JP2007074373A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of acquiring images of a high-definition workmanship prints superior in color reproducibility, even if the image is the one for a scene recorded at foot and shoulder regions on the characteristic curve of a film, and to provide an image processing method. <P>SOLUTION: The image processing apparatus applies predetermined image processing to input image data, obtained by optically reading an image recorded on a film by at least three primary colors of red, green, and blue, and acquires output image data for output. The density of each color in three primary colors for each pixel at the input image data is compared with the characteristic curve for three primary colors of the film. As for an input image data, having density of each color in three primary colors for a pixel located at a foot or a shoulder region of the characteristic curve, the amount of density correction of each color is established so as to obtain a proper color balance, and a compression condition of a dynamic range is established. As for an input image data other than the above, a compression condition of a dynamic range is established, without establishing the amount of correction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method for finishing an image or the like recorded on a film into an appropriate photographic print or the like, and in particular, color reproducibility regardless of the density range of an image recorded on a film. The present invention relates to an image processing apparatus and an image processing method capable of obtaining an image such as an excellent high-quality finished print.

  Conventionally, when printing on paper (printing paper) with a limited reproduction density range from media with a wide dynamic range of shooting brightness such as film, the image recorded on the film is appropriate for photographic printing etc. Various image processing is performed for finishing (see Patent Document 1 and the like).

For example, an image processing method called hypertone processing is used to finish a film image into an appropriate photographic print.
Hypertone processing separates input image data into low-frequency components and high-frequency components, performs gradation expansion on the low-frequency components, and further adds input image data to the image data with the expanded gradation. By adding the image processing, the gradation can be extended without impairing the sharpness of the image. Hypertone processing can reduce loss of highlights and shadows, especially when printing on media with a wide dynamic range of shooting brightness, such as film, on paper (printing paper) with a limited reproduction density range. .

6A is a block diagram showing a conventional image processing apparatus that performs hypertone processing, and FIG. 6B is a conversion table of a lookup table (LUT) in the conventional image processing apparatus of FIG. 6A. It is a graph which shows.
As shown in FIG. 6A, a conventional image processing apparatus 110 that performs hypertone processing includes a light / dark signal generation unit 112, a blurred image generation unit 114, a lookup table (hereinafter referred to as LUT) 116, and image analysis. Part 117 and adder 118. The input image data is obtained by reading a film on which a subject image is recorded with a scanner, and the pre-scan data is data obtained by reading at a resolution lower than that of the input image data.

The light / dark signal generation unit 112 generates binary light / dark image data (Y) from image data of each color of R, G, B of input image data (S _R , S _G , S _B ). The bright / dark image data (Y) is created, for example, by taking one third of the average value of the image data (S _R , S _G , S _B ) of each color of R, G, B. That is, the bright / dark image data is created by Y = (S _R + S _G + S _B ) / 3.

  The blurred image generation unit 114 obtains a low-frequency component (Y_b) (hereinafter referred to as blurred image data (Y_b)) of the light / dark image data created by the light / dark signal generation unit 112.

  The LUT 116 performs image processing on the blurred image data (Y_b) obtained by the blurred image generation unit 114 to create compression processing image data for compressing the dynamic range of the input image data. In the LUT 116, for example, as shown in FIG. 6B, a conversion table represented by a straight line 120 having a constant inclination is set. By this LUT 116, the density of the bright part of the image is added and the density of the dark part of the image is subtracted. Further, the central density of the image of the main subject or the like does not change.

  The image analysis unit 117 performs image analysis on the prescan data and sets a conversion table of the LUY 116 according to the scene.

The adder 118 adds the input image data (S _R , S _G , S _B ) and the blurred image data (Y_b) processed by the light / dark signal generation unit 112, the blurred image generation unit 114, and the LUT 116. . Thereby, output image data (O _R , O _G , O _B ) in which the dynamic range of the main image data is compressed is created.
Here, the relationship between the output image data (O _R , O _G , O _B ) and the input image data (S _R , S _G , S _B ) is expressed as the following mathematical formulas (1) to (3). Can do. In the following mathematical formulas (1) to (3), LUT (Y_b) indicates that blurred image data has been input to the conversion table.

_{O R = S R + LUT (} Y_b) ··· Equation (1)

O _G = S _G + LUT (Y_b) (2)

O _B = S _B + LUT (Y_b) (3)

In the conventional hypertone processing, the input image data is added to the blurred image data obtained by processing the input image data by the light / dark signal generation unit 112, the blur image generation unit 114, and the LUT 116. As shown in FIG. 7, the dynamic range of the data is compressed nonlinearly, and as shown in FIG. 7, the input image data 130a having the high-density side medium-frequency component 132a and the low-density side medium-frequency component 134a The output image data 130b in which the medium high frequency component 132b and the low density side medium high frequency component 134b are maintained can be obtained. In this way, the dynamic range of the output image data 130b, and the gradation and density of the bright part and the dark part are made appropriate. Therefore, a photographic print in which a high-quality image is reproduced can be obtained.
Further, in the conventional hypertone processing, as shown in the above formulas (1) to (3), the R, G, and B colors are changed by the same amount, the hue does not change, and the processing without feeling uncomfortable is performed. be able to.

Other image processing apparatuses using such hypertone processing have been proposed (see Patent Document 1).
Patent Document 1 discloses an image reproduction method for reproducing a digital image signal representing a color image as a visible image. In the image reproduction method of Patent Document 1, a digital image signal is converted into a light / dark signal, and a blurred image signal representing a blurred image of a color image is created based on the light / dark signal. Then, a difference signal is obtained by performing subtraction between the signals for the pixels corresponding to the digital image signal and the blurred image signal. The difference signal is subjected to predetermined image processing to obtain a processed image signal. By using this processed image signal, the contrast of the entire image is weakened, but the local contrast represented by the high-frequency component can produce a photographic print similar to the color image that is the original image. .

Japanese Patent No. 3568279

  In this way, conventionally, when the density range of the image signal is wider than the reproducible range of reproduction media such as photographic paper, only the low frequency component is extracted and compressed, so that the whole is compressed while maintaining the middle high frequency component And can be reproduced.

  However, when processing an image signal obtained by photoelectrically reading an image recorded on a negative film, as shown in FIG. 8, the exposure amount (the exposure amount is shown in logarithm) and density in the negative film In the red (R) characteristic curve 140, the G (green) characteristic curve 142, and the B (blue) characteristic curve 144 indicating the relationship, the foot α and the shoulder β of the characteristic curves 140, 142, and 144 The color balance of R, G, and B is broken. For this reason, when the recording density range of the image recorded on the negative film is wide and covers the foot part α and the shoulder part β of the film, the color balance of R, G, B is broken and recorded. In this way, when an image recorded with the color balance lost is compressed to the reproduction range of the photographic paper, the subject (recorded image) recorded on the film may be reproduced with a color different from the original color. There is. That is, there is a possibility that a color failure occurs. At present, no such color reproducibility is considered.

  The object of the present invention is to solve the problems based on the prior art, and even if the recorded image has the density of the foot and shoulder areas on the characteristic curve of the film, the color reproducibility is high. An object of the present invention is to provide an image processing apparatus and an image processing method capable of obtaining an image such as an excellent high-quality finished print.

  To achieve the above object, according to a first aspect of the present invention, there is provided a predetermined image as input image data obtained by photoelectrically reading an image recorded on a film with at least three primary colors of red, green, and blue. An image processing apparatus that performs processing to obtain output image data for output, and includes processing means for performing compression processing of a dynamic range of the input image data, and the processing means has a dynamic range of the input image data. A setting unit for setting compression conditions; the setting unit refers to a film database in which the characteristic curves of the three primary colors of the film are recorded for each type of film, and the film database. A characteristic curve of the three primary colors of the recorded film is obtained, and the characteristic curve of the three primary colors of the film and the density of each of the three primary colors of each pixel of the input image data In the input image data, the density of each of the three primary colors of the pixels is at the foot or shoulder of the characteristic curve so that the color balance is appropriate based on the characteristic curve. An image analysis unit that sets a correction amount of the density of each color and sets the compression condition of the dynamic range using the correction amount, and the image analysis unit has a density of each of the three primary colors of the pixel as described above. An object of the present invention is to provide an image processing apparatus characterized in that the compression condition of the dynamic range is set without setting a correction amount for a characteristic curve that is not a foot or a shoulder.

  In the present invention, the processing means is a creation means for creating bright and dark image data of the input image data, an extraction means for extracting a low frequency component of the bright and dark image data, and a compression condition set by the setting unit. Compression processing image data creating means for creating compression processing image data for compressing the input image data with a compression amount based on the low frequency component and the correction amount; and the compression processing image data; An adder for adding the input image data is preferably provided.

  Further, in the present invention, the processing means extracts a low-frequency component of the light / dark image data, creating means for creating light / dark image data of the input image data based on the input image data and the correction amount. Extraction processing; and compression processing image data creation means for creating compression processing image data for compressing the input image data with a compression amount based on the compression condition set by the setting unit, from the low frequency component; It is preferable that an adder that adds the image data for compression processing and the input image data is provided.

  Further, the second aspect of the present invention is to perform predetermined image processing on input image data obtained by photoelectrically reading an image recorded on a film with at least three primary colors of red, green, and blue, and for output. The image processing method for generating the output image data includes: specifying a density of each pixel of the input image data; specifying a film type on which the image is recorded; and specifying the three primary colors of the specified film. The characteristic curve is compared with the density of each of the three primary colors of each pixel of the input image data, and the characteristic of each of the three primary colors of the pixel at the foot or shoulder of the characteristic curve For the step of setting the correction amount of the density of each color so that the color balance is appropriate based on the curve, and the case where the density is on the foot or shoulder of the characteristic curve, using the correction amount information, The input image data If the density of each of the three primary colors of the pixel is not the foot or shoulder of the characteristic curve, set the dynamic range compression condition without setting the correction amount. And an image processing method characterized by comprising a step of compressing the dynamic range of the input image data in accordance with the set dynamic range compression condition.

  In the present invention, the step of setting the correction amount includes a step of creating bright and dark image data of the input image data and a step of extracting a low frequency component of the bright and dark image data after the step of setting the correction amount, The step of performing compression processing of the dynamic range of the image data is based on the low-frequency component and the correction amount for the compression processing image data for compressing the input image data with the compression amount based on the compression condition of the dynamic range. It is preferable that the image data for compression processing and the input image data are added.

  Further, in the present invention, a step of creating the light / dark image data based on the input image data and the correction amount is provided as a subsequent step of the step of setting the correction amount, and further, the light / dark image data A step of extracting a low frequency component of the image data and a step of compressing the dynamic range of the input image data include compression processing image data for compressing the input image data with a compression amount based on a compression condition of the dynamic range. Is preferably created based on the low-frequency component and adding the compression image data and the input image data.

  According to the image processing apparatus and the image processing method of the present invention, input image data obtained by photoelectrically reading an image recorded on a film with at least three primary colors of red, green, and blue, and an image are recorded. Compared to the characteristic curves of the three primary colors of the film, the color balance of the input image data that has the density of each of the three primary colors of the pixels at the foot or shoulder of the characteristic curve is based on the characteristic curve. Set the correction amount of the density of each color so that is appropriate, and set the compression condition of the dynamic range using this correction amount, and the density of each color of the three primary colors of the pixel is at the foot or shoulder of the characteristic curve For those that do not, the dynamic range compression condition is set without setting the correction amount, so that the image recorded on the film becomes the foot and shoulder areas of the film characteristic curve. Be one having a degree can be suppressed the occurrence of color failure to obtain an image such as a high-quality finished prints color reproducibility is excellent.

The image processing apparatus and the image processing method of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a block diagram showing a first embodiment of a printing system having an image processing apparatus of the present invention.
As shown in FIG. 1, the printing system 10 according to the present exemplary embodiment includes an input device 12 a, a receiving device 12 b, an operation unit 13, an image processing device 16, and a printer 18. The input device 12a and the receiving device 12b are connected to the image processing device 16, and the image processing device 16 and the printer 18 are further connected.

The input device 12 a photoelectrically reads an image of a subject photographed on a film and acquires input image data as digital image data. The input image data is output to the image processing device 16.
The input machine 12a is, for example, a scanner. This scanner is a device that photoelectrically reads images shot on a film one by one, and separates the light source, variable aperture, and images into the three primary colors R (red), G (green), and B (blue). A color filter plate that has three color filters of R, G, and B to rotate and acts on the optical path by rotating any color filter, and the reading light incident on the film is made uniform in the plane direction of the film A diffusion box, an imaging lens unit, a CCD sensor that is an area sensor that reads an image of one frame of film, an amplifier (amplifier), and R, G, and B output signals are converted into A / D (analog / digital). ) And a data processing unit (not shown) for performing conversion, log conversion (density conversion), DC offset correction, dark correction, shading correction, and the like.

  In addition, the scanner can be mounted on the main body of the scanner according to the type of film, such as a new photo system (Advanced Photo System) or 135-size negative (or reversal) film, the size, strips, slides, etc. A dedicated carrier that can be mounted is prepared, and various films can be handled by replacing the carrier. An image (frame) photographed on a film and used for print creation is conveyed and held at a predetermined reading position by this carrier.

The carrier corresponding to the 135 size film is provided with reading means for reading the DX code. Thereby, the sensitivity of the film, the number of shots, the frame number, the type of film, and the like can be read. Of these various types of information, at least the film type is output to the image processing device 16.
Further, as is well known, a magnetic recording medium is formed on the film of the new photographic system, and a cartridge ID or a film type is recorded. Further, at the time of shooting or development, the shooting date and time, Various data such as the presence / absence of strobe light emission, imaging magnification, shooting scene ID, main part position information, and developing machine type can be recorded. The carrier corresponding to the film (cartridge) of the new photographic system is provided with the magnetic information reading means, and reads the magnetic information when the film is conveyed to the reading position. The seed is output to the image processing device 16.

  In such a scanner, the reading light emitted from the light source, adjusted in light quantity by the variable aperture, passed through the color filter plate, adjusted in color, and diffused in the diffusion box is held at a predetermined reading position by the carrier. By entering and passing through one frame of the film, projection light carrying an image of this frame photographed on the film is obtained. The projection light of the film is imaged on the light receiving surface of the CCD sensor by the imaging lens unit, is read photoelectrically by the CCD sensor, the output signal is amplified by an amplifier, and sent to the image processing device 16. As the CCD sensor, for example, an area CCD sensor having 1380 × 920 pixels is used.

  In the scanner, such image reading is performed three times by sequentially inserting each color filter on the color filter plate, thereby separating and reading one frame image into three primary colors of R, G, and B.

  The scanner uses an area CCD sensor and adjusts the reading light with a color filter plate to separate the original image (film projection light) into three primary colors and read the image. As a scanner for supplying image data to the apparatus, three line CCD sensors corresponding to reading of the three primary colors of R, G, and B are used, and slit-like reading light (projection light) is scanned and conveyed by a carrier. The image reading apparatus may read an image by so-called slit scanning.

In addition, the scanner performs two image readings: a pre-scan that reads an image of each frame shot on a film, that is, an original image, at a low resolution and a fine scan that reads at a high resolution. In pre-scanning, the accumulation time and variable of the area CCD sensor are controlled so that the output of the area CCD sensor is not saturated even when the density of the image photographed on the film is extremely low (for example, an underexposed negative image). The film is read under the prescan reading conditions in which the aperture value of the aperture is set. Pre-scan data obtained by this pre-scan is output to the image analysis unit 32 of the LUT setting unit 30.
Further, fine scan data obtained by fine scan becomes input image data.

  The operation unit 13 is connected to the input device 12a and the image processing device 16, and inputs (settings) various conditions, processing selections, instructions, or colors to the input device 12a and the image processing device 16. / An operation system having a keyboard and a mouse for inputting instructions such as density correction, and a display for displaying acquired input images, various operation instructions, various condition setting / registration screens, etc. is there.

The reception machine 12b is installed on a counter such as a lab store or a convenience store, for example, on a counter, and an operator inputs order information data such as order contents and order items to receive and register in order to receive customer orders. In general, a personal computer (PC) having a monitor display screen is used. In addition, the installation place of the receiving machine 12b is not specifically limited.
In addition, the film that has been shot is received by a counter or the like provided with a receiving machine 12b. Note that the image recording form is not limited to recording on one side of the recording medium, and images may be formed on both sides of the recording medium.

  In the accepting machine 12b, when the order information data is input and the order is confirmed, for example, an acceptance number is given to the order information data, and the acceptance date and time is recorded. In addition, the order information data is collated, and if the customer is a previously input customer, a customer ID assigned in advance is assigned. On the other hand, if the customer has not been input before, a new customer ID is assigned. In this way, the accepting machine 12b gives the order information data the acceptance number, the reception date and time, and the customer ID, and outputs the order information data to the image processing device 16 together with the image data for which the print order has been placed. The accepting machine 12b is provided with a printer for printing a voucher issued when an order is confirmed. The form of the voucher is not particularly limited as long as the date and time when it can be received is recorded.

  In the present embodiment, the order information data input to the accepting machine 12b is customer information such as the customer's name, the customer's telephone number, and the customer's address. In addition, the order information data includes print processing contents (order contents) such as the type, size and number of prints, the finished image to be printed, and the presence or absence of decorative prints.

  The image processing device 16 performs predetermined image processing on the input image data acquired by the input machine 12a to obtain output image data for the print 18. The image processing device 16 will be described in detail later.

The printer 18 produces a photographic print based on the output image data. For example, the printer 18 exposes a photosensitive material with a light beam modulated in accordance with output image data output from the image processing device 16, develops it, and outputs it as a (finished) print.
Further, the printer 18 is not limited to the silver halide photographic type, and for example, a printer that records an image on a recording medium such as paper such as an ink jet printer, an electrophotographic type, and a thermal melting type printer is used. be able to. In addition, the printer 18 may be of a type according to the required image quality or print form, and may record an image on one side or both sides of a recording medium.

The image processing apparatus 16 of the present embodiment includes a basic image processing unit 14, a hypertone processing unit 20, an LUT setting unit 30, a data conversion unit 40, and a control unit 42. The hypertone processing unit 20 and the LUT setting unit 30 constitute processing means of the present invention.
The data converter 40 converts the obtained output image data into print image data that can be output by the printer 18. The conversion from the output image data to the print image data is performed by, for example, a three-dimensional lookup table.
The control unit 42 is connected to the basic image processing unit 14, the hypertone processing unit 20, the LUT setting unit 30, and the data conversion unit 40. The basic image processing unit 14, the hypertone processing unit 20, and the LUT setting unit. 30 and the data converter 40 are all controlled.

  The basic image processing unit 14 performs basic image processing for outputting an image having an appropriate color / density (tone reproduction, color reproduction), image structure (sharpness, graininess), and the like. By performing this basic image processing, the image is completed in terms of image quality. Basic image processing includes, for example, image enlargement or reduction (electronic scaling processing), tone correction, color / density correction, saturation correction, and sharpness processing.

  The hypertone processing unit 20 includes a light / dark signal generation unit (creation unit) 22, a blurred image generation unit (extraction unit) 24, a nonlinear conversion unit (compression processing image data generation unit) 26, and an adder 28. .

The light / dark signal generator 22 generates light / dark image data (Y) from input image data (S _R , S _G , S _B ) (image data of each color of R, G, and B) input from the input device 12a or the receiving device 12b. Is to create. An image based on light / dark image data is referred to as a light / dark image.
As a method of generating the bright and dark image data, a method of taking one third of the average value of the image data (S _R , S _G , S _B ) of each color of R, G, and B (Y = (S _R + S _G + S _B ) / 3), or a method of converting color image data into light and dark image data using the YIQ standard, etc. are exemplified. As a method of obtaining bright and dark image data (hereinafter also referred to as Y component data) using the YIQ standard, for example, only Y component (luminance) defined by the YIQ standard by Y = 0.3S _R + 0.59S _G + 0.11S _B Is calculated from image data of each color of R, G, and B.

  The blurred image generation unit 24 extracts a low-frequency component from the light / dark image data (Y) generated by the light / dark signal generation unit 22, thereby blurring the light / dark image two-dimensionally, and blur image data (Y_b) ( Low frequency component). As a filter used in the blurred image generation unit 24, a FIR (Finite Impulse Response) type low-pass filter that is normally used for generating blurred image data (Y_b) can be used. In addition, it is preferable to use an IIR (Infinite Impulse Response) type low-pass filter for the blurred image generation unit 24 in that blurred image data (Y_b) with a large blurred image can be generated with a small circuit.

  Furthermore, a median filter (hereinafter referred to as MF) may be used as the blurred image generation unit 24. By using MF, it is preferable in that the blurred image data (Y_b) obtained by preserving the edge of the bright and dark image and cutting the noise (high frequency component) in the flat portion is obtained. In addition, it is possible to generate blur image data (Y_b) with a large blurred image while taking advantage of MF, and using MF and LPF together, weighted addition of the images obtained by both is performed. Is particularly preferred.

The nonlinear conversion unit 26 performs image processing on the blurred image data (low frequency component) obtained by the blurred image generation unit 24, and uses a compression amount based on the compression condition set by the LUT setting unit 30 as described later. The image data for compression processing (LUT (Y_b)) for compressing the input image data is created based on the blurred image data (Y_b) and the correction amount, or the blurred image data (Y_b). This compression processing image data (LUT (Y_b)) indicates the compression amount of the input image data (S _R , S _G , S _B ). In the non-linear conversion unit 26, the image data for compression processing (LUT (Y_b)) for compressing the input image data (S _R , S _G , S _B ) with the compression amount set by the LUT setting unit 30 is blurred image. A conversion table such as a rewritable LUT (lookup table) created based on the data (Y_b) and the correction amount, or the blurred image data (Y_b) is provided.

The compression amount of the input image data (S _R , S _G , S _B ) indicated by the compression processing image data (LUT (Y_b)) created by the nonlinear conversion unit 26 is the image of the LUT setting unit 30 as will be described later. It is finally set based on the image analysis by the analysis unit 32, and each image is optimized for each scene. In addition, the compression amount of the dynamic range in the nonlinear conversion unit 26 differs for each scene. That is, the setting of the conversion table in the nonlinear conversion unit 26 is changed by the scene and LUT setting unit 30. Further, in the present invention, as will be described later, when the density corresponds to the foot or shoulder of the characteristic curve as a result of image analysis, correction is performed so that the color balance of the reproduced image is appropriate. .

The adder 28 adds the input image data (S _R , S _G , S _B ) and the compression processing image data (LUT (Y_b)) created by the nonlinear conversion unit 26. The input image data (S _R , S _G , S _B ) and the compression processing image data (LUT (Y_b)) are added by the adder 28, so that the dynamic range of the input image data is compressed, and the output image data output image data _{(O R, O G, O} B) are obtained. The adder 28 has the same configuration as the adder 118 (see FIG. 6A) of the conventional hypertone processing device 110 (see FIG. 6A).

The LUT setting unit 30 determines the compression amount of the dynamic range of the input image data (S _R , S _G , S _B ). The LUT setting unit 30 includes an image analysis unit 32 and a film database 34.

The image analysis unit 32 has a function of setting a basic conversion table in the nonlinear conversion unit 26 of the hypertone processing unit 20. The image analysis unit 32 sets the compression amount (dynamic range compression condition) of the dynamic range of the subject image (input image data (S _R , S _G , S _B )) using the pre-scan data. is there.
Here, as described above, in the film on which the image is recorded, the color balance is lost at the feet and shoulders of the characteristic curves of the three primary colors of red, green, and blue (see FIG. 8). For this reason, if the image pixels are recorded in the density areas of the foot and shoulders of the characteristic curve and the output image data is created as it is, the color print will be added to the resulting print. And color reproducibility is poor. From this, the image analysis unit 32 performs image analysis, and when the pixel density is within the density range of the foot or shoulder, the film database 34 is referred to so that the color balance is optimized. The correction coefficient (correction amount) is set, the dynamic range compression amount is set, and the occurrence of color failure is suppressed.

The film database 34 records characteristic curves of R, G, and B colors of the film for each film type. In the film database 34, correction coefficients for R, G, and B colors at the foot and shoulder of each film are recorded for each density.
The correction coefficient in the film database 34 is set in advance by a function or an experimental value or the like in each density region of each color of R, G, and B for each film, and a correction amount corresponding to the density is set. . The correction amount setting method is not particularly limited.

The image analysis unit 32 extracts data of a region corresponding to each frame (image) of the film based on the input prescan data of each image, detects the image position, and sets the image processing condition for each image and Fine scanning reading conditions are set (calculated).
In the image analysis unit 32, creation of a density histogram, average density, LATD (large area transmission density), highlight (lowest density), shadow (highest density), etc. for each image from the prescan data of each image. The image feature amount is calculated. Next, the state of the original image is judged from the information of the film type read by the carrier, and the area CCD sensor output is saturated at a density slightly lower than the lowest density of the original image for each image. The accumulation time or aperture value of the CCD sensor is calculated and used as the fine scan reading condition. Further, based on the density histogram, image feature amount, film information, and the like, image processing conditions for input image data (fine scan data) in the basic image processing unit 14 are set for each image.

In addition, the image analysis unit 32 compares the density histogram of each image with the characteristic curve of the film used for photographing, and specifies a pixel corresponding to the shoulder or foot of the characteristic curve. For pixels having a density that does not correspond to the shoulder or foot (the range of the characteristic curve latitude), the correction coefficient is set to 1 without correction.
On the other hand, when there is a pixel corresponding to the shoulder portion or the foot portion of the characteristic curve, the correction value set for each film is read into the film database 34 and the correction coefficient is set. To do.

The image analysis unit 32 of the present embodiment basically sets a conversion table of the nonlinear conversion unit 26.
As a result of image analysis using prescan data of each image, the density of each pixel of the image recorded on the film is compared with the characteristic curve of the film used for photographing, and the color balance is lost in the subject image. A density area is specified, and in an area where the color balance is lost, a correction amount for making the color balance appropriate is set, and a compression amount of the dynamic range of the input image data is set.
Further, in this embodiment, when the image does not correspond to the shoulder portion or the foot portion (the range of the characteristic curve latitude), the input image is not corrected but based on the prescan data of each image as in the conventional case. The compression amount of the dynamic range of data is set. As a result, compression is performed without changing the hue as in the past.

  The image analysis unit 32 according to the present exemplary embodiment finally outputs, to the nonlinear conversion unit 26, for example, a dynamic range compression amount that also considers the color balance correction amount as a gradation control signal. Thus, the color balance of the compression processing image data for compressing the dynamic range of the input image data obtained by the nonlinear conversion unit 26 is appropriate in each density region of the input image data corrected by the LUT setting unit 30. The compression amount of the dynamic range set as described above is instructed.

The relationship between the input image data (S _R , S _G , S _B ) and the output image data (O _R , O _G , O _B ) in this embodiment is expressed as the following mathematical formulas (4) to (6). It is. Note that LUT (Y_b) in the following mathematical formulas (4) to (6) indicates that blurred image data is input to the conversion table, and C _R , C _G , and C _B are R, G, respectively. , B are correction coefficients for each color.
In this embodiment, as shown in the following mathematical formulas (4) to (6), the colors R, G, and B change by an amount corresponding to the color balance, and the compression is performed by changing the hue. Correct.

O _R = S _R + LUT (Y_b) × C _R (4)

_{O G = S G + LUT (} Y_b) × C G ··· Equation (5)

O _B = S _B + LUT (Y_b) × C _B (Equation 6)

Next, the operation of the image processing apparatus 16 of this embodiment will be described.
FIG. 2 is a flowchart illustrating a compression amount setting method by the LUT setting unit of the image processing apparatus in the printing system according to the first embodiment of the present invention.

  Prior to fine scanning, first, pre-scanning is performed on each color of R, G, and B for the film, and pre-scan data for each color is acquired (step S10). At this time, the DX code or APS magnetic recording is read, and the film type is also specified.

  Next, in the image analysis unit, creation of a density histogram, average density, LATD (large area transmission density), highlight (lowest density), shadow (highest density), etc. for each image based on the prescan data. The feature of the image is calculated, and the state of the original image is judged from the film type information. For each image, the output from the area CCD sensor is saturated at a density slightly lower than the lowest density of the original image. As described above, the accumulation time or aperture value of the area CCD sensor is calculated, and fine scanning reading conditions are set (step S12).

  Next, based on the density histogram calculated by the image analysis unit, the density is calculated as an absolute density for each color of each pixel of the image. Thereby, the density range is specified (step S14). Thereby, the absolute density of each pixel from the base density of the film is obtained for each color.

Next, the film database is referred to (step S16). Thereby, the characteristic curve of the film used for photographing is obtained.
Next, the density of each color of each pixel obtained in step S14 is compared with the characteristic curve. At this time, for each pixel, it is determined whether or not the density is in the shoulder portion or the foot portion of the characteristic curve, and it is determined whether correction is necessary (step S18).
In step S18, if there is a pixel corresponding to the shoulder or foot of the characteristic curve among the pixels of the image, the film database is further referred to and preset for each film in accordance with each density. A correction coefficient is acquired and a correction coefficient is set (step S20).

On the other hand, if there is no pixel corresponding to the shoulder or foot of the characteristic curve among the pixels of the image in step S18, the correction coefficient is set to 1 (step S22).
In this embodiment, the correction coefficient is set to 1 even when the pixel density is within the latitude range of the characteristic curve.
In this way, the correction coefficient is set in this embodiment. This is performed for all images recorded on the film, and a correction coefficient is set for each pixel for each image. Then, in consideration of the correction coefficient, the conversion table of the nonlinear conversion unit is set according to the scene, and further set so that the color balance is appropriate. As described above, the color balance is corrected as necessary, and the compression condition of the dynamic range is set.

  Next, the film on which the image is recorded is again scanned with a scanner under the reading conditions set by the pre-scan to obtain input image data (fine scan data).

Next, input image data is input to the basic image processing unit 14, and the image color / density (tone reproduction, color reproduction), image structure (sharpness, graininess), etc., under the image processing conditions set by the pre-scan. Performs basic image processing to output an appropriate image.
Next, the input image data is output to the hypertone processing unit 20 (the light / dark signal generation unit 22 and the adder 28) of the image processing device 16. In the hypertone processing unit 20, first, the light / dark signal generation unit 22 creates Y component data (light / dark image data) (Y) of the input image data.

  Next, the Y component data (Y) is output from the light / dark signal generation unit 22 to the blurred image generation unit 24. Thereby, the blurred image generation unit 24 obtains the blurred image data (Y_b) of the Y component data (Y). This blurred image data (Y_b) is output to the nonlinear conversion unit 26.

  On the other hand, the dynamic range compression amount set value (including the correction coefficient (correction amount)) determined by the LUT setting unit 30 is output to the nonlinear conversion unit 26 of the hypertone processing unit 20 as, for example, a gradation control signal. . Thereby, the conversion table set in the non-linear conversion unit 26 is changed according to the compression amount, and the conversion table set in the non-linear conversion unit 26 is finally set.

Next, compression processing image data for compressing the input image data with the compression amount set by the LUT setting unit 30 is created from the low frequency component of the Y component data by the nonlinear conversion unit 26. Further, the compression processing image data is output to the adder 28. The adder 28 adds the input image data and the image data for compression processing to obtain output image data (O _R , O _G , O _B ) in which the dynamic resin is compressed.

Next, the output image data (O _R , O _G , O _B ) is output to the data converter 40 and converted into print image data suitable for the printer 18. In this way, in the image processing device 16, print image data that can be output by the printer 18 is generated. Based on this print image data, the printer 18 obtains a high-quality photographic print in which colors are reproduced appropriately in the density areas on the shadow side and highlight side regardless of the characteristics of the film on which the image is recorded. be able to.

  In the image processing apparatus 16 of the present embodiment, the digital image data of the image recorded on the film acquired by the input device 12a is referred to the characteristic curve corresponding to the film type, and correction according to the density of the image of the subject is performed. Then, by setting the compression amount (compression condition) of the dynamic range in each density area of the input image data and setting the conversion table set in the nonlinear conversion unit 26, the color balance is corrected, and the color is particularly appropriate. It is possible to obtain output image data capable of obtaining a high-quality photographic print reproduced in the above.

For example, an image 50 in which a man 52 wearing gray clothes and a woman 54 wearing white dresses as schematically shown in FIG. 3 has a density range D as shown in FIG. The density range D includes the shoulder β of the characteristic curve. In the conventional hypertone processing, the color balance of the image 50 is lost at the shoulder portion β of the characteristic curve, so that a color other than white is reproduced on the white dress.
However, in the image processing method of the present embodiment, correction is performed in consideration of the color balance, so that it is possible to suppress the color tone generated due to the color balance being lost. That is, the occurrence of color feria can be suppressed. As a result, even if the degree of compression is increased, the color balance is not lost, so the degree of freedom of the degree of compression can be increased.

Next, a second embodiment of the image processing apparatus of the present invention will be described.
FIG. 4 is a block diagram showing a second embodiment of the printing system having the image processing apparatus of the present invention.
In this embodiment, the same components as those of the print system 10 of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The print system 10a of this embodiment shown in FIG. 4 is different from the print system 10 of the first embodiment (see FIG. 1) in the configuration of the image analysis unit 32a and the light / dark signal generation unit 22a, and the image analysis unit 32a. The difference is that the light / dark signal generation unit 22a is connected, and the rest of the configuration is the same as that of the print system 10 of the first embodiment, and a detailed description thereof will be omitted.

  The image analysis unit 32a of the present embodiment is connected to the light / dark signal generation unit 22a, and differs from the image analysis unit 32 of the print system 10 of the first embodiment in that a correction coefficient is output to the light / dark signal generation unit 22a. Other configurations are the same.

In addition, the light / dark signal generation unit 22a of the present embodiment creates a light / dark signal based on the correction coefficient output from the image analysis unit 32a in that the light / dark signal generation unit 22a of the print system 10 of the first embodiment is different from the light / dark signal generation unit 22a. The other configurations are the same.
The bright and dark image data in this embodiment is calculated by Y = (S _R · C _R + S _G · C _G + S _B · C _B ) / (C _R + C _G + C _B ). Further, it may be bright and dark image data (Y = 0.3S _R · C _R + 0.59S _G · C _G + 0.11S _B · C _B ) using YIQ regulations.

  In this embodiment, the color balance is corrected in the light and dark image data, although the R, G, and B color data are not corrected by the conversion table in the nonlinear conversion unit 26. In this way, the same effect as that of the print system 10 of the first embodiment can be obtained by correcting the bright and dark image data.

Next, the operation of the print system 10a of this embodiment will be described.
FIG. 4 is a flowchart illustrating a compression amount correction method by the LUT setting unit of the image processing apparatus in the printing system according to the second embodiment of the present invention.

  In the present embodiment, as compared with the print system 10 of the first embodiment, the correction coefficient is set by the image analysis unit 32a using the pre-scan data as described above (step S20), or the correction coefficient is set. After 1 (step S22), the correction coefficient is output to the light / dark signal generator 22a (steps S30 and S32). Further, the image analysis unit 32a performs image analysis using the pre-scan data, sets the dynamic range compression amount without considering the color balance, and outputs it to the nonlinear conversion unit 26 as, for example, a gradation control signal. Since the other image processing methods are the same as those of the print system 10 of the first embodiment, detailed description thereof is omitted.

Also in the printing system 10a of this embodiment, as in the first embodiment, for example, when the dynamic range is compressed for the image 50 (see FIG. 3) of the woman 54 wearing a white dress, the color balance is lost. It is suppressed that the color which arises due to is attached. That is, the occurrence of color feria can be suppressed. That is, also in the printing system 10a of the present embodiment, a high-quality print can be obtained as in the first embodiment.
Further, in this embodiment, since the bright / dark image data is corrected, the amount of compression by the conversion table of the nonlinear conversion unit 26 can be suppressed. Accordingly, it is possible to suppress the loss of black tightening and the loss of white while maintaining the color balance.

In any of the embodiments, a densitometer for measuring the density of the film may be provided. By providing the densitometer, the accuracy of image density measurement can be further increased, and the accuracy of color balance correction can be further increased. As a result, a higher quality print can be obtained.
In any embodiment, the film type may be directly input to the image analysis unit 32 from the receiving machine 12b or the operation unit 13. Further, when the film type cannot be specified, all correction coefficients are set to 1.

  The image processing apparatus of the present invention may be an apparatus having a function of compressing the dynamic range of an input image, but may be realized by, for example, a general personal computer system and a software program operating on the personal computer system. It is. Further, the program for compressing the dynamic range of the input image of the present invention applies the image processing method of the present invention to create output image data in which the dynamic range of the input image is compressed.

  The present invention is basically as described above. Although the image processing apparatus and the image processing method of the present invention have been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements or modifications can be made without departing from the spirit of the present invention. Of course it is good.

1 is a block diagram showing a first embodiment of a printing system having an image processing apparatus of the present invention. FIG. 3 is a flowchart illustrating a compression amount setting method by an LUT setting unit of the image processing apparatus in the print system according to the first exemplary embodiment of the present invention. It is a schematic diagram which shows an example of an input image. It is a block diagram which shows 2nd Example of the printing system which has an image processing apparatus of this invention. 10 is a flowchart illustrating a compression amount correction method by an LUT setting unit of an image processing apparatus in a print system according to a second embodiment of the present invention. (A) is a block diagram showing a conventional image processing apparatus that performs hypertone processing, and (b) shows a conversion table of a lookup table (LUT) in the conventional image processing apparatus of FIG. 6 (a). It is a graph. It is a graph which shows the conventional image processing method, taking image density on the vertical axis and taking the image position on the horizontal axis. It is a graph which shows the characteristic curve of each color of the negative film of red, green, and blue, with density on the vertical axis and exposure on the horizontal axis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a Print system 12a Input machine 12b Reception machine 13 Operation part 14 Basic image processing part 16 Image processing apparatus 18 Printer 20 Hypertone processing part 22, 22a Brightness / darkness signal generation part 24 Blurred image generation part 26 Nonlinear conversion part 28 Adder 30 LUT setting unit 32 Image analysis unit 34 Film database 40 Data conversion unit 50 Image 140 Red characteristic curve 142 Green characteristic curve 144 Blue characteristic curve α Foot β Shoulder

Claims (6)

An image processing apparatus that performs predetermined image processing on input image data obtained by photoelectrically reading an image recorded on a film with at least three primary colors of red, green, and blue, and producing output image data for output. And
Processing means for performing compression processing of the dynamic range of the input image data;
The processing means includes a setting unit that sets a compression condition of a dynamic range of the input image data.
The setting unit refers to the film database in which the characteristic curves of the three primary colors of the film are recorded for each type of film, and the characteristic database of the three primary colors of the film in which the image is recorded, The characteristic curve of the three primary colors of the film is compared with the density of each of the three primary colors of each pixel of the input image data, and the density of each of the three primary colors of the pixel of the input image data is the characteristic curve. For those on the foot or shoulder, set the correction amount of the density of each color so that the color balance is appropriate based on the characteristic curve, and set the compression condition of the dynamic range using the correction amount An image analysis unit that performs
The image analysis unit sets the compression condition for the dynamic range without setting a correction amount for a pixel whose density of each of the three primary colors is not a foot or a shoulder of the characteristic curve. An image processing apparatus.   The processing means includes a creating means for creating bright and dark image data of the input image data, an extracting means for extracting a low frequency component of the bright and dark image data, and a compression amount based on a compression condition set by the setting unit. Compression processing image data creating means for creating compression processing image data for compressing input image data based on the low frequency component and the correction amount; the compression processing image data; and the input image data; The image processing apparatus according to claim 1, further comprising: an adder that adds.   The processing unit includes a creating unit that creates bright and dark image data of the input image data based on the input image data and the correction amount, an extracting unit that extracts a low frequency component of the bright and dark image data, and the setting unit Compression processing image data creating means for creating, from the low frequency component, compression processing image data for compressing the input image data with a compression amount based on the compression condition set by the compression processing image data, The image processing apparatus according to claim 1, further comprising an adder that adds the input image data. This is an image processing method in which predetermined image processing is performed on input image data obtained by photoelectrically reading an image recorded on film with at least three primary colors of red, green, and blue to obtain output image data for output. And
Identifying the density of each pixel of the input image data;
The type of film on which the image is recorded is specified, the characteristic curve of the three primary colors of the specified film is compared with the density of each of the three primary colors of each pixel of the input image data, and the three primary colors of the pixel are compared. For the density of each color at the foot or shoulder of the characteristic curve, a step of setting the correction amount of the density of each color so that the color balance is appropriate based on the characteristic curve,
For the case where the density is at the foot or shoulder of the characteristic curve, the compression amount information is used to set the dynamic range compression condition of the input image data, and the density of each of the three primary colors of the pixel is What is not the foot or shoulder of the characteristic curve is a step of setting the compression condition of the dynamic range without setting a correction amount;
And a step of compressing the dynamic range of the input image data in accordance with the set dynamic range compression condition. In a subsequent process of setting the correction amount,
Creating light and dark image data of the input image data; and extracting low frequency components of the light and dark image data;
The step of compressing the dynamic range of the input image data includes the step of compressing the input image data with a compression amount based on the compression condition of the dynamic range, the low frequency component and the correction amount. 5. The image processing method according to claim 4, wherein the image processing method is configured to add the image data for compression processing and the input image data. In a subsequent process of setting the correction amount,
Based on the input image data and the correction amount, creating the bright and dark image data,
A step of extracting a low frequency component of the light and dark image data;
The step of performing compression processing of the dynamic range of the input image data creates image data for compression processing for compressing the input image data with a compression amount based on the compression condition of the dynamic range based on the low frequency component. The image processing method according to claim 4, further comprising a step of adding the image data for compression processing and the input image data.

Images