculated based on the backlight intensity correction function that gradually increases with the increase of the ratio when the ratio is greater than or equal to the predetermined ratio, and the first contrast correction value is calculated only for the backlight intensity correction value. A first contrast correction value calculation unit that calculates a smaller value as a new first contrast correction value, and having the density correction value as a variable and having a minimum value in the setting range of the density correction value A second contrast correction value calculation unit that calculates a second contrast correction value based on a predetermined quadratic function that is convex, and a large curve in which the density characteristic becomes convex upward as the first contrast correction value increases. As shown in the drawing, the pixels corresponding to the highlight area are subjected to contrast correction processing, and the smaller the second contrast correction value, the larger the density characteristic becomes downward. And a processing execution unit that performs contrast correction processing on the pixels .

The density correction processing unit corrects the density of original image data captured by the digital camera based on an exponential function having a predetermined density correction value as an index so that the density information of the image is expanded. When the density correction value is set to a value larger than 1, the original image data is subjected to density correction processing so as to be bright. When the density correction value is set to a value smaller than 1, the original image data Is subjected to density correction processing so as to be dark. If the original image data is dark overall, the density correction value is set to a value larger than 1, so that the entire image is corrected to be brighter and the gradation range is expanded. In the case of a brighter image, the density correction value is set to a value smaller than 1, thereby correcting the darkness as a whole and expanding the gradation range.

In the contrast correction processing unit, the original image data is divided into a highlight area brighter than a predetermined density value and a shadow area darker than the predetermined density value, and is calculated based on the contrast correction value calculated corresponding to each. To correct the contrast. A first contrast correction value corresponding to a highlight area is calculated based on a predetermined quadratic function having a maximum value in the density correction value setting range and having a maximum value in the density correction value setting range. A second contrast correction value corresponding to the region is calculated based on a predetermined quadratic function that protrudes downward and has the minimum value in the setting range of the density correction value, with the density correction value as a variable.

Then, the pixel corresponding to the highlight region is subjected to contrast correction so as to draw a large curve in which the density characteristic is convex upward as the first contrast correction value is larger, and the density is smaller as the second contrast correction value is smaller. The pixels corresponding to the shadow area are subjected to contrast correction so as to draw a large curve whose characteristic is convex downward. That is, the contrast correction value is determined depending on the density correction value, and correction is performed so that the contrast is maximized with respect to the appropriate density correction value.

At this time, if the original image data is captured with backlighting, if the first contrast correction value is used for correction, the surrounding highlight area may fly white. Since a value obtained by reducing the correction value by the backlight intensity correction value is used as a new first contrast correction value, even an image photographed with backlight can be corrected with an appropriate contrast.

In the second feature configuration, as described in claim 2, in addition to the first feature configuration described above, the contrast correction processing unit further calculates an average chromaticity and an average saturation of the original image data. An image color calculation unit for calculating, and the first contrast correction value calculation unit calculates a color correction value set in advance corresponding to the average chromaticity and average saturation calculated by the image color calculation unit; A value obtained by increasing the first contrast correction value by the color correction value is calculated as a new first contrast correction value .

For example, when the original image data has a blue or cyan color cast, the image has a light finish and the highlight area is insufficiently missing. By increasing the first contrast correction value by a predetermined color correction value corresponding to the average chromaticity and average saturation calculated by the image color calculation unit, the contrast in the highlight region is increased. At the same time, the density value of the image becomes darker (darker), and the omission of the highlight area can be improved.

In the third feature configuration, in addition to the first or second feature configuration described above, the contrast correction processing unit may further include a human region included in the original image data. A landscape person degree calculation unit that calculates a ratio of the area area other than the person to the area as a landscape person degree, and the second contrast correction value calculation unit uses the ratio calculated by the landscape person degree calculation unit as a variable, When the ratio is less than the predetermined ratio, the landscape portrait correction value gradually decreases as the ratio decreases, and when the ratio is greater than or equal to the predetermined ratio, the landscape portrait correction is performed based on a constant landscape portrait correction value. A value is calculated, and a value obtained by reducing the second contrast correction value by the landscape portrait correction value is calculated as a new second contrast correction value.

For example, in the case of a landscape image with a low degree of landscape personality, such as when the original image data does not include any person, there is a tendency that a finish with a tight contrast feeling in a shadow area, that is, a hard finish is preferred. Therefore, the ratio of the area area other than the person to the area area of the person included in the original image data is calculated as the scenery person degree by the scenery person degree calculating unit. If the ratio is large, it is determined as a person image, and if the ratio is small, it is determined as a landscape image. The second contrast correction value is corrected to be smaller by a correction value obtained by a landscape person degree correction function using the ratio as a variable, and is corrected to be smaller as the image is a landscape image. As a result, it is possible to correct the image with a tight contrast in the shadow area.

According to the first characteristic configuration of the image processing method of the present invention, as described in claim 4, the original image data photographed by the digital camera is based on an exponential function having a predetermined density correction value as an index. A density correction step in which density correction processing is performed by expanding the density range of pixels included in the original image data to a density range wider than the density range, and the image data subjected to density correction processing by the density correction step is set to a predetermined contrast correction value. A contrast correction step for performing a contrast correction process based on the image processing method, wherein the contrast correction step includes: highlighting the original image data with a highlight area brighter than a predetermined density value; and An area separation step for separating the area into a dark shadow area; A backlight intensity calculating step for calculating the ratio of the average density value of the pixel area as the backlight intensity, and a predetermined quadratic function having a maximum value in the density correction value setting range with the density correction value as a variable. The first contrast correction value is calculated based on the ratio, and the ratio calculated by the backlight intensity calculating step is used as a variable. When the ratio is less than the predetermined ratio, the constant backlight intensity correction value is obtained. As the ratio increases, the backlight intensity correction value is calculated based on the backlight intensity correction function, which gradually becomes a larger backlight intensity correction value, and a value obtained by reducing the first contrast correction value by the backlight intensity correction value is set as a new first intensity correction value. A first contrast correction value calculating step for calculating as a contrast correction value, and a predetermined convexity having a minimum value in a setting range of the density correction value, using the density correction value as a variable A second contrast correction value calculating step for calculating a second contrast correction value based on a quadratic function, and a large curve in which the density characteristic becomes convex upward as the first contrast correction value increases. Contrast correction processing is performed on the pixels corresponding to the highlight region, and contrast correction processing is performed on the pixels corresponding to the shadow region so as to draw a large curve in which the density characteristic is convex downward as the second contrast correction value is smaller. And a process execution step .

In the second feature configuration, in addition to the first feature configuration described above, the contrast correction step further calculates an average chromaticity and an average saturation of the original image data. An image color calculation step, wherein the first contrast correction value calculation step calculates a color correction value set in advance corresponding to the average chromaticity and the average saturation calculated by the image color calculation step; A value obtained by increasing one contrast correction value by the color correction value is calculated as a new first contrast correction value.

According to the third feature configuration, in addition to the first or second feature configuration described above, the contrast correction processing step further includes a region area of a person included in the original image data. A ratio of the area area other than the person to the landscape person degree calculation step for calculating the ratio of the area area other than the person as the scenery person degree, wherein the second contrast correction value calculation step uses the ratio calculated by the scenery person degree calculation step as a variable, When the ratio is less than the predetermined ratio, the landscape portrait correction value gradually decreases with the decrease of the ratio, and when the ratio is greater than or equal to the predetermined ratio, the landscape portrait correction value becomes a constant landscape portrait correction value. And a value obtained by reducing the second contrast correction value by the landscape portrait correction value is calculated as a new second contrast correction value.

  As described above, according to the present invention, it is possible to provide an image processing apparatus and method capable of making a digital image in which image density information is compressed an original image.

Embodiments of a photographic image processing apparatus incorporating an image processing apparatus according to the present invention will be described below. As shown in FIG. 2, the photographic image processing apparatus 1 includes a photographic printer 2 that performs an exposure process on the photographic paper P based on output image data and develops the exposed photographic paper, and a developed photographic film F. A media driver 32 that reads image data from an image data storage medium M such as a memory card that stores image data taken by a film scanner 31 or a digital still camera that reads an image from the camera, a general-purpose computer as a controller 33, and the like The print data is set and inputted with the print order information for the inputted photographic image as the original image, and is provided with the operation station 3 for performing various image correction processes, and the print data edited from the original image by the operation station 3 Is output to the photographic printer 2 to produce a desired photographic print. That.

  As shown in FIGS. 2 and 3, the photographic printer 2 has two systems of photographic paper magazines 21 containing roll-shaped photographic paper P, and photographic paper P drawn from the photographic paper magazine 21 with a predetermined print. A sheet cutter 22 that cuts into a size; a back print unit 23 that prints print information such as a frame number on the back of the cut photographic paper P; an exposure unit 24 that exposes the photographic paper P based on the print data; A development processing unit 25 including a plurality of processing tanks 25a, 25b, and 25c filled with processing solutions for developing, bleaching, and fixing the exposed photographic paper P is disposed along the transport path of the photographic paper P. The laterally-feeding conveyor 26 that discharges the photographic paper P that has been dried after the development process, and the sheet-paper (photo print) P that is stacked on the laterally-feeding conveyor 26 is sorted in order units. Configured to include the data 27.

  The exposure unit 24 receives a laser beam bundle of RGB three colors modulated based on the print data in the main scanning direction orthogonal to the conveyance direction with respect to the photographic paper P conveyed in the sub-scanning direction by the conveyance mechanism 28. An exposure head 24a for outputting and exposing is accommodated.

  A transport mechanism 28 including a plurality of roller pairs that transport the photographic printing paper P at a process speed corresponding to the exposure unit 24 and the development processing unit 25 disposed along the transport path is disposed before and after the exposure unit 24. Is provided with a chucker-type transport mechanism 28a capable of transporting photographic paper P in multiple rows.

  The controller 33 provided in the operation station 3 is installed with an application program that operates under the control of a general-purpose operating system and executes various controls of the photographic processing apparatus 1, and a monitor 34 as an operation interface with the operator. A keyboard 35, a mouse 36, and the like are connected.

  The photographic processing process executed by the cooperation of the hardware and software of the controller 33 will be described in functional blocks. As shown in FIG. 4, photographic image data read by the film scanner 31 and the media driver 32 is received. An image input unit 40 that performs predetermined preprocessing and transfers it to a memory 41, which will be described later, and print order information and image editing information are displayed on the screen of the monitor 34, and an operation for inputting necessary data for them. A graphic user interface unit 42 that generates a graphic operation screen for displaying an icon or generates various control commands based on an input operation from the keyboard 35 or mouse 36 to the displayed graphic operation screen, and the image input Photos transferred from the section 40 A memory 41 in which image data and photographic image data after correction processing by an image processing unit 47 (to be described later), correction parameters at that time, and set print order information are stored in a predetermined area, and print order information An order processing unit 43 for generating image data, an image processing unit 47 for performing density correction processing and contrast correction processing for each photographic image data stored in the memory 41, and display commands from the graphic user interface unit 42. A display control unit 46 having a video RAM for displaying the image data and various input / output graphic data developed in the memory 41 on the monitor 34 and the final correction after the various correction processes are completed. Print data for generating print data for outputting an image to the photo printer 2 A generating unit 44, and the like formatter 45 which converts the final corrected image according to customer orders to a file format for writing in a storage medium such as a CD-R.

  The film scanner 31 is configured to operate in two modes: a pre-scan mode that reads an image recorded on the film F at a high speed although it has a low resolution, and a main scan mode that reads a high-resolution image at a low speed. Various correction processes are performed in the pre-judge mode (described in detail in the pre-judge process described later) on the low resolution image read in the can mode, and the correction parameters stored in the memory 41 at that time are changed. Based on this, the final correction processing for the high-resolution image read in the main scan mode is executed and output to the printer 2.

  Similarly, the image file read from the media driver 32 includes a high-resolution captured image and its thumbnail image, and various correction processes described later are performed on the thumbnail image. Based on the stored correction parameters, a final correction process is performed on the high-resolution captured image. When the image file does not include a thumbnail image, the image input unit 40 generates a thumbnail image from the high-resolution captured image and transfers it to the memory 41. In this way, the calculation load of the controller 33 is reduced by executing various editing processes that are frequently trial and error on low-resolution images.

  As shown in FIG. 1, the image processing unit 47 includes a density correction processing unit 10 that performs density correction processing on input original image data based on a predetermined density correction value, and the density correction processing unit 10. And a contrast correction processing unit 11 that performs contrast correction processing on the image data subjected to density correction processing based on a predetermined contrast correction value.

  A configuration including a distortion correction unit that corrects distortion caused by the photographing lens, a sharpening processing unit that enhances the edge of an image to reduce noise, an enlargement / reduction processing unit that converts the image size to a size suitable for a photographic print, and the like. It is good.

  The density correction processing unit 10 is set with a density correction value Gamma, which will be described later, and the density correction value is set for each pixel in the input original image data in accordance with a preset function as shown in [Equation 1]. A new density value Nout (i) is calculated from Gamma and the density value Nin (i) of the pixel in the input original image data, and the pixel data of each pixel, that is, the density value Nin (i) is calculated. The density correction process of the original image data is performed by performing the replacement process with the new density value Nout (i).

  The L is the maximum density setting value in the original image data. For example, when the density is set between 0 gradation and 255 gradation in 8 bits, the L is 255. . The Max is the maximum density value of the original image data, that is, the density value of the brightest pixel, and the Min is the minimum density value of the original image data, that is, the density value of the darkest pixel. It is. The Cmin is a value for arbitrarily correcting new pixel data Nout (i), and is normally set to 0. I indicates a pixel number.

  Here, when Nout (i) is smaller than 0, rounding is performed to 0, and when Nout (i) is larger than 255, rounding is performed to 255.

  That is, as shown in FIG. 5, when the density correction value Gamma is set to a value larger than 1, the original image data is subjected to density correction processing so as to become brighter, and the density correction value Gamma is set to 1. When set to a smaller value, the original image data is subjected to density correction processing so as to be dark. Further, the density value range included in the original image data, that is, the range from Min to Max is reset from a new expanded density value range, that is, 0 gradation to 255 gradation. .

  By the way, the density correction value Gamma can be set based on the original image data in accordance with, for example, [Formula 2] stored in advance. Moreover, it is good also as a structure which can be set suitably by the user.

  Note that, as shown in FIG. 22, Maxg is the maximum density value of the original image data, that is, the density value of the brightest pixel, and Ming is the minimum density value of the original image data. Value, that is, the density value of the darkest pixel, and the Mass is a density value that is an average density of the original image data. The Maxk is the maximum value of the density setting value in the original image data. For example, when the density is set between 0 gradation and 255 gradation in 8 bits, Maxk is set to 255. The Mink is the minimum density setting value in the original image data. For example, the Mink is set to 0 when the density is set between 0 gradation and 255 gradation in 8 bits.

  The contrast correction processing unit 11 divides the input original image data into a highlight region brighter than a predetermined density value and a shadow region darker than the predetermined density value, and the density A first contrast correction value calculating unit 16 that calculates a first contrast correction value based on a first correction value obtained from a correction value Gamma and a first function corresponding to the highlight area; and the density correction value A second contrast correction value calculating unit 17 that calculates a second contrast correction value based on a second correction value obtained from Gamma and a second function corresponding to the shadow region; and the first contrast correction value. Based on the second contrast correction value, a contrast correction process is performed on the pixel corresponding to the highlight area. Serial is configured by a processing execution unit 18 for performing the contrast correction processing with respect to pixels corresponding to the shadow area.

  The region separation unit 12 detects, as a highlight region, a region composed of pixels that are brighter than a predetermined density value set in advance, for example, 128 gradations, from the input original image data. By detecting an area composed of dark pixels as a shadow area, the input original image data is separated into a highlight area brighter than a predetermined density value and a shadow area darker than a predetermined density value. It is configured.

  The predetermined density value can be set in advance as appropriate. For example, a density histogram is generated from the input original image data and set based on the density histogram. Also good. In this case, the density value having the maximum frequency in the generated density histogram may be set as the predetermined density value, and the average density value in the original image data may be set as the predetermined density value. In any case, it is preferable that the highlight area and the shadow area are separated by an average density value of the original image data. It is also possible to generate a density histogram from the image data that has been subjected to density correction by the density correction processing unit 10 and to set the density histogram based on the density histogram after the density correction process. Here, the predetermined density value may be appropriately included in the highlight area or may be included in the shadow area.

  The first contrast correction value calculation unit 16 calculates a first contrast correction value Cr1 based on a first correction value obtained from a first function composed of the density correction value Gamma corresponding to the highlight region. For example, the first correction value Re1 obtained from the first function as shown in FIG. 6A and [Equation 3], which is one of the empirically obtained by the conventional sensory test or the like. Is calculated as the first contrast correction value Cr1.

  The second contrast correction value calculation unit 17 calculates a second contrast correction value Cr2 based on a second correction value obtained from a second function composed of the density correction value Gamma corresponding to the shadow region. For example, the second correction value Re2 obtained from the second function as shown in FIG. 6B and [Equation 4], which is one of the empirically obtained by the sensory test so far, is obtained. The second contrast correction value Cr2 is calculated.

  The processing execution unit 18 performs a contrast correction process on the pixel corresponding to the highlight area based on the first contrast correction value Cr1, and also performs the shadow area based on the second contrast correction value Cr2. The density correction processing unit 10 performs the density correction processing on the pixels corresponding to the highlight area by the density correction processing unit 10 according to the third function shown in [Formula 5] for the pixels corresponding to the highlight area. Contrast correction processing is performed on the corrected image data, and the density correction processing unit 10 performs density correction on the pixel corresponding to the shadow area according to the fourth function as shown in [Equation 6]. Contrast correction processing is performed on the processed image data. That is, a new density value Cout (i) is calculated from the density value Nout (i) subjected to the density correction processing for each pixel according to the function corresponding to each area, and the pixel data of each pixel is obtained. By performing replacement processing with the new density value Nout (i), contrast correction processing is performed on the image data subjected to the density correction processing.

  The NA is a density value obtained by density conversion processing according to [Equation 1] for a predetermined density value, for example, 128 gradations when the highlight area and the shadow area are separated.

  Further, when Cout (i) is smaller than 0, rounding is performed to 0, and when Nout (i) is larger than 255, rounding is performed to 255.

  That is, as shown in FIG. 7A, the pixels corresponding to the highlight region are configured such that the contrast increases as the first contrast correction value Cr1 increases. Further, as shown in FIG. 7B, the pixel corresponding to the shadow region is configured such that the contrast increases as the second contrast correction value Cr2 increases negatively.

  The operation of the image processing unit 47 will be described below with reference to the flowchart of FIG. When the original image data is input to the memory 41 (SA1), a density histogram in the original image data is generated (SA2), and the density correction processing unit 10 determines the density value of the original image data from the density histogram. , That is, the density value Maxg of the brightest pixel, the minimum density value of the original image data, that is, the density value Ming of the darkest pixel, and the density value Mass that is the average density of the original image data. And the density correction value Gamma is calculated based on the above [Equation 2] (SA3).

  The first contrast correction value calculation unit 16 sets the first correction value Re1 obtained from the first function composed of the density correction value Gamma corresponding to the highlight area shown in [Equation 3] described above to the first. The contrast correction value Cr1 is calculated (SA4, SA5). Further, the second contrast correction value calculation unit 17 obtains a second correction value Re2 obtained from a second function made up of the density correction value Gamma corresponding to the shadow area shown in [Expression 4]. The second contrast correction value Cr2 is calculated (SA6, SA7).

  The density correction processing unit 10 performs density correction processing based on the density correction value Gamma on the original image data. That is, a new density value Nout (i) is calculated from the density correction value Gamma and the density value Nin (i) of the pixel in the input original image data according to the function expressed by the above [Equation 1] ( SA8), the pixel data is replaced with the new density value Nout (i) (SA9).

  On the other hand, the region separation unit 12 detects a region having pixels with a predetermined density value, for example, brighter than 128 gradations, as a highlight region from the input original image data, By detecting an area composed of pixels darker than the tone as a shadow area, the input original image data is divided into a highlight area brighter than a predetermined density value and a shadow area darker than a predetermined density value. (SA10). Here, it is assumed that 128 gradations are included in the shadow area.

  The processing execution unit 18 performs, for the pixel corresponding to the highlight area, that is, for a pixel brighter than 128 gradations, according to the third function shown in the above [Equation 5]. A new density value Cout (i) is calculated from the density correction-processed density value Nout (i), the first contrast correction value Cr1, and the like (SA11). Further, for the pixel corresponding to the highlight area, that is, for the pixel darker than 128 gradations, the density correction processing is performed according to the fourth function as shown in the above [Equation 6]. A new density value Cout (i) is calculated from the density value Nout (i), the second contrast correction value Cr2, and the like (SA12). Then, the pixel density value Nout (i) in the image data is replaced with the new density value Cout (i) (SA13).

  The processing from Step SA8 to Step SA13 is performed on all the pixels constituting the original image data (SA14).

  That is, the contrast correction process corresponding to the highlight area is performed separately from the shadow area, and the contrast correction process corresponding to the shadow area is performed separately from the highlight area.

  Hereinafter, another embodiment will be described. As shown in FIG. 9, the contrast correction processing unit 11 includes a backlight intensity calculator 13 that calculates the backlight intensity of the input original image data, and the first contrast correction value calculator 16 includes the first contrast correction value calculator 16. The first contrast correction value Cr1 may be calculated by subtracting the third correction value Re3 corresponding to the backlight level from the correction value Re1. Hereinafter, for convenience, the first contrast correction value calculation unit 16 will be described as a first contrast correction value calculation unit 26, and the contrast correction processing unit 11 will be described as a contrast correction processing unit 21 with different reference numerals.

  As shown in FIG. 10, the backlight intensity calculation unit 13 calculates an average value EEave of density values of a predetermined peripheral pixel area EE in the original image data and a density value of a predetermined center pixel area EC in the original image data. The concentration average value ratio EEave / ECave with the average value ECave is calculated as the backlight level, and the third correction value Re3 corresponding to the backlight level is calculated from a preset fifth function. .

  For example, as shown in FIG. 11, the fifth function is configured such that the third correction value Re3 is calculated larger as the degree of backlight in the original image data is larger.

  The first contrast correction value calculation unit 26 is configured to calculate the first contrast correction value Cr1 by subtracting the third correction value Re3 from the first correction value Re1. That is, the first contrast correction value Cr1 is calculated to be smaller as the degree of backlighting in the original image data is larger.

  Hereinafter, the operation of the contrast correction processing unit 21 for calculating the first contrast correction value Cr1 will be described with reference to the flowchart of FIG. 12. Original image data is input to the memory 41 (SB1), and the density correction is performed. When the value Gamma is set (SB2), the backlight intensity calculating unit 13 calculates an average value EEave of density values of a predetermined peripheral pixel area EE in the original image data (SB3), and the original image data The average value ECave of the density values of the predetermined central pixel area EC is calculated (SB4). Further, a density average value ratio EEave / ECave between the average value EEave of the density values of the peripheral pixel area EE and the average value ECave of the density values of the central pixel area EC is calculated as the degree of backlight (SB5). Then, a third correction value Re3 corresponding to the degree of backlight is calculated from the fifth function shown in FIG. 11 (SB6).

  The first contrast correction value calculation unit 26 calculates a first correction value Re1 obtained from a first function composed of the density correction value Gamma corresponding to the highlight area shown in the above [Equation 3]. (SB7) The first contrast correction value Cr1 is calculated by subtracting the third correction value Re3 from the first correction value Re1 (SB8).

  That is, the first contrast correction value Cr1 is calculated to be small when the degree of backlighting is large, such as when the density value of the pixel in the central area of the original image data is dark and the density value of the pixel in the peripheral area of the original image data is bright. The image compression state in the highlight area is relaxed. The third correction value Re3 may be calculated based on a difference between an average value EEave of density values in the peripheral pixel area EE and an average value ECave of density values in the central pixel area EC. .

  Further, as shown in FIG. 13, the contrast correction processing unit 11 includes an image color calculation unit 14 that calculates average chromaticity and average saturation of the input original image data, and calculates the first contrast correction value. The unit 16 may add the fourth correction value Re4 corresponding to the average chromaticity and the average saturation to the first correction value Re1 to calculate the first contrast correction value Cr1. Hereinafter, for convenience, the first contrast correction value calculation unit 16 will be described as a first contrast correction value calculation unit 36, and the contrast correction processing unit 11 will be described as a contrast correction processing unit 31, with reference numerals being changed.

  For example, the image color calculation unit 14 can plot in a PQ color space in which the distance from the center O of the circular coordinates as saturation and the azimuth angle as chromaticity as shown in FIG. 14 can be plotted. An average chromaticity and an average saturation of the input original image data are calculated, and a fourth correction value Re4 corresponding to the area of the PQ color space plotted as the average chromaticity and the average saturation is calculated. It is configured.

  The fourth correction value Re4 is, for example, a green region Eg, a yellow region Ey, a red color so that the average chromaticity and the average saturation are uniformly 0.3 when the average chromaticity and the average saturation are the blue region Eb in the PQ color space. The area Er, the purple area Ep, and the low saturation area En are configured to be calculated as 0 uniformly.

  The first contrast correction value calculation unit 36 is configured to calculate the first contrast correction value Cr1 by adding the fourth correction value Re4 to the first correction value Re1. In other words, the first contrast correction value Cr1 is calculated to be large when the original image data has a blue or cyan color cast.

  Hereinafter, the operation of the contrast correction processing unit 31 relating to the calculation of the first contrast correction value Cr1 will be described with reference to the flowchart of FIG. 15. Original image data is input to the memory 41 (SC1), and the density correction is performed. When the value Gamma is set (SC2), the image color calculation unit 14 calculates the average chromaticity and average saturation of the original image data (SC3), and the average chromaticity and average saturation are in the PQ color space. If the region is the blue region Eb (SC4), the fourth correction value Re4 is calculated as 0.3 (SC5). If the region is different from the blue region Eb, the fourth correction value Re4 is calculated. Re4 is calculated as 0 (SC6).

  The first contrast correction value calculation unit 26 calculates a first correction value Re1 obtained from a first function composed of the density correction value Gamma corresponding to the highlight area shown in [Expression 2]. (SC7) The first contrast correction value Cr1 is calculated by adding the fourth correction value Re4 to the first correction value Re1 (SC8).

  That is, when the original image data has a blue or cyan color cast, the first contrast correction value Cr1 is greatly calculated to increase the contrast in the highlight area and By increasing the density value (darkening), the omission of the highlight area is improved.

  Further, as shown in FIG. 16, the contrast correction processing unit 11 includes a landscape person degree calculation unit 15 that calculates a scenery person degree in the input original image data, and the second contrast correction value calculation unit 17 includes A configuration may be adopted in which the second contrast correction value Cr2 is calculated by adding a fifth correction value Re5 corresponding to the landscape portrait to the second correction value Re2. Hereinafter, for convenience, the second contrast correction value calculation unit 17 will be described as a second contrast correction value calculation unit 27, and the contrast correction processing unit 11 will be described as a contrast correction processing unit 41 with different reference numerals.

  The landscape person degree calculating unit 15 detects a person included in the original image data, and calculates a region area ratio between the detected person area and a region other than the detected person as a scenery person degree. The fifth correction value Re5 corresponding to the scene portrait is calculated from a preset sixth function.

  The detection of the person included in the original image data is performed by determining whether or not the contour based on the density edge and the color edge extracted from the original image data is a face region. In addition, a known technique such as detection based on a pattern recognition technique by evaluating the degree of coincidence with a plurality of element arrangement patterns such as mouths and ears can be used. Further, specifically, the landscape portrait can be a ratio Hm / Hx between the number of pixels Hm of the area constituting the detected person and the number of pixels Hx of the other areas. For example, as shown in FIG. 17, the sixth function corresponding to the landscape portrait is configured such that the fifth correction value Re5 is calculated to be negatively larger as the landscape portrait is smaller.

  The second contrast correction value calculation unit 27 is configured to calculate the second contrast correction value Cr2 by adding the fifth correction value Re5 to the second correction value Re2. That is, the second contrast correction value Cr2 is calculated to be negatively larger as the scene portrait in the original image data is smaller.

  Hereinafter, the operation of the contrast correction processing unit 41 relating to the calculation of the second contrast correction value Cr2 will be described based on the flowchart of FIG. 18. Original image data is input to the memory 41 (SD1), and the density correction is performed. When the value Gamma is set (SD2), the landscape person degree calculation unit 15 detects a person included in the original image data (SD3), and the number of pixels Hm of the area constituting the detected person and The pixel number Hx of the area other than the above is calculated (SD4, SD5), and the ratio Hm / Hx between the pixel number Hm and the pixel number Hx is calculated as the landscape portrait (SD6). Then, a fifth correction value Re5 corresponding to the scene portrait is calculated from the sixth function shown in FIG. 17 (SD7).

  The second contrast correction value calculation unit 27 calculates a second correction value Re2 obtained from a second function composed of the density correction value Gamma corresponding to the shadow area shown in the above [Equation 4] ( SD8), the second contrast correction value Cr2 is calculated by adding the sixth correction value Re6 to the second correction value Re2 (SD9).

  In other words, when the original image data is a landscape image with a low landscape portrait such as no original person is included in the original image data, the shadow region is calculated by calculating the second contrast correction value Cr2 to be negatively large. By increasing the contrast in, the contrast in the shadow area is tightened, and an appropriate correction is performed in reproducing the landscape image.

  As shown in FIG. 19, the contrast correction processing unit 11 includes the backlight intensity calculation unit 13, the image color calculation unit 14, and the landscape person degree calculation unit 15, and the first contrast correction value calculation unit 16. Subtracts a third correction value Re3 corresponding to the degree of backlight from the first correction value Re1, and further adds a fourth correction value Re4 corresponding to the average chromaticity and average saturation to add the first correction value Re3. The second contrast correction value calculation unit 17 adds the fifth correction value Re5 corresponding to the scene person degree to the second correction value Re2 to calculate the second contrast correction value Cr1. The contrast correction value Cr2 may be calculated. It is possible to comprehensively reduce the compression state of the image in the highlight area, improve the omission of the highlight area, and tighten the contrast in the shadow area.

  Further, the contrast correction processing unit 11 is configured such that the result calculated or detected by the backlight intensity calculating unit 13, the image color calculating unit 14, and the landscape portrait calculating unit 15 is the first contrast correction value Cr1 or the first contrast correction value Cr1. A configuration in which the two contrast correction values Cr2 are mutually considered may be employed.

  For example, specifically, as shown in FIG. 20, the contrast correction processing unit 11 further includes an area density value average calculating unit 19 that calculates an average value of density values in a predetermined area in the original image data. Calculated or detected by the backlight intensity calculator 13, the image color calculator 14 and the landscape portrait calculator 15 based on the average density value in a predetermined area calculated by the area density average calculator 19 The calculated result may be mutually considered when calculating the first contrast correction value Cr1 or the second contrast correction value Cr2. Hereinafter, for the sake of convenience, the first contrast correction value calculation unit 16 will be referred to as a first contrast correction value calculation unit 56, and the second contrast correction value calculation unit 17 will be referred to as a second contrast correction value calculation unit 57. The processing unit 11 will be described as the contrast correction processing unit 51 with different reference numerals.

  For example, a description will be given of a case where a person is included in the original image data by the landscape person degree calculation unit 15 based on the flowchart of FIG. 21. The scene person degree calculation unit 15 adds the original image data to the original image data. When an included person is detected (SE1), the average value Ta of the density values of the detected person's area and the average value Tx of the density values of the entire original image data are calculated as the area density value average calculating unit 19. For example, in 8-bit data, the average value Ta of the density values of the person area is less than 100 gradations, and the average density value Tx of the whole original image data is 130 gradations or more. When the density value of the person is darker than (SE2), the second contrast correction value calculation unit 57 calculates the second contrast correction value Cr2 to be negatively larger. That (SE3). That is, the contrast correction processing unit 51 does not reach a backlight scene, but there is a bright background, and the contrast of the shadow area is increased when the density value of the person area is dark. Perform correction processing.

  In addition, an average value Ta of density values of the detected area of the person and an average value Tc of density values of the areas other than the detected person are calculated by the area density value average calculating unit 19, and the area of the person is calculated. The average value Ta of the density values is equal to or greater than a predetermined density value Tb (SE4), or the average value Ta of the density values of the person area is compared with the average value Tc of the density values of the areas other than the person. When brighter than the predetermined density value Td (SE5), the first contrast correction value calculation unit 56 calculates the first contrast correction value Cr1 to be small (SE6). That is, when the density value of the person is bright with respect to the peripheral density value of the person, the contrast correction processing unit 51 has the highlight information in order to relieve the density information of the person image. Contrast correction processing is performed so that the contrast of the region is reduced.

  On the other hand, when the average value Ta of the density values of the person area is darker than a predetermined density value Te as compared with the average value Tc of the density values of areas other than the person (SE7), the second contrast correction value calculation unit 57 calculates so that the second contrast correction value Cr2 becomes negatively larger (SE8). In other words, in the case of a backlight scene in which the density value of the person is dark with respect to the peripheral density value of the person, the contrast correction processing unit 51 makes the density information of the background portion fly out when the density value of the entire image is increased. Therefore, while the density correction processing itself is supposed to be suppressed, by increasing the contrast of the shadow portion, the density value of the person is brightened, and the density information of the background portion is suppressed from being skipped. .

  Further, the average value Ta of the density values of the person area is equal to or lower than a predetermined density value Tf (SE9), and the average value Ta of the density values of the person area and the average of the density values of the areas other than the person are included. When the difference from the value Tc is within the range of the predetermined density value Tg (SE10), the first contrast correction value calculation unit 56 calculates the first contrast correction value Cr1 so as to increase (SE11). That is, the contrast correction processing unit 51 increases the contrast of the highlight region in the case of an under-prone image in which both the density value of the person and the density value of the surrounding area are dark as well.

  Note that the above-described embodiment is merely an example of the present invention, and it is needless to say that the specific configuration and the like of each block can be changed and designed as appropriate within the scope of the effects of the present invention.

Explanatory drawing of functional block configuration in image processing unit Explanatory drawing of the external configuration of the photographic image processing apparatus Illustration of photo printer Explanatory drawing of functional block configuration of photographic image processing apparatus Explanatory drawing of density value transition in density correction processing (A) is explanatory drawing of the 1st function which consists of the density | concentration correction value Gamma corresponding to the highlight area | region for calculating a 1st correction value, (b) is a shadow area | region for calculating a 2nd correction value. Explanatory drawing of the 2nd function which consists of density correction value Gamma corresponding to (A) is explanatory drawing of density value transition in the contrast correction process based on the first contrast correction value, (b) is explanatory drawing of density value transition in the contrast correction process based on the second contrast correction value. Flow chart for explaining the operation of the image processing unit Explanatory drawing of the functional block structure in the image processing part in another embodiment provided with the backlight intensity calculation part Explanatory drawing of the peripheral pixel area and the central pixel area in the original image data Explanatory drawing of the 5th function for calculating 3rd correction value Re3 The flowchart for demonstrating the operation | movement concerning calculation of the 1st contrast correction value in another embodiment provided with the backlight intensity calculation part. Explanatory drawing of the functional block structure in the image processing part in another embodiment provided with the image color calculation part Explanatory drawing of blue area, green area, yellow area, red area, purple area, and low saturation area in PQ color space Flowchart for explaining an operation related to the calculation of the first contrast correction value in another embodiment provided with an image color calculation unit Explanatory drawing of the functional block structure in the image processing part in another embodiment provided with the landscape person degree calculation part Explanatory drawing of the 6th function for calculating 5th correction value Re5 The flowchart for demonstrating the operation | movement concerning calculation of the 2nd contrast correction value in another embodiment provided with the landscape person degree calculation part. Explanatory drawing of the functional block structure in the image processing part in another embodiment provided with the backlight intensity calculation part, the image color calculation part, and the landscape portrait degree calculation part Explanatory drawing of the functional block structure in the image processing part in another embodiment provided with the area | region density value average calculation part. The flowchart for demonstrating the operation | movement concerning calculation of the 1st contrast correction value and 2nd contrast correction value in another embodiment. Explanatory drawing of density histogram for calculating density correction value

1: Photo image processing apparatus 10: Density correction processing unit 11: Contrast correction processing unit 12: Area separation unit 13: Backlight intensity calculation unit 14: Image color calculation unit 15: Landscape portrait degree calculation unit 16: First contrast correction value calculation Unit 17: Second contrast correction value calculation unit 18: Process execution unit 19: Area density value average calculation unit

Claims (6)

Based on an exponential function with a predetermined density correction value as an index, the density range of pixels included in the original image data is expanded to a density range wider than the density range, and the density of the original image data captured by the digital camera is increased. An image processing apparatus comprising: a density correction processing unit that performs correction processing; and a contrast correction processing unit that performs contrast correction processing on the image data subjected to density correction processing by the density correction processing unit based on a predetermined contrast correction value. ,
The contrast correction processing unit
An area separation unit for separating the original image data into a highlight area brighter than a predetermined density value and a shadow area darker than the predetermined density value;
A backlight intensity calculating unit that calculates a ratio of the density average value of the peripheral pixel area to the density average value of the central pixel area of the original image data as the backlight intensity;
Using the density correction value as a variable, the first contrast correction value is calculated based on a predetermined quadratic function having a maximum value in the density correction value setting range and is calculated by the backlight intensity calculation unit. Based on the inverse brightness correction function that becomes a constant backlight intensity correction value when the ratio is less than the predetermined ratio and becomes gradually larger as the ratio increases when the ratio is equal to or greater than the predetermined ratio. A first contrast correction value calculating unit that calculates a backlight intensity correction value and calculates a value obtained by reducing the first contrast correction value by the backlight intensity correction value as a new first contrast correction value;
A second contrast correction value calculation unit that calculates the second contrast correction value based on a predetermined quadratic function that protrudes downward with the density correction value as a variable and having a minimum value in the setting range of the density correction value;
As the first contrast correction value is larger, the pixels corresponding to the highlight area are subjected to contrast correction processing so as to draw a large curve in which the density characteristic is convex upward, and the smaller the second contrast correction value is, the smaller the second contrast correction value is. An image processing apparatus comprising: a processing execution unit that performs contrast correction processing on pixels corresponding to the shadow area so as to draw a large curve with a density characteristic that protrudes downward . The contrast correction processing unit further includes an image color calculation unit that calculates average chromaticity and average saturation of the original image data,
The first contrast correction value calculation unit calculates a preset color correction value corresponding to the average chromaticity and the average saturation calculated by the image color calculation unit, and sets the first contrast correction value The image processing apparatus according to claim 1, wherein a value increased by the color correction value is calculated as a new first contrast correction value. The contrast correction processing unit further includes a landscape person degree calculation unit that calculates a ratio of a region area other than a person to a region area of a person included in the original image data as a scenery person degree.
The second contrast correction value calculation unit uses the ratio calculated by the landscape person degree calculation unit as a variable, and when the ratio is less than a predetermined ratio, gradually becomes a smaller landscape person degree correction value as the ratio decreases. A landscape portrait correction value is calculated based on a landscape portrait correction function that becomes a fixed landscape portrait correction value when the ratio is equal to or greater than the ratio, and the second contrast correction value is reduced by the landscape portrait correction value. The image processing apparatus according to claim 1, wherein the image processing apparatus calculates a new second contrast correction value. Based on an exponential function with a predetermined density correction value as an index, the density range of pixels included in the original image data is expanded to a density range wider than the density range, and the density of the original image data captured by the digital camera is increased. An image processing method comprising: a density correction step for performing a correction process; and a contrast correction step for performing a contrast correction process on the image data subjected to the density correction process in the density correction step based on a predetermined contrast correction value.
The contrast correction step includes
An area separation step of separating the original image data into a highlight area brighter than a predetermined density value and a shadow area darker than the predetermined density value;
A backlight intensity calculating step of calculating a ratio of the density average value of the peripheral pixel area to the density average value of the central pixel area of the original image data as the backlight intensity;
Using the density correction value as a variable, a first contrast correction value is calculated based on a predetermined quadratic function having a maximum value in the setting range of the density correction value and is calculated by the backlight intensity calculation step. Based on the inverse brightness correction function that becomes a constant backlight intensity correction value when the ratio is less than the predetermined ratio and becomes gradually larger as the ratio increases when the ratio is greater than the predetermined ratio. A first contrast correction value calculating step of calculating a backlight intensity correction value and calculating a value obtained by reducing the first contrast correction value by the backlight intensity correction value as a new first contrast correction value;
A second contrast correction value calculating step for calculating a second contrast correction value based on a predetermined quadratic function that protrudes downward with the density correction value as a variable and having a minimum value in a setting range of the density correction value;
As the first contrast correction value is larger, the pixels corresponding to the highlight region are subjected to contrast correction processing so as to draw a large curve in which the density characteristic is convex upward, and the smaller the second contrast correction value is, the smaller the second contrast correction value is. An image processing method comprising: a process execution step of performing a contrast correction process on pixels corresponding to the shadow area so as to draw a large curve having a downwardly convex density characteristic. The contrast correction step further includes an image color calculation step for calculating average chromaticity and average saturation of the original image data,
The first contrast correction value calculating step calculates a color correction value set in advance corresponding to the average chromaticity and the average saturation calculated by the image color calculating step, and calculates the first contrast correction value The image processing method according to claim 4, wherein a value increased by the color correction value is calculated as a new first contrast correction value. The contrast correction processing step further includes a landscape person degree calculation step of calculating a ratio of the area area other than the person to the area area of the person included in the original image data as the scenery person degree,
In the second contrast correction value calculation step, the ratio calculated in the landscape portrait calculation step is used as a variable, and when the ratio is less than a predetermined ratio, the landscape portrait correction value gradually becomes smaller as the ratio decreases. A landscape portrait correction value is calculated based on a landscape portrait correction function that becomes a fixed landscape portrait correction value when the ratio is equal to or greater than the ratio, and the second contrast correction value is reduced by the landscape portrait correction value. 6. The image processing method according to claim 4, wherein the image processing method is calculated as a new second contrast correction value.