JP4375223B2 - Image processing apparatus, image processing method, and image processing program - Google Patents

Description

The present invention relates to an image processing apparatus, it relates to an image processing method and an image processing program.

In a device such as a camera that forms an image with light acquired through a lens, image quality may be deteriorated due to the formation of an image through the lens. Examples of such deterioration include a decrease in the amount of peripheral light. Conventionally, various techniques have been developed as a technique for correcting such deterioration. For example, the amount of peripheral light is reduced by changing the brightness for each position of an image by γ correction (see Patent Document 1 and the like). Can be suppressed.
JP 2001-144958 A

In the conventional technology, there is a case where image quality deterioration at each position is emphasized due to correction. That is, assuming that image data is acquired by an input device such as a digital camera, the above-described γ correction is performed by an IC chip provided in the input device or an application program that processes the image data to eliminate image quality degradation. It will be. However, image quality deterioration characteristics in an image vary depending on shooting conditions and the like, and an appropriate correction amount according to these conditions cannot always be selected. As a result, it may occur that correction is excessively performed. If correction is performed excessively, image quality degradation is emphasized depending on the position of the image. For example, since the change characteristic of the peripheral light amount is caused by a lens or an aperture, it has been difficult to perform an appropriate peripheral light amount correction on image data created by a digital camera or the like that can change the lens or the aperture. .
The present invention prevents the gradation collapse occurs with the noise added in the high tone range, the image processing apparatus capable of preventing the occurrence of image degradation, an image processing method and image processing program The purpose is to do.

  In order to achieve the above object, in the present invention, a predetermined noise is further added after correction is performed according to the distance from the reference position in the image. As a result, even if image quality deterioration depending on the distance remains after correction according to the distance from the reference position, the image quality deterioration can be made inconspicuous by noise, and the image quality deterioration can be eliminated. Accordingly, it is possible to accurately prevent the occurrence of image quality deterioration.

  In the image indicated by the image data acquired by the image data acquisition unit, image quality deterioration depending on the distance, such as a decrease in peripheral light amount, may or may not occur before correction by the correction unit. If image quality degradation depending on the distance occurs, image quality degradation such as tone jump caused by excessive correction by the correction means can be eliminated. Further, it is possible to eliminate the remaining image quality deterioration due to the lack of correction amount by the correction means.

  Furthermore, if there is no image quality deterioration depending on the distance, the correction unit does not perform appropriate correction, and even if the image quality deterioration is given, the image quality deterioration can be eliminated. In general, the image quality degradation depending on the distance varies depending on conditions when creating image data, for example, a lens, an aperture, and a focal length. Therefore, it is difficult to correct these conditions appropriately. According to the present invention, it is not required that the correction by the correction means is perfect, and the design of the image processing apparatus becomes very easy. Note that, in the image indicated by the image data, if the brightness does not change according to the distance from the reference position, the brightness is excessively corrected by the correction means, causing the tone jump. Therefore, it is particularly preferable as an application target of the present invention.

  Here, the image data may be data indicating the content of the image. For example, data that configures an image with a plurality of pixels and specifies a gradation value for each color component for each pixel may be employed. Of course, it may be image data that can express multiple colors by employing three or more color components as color components, or image data that expresses a color with a single color component such as an achromatic color.

  The correction unit only needs to be able to correct image data while varying the correction amount according to the distance from the reference position. In the correction, it suffices if the feature amount of the image can be changed by changing the gradation value for each color component in the image data. The color value of the image such as brightness, saturation, hue, and the like, and the color component value of RGB, etc. Various feature quantities such as the sharpness and the sharpness can be corrected. The reference position may be any position in the image, and a predetermined position such as the center of the image can be used as the reference position.

  Further, in the correction means, the correction amount is changed according to the distance in order to eliminate the image quality degradation that occurs according to the distance from the reference position. For this purpose, correction data for specifying a correction amount corresponding to the distance may be prepared in advance, or may be added to the image data, and various configurations can be employed. However, in general, it is difficult to create correction data for accurately eliminating image quality degradation for each image. Therefore, by adding noise according to the present invention, it is possible to accurately eliminate image quality degradation according to various conditions.

  Note that various configurations can be adopted as the configuration for executing correction by the correction unit. For example, the tone value of the image data is referred to with reference to input / output characteristics determined according to the distance from the reference position. It is possible to adopt a configuration that performs input / output conversion using as an input value. That is, if the input / output characteristics are determined for each distance from the reference position, the correction can be easily performed with a correction amount corresponding to the distance. However, in this configuration, it is easy to set a correction amount according to the distance, but it is difficult to set an accurate correction amount according to various conditions. Therefore, by adding noise according to the present invention, it is possible to accurately eliminate image quality degradation according to various conditions.

  As a configuration example of the correction unit, it is possible to employ a configuration that corrects the brightness that varies depending on the distance from the center of the image due to the shooting conditions when the image is created. That is, when correcting such a change in the peripheral light amount, the lightness is corrected while changing the correction amount according to the distance from the center of the image. Therefore, if the correction is not performed accurately, the image quality is deteriorated due to excessive correction or insufficient correction amount.

  In particular, in an image including many substantially uniform parts such as an image of the sky or the sea, a lightness tone jump appears remarkably. Therefore, by applying the noise adding means according to the present invention along with such correction, it is possible to suppress image quality deterioration even when the peripheral light amount correction cannot be performed accurately. Note that the photographing conditions include various conditions such as the type of lens, aperture, and focal length.

  Furthermore, as a configuration example of the correction unit, a configuration in which the brightness of the image is increased or decreased according to the distance from the reference position can be employed. In other words, even when correction according to the distance is performed on the image data without corresponding to the shooting conditions at the time of creating the image, image quality deterioration according to the distance from the reference distance is caused by this correction. Can occur. For example, when the user selects a lightness correction amount and the correction means performs correction based on this selection, image quality deterioration may occur due to excessive correction or insufficient correction amount.

  Therefore, if noise is added according to the present invention, this image quality degradation can be eliminated. Note that such correction includes correction for reducing the peripheral light amount. That is, even when the user desires such a style, the correction can prevent the image quality deterioration such as the tone jump from occurring.

  The noise adding means only needs to be able to eliminate image quality deterioration caused by the correction by adding predetermined noise to the image data corrected by the correcting means. For example, when a tone jump occurs due to brightness correction, if a predetermined noise is superimposed on the gradation value, the tone jump becomes inconspicuous, and as a result, the tone jump can be eliminated. The predetermined noise is preferably the minimum noise necessary for eliminating the image quality deterioration caused by the correction. In addition, it is possible to adopt a configuration in which a noise pattern, that is, a range to which noise is applied and a size of noise to be applied for each pixel are specified in advance and this noise is added to a position to which noise is applied. .

Furthermore, it is preferable to perform correction by the correction unit in consideration of adding noise by the noise addition unit. When the gradation value of a predetermined color component in the image data is targeted for correction, P _max ≧ M _max + N It shall be the _max. Here, P _max is the upper limit value of the gradation value range of the color component to be corrected, M _max is the maximum value of the gradation value after correction, and N _max is the maximum value of noise added by the noise adding means. According to this configuration, when adding noise by the noise adding means, it is possible to add noise so as to be within the gradation value range of the color component. Accordingly, it is possible to prevent the occurrence of gradation collapse due to the addition of noise in the high gradation area.

  Furthermore, a configuration that adds noise to data in a gradation range that is wider than the gradation range of the image data used when outputting an image with a predetermined output device is adopted as a suitable configuration for adding noise. Is possible. That is, in image data, a certain color component value of a certain pixel is usually expressed by a limited amount of information (for example, 8 bits). For this reason, although the gradation value range is limited, the smaller the amount of information, the greater the effect that adding noise has on the image.

  Therefore, when it is assumed that an image is output by a predetermined output device, noise is generated with respect to image data expressing a color component in a gradation value range wider than the gradation value range used when the image data is handled by the output device. Is added. That is, image data to be corrected is configured by expressing a certain color component value of a certain pixel with a larger amount of information (for example, 10, 12, 16 bits, etc.). As a result, it is possible to add very small noise, and the influence on the image by adding noise can be suppressed.

  Furthermore, as a configuration example when adding noise by a predetermined noise pattern, a configuration in which the noise pattern is changed according to the distance from the reference position may be adopted. That is, in the correction means according to the present invention, the amount of correction varies depending on the distance from the reference position. Therefore, if the degree of noise addition is changed by changing the noise pattern, more appropriate noise can be added according to the distance from the reference position. Of course, the noise pattern may be changed according to the correction amount in the correction means.

  The invention can also be realized as a print control apparatus that executes printing based on image data to which noise is added as described above. That is, when image data representing an image is acquired and this image is printed, various corrections and noises are added by the same process as described above, and the image is printed based on the processed image data. Even when the image characteristics vary depending on the shooting conditions, it is possible to print an image while accurately preventing the occurrence of image quality degradation.

By the way, the image processing apparatus and the print control apparatus described above may be implemented independently, or may be implemented together with other methods in a state of being incorporated in a certain device. It includes embodiments and can be changed as appropriate. In addition, the above-described image processing and print control methods can also be applied as methods, and basically the same operation is achieved in the invention relating to the image processing method and the print control method .

When trying to implement the present invention, a predetermined program may be executed by an image processing apparatus or a print control apparatus. Therefore, the present invention can also be implemented as the program, and basically the same operation is achieved in the invention relating to the image processing program and the print control program . Of course, it is possible to make the configuration described in the dependent claims correspond to the above method or program. Any storage medium can be used to provide the program. For example, a magnetic recording medium or a magneto-optical recording medium may be used, and any recording medium that will be developed in the future can be considered in the same manner. In addition, even when a part is software and a part is realized by hardware, the idea of the present invention is not completely different, and a part is recorded on a recording medium and is appropriately changed as necessary. It includes a reading form. Furthermore, the same is true for the replication stage such as the primary replica and the secondary replica.

Hereinafter, embodiments of the present invention will be described in the following order.
(1) Configuration of image processing apparatus and print control apparatus:
(2) Print control processing:
(2-1) Peripheral light amount correction processing:
(2-2) Noise addition processing:
(3) Other embodiments:

(1) Configuration of image processing apparatus and print control apparatus:
FIG. 1 shows a schematic configuration of an image processing apparatus and a print control apparatus according to an embodiment of the present invention. In the present embodiment, an image processing apparatus and a print control apparatus are realized by some of the functions of the computer 10. The computer 10 includes a CPU 11 serving as the center of arithmetic processing, and the CPU 11 controls the entire computer 10 via a system bus 10a. Connected to the system bus 10a are a ROM 12, a RAM 13, a hard disk drive 14, a USB I / F 15, a CRTI / F (not shown), an input device I / F, and the like.

  The hard disk drive 14 stores an operating system (OS) as software, an image processing utility 30 for performing image processing, a printer driver (PRTDRV) 31, and the like. These software are appropriately stored in the RAM 13 by the CPU 11 during execution. Transferred. The CPU 11 executes various programs under the control of the OS while appropriately accessing the RAM 13 as a temporary work area.

  A keyboard 16a and a mouse 16b are connected to the input device I / F as operation input devices. A display 17a for display is connected to the CRTI / F. Therefore, the computer 10 can accept the operation contents by the keyboard 16a and the mouse 16b, and can display various information on the display 17a. Further, a printer 20 is connected to the USB I / F 15 and an image can be printed based on data output from the computer 10. Of course, the connection I / F with the printer 20 is not limited to the USB I / F, and various connection modes such as a parallel I / F, a serial I / F, and a SCSI connection can be adopted, and any one to be developed in the future. The same applies to the connection mode.

  The printer 20 used in the present embodiment may be an ink jet printer or a laser printer, and various printers can be employed. In any case, the computer 10 creates print data that can be interpreted by the printer 20 and outputs the print data via the USB I / F 15. The printer 20 prints an image by recording a recording material for each pixel constituting the image based on the print data.

(2) Print control processing:
The CPU 11 executes printing by executing the image processing utility 30 and the PRTDRV 31. In other words, the image processing utility 30 has a function of performing peripheral light amount correction and adding noise to the corrected image when executing printing. The PRTDRV 31 executes printing based on the image data processed by the image processing utility 30.

  FIG. 1 illustrates functional blocks of the image processing utility 30, and FIG. 2 illustrates a flowchart of processing executed by the image processing utility 30 and the PRTDRV 31. As shown in FIG. 1, the image processing utility 30 includes an image data acquisition unit 30a, a γ correction unit 30b, and a noise addition unit 30c.

  The image data acquisition unit 30a can read out various types of image data 14a stored in the hard disk drive 14, acquires the image data 14a to be printed (step S100), and displays it as a print candidate on the display 17a. Display. In this embodiment, the image data 14a expresses each color component of YCbCr with 1024 gradations (gradation values 0 to 1023) for each of a plurality of pixels constituting the image, and expresses the color of each pixel by this combination. .

  The image data 14a is image data generated in advance by an image input device such as a digital still camera. When the image data 14a is generated by the image input device, a gradation value with an information amount of 10 bits for each color component. Is expressed. On the other hand, the PRTDRV 31 handles image data in which each color component is expressed in 256 gradations, and after performing γ correction and noise addition as described later, the level of information is 8 bits for each color component. It will be converted into data representing the key value.

  Of course, various other configurations can be employed for acquiring images, and the image input device and the computer 10 are connected to acquire image data from a recording medium inserted in the image input device. You may do it. Further, a recording medium on which image data is recorded may be inserted into the interface of the computer 10 and the image data may be acquired from this recording medium. In any case, the process in step S100 corresponds to the process in the image data acquisition unit.

(2-1) Peripheral light amount correction processing:
The γ correction unit 30b performs peripheral light amount correction by performing γ correction on the image data. For this reason, the γ correction unit 30b selects data to be applied for correction from the light amount reduction data 14b. That is, the light quantity reduction data 14b is recorded in advance in the hard disk drive 14, and the light reduction rate is defined corresponding to the combination of the aperture and the focal length used when taking an image. Therefore, the γ correction unit 30b should display the GUI for selecting the light amount reduction data 14b on the display 17a, and accept the selection instruction via the keyboard 16a or the mouse 16b, and apply it from each data. Data is specified (step S105).

ここで、Ｌ_mは基準の画像を撮影した場合に得られる明度の実測値であり、画像の中心からの距離毎に得られる実測値である。Ｌ_tは基準の画像を撮影した場合に得られる基準の明度である。 FIG. 3 is a diagram illustrating a configuration example of the light amount reduction data 14b. The light amount reduction data 14b is data in which the position of the image is associated with the light attenuation rate, and in this embodiment, the light attenuation rate at the distances Y ₁ , Y ₂ , Y ₃ , and Y ₄ from the center of the image. It is described. The light attenuation rate R _m is defined by the following equation (1).

Here, L _m is an actually measured value of brightness obtained when a reference image is taken, and is an actually measured value obtained for each distance from the center of the image. L _t is a reference brightness obtained when a reference image is taken.

  The lightness of the reference only needs to be lightness that serves as a reference for comparing the decrease in the amount of light. In the present embodiment, the lightness is a measured value of lightness at the center of the image. Needless to say, the brightness when the light amount reduction due to the lens does not occur may be used as the reference brightness, and various standards can be adopted. Further, since the light attenuation rate varies depending on the photographing condition of the image data 14a, in the present embodiment, the light attenuation rate is associated with the combination of the aperture and the focal length (mm).

For example, when the aperture is 3.5 and the focal length is 28 mm, the light attenuation rate corresponding to the distance Y ₁ is R _m1 , the light attenuation rate corresponding to the distance Y ₂ is R _m2 , and the light attenuation rate corresponding to the distance Y ₃ is R _m3. The dimming rate corresponding to the distance Y ₄ is R _m4 . Of course, various other configurations can be adopted as the light amount reduction data 14b, and the light attenuation rate may be associated with the type and name of the lens. A dimming rate may be associated with a combination of a plurality of focal lengths and apertures.

In this embodiment, the light attenuation rate at _four distances (Y _{1 to} Y ₄ ) is used as the light amount reduction data 14b. However, the light attenuation rate may be defined for more distances. Further, although the light attenuation rate in this embodiment depends only on the distance from the center, it is needless to say that the light attenuation rate may be defined for each position of the image, not just the distance from the center.

  If the light quantity reduction data 14b is selected in step S105, an adjustment for obtaining a user desired light reduction rate is accepted (step S110). That is, in this embodiment, in order to be able to change the light attenuation rate characteristic more flexibly, the adjustment by the user is accepted. Specifically, the γ correction unit 30b displays a GUI such as the graph shown on the left side of FIG. 4 on the display 17a, and accepts adjustments using the keyboard 16a, the mouse 16b, and the like. That is, in the graph shown on the left side of FIG. 4, the horizontal axis indicates the distance from the center of the image, the vertical axis indicates the light reduction rate (%), and the white circle is the data described in the light amount reduction data 14b.

  If it is assumed that the light reduction rate is 0% at the distance “0” from the center, and if interpolation such as spline interpolation is performed using the upper left corner of the graph and the white circle, the solid line in the left graph of FIG. As in the curve shown by, the light attenuation rate for an arbitrary distance can be calculated. In view of this, the γ correction unit 30b displays a UI like this graph on the display 17a, and moves the solid curve up and down by the input operation of the mouse 16b and the like, and exhibits the light attenuation rate characteristic as shown by the broken line. Configure to change.

  When a change in the light attenuation rate characteristic is received in this way, a γ table indicating the correspondence between the distance from the center of the image and the γ value is calculated in order to perform γ correction with the adjusted characteristic (step S115). ). The graph on the right side of FIG. 4 is an explanatory diagram for explaining processing for calculating the γ table. In the present embodiment, it is assumed that the light attenuation rate determined in step S110 is the light attenuation rate with respect to the median value (512) of the lightness gradation values. Under this assumption, it can be estimated that the image data whose brightness should be “512” when the light amount has not decreased is “512 × light reduction rate” due to light reduction. Therefore, the γ value is determined so that the value “512 × light attenuation rate” in the image data is corrected to “512” by the γ correction.

The graph on the right side of FIG. 4 is an explanatory diagram illustrating γ correction for the distance Y ₃ from the center. That is, it is estimated that the brightness of the pixel at the distance Y ₃ from the center is “512 × R _m3 ” in the uniform image where the brightness is “512” when the amount of light is not reduced. Therefore, the γ value is calculated by the following equation (2) so that the output value for the input value “512 × R _m3 ” becomes “512”.

This equation can be applied to the light attenuation rate for each distance (graph on the left side of FIG. 4) determined as described above, and the γ value is calculated for each distance from the center as well as the distance Y _3. can do. Since the γ value for each distance is a γ value for correcting a decrease in light quantity at each distance, the data for each distance is the γ table. In this embodiment, the maximum value after γ correction is set to be lower than the upper limit “1023” of the gradation value range in order to prevent the data from exceeding the gradation value range due to subsequent noise addition. Specifically, as will be described later, since the maximum value of noise is “3”, in the case of normal γ correction, the first coefficient in equation (2) is “1023”. And the maximum value after γ correction is set to “1020”.

  In addition, the configuration for calculating data for correcting the light amount decrease is not limited to the above-described configuration, and various configurations can be employed. For example, it is not essential that the gradation value to be substituted into the expression (2) is the median value of the gradation value, and correction other than the γ correction may be performed by multiplying the reciprocal of the offset or the light attenuation rate. However, in the correction by multiplying the reciprocal of the offset or the light attenuation rate, the gradation value may be saturated in a high gradation region, and therefore γ correction is preferable in order to prevent the saturation of the gradation value.

  In the present embodiment, image modification processing is performed by paying attention to one pixel in the image data 14a. When the image modification processing is completed, the pixel of interest is moved and the same processing is continued. In order to perform the peripheral light amount correction in this processing procedure, first, the target pixel is determined in the image data 14a, and the γ value of the target pixel is acquired with reference to the γ table created in step S115 (step S115). S120). That is, the γ value corresponding to the distance between the target pixel and the center of the image is acquired by referring to the γ table.

  When the γ value of each pixel of interest is acquired, γ correction is performed on the lightness value Y of each pixel of interest using the γ value of each pixel, and light amount reduction correction is performed (step S125). Then, it is determined whether or not the processing has been completed for all the image data 14a as the target pixel (step S130). If it is not determined that the processing has been completed for all the pixels, the target pixel is changed to an unprocessed pixel. (Step S135), the processing after Step S120 is repeated. In the present embodiment, the processing in steps S120 to S135 corresponds to the correction means.

(2-2) Noise addition processing:
Although the peripheral light amount correction is performed as described above, as described above, even if the combination of the diaphragm and the focal length is associated with the dimming rate at a plurality of distances, the light amount is appropriately reduced for all photographing conditions. It is difficult to describe characteristics. In particular, when the lens can be exchanged in the image pickup apparatus, accurate correction becomes difficult. In addition, it is rare that the dimming rate determined in step S110 accurately corresponds to the dimming rate characteristic in the image data 14a.

  If correction is performed based on a light attenuation rate that does not accurately correspond to the light attenuation rate characteristic in the image data 14a, lightness tone jump is caused due to excessive correction or insufficient correction amount. Can occur. Therefore, in the present embodiment, noise addition processing is subsequently performed. In order to perform this processing, noise pattern data 14c is recorded in the hard disk drive 14 in advance.

  The noise pattern data 14c is data indicating noise to be added to the image data after γ correction. For example, the noise pattern data 14c is constituted by data defining noise in the unit region, with two vertical and horizontal pixels as unit regions. be able to. In FIG. 5, a noise pattern Pt is shown as an example. That is, in this example, the noise to be added in the unit area of 2 pixels vertically and horizontally is defined as “0” in the upper left, “2” in the upper right, “3” in the lower left, and “1” in the lower right. Is added to the image data after γ correction as noise.

  After the γ correction, the noise adding unit 30c acquires the noise pattern data 14c from the hard disk drive 14 (step S140), paying attention to a pixel in the image data after the γ correction, and a total of four pixels adjacent to the pixel. Noise is added to the individual (step S145). That is, if the upper left of the noise pattern Pt is made to correspond to a certain target pixel, the gradation value “0” is added to the target pixel, and the gradation value “2” is added to the pixel adjacent to the right side of the target pixel. The gradation value “3” is added to the pixel adjacent to the target pixel, and the gradation value “1” is added to the pixel diagonally to the lower right of the target pixel.

  If noise is added, it is determined whether or not noise addition processing has been completed for all pixels of the image data after γ correction (step S150). If it is not determined that all pixels have been completed in step S150, the target pixel is changed. (Step S155), and the processing after Step S145 is repeated. Since the noise pattern Pt is 2 pixels in the vertical and horizontal directions, when changing the target pixel in step S155, the target pixel after the change, the right adjacent, lower adjacent, and diagonally lower right pixels are not added with noise. Change the pixel to be a pixel. In the present embodiment, the processes in steps S140 to S155 correspond to the noise adding means.

  If it is determined in step S150 that the noise addition processing has been completed for all pixels, the information amount for each color component is converted from 10 bits to 8 bits in order to print the image after noise addition (step S160). Then, an image is printed based on the obtained 8-bit image data (step S165). That is, the noise adding unit 30c transfers the image data after adding the noise to the PRTDRV 31, and the PRTDRV 31 performs a color conversion process on each pixel of the transferred image data, performs a halftone process, and the printer 20 Are output to the printer 20 while being rearranged in the order used. As a result, in the printer 20, a recording material is formed on the recording medium so as to form an image with added noise.

  As described above, in the present embodiment, noise is added to the image data after γ correction, and therefore a tone jump according to the distance from the center of the image occurs due to excessive γ correction or insufficient correction. Even so, this tone jump can be eliminated. FIG. 5 shows this state. The left side of the figure shows an image in which many parts are empty. In this example, a ring noise Nr (tone jump) is generated concentrically with respect to the center O of the image.

  Such ring noise occurs when a decrease in the amount of peripheral light occurs, when γ correction is excessively performed, when γ correction is insufficient, or the like. The graph on the right side of FIG. 5 schematically shows this ring noise Nr. In the figure, the horizontal axis indicates the distance from the center O, and the vertical axis indicates the gradation value of lightness. The gradation value should be almost constant, but the gradation value becomes smaller (darker as the distance from the center increases). In addition, the gradation value fluctuates in a stepwise manner. This results in a tone jump.

  Therefore, when noise is added by the noise pattern Pt as in the present embodiment, as shown in the enlarged view A, noise irregularly (enlarged view) with respect to a stepwise gradation value change (broken line in the enlarged view A). A solid line A) is overlaid, and the tone jump becomes inconspicuous. In the present embodiment, each color component of the image data is expressed by 1024 gradations. On the other hand, the magnitude of noise is 0-3. Therefore, the noise itself does not stand out, and the image quality is not deteriorated by the noise. According to the experiment by the applicant, even with such a small noise, the effect of making the tone jump inconspicuous is exhibited, and the image quality can be improved in the sense of tone jump reduction.

(3) Other embodiments:
The above embodiment is an example for realizing an image processing apparatus, an image processing method, an image processing program, a print control apparatus, a print control method, and a print control program according to the present invention, and other configurations can of course be employed. . In the above example, image correction is performed by a general-purpose computer and print control is performed. Of course, image correction and print control need not be performed by one computer, and are incorporated in a printing apparatus. These processes may be performed by a computer.

  Further, image correction or print control may be performed in a computer that provides an image to be printed to a printing apparatus, such as a digital still camera or a mobile phone. Furthermore, the processor responsible for processing is not limited to a general-purpose processor such as a CPU, and may be a custom IC. The printer is not necessarily a single printing apparatus, and may be a multifunction machine or a copier incorporating a plurality of functions such as a scanner and a fax machine.

  Furthermore, in the above-described embodiment, the image processing utility is provided as a single program. However, it can be provided as a function of PRTDRV, or can be provided as a function of an application program such as image retouching software.

Furthermore, in the above-described embodiment, it is also possible to perform another image modification process with the peripheral light amount correction. For example, in an image in which a decrease in the amount of light occurs, a decrease in saturation is likely to occur as the amount of light decreases. Therefore, it is preferable to perform the peripheral light amount correction and the saturation enhancement process. As saturation enhancement, various configurations can be employed. For example, saturation enhancement can be performed by the following expression.

  Here, Cb ′ is a Cb value after saturation enhancement, Cr ′ is a Cr value after saturation enhancement, and Co is a correction coefficient. The correction coefficient Co may be determined in advance or may be determined according to the degree of peripheral light amount correction. For example, since the γ value indicates the amount of light correction, Co may be defined so as to depend on the γ value. In any case, if the saturation enhancement process is performed along with the peripheral light amount correction, the saturation can be enhanced along with the light amount correction so that a more natural image can be corrected.

  Furthermore, it is possible to change the processing procedure shown in FIG. For example, the above γ correction may be performed on pixels corresponding to the size of the noise pattern, and noise may be added to these pixels, and this process may be repeated to process all the pixels of the image data. Is possible. According to this procedure, noise can be added before the peripheral light amount correction is completed, so that the buffer capacity can be saved.

  Further, it is not essential that the light quantity reduction data 14b and the noise pattern data 14c necessary for the above processing are recorded in the hard disk drive 14 in advance, and are added to the image data 14a when creating the image data 14a. Alternatively, it may be created by the user himself. Of course, it is not essential that the noise pattern data 14c has the configuration as shown in FIG. 5, and the size and gradation value of the noise pattern can be changed.

  Also, the noise pattern can be changed according to the γ value and the distance from the center of the image. For example, a configuration in which the noise pattern is increased and the noise value range is increased as the correction amount by the γ value is increased, or a configuration in which the noise pattern is increased and the noise value range is increased as the distance from the center is increased.

  Further, in the above-described embodiment, since image printing is assumed, the image data after adding noise is converted from 10 bits to 8 bits so that the PRTDRV 31 can recognize it. Therefore, if the PRTDRV 31 can recognize 10-bit data, it is not necessary to perform this conversion. Further, if the purpose is to modify an image instead of printing, conversion from 10-bit data to 8-bit is not essential.

  Further, in the above embodiment, it is assumed that the decrease in the peripheral light amount is corrected. However, the present invention is not limited to the decrease in the light amount, and may be configured to correct the variation in the light amount. For example, in step S110, the vertical axis characteristic can be adjusted in the positive direction. At this time, the γ correction characteristic is a characteristic in which the input value is reduced and the output value is calculated, and correction for reducing the amount of light is performed. Even in this case, image quality degradation may occur due to correction, and therefore it is possible to suppress image quality degradation by adding noise according to the present invention.

1 is a schematic configuration diagram of an image processing apparatus and a print control apparatus. It is a flowchart of a printing control process. It is a figure which shows the structural example of light quantity fall data. It is explanatory drawing explaining the process which calculates (gamma) table. It is explanatory drawing explaining the process which adds noise.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Computer, 10a ... System bus, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... Hard disk drive, 14a ... Image data, 14b ... Light quantity reduction data, 14c ... Noise pattern data, 16a ... Keyboard, 16b ... Mouse , 17a ... display, 20 ... printer, 30 ... image processing utility, 30a ... image data acquisition unit, 30b ... gamma correction unit, 30c ... noise addition unit

Claims (4)

Image data acquisition means for acquiring image data;
Correction means for performing correction on the image data, the correction amount of which varies according to the distance from the reference position in the image;
A noise adding means for adding predetermined noise to the corrected image data ;
The correction means takes a gradation value of a predetermined color component in the image data as a correction target, and a value obtained by subtracting the maximum value of noise added by the noise addition means from the upper limit value of the gradation value range of the predetermined color component An image processing apparatus that performs the correction with respect to the maximum value on the image data .   The noise adding means adds the predetermined noise to the corrected image data by a predetermined noise pattern,
  The correction is performed on the pixels corresponding to the size of the noise pattern by the correction means, and the process of adding noise to the pixels by the noise addition means is repeated to perform the correction on all the pixels of the image data. The image processing apparatus according to claim 1, wherein execution and addition of noise are performed. An image processing method for modifying an image,
An image data acquisition process for acquiring image data;
A correction step of performing correction on the image data, the correction amount of which varies according to the distance from the reference position in the image;
A noise addition step of adding predetermined noise to the corrected image data ,
In the correction step, a gradation value of a predetermined color component in the image data is a correction target, and a value obtained by subtracting the maximum value of noise added in the noise addition step from the upper limit value of the gradation value range in the predetermined color component An image processing method, wherein the correction with the maximum value is performed on the image data . An image processing program for causing a computer to perform a function of modifying an image,
An image data acquisition function for acquiring image data;
A correction function for performing correction on the image data, the correction amount of which varies according to the distance from the reference position in the image;
The image data after the correction, was revealed real and noise adding function for adding a predetermined noise,
The correction function has a gradation value of a predetermined color component in the image data as a correction target, and is a value obtained by subtracting the maximum value of noise added by the noise addition function from the upper limit value of the gradation value range of the predetermined color component. An image processing program for performing the correction with the maximum value on the image data .

Images