JP4793292B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention calculates an automatic density correction based on a reference correction gamma curve generated based on a reference correction gamma curve generated so as to calculate a reference density value based on a characteristic value of an input image, and the reference density value becomes a target density value. And an image processing apparatus and an image processing method including a manual density correction operation unit that manually changes the reference density value with respect to a corrected image corrected by the automatic density correction unit, and particularly suitable for film image processing The present invention relates to an image processing apparatus and an image processing method.

  In general, the quality of photographic prints depends greatly on density and contrast. In particular, the photographic film has a large gradation reproduction range corresponding to different exposure amounts depending on various shooting conditions. In order to obtain a good photographic print, the photographic processing device automatically corrects the density and contrast. A density correction unit is provided.

  In such an automatic density correction unit, the average brightness, maximum brightness, minimum brightness, etc. calculated for each of a plurality of regions such as the entire image, the image center, and the top, bottom, left, and right of the image are based on the characteristic values of the input image, for example, multivariate A reference density value of the input image is calculated by an analysis method or the like, and a reference correction gamma curve is generated so that the reference density value becomes a preset target density value. When the input image is density-corrected with such a reference correction gamma curve, whiteout in the high luminance part and black crushing in the low luminance part are effectively suppressed, and a high-quality photo print is generated. Become.

  For example, Patent Document 1 sets a reference gamma curve and outputs the reference gamma curve as an image processing method for converting the luminance of each pixel constituting an input image into output luminance by a gamma curve. A data table is set for each of the above areas, which is divided into multiple areas based on the side reference, and defines the adjustment rate for changing the input luminance range that can be taken by the reference gamma curve with respect to the representative value of the image luminance. Then, the representative value of the luminance of the input image is obtained from the luminance of each pixel constituting the input image, and the adjustment rate corresponding to the input image is detected for each region from the obtained representative value and the data table. By applying an adjustment rate according to the input image to the input luminance range that the reference gamma curve can take, while maintaining the range of output luminance that the reference gamma curve can take, the reference and That the gamma curve shape to the compression or decompression of has been proposed an image processing method to connect the gamma curve of each region adjacent to each other.

  However, since the input image corrected by the above-described automatic density correction does not necessarily exhibit a preferable image characteristic, the reference density value for the corrected image corrected by the automatic density correction unit is stored in the image processing apparatus. A manual density correction operation unit for manually changing the color density is provided, and the manual density correction by the operator is possible.

Patent Document 2 discloses contrast correction based on Lo points (black points) and Hi points (white points) obtained from luminance histograms of RGB color components of a multi-valued image, and the following expression output = ((input / 255) ^ gamma) * Two automatic corrections of gamma correction are performed to correct according to the gamma value gamma by 255, and the Lo point (black point), Hi point (white point) and gamma value gamma are each manually operated with a slide bar. A technique for correcting the density is disclosed.
JP 2003-304398 A JP 2001-61075 A

  However, the manual correction according to Patent Document 2 can perform a correction operation with a high degree of freedom, but it is difficult to perform an optimal correction unless a skilled operator. Further, in the automatic density correction as described in Patent Document 1, if an image correction process is performed after newly generating a gamma curve corresponding to a manually corrected density value set by an operator, a very long calculation time is required. Therefore, there is a problem that the response is lowered and the operability is lowered. Therefore, in the conventional manual density correction, as shown in FIG. 12, contrast correction is performed by translating the gamma curve obtained by the automatic density correction as it is with respect to the manual correction density value set by the operator. It was. For this reason, there is a possibility that whiteout in a high luminance part and black crushing in a low luminance part may occur.

  The present invention has been made in view of the above-described conventional problems, and provides an image processing apparatus capable of performing appropriate contrast correction without causing a decrease in response in response to a density correction value by manual correction. Objective.

In order to achieve the above-described object, the characteristic configuration of the image processing apparatus according to the present invention calculates a reference density value based on a characteristic value of an input image as described in claim 1 of the claims, and Generated by parallel translation or expansion / contraction of a reference gamma curve prepared in advance on the coordinates with the input density as the horizontal axis and the output density as the vertical axis so that the reference density value becomes the target density value An automatic density correction unit that corrects the density of the input image based on a reference correction gamma curve, and a manual density correction operation unit that manually changes the reference density value for the correction image corrected by the automatic density correction unit. an image processing apparatus are, in the automatic density correction unit, manually changeable range least the manual density correction operation unit, the single addition of a predetermined positive or negative offset value to the reference concentration value or In response to the correction density value of the number, the corrected so that the concentration value becomes the target density value, a single or plurality of preliminary correction gamma move or stretch-processing parallel the reference gamma curve in the horizontal axis direction on the coordinate A preliminary density correction unit for generating a curve, and the input based on either the reference correction gamma curve or the preliminary correction gamma curve corresponding to the manually corrected density value manually changed via the manual density correction operation unit A manual density correction unit for correcting the density of the image is provided.

According to the above configuration, when the automatic density correction process is executed by the automatic density correction unit, the preliminary density correction unit provided in the automatic density correction unit can at least be manually changed by the manual density correction operation unit. A single or a plurality of preliminary correction gamma curves are generated in advance corresponding to a single or a plurality of correction density values obtained by adding a predetermined positive or negative offset value to the reference density value. When the density correction input is made from the unit, the manual density correction unit promptly performs the correction process based on either the already generated reference correction gamma curve or preliminary correction gamma curve.

  According to the second characteristic configuration described in the second aspect, in addition to the first characteristic configuration described above, the manual density correction unit may calculate the manual correction density value from the reference correction gamma curve or the preliminary correction gamma curve. The gamma curve closest to is selected, and the input image is subjected to density correction based on the selected gamma curve.

  According to the above configuration, since the gamma curve closest to the manual correction density value is selected by the manual density correction unit, it is corrected to an inconvenient contrast such as whiteout in a high luminance part or black crushing in a low luminance part. There is no such a situation.

  According to the third feature configuration, in addition to the first or second feature configuration described above, the manual density correction unit may be configured so that the manual density correction unit performs the manual correction from the reference correction gamma curve or the preliminary correction gamma curve. Two gamma curves closest to the corrected density value are selected, a new gamma curve is generated by interpolation from the selected gamma curve, and the input image is density corrected based on the gamma curve.

  According to the above-described configuration, an optimum gamma curve for the manual correction density value is interpolated from the two front and rear gamma curves closest to the manual correction density value, so that more preferable contrast correction can be realized.

  In the fourth feature configuration, as described in claim 4, in addition to any of the first to third feature configurations described above, the preliminary density correction unit may include a predetermined range before and after the reference density value. Among them, a preliminary correction gamma curve is generated for a plurality of density values.

  When the operator performs density correction operation via the manual density correction operation unit, the density is extremely different from the reference density, regardless of whether the density is corrected with respect to the reference density calculated by the automatic density correction unit. It is rare to correct it. Therefore, if a preliminary correction gamma curve is generated for a plurality of density values within a predetermined range before and after the reference density value by the preliminary density correction unit, it can sufficiently cope with manual density correction, resulting in an increase in calculation load. There is no need to generate a preliminary correction gamma curve.

Structure of the image processing method according to the invention, as described in the claim 5, calculates a reference density value based on the characteristic values of the input image, as the reference density value becomes the target density value, input density The input image is subjected to density correction based on a reference correction gamma curve generated by parallel translation or expansion / contraction processing of a reference gamma curve prepared in advance on a coordinate having the horizontal axis as the horizontal axis and the output density as the vertical axis. An image processing method comprising: an automatic density correction step; and a manual density correction operation step for manually changing the reference density value with respect to the corrected image corrected by the automatic density correction step. , manually changeable range least the manual density correction operation unit, corresponding to single or multiple corrected density value plus a positive or negative predetermined offset value to the reference density value Te, wherein as corrected density value becomes the target density value, preliminary density correction step of producing a single or multiple pre-compensation gamma curve has been moved or stretching process parallel the reference gamma curve in the horizontal axis direction on the coordinate A manual density correction step for correcting the density of the input image based on either the reference correction gamma curve or the preliminary correction gamma curve corresponding to the manually corrected density value manually changed in the manual density correction operation step. It is in the point to have.

  As described above, according to the present invention, it is possible to provide an image processing apparatus capable of performing appropriate contrast correction without causing a decrease in response in response to a density correction value by manual correction.

  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 operation station 3 is configured to input and set print order information for a photographic image as an input original image, and to perform various image correction processes including image processing according to the present invention. The print data edited from is output to the photo printer 2 Nozomu of the photographic print is generated.

  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 (hereinafter referred to as a “GUI unit”) that generates a graphic operation screen for displaying an icon for use or generates various control commands based on input operations from the keyboard 35 and mouse 36 to the displayed graphic operation screen. 42) and the picture. Photo image data transferred from the input unit 40, photo image data after correction processing by the image processing unit 47, which will be described later, correction parameters at that time, and set print order information are partitioned into predetermined areas and stored. A memory 41, an order processing unit 43 for generating print order information, an image processing unit 47 for performing density correction processing and contrast correction processing on each photographic image data stored in the memory 41, and the graphic user A display control unit 46 including a video RAM for displaying the image data and various input / output graphic data developed in the memory 41 based on a display command from the interface unit 42 on the monitor 34; Print for outputting the final corrected image after the correction processing to the photographic printer 2 A print data generating unit 44 that generates over data, 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 distortion caused by the photographing lens. A distortion correction unit 11 that corrects the image, a sharpening processing unit 12 that enhances the edges of the image to reduce noise, a color correction processing unit 13 that corrects the color tone of the image, and an enlargement / reduction process that converts the image size to the size of the photo print A part 14 and the like are provided.

  The density correction processing unit 10 calculates a reference density value based on a characteristic value of the input image, and density corrects the input image based on a reference correction gamma curve generated so that the reference density value becomes a target density value. Automatic density correction unit 10a for performing manual density correction operation unit 10d for manually changing the reference density value for the corrected image corrected by automatic density correction unit 10a, and manual operation via manual density correction operation unit 10d. A manual density correction unit 10c is provided for correcting the density of the input image corresponding to the changed manual correction density value.

  The automatic density correction unit 10a further includes a preliminary density correction unit 10b that generates a single or a plurality of preliminary correction gamma curves corresponding to a single correction density value or a plurality of correction density values different from the reference density value. The density correction unit 10c corrects the density of the input image based on either the reference correction gamma curve or the preliminary correction gamma curve corresponding to the manually corrected density value manually changed through the manual density correction operation unit 10d. It is configured.

  The density correction processing unit 10 will be described in detail below based on the flowchart shown in FIG. The automatic density correction unit 10a calculates the characteristic value (SA) of the input image read in the prescan mode by the film scanner 31 and stored in the memory 41 (SA1).

As characteristic values, as shown in FIGS. 10A to 10E, the average density, the maximum density, the minimum density, and the density average deviation of the entire input image, the average of the central portion and the peripheral portion where the main subject of the input image is located. Density, maximum density and minimum density, average density and maximum density and minimum density on the left and right sides of the input image, average density and maximum density and minimum density on the upper and lower sides of the input image The average value of the difference between the average densities of blocks adjacent to each other in the upper and lower sides of each region divided into blocks by the pixel size is calculated. Here, the density is a luminance component of a YCC signal indicating a luminance color difference calculated based on [Equation 1] from R (red), G (green), and B (blue) components of a pixel constituting an input image. Y means, for example, the average density of the entire input image indicates the average value of the luminance component of each pixel. In addition, as the density, an average value of R (red), G (green), and B (blue) components of pixels constituting the input image may be used.

The automatic density correction unit 10a, multivariate analysis of the calculated characteristic values and variables, here calculates the appropriate reference density value D _SI by multiple regression analysis (SA3). That is, a correlation coefficient between the above-described image characteristic value and an appropriate reference density value corrected by manual correction or the like is obtained in advance for a plurality of sample images, and the characteristics of the newly input image are obtained. An appropriate reference density value _DSI of the image is calculated from the value. As a method for calculating the reference density value _DSI from the characteristic value of the input image, other estimation methods such as a neural network can be used in addition to the multivariate analysis.

Next, the automatic density correction unit 10a has a two-dimensional plane in which the horizontal axis shown in FIG. 5A is the density of the input image, the vertical axis is the conversion density to the output image, and the number of pixels of the input image (frequency). The reference gamma curve γ _b prepared for each film type is translated so that the reference density value _DSI becomes a preset target density value _DSO, and the reference gamma curve γ _b is input. Range Rng which is the upper limit side and lower limit side of the envelope connecting the peak values of the density histogram of the image (indicated by the symbol HG), or the number of pixels of several percent of the total number of pixels from the upper limit side and the lower limit side The reference correction gamma curve γ _S subjected to the expansion / contraction processing so as to enter is generated, and the reference correction gamma curve γ _S is stored in the memory 41 (SA4).

Such a reference correction gamma curve γ _S is actually in the form of a lookup table in which the relationship between Din and Dout along the reference correction gamma curve γ _S is tens of points, specifically 20 points. Generated. Accordingly, the density of an arbitrary pixel constituting the input image is converted into an output pixel subjected to contrast correction based on the lookup table, and intermediate value pixels not defined in the lookup table are converted into those in the lookup table. Linear interpolation is performed between the previous and next values.

The preliminary density correction unit 10b provided in the automatic density correction unit 10a has a predetermined positive or negative offset to the reference density _DSI when the lookup table based on the reference density value _DSI is generated. Four or more corrected density values, in this case, D _SI−− , D _SI− , D _{SI +} , D _{SI ++} are calculated, and the corrected density values D _SI−− , D _{In the same} manner as described above, the reference gamma curve γ _b is translated in the direction of the horizontal axis and expanded and contracted so that each of _SI− , D _{SI +} , and D _{SI ++ has} the above target density value _DSO . A lookup table indicating the preliminary correction gamma curves γ ₋₋ , γ ₋ , γ ₊ , γ ₊₊ as shown by the alternate long and short dash line in (b) is generated and stored in the memory 41 (SA5).

When pre-correction gamma curve is generated by the preliminary density correction unit 10b, the automatic density correction unit 10a an image density and contrast correction based on a lookup table of the reference correction gamma curve gamma _S to the input image Automatic contrast correction processing displayed on the monitor 34 is executed (SA6, SA7).

When the operator who has evaluated the corrected image displayed on the monitor 34 determines that further correction is preferable, a density correction operation is performed via the manual density correction operation unit 10d (SA8). The manual density correction operation unit 10d is based on a correction input from a density correction key provided on the keyboard 35 or a correction input operated by the mouse from the density correction soft key displayed on the monitor 34 via the GUI unit 42. A value obtained by adding or subtracting a preset correction value to the reference density _DSI is generated as a manual correction density value. For example, four values for setting whether to correct a unit correction value preset for the current reference density value _{DSI on} the keyboard 35 in one or two steps of brightening or darkening are set. A density correction key is provided, and the manual density correction operation unit 10d recognizes which key is operated, and generates corresponding manual correction density values _DSIM-- , _DSIM- , _{DSIM +} , _{DSIM ++} . It can be constituted as follows.

The manual density correction unit 10c, gamma curve gamma generated by the automatic density correction unit _{10a -, γ -, γ S} , γ +, manually recognized by the manual density correction operating section 10d from gamma ₊₊ corrected density value by selecting a gamma curve as a value closest to the target density value D _SO described above, is displayed on the monitor 34 by correcting the input image based on the gamma curve selected (SA9, SA10).

For example, in the case shown in FIG. 6 (a), the gamma curve γ closest to the manually corrected density value D _{SIM +} corrected by one level brighter than the reference density value D _SI by the manual density correcting unit 10c. _{When +} is selected, the input image is corrected and displayed on the monitor 34.

  As a result, when it is determined that the operator has obtained an appropriate image (SA11), information for specifying a density correction gamma curve for the input image, that is, a correction parameter is stored in the memory 41 in association with the input image ( (SA12), density and contrast correction is performed on the input image read in the above-described main scan mode based on the gamma curve specified by the correction parameter (SA13).

  The corrected image is returned to the pixel data of the R (red), G (green), and B (blue) components by the inverse transformation operation of [Equation 1].

  According to the above-described configuration, it is not necessary to generate a new gamma curve every time the density correction operation is performed by the operator, so that manual correction processing with good key response can be realized.

The preliminary density correction unit 10b is within a predetermined range around the reference density value _{D SI,} i.e., the manual density correction operation unit maximum and minimum settings operable 10d manually corrected density value _{D SIM-- D} substantially _{SIM ++} Any method may be used as long as it generates a preliminary correction gamma curve for a single or a plurality of correction density values _DSI within a corresponding range. Alternatively, the manual correction density value and the correction density value may be configured to match.

  Although not described in detail, the image processing unit 47 outputs to the photographic printer 2 after performing distortion correction processing, sharpening processing, color correction processing, and enlargement / reduction processing in addition to the above-described density correction processing. A photo print is generated.

Hereinafter, another embodiment will be described. In the above-described embodiment, as shown in step SA9, the case where the manual density correction unit 10c selects and corrects one gamma curve generated in advance corresponding to the manual density correction operation has been described. The correction unit 10c has two gamma curves before and after the reference correction gamma curve γ _S or the preliminary correction gamma curves γ ₋₋ , γ ₋ , γ ₊ , γ ₊₊ closest to the manual correction density value D _SIM , that is, the manual correction density. value selects the two gamma curve of the gamma curve close and the next gamma curve becomes a value closest to the target density value D _SO described above, interpolated generates a new gamma curve from gamma curve selected, the gamma curve The input image may be configured to correct the density.

For example, as shown in FIGS. 7A and _7B , the gamma curves γ ₋₋ and γ ₋ are selected as the closest two gamma curves before and after the manually corrected density value D _SIM− , and FIG. as shown in a), so that the manual correction density value D _SIM-becomes the target density value D _sO, is to generate a new gamma curve γ'that linear interpolation the two gamma curve. FIG. 8B shows how the gamma curve γ ′ is interpolated based on the gamma curves γ ₋₋ and γ ₋ .

  In this case, the calculation time for generating a new gamma curve γ ′ does not take so long, so that manual correction processing with good key response and excellent correction characteristics can be realized.

In the embodiment described above, the automatic density correction unit 10a translates the reference gamma curve γ _b prepared in advance in the horizontal axis direction so that the reference density value _DSI becomes a preset target density value _DSO. The method of generating the reference correction gamma curve γ _S as shown in FIG. 5A after the expansion / contraction processing has been described, but the method of generating the reference correction gamma curve γ _S is limited to such a method. Instead, for example, a method described in detail in Japanese Patent Laid-Open No. 2003-304398 may be adopted.

  Specifically, an image processing method for converting the luminance of each pixel constituting an input image into an output luminance using a gamma curve, wherein the reference gamma curve is set and the reference gamma curve is set on the output side. A data table that divides into multiple areas by reference and sets the adjustment rate for changing the input luminance range that can be taken by the reference gamma curve with respect to the representative value of image brightness is set for each area and input The representative value of the brightness of the input image is obtained from the brightness of each pixel constituting the image, the adjustment rate corresponding to the input image is detected from the obtained representative value and the above data table for each area, and the reference gamma is obtained for each area. The output luminance range that can be taken by the curve is fixed, and the adjustment rate according to the input image is applied to the input luminance range that can be taken by the reference gamma curve. Jo is compressed or extended, and it is to generate so as to connect the gamma curve of each region adjacent to each other.

Further, the automatic density correction unit 10a calculates a gamma Gamma value based on [Equation 2] so that the reference density value _DSI becomes a preset target density value _DSO, and based on the value, A reference correction gamma curve γ _S as shown in FIG. 11A may be generated based on [Equation 3] and stored in the memory 41.

In [Expression 2], Max is the maximum density value that the input image can take, that is, the density value of the brightest pixel, and Min is the density that the input image can take, as shown in FIG. The minimum value, that is, the darkest pixel density value. Accordingly, when the pixel component of the input image is represented by 8 bits, the density is expressed from 0 gradation (Min) to 255 gradation (Max). In the figure, a curve indicated by reference numeral HG represents a density histogram of an input image with the vertical axis representing the frequency.

  In [Equation 3], L is the maximum value of the density conversion value that can be taken by the input image. For example, when density conversion is performed between 0 gradation and 255 gradation in 8 bits, 255 is obtained. It becomes. Max is the maximum density value that the input image can take, and Min is the minimum density value that the input image can take. I indicates a pixel number.

  The gamma curve shown in [Equation 3] is a theoretical formula. In practice, the relationship between Din and Dout along the gamma curve is generated in the form of a look-up table composed of several tens of points, specifically 20 points. Is done. Accordingly, the density of an arbitrary pixel constituting the input image is converted into an output pixel subjected to contrast correction based on the lookup table, and intermediate value pixels not defined in the lookup table are converted into those in the lookup table. Linear interpolation is performed between the previous and next values.

Then, the automatic density correction unit preliminary density correction unit 10b provided in 10a, when the look-up table based on the reference density value D _SI mentioned above is generated, a predetermined positive or negative to the reference density D _{SI Are} calculated, and four corrected density values D _SI-- , D _SI- , D _{SI +} , D _{SI ++} are calculated, and the corrected density value D _SI-- , D _SI− , D _{SI +} , D _{SI ++} , the gamma Gamma value is calculated based on [Equation 2] so that the above-mentioned target density value _DSO is obtained. Based on the above, a lookup table showing preliminary correction gamma curves γ ₋₋ , γ ₋ , γ ₊ , γ ₊₊ as shown by a one-dot chain line in FIG. 11B is generated and stored in the memory 41. Stuff It may be.

  In the above-described embodiment, the image processing apparatus and the image processing method according to the present invention are applied to the photographic image processing apparatus. However, the present invention is not limited to those incorporated in such a dedicated machine. The image processing method according to the present invention can be configured by a personal computer, a digital camera, or the like installed with an application program.

  An application program is a computer that calculates a reference density value based on a characteristic value of an input image, and corrects the density of the input image based on a reference correction gamma curve generated so that the reference density value becomes a target density value. And an image processing program that functions as a manual density correction operation unit that manually changes the reference density value with respect to the corrected image corrected by the automatic density correction unit. Preliminary density correction unit that generates single or multiple preliminary correction gamma curves corresponding to different single or multiple correction density values, and manual correction density values manually changed via the manual density correction operation unit And function as a manual density correction unit for correcting the density of the input image based on either the reference correction gamma curve or the preliminary correction gamma curve. That is an image processing program.

  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.

Functional block diagram of the image processing unit Explanatory drawing of the external configuration of the photographic image processing apparatus Illustration of photo printer Functional block diagram of photographic image processing device (A) is a characteristic diagram of a reference correction gamma curve generated by automatic density correction processing, and (b) is a characteristic diagram of a preliminary correction gamma curve generated by automatic density correction processing. (A) is explanatory drawing which shows the relationship between a manual correction | amendment density value and a preliminary | backup correction gamma curve, (b) is the characteristic figure of the gamma curve selected corresponding to the manual density correction value. (A) is explanatory drawing which shows the relationship between a manual correction density value and a preliminary | backup correction gamma curve, (b) is a characteristic figure of the original gamma curve produced | generated by interpolation corresponding to a manual correction density value Characteristic diagram of gamma curve generated by interpolation corresponding to manually corrected density value The flowchart which shows a density | concentration correction process. Area explanatory diagram of target image for which image characteristic value is calculated 4A and 4B show a characteristic diagram of a reference correction gamma curve generated by automatic density correction processing, and FIG. 5B shows a characteristic diagram of a preliminary correction gamma curve generated by automatic density correction processing. Characteristic diagram of gamma curve used in conventional manual density correction

1: Photo image processing apparatus 10: Density correction processing unit 10a: Automatic density correction unit 10b: Preliminary density correction unit 10c: Manual density correction unit 10d: Manual density correction operation unit 47: Image processing unit

Claims (5)

A reference density value is calculated based on the characteristic value of the input image, and a reference prepared in advance on coordinates where the input density is the horizontal axis and the output density is the vertical axis so that the reference density value becomes the target density value. An automatic density correction unit that corrects the density of the input image based on a reference correction gamma curve generated by parallel translation or expansion / contraction processing of the gamma curve in the horizontal axis direction, and a corrected image corrected by the automatic density correction unit An image processing apparatus comprising a manual density correction operation unit for manually changing the reference density value,
The automatic density correction unit corresponds to one or a plurality of correction density values obtained by adding a predetermined positive or negative offset value to the reference density value within a range that can be manually changed by at least the manual density correction operation unit. A preliminary density correction unit that generates one or a plurality of preliminary correction gamma curves obtained by translating or expanding the reference gamma curve in the horizontal axis direction on the coordinates so that the correction density value becomes a target density value. A manual density correction unit for correcting the density of the input image based on either the reference correction gamma curve or the preliminary correction gamma curve corresponding to the manually corrected density value manually changed via the manual density correction operation unit An image processing apparatus.   2. The manual density correction unit selects a gamma curve closest to the manual correction density value from the reference correction gamma curve or the preliminary correction gamma curve, and corrects the density of the input image based on the selected gamma curve. Image processing apparatus.   The manual density correction unit selects the two front and rear gamma curves closest to the manual correction density value from the reference correction gamma curve or the preliminary correction gamma curve, and generates a new gamma curve by interpolation from the selected gamma curve, The image processing apparatus according to claim 1, wherein the density of the input image is corrected based on the gamma curve.   The image processing apparatus according to claim 1, wherein the preliminary density correction unit generates a preliminary correction gamma curve for a plurality of density values within a predetermined range before and after the reference density value. A reference density value is calculated based on the characteristic value of the input image, and a reference prepared in advance on coordinates where the input density is the horizontal axis and the output density is the vertical axis so that the reference density value becomes the target density value. An automatic density correction step for correcting the density of the input image based on a reference correction gamma curve generated by parallel translation or expansion / contraction processing of the gamma curve in the horizontal axis direction, and a correction image corrected by the automatic density correction step An image processing method comprising a manual density correction operation step for manually changing the reference density value,
The automatic density correction step corresponds to one or a plurality of corrected density values obtained by adding a predetermined positive or negative offset value to the reference density value within a range that can be manually changed by at least the manual density correction operation unit. A preliminary density correction step for generating a single or a plurality of preliminary correction gamma curves obtained by translating or expanding the reference gamma curve in the horizontal axis direction on the coordinates so that the correction density value becomes a target density value. A manual density correction step for correcting the density of the input image based on either the reference correction gamma curve or the preliminary correction gamma curve corresponding to the manually corrected density value manually changed in the manual density correction operation step. Image processing method.

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