JP4539982B2 - Image storage apparatus, method, program, and recording medium - Google Patents

Description

  The present invention has an image storage device such as a color copying machine having a hard disk, which has a function of temporarily storing an image on a hard disk, transmitting the stored image to an external device, or designating the stored image and outputting it to a printer. The present invention relates to a method, a program, and a recording medium.

  Color copiers that store images store in a preselected format (color space, number of bits to quantize, etc.). When selecting an accumulation space, when taking an image outside or inputting an image from the outside, it is not an RGB signal read by a scanner or a CMYK signal for printer output, but a device that does not depend on the characteristics of the scanner or printer. Accumulate with dependent color space signals. This is because when the stored image is taken out to an external device, displayed on an external monitor, and output by an external printer, color reproducibility is not guaranteed unless it is a device-independent signal defined as a standard. Therefore, in order to collectively manage the scanner input image and the external input image with a single storage unit, it is desirable to store both input images in the same color space. Accumulate with independent signals.

  As a device-independent color signal for accumulation, a signal having a color gamut that includes the color gamut of the scanner input RGB and the printer output CMYK is suitable. For example, bg-sRGB, which is a signal defined as a standard, is one of the so-called extended color spaces in which the color gamut is expanded with respect to sRGB, which is generally used as the color space of the current monitor. ˜1, bg-sRGB is −0.75 to 1.25 for each RGB, and has a sufficiently wide color gamut. Therefore, one of the color spaces suitable for the accumulated color space due to the wide color gamut. It is. Note that bg-sRGB matches sRGB in the range of 0-1. Although sRGB has insufficient color gamut for some colors (green, etc.) with respect to the color gamut of printed materials, silver halide photographs, and printers, the color gamut can be sufficiently covered by using bg-sRGB. Note that there are several other extended color spaces described above, and a device-independent signal that is defined independently may be used instead of a signal defined as a standard.

  By the way, when the extended color space is used as the storage color space, a trade-off between the storage capacity and the quantization accuracy becomes a problem. sRGB is 8 bits as standard, whereas bg-sRGB is 10 bits, 12 bits, and 16 bits as standard. This is because if the color gamut is expanded with 8 bits, the gradation that can be expressed per unit becomes coarse, the quantization error increases, and gradation skipping and gradation collapse occur. In order to eliminate the deterioration of gradation due to quantization accuracy, the number of bits larger than 8 bits is required, but the capacity for image storage increases.

  In view of this, an apparatus that maintains the number of expression colors by using wRGB having a wider color gamut than sRGB for printer output has been proposed (for example, see Patent Document 1). However, in Patent Document 1, it is necessary to increase the number of bits in order to actually maintain the number of gradations, and the size of the image data becomes enormous.

  There is also an apparatus that selects and accumulates a color space according to the capability of a destination device when an image read by a scanner is accumulated and transmitted to the outside (see, for example, Patent Document 2). In this apparatus, when transmitting to a facsimile that can output only a monochrome binary image, the image is stored as a monochrome binary image, the storage capacity can be suppressed to the minimum necessary, but the stored image is transmitted to another color facsimile. In this case, it is necessary to input an image again with a scanner, which is not suitable for an apparatus for reusing a stored image.

JP 2002-344664 A JP 2003-153014 A

  Although the sRGB color gamut described above is not sufficient, there are many cases where pixel values do not exist in the color gamut that is insufficient in an actual image, so there is no problem even if sRGB is used as the accumulated color space. Further, the image quality becomes a problem due to the difference in the number of bits in a photographic paper photograph where the density changes gently, a gradation image created by an application, or the like. However, such images are generally not frequently used except for special purposes. Further, a character image that does not place much importance on gradation or a halftone dot image with a high frequency does not appear as a difference in image quality even if it is quantized with 10 bits or 8 bits.

  An object of the present invention is to provide an image storage device, method, program, and recording medium that can achieve both color reproducibility and gradation while suppressing storage capacity when storing photographic paper photographs and the like.

In the present invention, the first color space signal of sRGB or a little wider color sRGB that covers most of the color gamut, although the color gamut is not sufficient, and the first color space that has a sufficient color gamut. The second color space signal such as bg-sRGB, which has insufficient gradation with the same number of bits as the signal, is stored in the hard disk, and the color gamut size, photographic paper image, character image, etc. By determining the image attributes and finally leaving at least one of the first color space signal and the second color space signal in the hard disk, the storage capacity is suppressed and both the color gamut and the gradation are secured. Let Further, in the present invention , the second color space signal is stored with the number of bits smaller than the number of bits originally necessary to ensure the same gradation as the first color space signal, and all the images are originally necessary. The storage capacity is reduced as compared with the case of storing with a small number of bits, and in the present invention, processing is facilitated by setting both the first color space signal and the second color space signal to 8 bits.

According to the present invention, in addition to image 1 and image 2, image 3 having a wide color gamut and dense quantization is generated, and for an input image that requires a wide color gamut and strict gradation, the image Since 3 is stored and held, any input image can be handled, and both color reproducibility and gradation can be ensured while reliably suppressing the storage capacity.

According to the present invention, since the color space (color gamut and number of bits) of the stored image is switched based on the color gamut and attributes of the input image, color reproducibility and gradation characteristics can be efficiently suppressed for each image while suppressing the storage capacity. It is possible to ensure both.

According to the present invention, according to the present invention, the color space is selected and stored for the external input image, and the same color space is always used for the scanner input image that is greatly affected by noise and does not make sense of strict gradation. Since non-selective accumulation is performed, circuits such as color conversion and erased image selection are not unnecessarily increased according to the characteristics of the input image.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1:
FIG. 1 shows the configuration of Embodiment 1 of the present invention. The input image of this embodiment is a scanner input image. The first color conversion unit 11 converts the device-dependent RGB signal of the scanner input into a device-independent RGB signal (hereinafter referred to as rgb (small)) having a relatively narrow color gamut, and the second color conversion unit 12 The device-dependent RGB signal of the scanner input is converted into a device-independent RGB signal (hereinafter, RGB (big)) having a relatively wide color gamut. RGB (big) and rgb (small) are device-independent signals in which the chromaticity value xy of the three primary colors, the tristimulus value XYZ of the white point, and the γ curve are defined.

  FIG. 2 conceptually represents on the LC plane the difference in color gamut and the difference in quantization density that rgb (small) and RGB (big) respectively cover. In this embodiment, both color spaces are quantized with 8 bits. RGB (big) has a larger mesh and coarser quantization. Note that the color conversion method described above uses an existing method such as a method using a 3D-LUT and interpolation or a method using linear matrix conversion.

  In order to store the image, the image compression unit 14 compresses each 8-bit image in the rgb (small) color space, and the image compression unit 15 compresses each 8-bit image in the RGB (big) color space. Two compressed images of image 1 and image 2 are generated. For example, JPEG may be used as the compression method. Since the number of bits is 8 bits, it corresponds to the baseline method of JPEG and is highly versatile for taking out to an external device.

  The image accumulating unit 17 accumulates two compressed images of image 1 and image 2 in units of pages.

  The image attribute determination unit 10 determines the attribute (type) of the input image (original). Here, the attribute of the input image is determined by a method similar to that of the document determination circuit described in JP-A-6-197218. The original determination circuit automatically determines the original type of halftone dot photograph, silver halide photograph (photographic paper photograph), and halftone dot / silver salt photograph. In the present invention, it is necessary to determine whether or not an input image (original) is a photographic paper photographic original. Here, a method for determining a photographic paper photographic original will be described.

  When a photographic paper photograph original is read, there are many pixels taking intermediate levels, and these pixels have a certain amount of chunks. By utilizing such characteristics of a photographic document, a pixel of a photographic document is detected, and the count value (histogram) is used to determine whether or not the target document (input image) is a photo. Use to determine. For determination of the intermediate level pixel, two threshold values p_th1 and p_th2 (p_th1 <p_th2) are set in advance, the input RGB are compared, and p_th1 <R <p_th2 and p_th1 <G <p_th2 and p_th1 <B <p_th2 Is determined to be an intermediate level pixel.

  The color gamut determination unit 13 determines whether data outside the color gamut of rgb (small) exists in the page among the colors converted to RGB (big). RGB (big) and rgb (small) are device-independent signals in which chromaticity values xy of the three primary colors and tristimulus values XYZ and γ curves of the white point determined by the observation light source are defined. Such device-independent signals can be converted from XYZ to N-bit device-independent signals as shown in FIG.

  The 3 × 3 matrix calculation unit 101 calculates the expression (1). Here, m11 to m33 are parameters determined by the chromaticity value xy of the three primary colors and the tristimulus value of the white point.

In clipping 102, a value less than 0 is rounded to 0, and a value greater than 1 is rounded to 1 (usually defined as 0 to 1 and will be described as 0 to 1).
Here, pixels less than 0 or more than 1 clipped are values outside the color gamut of the color space.
r ′ = max (0, min (r, 1))
g ′ = max (0, min (g, 1))
b ′ = max (0, min (b, 1))
The γ conversion 103 performs the calculation of Expression (2). Depending on the light source, Damma is generally Gamma = 2.2, and D50 is Gamma = 1.8.

  The N-bit conversion 104 performs the calculation of Expression (3).

  In reverse conversion (device-independent RGB → XYZ), reverse conversion of processing other than clipping may be performed (FIG. 3B). The 3 × 3 matrix used in the matrix calculation 203 is an inverse matrix of the matrix in FIG.

  The conversion from RGB (big) to rgb (small) is performed by converting RGB (big) to XYZ as shown in FIG. 3B, and XYb is converted to rgb (small) as shown in FIG. It is possible by converting to. That is, as shown in FIG. 3C, if a composite matrix 303 of two matrices is used, it can be realized by a single matrix calculation.

Further, as described in the clipping in FIG. 3A, the pixels clipped in less than 0 or more than 1 in FIG. 3C are within the gamut in RGB (big), but out of the gamut in rgb (small). Represents the value of.
Therefore, the color gamut determination is performed as shown in FIG.

  The determination 307 as to whether or not out of the color gamut is “1” assuming that the pixel value is out of the color gamut of rgb (small) if min (r, g, b) <0 or max (r, g, b)> 1. "Is output, otherwise" 0 "is output.

  Next, the number of pixels outside the color gamut is counted 308. That is, the number of “1” pixels in the page is counted. A threshold value determination 309 is performed on the count value, and if the counted number of pixels “1” is equal to or greater than a predetermined threshold value, it is determined that a value outside the color gamut of rgb (sall) exists in the page. Note that when the predetermined threshold value = 1, there is a risk of misjudgment of being out of the color gamut due to noise components, so it is preferable to set a value with a little margin. Color gamut determination is also performed using the time during which images are stored, and the determination result is output.

  Based on the result of the image attribute determination unit 10 and the result of the color gamut determination unit 13, the erased image selection unit 16 selects an image to be deleted from the images stored in the image storage unit 17, and the selected image is stored in the image storage unit. Delete from 17. The reason for adopting a configuration in which data is once stored and then deleted is that the determination result is obtained when the image attribute determination unit 10 or the color gamut determination unit 13 refers to the image in the page to the end. Note that the image 1 and the image 2 may be stored in the buffer memory, and the selected image may be stored in the image storage unit 17. The image finally left in the storage unit 17 is at least one of the two stored images (image 1 and image 2) as shown in FIG. As a result of the color gamut determination, if all the colors in the page are in the rgb (small) color gamut, the image 1 is sufficient, so the image 1 is left and the image 2 is selected as the erased image and erased. If there is a color out of the rgb (small) color gamut, the image 2 is left with emphasis on color reproducibility. In the case of a character image or halftone dot image that is not a photographic paper photograph, the gradation is not so important, so image 1 is selected and erased. However, in the case of photographic paper photographs, gradation is also important, so if you want to reduce the storage capacity, you can leave only one of them, but in this embodiment, leave both image 1 and image 2 and delete them. do not do. By holding both the image 1 and the image 2 in the storage unit 17, a composite image of the image 1 and the image 2 can be created. The composite image of the image 1 and the image 2 is finely quantized within the rgb (small) color gamut and becomes a coarsely quantized image outside the rgb (small) color gamut. The color out of the rgb (small) gamut is a high-saturation color gamut away from the achromatic axis in FIG. 2, and gradation skipping is not conspicuous compared to the achromatic axis. Relatively small. Only in this case, two images are stored for one input image, and the storage capacity increases. However, if there are many other cases as input images, the storage capacity can be comprehensively suppressed.

  The example in which the input image is the scanner input has been described above, but the same applies to the case where the input image is not a scanner input but a printer input image received from an external device. This will be described below.

When document data created by an application on an external PC is output to a printer, the document data is transferred to the page description language (Page
It is converted into a command string expressed in Description Language (PDL), and the PDL is transmitted to the printer side. The printer side develops the received PDL into a bitmap image. The developed bitmap image corresponds to the input image of FIG. In this case, the input image is generally an image expressed in the sRGB color space, and the first color conversion unit 11 and the second color conversion unit 12 are realized by conversion using mathematical formulas (3 × 3 matrix conversion and γ conversion). it can.

  The image attribute determination unit 10 analyzes the PDL and determines whether there is a character object in the page. In general, a PDL is composed of three objects: a character object, a graphic object such as a graphic, and a bitmap object such as an image taken by a scanner or a digital camera. Depending on the presence / absence of a character object, as shown in FIG. 5, image 1 is held when it is within the color gamut, and image 2 is held without giving importance to gradation when there is a color outside the color gamut and there is a character object. If there is no character object (only a graphic object or a bitmap object), the image 1 (+ image 2) is held with emphasis on gradation.

  As described above, according to the present embodiment, since image accumulation is performed with a color space and quantization accuracy corresponding to a color gamut and image attribute for each image, both color reproducibility and gradation can be achieved while suppressing accumulation capacity.

Example 2:
FIG. 6 shows the configuration of the second embodiment of the present invention. In the first embodiment, when the photographic paper photograph has a wide color gamut, the image 1 and the image 2 are held in the storage unit. However, in the present embodiment, the image 3 is prepared and is a photographic paper photograph having a wide color gamut. Only one (image 3) is finally held (FIG. 8).

  Hereinafter, processing blocks (second color conversion unit 22 and bit truncation unit 23) different from the first embodiment will be described. The second color conversion unit 22 outputs a signal (12 bits) quantized with a bit number larger than 8 bits in the second color space RGB (big) having a wide color gamut. FIG. 7 is a conceptual diagram similar to FIG. An image obtained by compressing the image by the image compression unit 27 is an image 3. Further, if the bit truncation unit 23 truncates the lower bits of the signal output from the second color conversion unit 22 in 12 bits and converts it to 8 bits, the same RGB (big) 8-bit signal as in the first embodiment is obtained. The image 2 is obtained by compressing this. Since the image 3 has 12 bits, the storage capacity increases as compared with the images 1 and 2, and the image compression unit 27 also has a restriction such as a compression method (for example, JPEG expansion method) corresponding to 12 bits. However, the storage capacity can be reliably suppressed as compared to the case of holding two 8-bit images as in the first embodiment.

  As described above, according to this embodiment, 12-bit image 3 is stored for an image that requires a wide color gamut and strict gradation, so that two 8-bit images of image 1 and image 2 are stored. The storage capacity can be reduced rather than doing so. If the present invention for switching the color space and quantization accuracy according to the color gamut and attribute of the image is not implemented, in order to obtain the same level effect from the image quality aspect, image storage is performed with a 12-bit image 3 for all images. However, compared with that case, the storage capacity can be further reduced.

Example 3:
FIG. 9 shows the configuration of the third embodiment of the present invention. Since the scanner input image is a signal on which noise is superimposed due to vibration at the time of input or the like, although it depends on the noise level, it is not necessary to strictly consider gradation.

  FIG. 10 shows the difference in gradation between the case where the quantization is coarse and the case where the quantization is dense, in the absence of noise. FIG. 11 shows the difference in gradation in the presence of noise when the quantization is coarse and when the quantization is dense. When there is no noise, the closer the quantization, the better the gradation skip and the better. However, when there is noise as shown in FIG. 11, the influence of the noise on the gradation is not changed regardless of whether the quantization is coarse or dense. In this case, there is no problem even if the scanner input image is always converted and accumulated into a signal that is relatively coarsely quantized in a color space with a large color gamut.

On the other hand, an external input signal input via an external I / F (interface) 37 is a noise-free image created by application software of an external PC, and the noise amplitude is smaller than the quantization error. Since an image read by an accurate scanner is input, it is necessary to emphasize gradation. Therefore, for the external input image, as in the first embodiment described above, a configuration in which an image having different color gamut width and quantization density is selectively stored in the storage means is adopted (inside the dotted line in FIG. 9 ). ).

  The scanner color correction unit 31 converts RGB signals read by the scanner 30 into 8-bit signals of RGB (big), which is the second color space, and performs compression processing by the image compression unit 32, and then the image storage unit 33. To accumulate. The image accumulating unit 33 accumulates and manages the scanner input image 30 and the external input image 37 collectively.

  The image expansion unit 34 reads the stored image stored in the image storage unit 33 and expands the image. The printer color correction unit 35 converts RGB into CMYK and outputs the image to the printer 36.

  As described above, according to the present embodiment, in the case of an external input image, an image in which the color gamut and quantization accuracy are switched is selectively retained. However, in the case of a scanner input image, the same color space (the same color gamut, the same bit) is always used. The number of the images is non-selectively stored, so that a circuit for color conversion, erased image selection, or the like is not required for a scanner input image having a large noise, so that an increase in cost can be suppressed.

Example 4:
FIG. 12 shows the configuration of Embodiment 4 of the present invention. In the above-described first to third embodiments, an image expressed in two color spaces of rgb (small) and RGB (big) is acquired from an input image. Therefore, the first color conversion unit and the second color conversion unit The configuration including the two color conversion means is adopted.

  In this embodiment, rgb (small) and RGB (big) are set to the same color space in the rgb (small) color gamut, such as sRGB and bg-sRGB, for example, so that one color conversion is performed. Consists only of means and reduces the addition of hardware.

  The color conversion unit 50 converts the input image into a signal quantized with more than 8 bits of RGB (big). In the clipping unit 52, the color gamut is limited and clipped to an 8-bit signal to generate rgb (small). The image compression unit 55 compresses rgb (small) to generate image 1.

  On the other hand, the bit truncation unit 53 generates an 8-bit signal, RGB (big), with the lower-order bits truncated to coarsely quantize. Image compression unit 56 compresses RGB (big) to generate image 2. When the image 3 is stored as in the second embodiment, the signal after conversion by the color conversion unit 50 may be stored.

  FIG. 13 shows the relationship between rgb (small) and RGB (big) in the present embodiment, and the relationship is such that the rgb (small) cube is completely included in the RGB (big) cube in the RGB space. FIG. 14 shows the size of one unit of quantization of an image 1 obtained by quantizing rgb (small) with 8 bits and an image 2 obtained by quantizing RGB (big) with 8 bits, respectively, as a mesh. For simplicity, it is represented by a two-dimensional RG plane. The mesh size relationship is the same as in FIG. FIG. 15 similarly shows the image 3.

  Instead of adopting a configuration for accumulating the image 3, a configuration for accumulating the two images 1 and 2 as in the first embodiment may be used. In this case, as described above, a composite image can be generated after reading out two stored images of image 1 and image 2, and the quantization mesh of the composite image is as shown in FIG. Fine quantization in the rgb (small) color gamut and coarse quantization in the outer color gamut. In this embodiment, since the same signal is used in the rgb (small) color gamut, synthesis is easy. .

  As described above, according to the present embodiment, as in the conventional case where all data is stored in the same color space (the same color gamut and the same number of bits), it can be realized by one color conversion, and an increase in cost can be suppressed.

Example 5:
FIG. 17 shows the configuration of the fifth embodiment of the present invention. The embodiment described above is an embodiment that employs a configuration in which at least one image is left in the storage means by erasing the image once stored.

  In this embodiment, the user gives an instruction on the operation panel 60, and according to the instruction, at least one of the image 1 and the image 2 is finally selected as an image to be held, and is held from the start of processing. It is possible to store only images.

  The selector 65 selects an image to be held, and the image storage unit 66 stores only the selected image. Unlike the configuration in which two images are always stored once and then unnecessary ones are erased as in the above-described embodiment, the storage capacity does not increase temporarily. Note that the user instruction on the operation panel may directly select the color space, and select the image quality mode such as the character mode, character / print photo mode, character / print paper photo mode, print photo mode, or photographic paper mode. It may be an indirect instruction. In this case, in modes other than the character / photographic paper photograph mode and the photographic paper mode, the gradation is not considered important, and relatively coarse quantization may be performed (image 2 is selected).

  As described above, according to the present embodiment, when an image to be stored in the storage unit can be selected before image storage, it is possible to suppress an increase in storage capacity temporarily by selecting first and storing only the image. .

  In the present invention, a storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus is stored in the storage medium. This can also be achieved by reading and executing the program code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

  Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes a case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

The structure of Example 1 of this invention is shown. The difference between the color gamut of rgb (small) and RGB (big) and the density of quantization are shown. It is a figure explaining color gamut determination. The example of the accumulation | storage image according to the color gamut and image attribute of Example 1 is shown. Another example of the accumulated image corresponding to the color gamut and image attribute of the first embodiment is shown. The structure of Example 2 of this invention is shown. The RGB (big) color gamut and quantization of Example 2 are shown. The example of the accumulation | storage image according to the color gamut and image attribute of Example 2 is shown. The structure of Example 3 of this invention is shown. In a state where there is no noise, a difference in gradation is shown between when the quantization is coarse and when the quantization is dense. In a state where there is noise, a difference in gradation is shown between when the quantization is coarse and when the quantization is dense. The structure of Example 4 of this invention is shown. The relationship between rgb (small) and RGB (big) in Example 4 is shown. The quantization mesh of the image 1 of Example 4, and the image 2 is shown. The quantization mesh of the image 3 of Example 4 is shown. The quantization mesh of the synthesized image of the image 1 and the image 2 in Example 4 is shown. The structure of Example 5 of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image attribute determination part 11 1st color conversion part 12 2nd color conversion part 13 Color gamut determination part 14, 15 Image compression part 16 Erase image selection part 17 Image storage part

Claims (4)

  Image storage apparatus comprising: internal input means for optically reading a document and acquiring an internal input image signal; external input means for acquiring an external input image signal from an external device via an external interface; and storage means for storing an image A first color conversion means for converting the external input image signal into a first color space signal quantized with L bits, and a color gamut wider than the first color space signal. Second color conversion means for converting to a second color space signal quantized with L bits, and at least one of the first color converted image or the second color converted image. Selection means for selecting one image, and scanner color correction means for converting the internal input image signal into the second color space signal quantized with L bits, and the internal input image signal is received from the internal input means. Acquired In this case, the image signal converted by the scanner color correction unit is held in the storage unit, and when the external input image signal is acquired from the external input unit, the image selected by the selection unit is An image storage device characterized by being held in storage means.   Image storage step comprising: an internal input step for optically reading a document and acquiring an internal input image signal; an external input step for acquiring an external input image signal from an external device via an external interface; and an accumulation step for accumulating images A first color conversion step of converting the external input image signal into a first color space signal quantized with L bits, and a color gamut wider than the first color space signal of the external input image signal And a second color conversion step for converting to a second color space signal quantized with L bits, and at least one of the first color converted image or the second color converted image. A selection step of selecting two images, and a scanner color correction step of converting the internal input image signal into the second color space signal quantized with L bits, and the internal input image signal is converted from the internal input step. Acquired In the case, the image signal converted in the scanner color correction step is held in the accumulation step, and when the external input image signal is acquired from the external input step, the image selected in the selection step is An image accumulating method characterized in that the image accumulating step holds the image. A program for causing a computer to realize the image storage method according to claim 2 . A computer-readable recording medium recording a program for causing a computer to implement the image storage method according to claim 2 .

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