JP2000295467A - Method and device for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for processing image, with which artifacts generated in multiplying (expanding/reducing) processing of an image can be suppressed. SOLUTION: Multiplying processing with a prescribed power, which is s1 in a first direction and is s2 in a second direction orthogonal with this first direction is performed, while being divided into two times of first multiplying processing with the respective powers in the first and second directions, which are (s1+1)2 and (s2+1)/2, and second multiplying processing with the respective powers in the first and second directions, which are 2s1/(s1+1) and 2s2/(s2+1), and in the first and second times of multiplying processing, the starting position of first multiplying processing and the start position of second multiplying processing are deviated relatively, so as to relatively invert the phases of first and second pixel positions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing method and an image processing apparatus, and more particularly to an image processing technique for suppressing artifacts generated in image scaling processing.

[0002]

2. Description of the Related Art Conventionally, printing of an image photographed on a photographic film original such as a negative film or a reversal film onto a photosensitive material such as photographic paper is performed by projecting an image of the film original onto the photosensitive material. Exposure was performed by so-called direct exposure.

On the other hand, in recent years, a printing (printing) system using digital exposure, that is, after reading image information recorded on a film photoelectrically and converting the read image into a digital signal, various methods have been proposed. A digital printing system that performs image processing to form image information for recording, scans and exposes a photosensitive material with a recording light modulated according to the image information, records an image (latent image), and develops and prints the image. Digital photo printers that have been proposed and that specifically implement this system are under development.

In a digital print system, an editing layout of a print image, such as editing such as synthesis of a plurality of images, division of an image, editing of characters and images, color / density adjustment, electronic scaling, and sharpness enhancement of an outline. Various types of image processing such as (sharpness enhancement) can be freely performed, and a finished print that has been freely edited and image-processed can be output according to the application.

At this time, it is necessary to scale (enlarge or reduce) the image according to the size of the output image. Or, in particular, a part of the image may be enlarged and reproduced. In such a case, electronic scaling processing is performed. Also, in an image forming apparatus such as a digital copying machine and a facsimile, a scaling process is performed on an image input by a scanner as necessary.

[0006]

However, conventionally,
When scaling an input image, the sampling pitch at the time of inputting the image and the resampling pitch at the time of performing the scaling process interfere with each other, causing artifacts such as moire and beats that are streak-like unevenness. There was a problem. On the other hand, for example, Japanese Unexamined Patent Application Publication No.
Japanese Patent Laid-Open Publication No. 2000-209873 generates a random coefficient used for enlarging or reducing an image, multiplies the generated random coefficient by a pixel value within a predetermined range including a target pixel in the processing target image data, and enlarges or reduces the image. An image processing apparatus that suppresses artifacts generated by interference between a sampling pitch of a scanner and a resampling pitch of enlargement / reduction by forming the above image data is disclosed.

However, in the apparatus disclosed here, the possibility of artifacts is diffused by a random coefficient, and processing cannot be performed according to the frequency of an image, and frequency characteristics cannot be realized. When a further reduction effect is to be obtained, there is a problem that it is difficult to obtain an appropriate artifact reduction effect according to the image for any image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an image processing method and apparatus capable of suppressing artifacts generated in image scaling (enlargement / reduction) processing. And

[0009]

According to another aspect of the present invention, there is provided an image processing method for performing a scaling process at a predetermined magnification, the method comprising: The predetermined magnification is s ₁ in a first direction and s ₂ in a _second direction orthogonal to the first direction. At this time, the magnifications in the first and second directions of the first scaling process are (s ₁ +1) / 2 and (s ₂ +1) / 2, respectively, and the magnification of the second scaling process is The magnifications in the first and second directions are 2s ₁ / (s ₁ +1) and 2s ₂ / (s
₂ +1), and in the first and second scaling processes, the start position of the first scaling process and the second position are set so that the phases of the first and second pixel positions are mutually inverted. It is an object of the present invention to provide an image processing method characterized by relatively shifting the start position of the second scaling process.

Here, it is preferable that the magnification s _{1 in the first} direction is equal to the magnification s _{2 in} the second direction. In the first and second scaling processes, the start position of the first scaling process and the start position of the second scaling process are relatively set in the first direction and the second direction. It is preferable to shift in the second direction orthogonal to the first direction. In the first and second scaling processes, the start position of the first scaling process and the start position of the second scaling process Is relatively shifted in the first direction and the second direction by の of the pixel period, and further, the start position of the second scaling process is changed to the first scaling process. It is preferable that the pixel is shifted by a half of the pixel period in the first direction and the second direction with respect to a processing start position. Further, it is preferable that the scaling process at the predetermined magnification is performed on a multi-valued image.

[0011] Similarly, in order to solve the above-mentioned problem, the present invention provides a method according to the present invention, wherein a magnification in a first direction is s ₁ and a magnification in a second direction orthogonal to the first direction is s _2. An image processing apparatus for performing scaling processing of a magnification, wherein the magnification in the first and second directions is (s ₁ +1) / 2 and (s ₂ +1) / 2, respectively. Means for performing
The magnification in the first and second directions is 2s ₁ /
Means for performing a second scaling process of (s ₁ +1) and 2 s ₂ / (s ₂ +1), the first scaling process, and the second scaling process.
In the scaling process, the start position of the first scaling process and the second position are relatively shifted so that the phases of the pixel positions are inverted with each other.
And a means for shifting the start position of the scaling process of the image processing apparatus.

Here, the magnification s _{1 in} the first direction is preferably equal to the magnification s _{2 in} the second direction. Further, the means for shifting the start positions of the first and second scaling processes includes a start position of the first scaling process and a second position.
It is preferable that the start position of the scaling process is relatively shifted in the first direction and the second direction by の of the pixel period. Further, the means for shifting the start positions of the first and second scaling processes is provided by the second
Preferably, the start position of the scaling process is shifted by の of the pixel period in the first direction and the second direction with respect to the start position of the first scaling process. Further, it is preferable that the scaling process at the predetermined magnification is performed on a multi-valued image.

Further, the image processing method according to the present invention is an image processing method for performing a scaling process at a predetermined magnification, wherein the scaling process at the predetermined magnification is performed by a first scaling process and a second scaling process. The first and second scaling operations are performed in such a manner that the phases of the first and second pixel positions are inverted with respect to each other. The position may be relatively shifted from the start position of the second scaling process. Here, the predetermined magnification is
When s, the magnification of the first and second scaling processes is preferably (s + 1) / 2 and 2s / (s + 1), and the magnification of the first scaling process is
(S + 1) / 2, and the magnification of the second scaling process is preferably 2s / (s + 1). Further, the image processing method of the present invention is an image processing method for performing scaling processing of a multi-valued image, wherein the scaling processing of the magnification s is divided into two times, and the first scaling processing is performed at a magnification α = (S + 1) / 2, and the second scaling process is performed with the magnification β = s / α and the second start position with respect to the start position of the first process in the horizontal direction.
The shift may be performed by shifting the pixel cycle by の in the vertical direction.

Further, the image processing apparatus according to the present invention is an image processing apparatus for performing a scaling process at a predetermined magnification, wherein a unit for performing a first scaling process, a unit for performing a second scaling process, In the first scaling process and the second scaling process, the start position of the first scaling process and the second scaling process are so set that the phase of the movement of the pixel position is reversed. Means for relatively shifting the start position. Here, when the predetermined magnification is s, the magnifications of the first and second scaling processes are (s + 1) / 2 and 2s / (s +
1), and the magnification of the first scaling process is
(S + 1) / 2, and the magnification of the second scaling process is
2s / (s + 1), and the means for shifting the start position of the first and second scaling processes is the first scaling process and the second scaling process. The means for relatively shifting the start position of the first scaling process and the start position of the second scaling process in a first direction and a second direction orthogonal to the first direction is provided. Good. The image processing apparatus according to the present invention is an image processing apparatus that performs a scaling process on a multi-valued image.
= (S + 1) / 2 means for performing a scaling process, and the magnification α
, The start position of the scaling process is shifted in the horizontal and vertical directions by の of the pixel period, and the magnification β = s /
means for performing a scaling process of α.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing method and apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram schematically showing a digital photo printer to which an image processing apparatus for performing an image processing method according to an embodiment of the present invention is applied. A digital photo printer (hereinafter, referred to as a photo printer) 10 illustrated in FIG. 1 includes a scanner (image reading device) 12 that photoelectrically reads an image captured on a film F, and an image data read by the scanner 12. Image processing such as scaling (enlargement / reduction) processing, edge portion detection, sharpness enhancement (sharpness enhancement), and smoothing processing (granularity suppression), and operations and control of the entire photo printer 10, which are features of the present invention. It has a processing device 14. The photo printer 10 also performs image exposure on a photosensitive material (photographic paper) with a light beam modulated in accordance with image data output from the image processing device 14, develops the image, and outputs a (finished) image as a print. It has a recording device 16. Image processing device 1
4 includes input and setting of various conditions, selection and instruction of processing,
An operation system 18 having a keyboard 18a and a mouse 18b for inputting instructions such as color / density correction and the like, an image read by the scanner 12, various operation instructions, and setting / registration screens for various conditions are displayed. The monitor 20 is connected.

The scanner 12 is a device for photoelectrically reading an image photographed on a film F or the like one frame at a time.
A variable aperture 24, a diffusion box 26 for making the reading light incident on the film F uniform in the surface direction of the film F, a carrier 28 of the film F, and an imaging lens unit 30
, An image sensor 32 having a line CCD sensor corresponding to reading of image densities of R (red), G (green) and B (blue), an amplifier (amplifier) 33, and an A / D (analog / digital) And a converter 34.

In the photo printer 10, a dedicated carrier 28 which can be freely attached to the main body of the scanner 12 is provided with a film F such as a new photographic system (Advanced Photo System) or a 135 size negative (or reversal) film.
Are prepared in accordance with the type and size of the film, the form of the film such as strips and slides, and the like, and can be adapted to various films and processes by replacing the carrier 28. An image (frame) photographed on a film and provided for printing is conveyed by the carrier 28 to a predetermined reading position.

When the scanner 12 reads an image photographed on the film F, the image is emitted from the light source 22.
The uniform reading light, the light amount of which is adjusted by the variable aperture 24 and the diffusion box 26, enters the film F positioned at a predetermined reading position by the carrier 28, and is transmitted therethrough, thereby carrying the image captured on the film F. To obtain the projected light. The color image signal is not limited to the signal input by reading the light transmitted through the film as described above, and may be the signal input by reading the light reflected by a reflective original, or a digital camera. A color image signal of an image captured by the camera may be used.

In the illustrated example, the carrier 28 is a 24
It corresponds to a long film F (strips) such as a 35-size film or a cartridge of a new photo system. The film F is positioned at the reading position by the carrier 28, and receives reading light while being conveyed in the sub-scanning direction orthogonal to the main scanning direction, which is the direction in which the RGB line CCD sensors extend. As a result,
The film F is slit-scanned two-dimensionally, and the film F
Is read.

The projection light of the film F is imaged on the light receiving surface of the image sensor 32 by the imaging lens unit 30. R, G and B output from the image sensor 32
Are amplified by an amplifier 33, sent to an A / D converter 34, and converted into, for example, 12-bit RGB digital image data in the A / D converter 34, respectively. Is output to

When reading an image captured on the film F, the scanner 12 performs a prescan (first image reading) for reading at a low resolution and a fine scan (second scan) for obtaining image data of an output image. Image reading) is performed twice. Here, the pre-scan is performed under preset pre-scan reading conditions so that the image sensor 32 can read all images of the film F to be scanned by the scanner 12 without saturation.
Fine scan, on the other hand, uses pre-scan data
The scanning is performed under the fine scan reading conditions set for each frame so that the image sensor 32 is saturated at a density slightly lower than the minimum density of the image (frame). The prescan and fine scan output image signals are basically the same image data except that the resolution and the output image signal level are different.

Note that the scanner 12 used in the photo printer 10 is not limited to the one that performs the slit scanning reading, and may be the one that performs the surface reading that reads the entire surface of the film image of one frame at a time. Good.

As described above, the digital image data signal output from the scanner 12 is output to the image processing device 14 that performs the image processing method of the present invention. FIG. 2 is a block diagram of the image processing apparatus (hereinafter, referred to as a processing apparatus) 14. The processing device 14 includes a scanner correction unit 36,
LOG converter 38, prescan (frame) memory 4
0, a fine scan (frame) memory 42, a pre-scan data processing unit 44, a fine scan data processing unit 46, and a condition setting unit 48. Note that FIG.
Denotes a part mainly related to image processing. The processing device 14 includes a CPU that controls and manages the entire photo printer 10 including the processing device 14, and is necessary for the operation of the photo printer 10, and the like. A memory for recording important information is provided, and the operation system 18 and the monitor 20 are connected to the CPU.
(CPU bus).

The R, G, and B image signals input from the scanner 12 to the processing device 14, for example, 12-bit digital image data, are input to the scanner correction unit 36.
The scanner correction unit 36 performs DC offset correction, dark correction, and defective pixel correction to correct the sensitivity variation and dark current of each pixel of the RGB digital image data due to the RGB line CCD sensor of the image sensor 32 of the scanner 12. And data correction of the read image data such as shading correction. The digital image signal that has been subjected to the correction processing of the sensitivity variation and dark current for each pixel by the scanner correction unit 36 is output to the LOG conversion processor. The LOG converter 38 converts the digital image data into gradation data by performing logarithmic conversion processing, and converts the digital image data into digital image density data. For example, the LOG converter 38 corrects the digital image data using the lookup table (LUT) by the scanner correction unit 36. The obtained 12-bit digital image data is, for example, 10 bits (0 to 1023)
To digital image density data.

The digital image density data converted by the LOG converter 38 is stored (stored) in the pre-scan memory 40 if it is pre-scan image data and in the fine scan memory 42 if it is fine scan image data. . The pre-scan memory 40 is obtained by pre-scanning the film F by the scanner 12,
This is a frame memory for storing or storing the low-resolution image density data of the entire frame of the film F subjected to various data correction and logarithmic conversion processing for each of the RGB colors. The pre-scan memory 40 stores at least the film F
It is necessary to have a capacity capable of storing image density data of one frame of three colors of RGB. However, a memory having a capacity capable of storing image density data of a plurality of frames may be used. It may be provided. The pre-scan image data stored in the pre-scan memory 40 is read by the pre-scan data processing unit 44.

On the other hand, the fine scan memory 42 stores the high-resolution image density data of the entire frame of the film F obtained by the fine scan of the film F by the scanner 12 and subjected to various data correction and logarithmic conversion processing. This is a frame memory for storing or storing for each color. The fine scan image data stored in the fine scan memory 42 is read out by the fine scan data processing unit 46.

The pre-scan data processing section 44 has an image processing section 50 and an image data conversion section 52. The pre-scan data processing section 44 displays the pre-scan image data stored in the pre-scan memory 40 on the monitor 20. Perform various necessary image processing. The image processing unit 50 includes a condition setting unit 48 described below.
The image data read by the scanner 12 and stored in the pre-scan memory 40 in accordance with the image processing conditions set by the
By a lookup table (hereinafter, represented by an LUT) or a matrix (hereinafter, represented by MTX) calculation, predetermined corrections such as gradation correction, color conversion, and density conversion are performed so that a color image can be reproduced on the T display screen. This is for performing image processing. The image data conversion unit 52 includes an image processing unit 50
The image data processed according to (3) is scaled as necessary to match the resolution of the monitor 20.
Using a (three-dimensional) LUT or the like, the image data is converted into image data corresponding to display on the monitor 20, and image data to be displayed on the monitor 20 is output. The image processing conditions in the image processing unit 50 are set by a condition setting unit 48 described later.

The fine scan data processing section 46 has an image processing section 54 and an image data conversion section 56. The fine scan image data stored in the fine scan memory 42 is converted from the image recording device 16 into a color print. Various image processing necessary for output and the image processing method of the present invention are executed. The image processing unit 54, according to the image processing conditions set by the condition setting unit 48 described below,
The image data read by the scanner 12 and stored in the fine scan memory 42 is subjected to predetermined image processing so that a high-quality image can be reproduced on color paper with a desired density, gradation and color tone as a color print. Is what you do. For this reason, the image processing unit 54 performs color balance adjustment, gradation adjustment, color adjustment, density adjustment, saturation adjustment, and scaling (enlargement) on the image data by using an LUT, MTX calculator, low-pass filter, adder / subtractor, and the like. Various image processing such as reduction (reduction) and sharpness enhancement (edge enhancement; sharpening) are performed.

The image data conversion unit 56 includes an image processing unit 54
Is converted into image data corresponding to image recording by the image recording device 16 using a standard gradation lookup table such as a 3DLUT and supplied to the image recording device 16. Image recording device 16
Outputs a finished print in which a color image is reproduced based on the image data output from the fine scan data processing unit 46.

The image processing conditions in the image processing section 54 are as follows:
It is set by the condition setting unit 48. The condition setting unit 48 sets various processing conditions such as a reading condition of the fine scan and image processing conditions in the pre-scan data processing unit 44 and the fine scan data processing unit 46. The condition setting unit 48 includes a setup unit 58, a key correction unit 60, and a parameter integration unit 62. Setup part 5
8 sets the fine scan reading conditions using the prescan image data and supplies the same to the scanner 12, and creates the image processing conditions of the prescan data processing unit 44 and the fine scan data processing unit 46 (calculation). )
Then, the parameter is supplied to the parameter integration unit 62.

The key correction unit 60 includes an adjustment amount such as density (brightness), color, contrast, sharpness, and saturation set by a key (not shown) provided on the keyboard 18a and the operation system 18, and a mouse 18b. The amount of adjustment of image processing conditions (for example, LU
A correction amount of T) is calculated, parameters are set, and the parameters are supplied to the parameter integration unit 62. The parameter integration unit 62 receives the image processing conditions set by the setup unit 58, and transmits the supplied image processing conditions to the image processing unit 50 of the pre-scan data processing unit 44 and the image processing unit 54 of the fine scan data processing unit 46. After setting, the image processing condition set for each part is corrected (adjusted) or the image processing condition is reset according to the adjustment amount calculated by the key correction unit 60.

Next, the image processing unit 54 of the fine scan data processing unit 46 that performs image processing such as scaling (enlargement / reduction) processing, which is a feature of the present invention, will be described in detail.
FIG. 3 is a block diagram schematically illustrating an embodiment of the image processing unit 54. As shown in the figure, the image processing unit 54 includes a color density gradation conversion unit 64 that converts the density, color, and gradation of the image data, a saturation conversion unit 66 that converts the saturation of the image data, A digital magnification conversion (electronic magnification) means 68 for converting the number of pixels to change the magnification is provided, and an image processing block 70 for performing various image processing such as sharpness enhancement and graininess suppression.

In the image processing section 54, the color density gradation conversion means 64 converts the image data into density data, color data and gradation data according to an LUT or the like. Further, the saturation conversion means 66 includes a color density gradation conversion means 6.
4 converts the image data obtained in Step 4 into saturation data in accordance with an MTX operation or the like. The electronic scaling unit 68 interpolates the image data subjected to the saturation conversion by the saturation conversion unit 66 according to the size of the color image output to the color paper in the image recording device 16 and according to the output pixel density. In this case, the number of pixel data of the image data is increased or decreased by thinning or thinning. The image processing block 70 performs image processing such as sharpness enhancement and graininess suppression.

FIG. 4 shows an electronic variable power unit 6 according to this embodiment.
8 is a block diagram illustrating a schematic configuration of FIG. In the image scaling (enlargement / reduction) process according to the present invention, the scaling process by interpolation of image data is divided into two, and the periods of artifacts generated in the first and second times are made equal, and By performing interpolation so that the phase is inverted, artifacts are suppressed.

In the present invention, the interpolation kernel is decomposed in a first direction, for example, a horizontal direction and a second direction, for example, a vertical direction orthogonal to the first direction, for example, a vertical direction, and the image, particularly a multi-valued image, is resized. Can be applied to an image processing method that performs the following.
In the following description, the first direction is a horizontal direction,
A second direction orthogonal to the first direction is defined as a vertical direction, a coefficient matrix representing an interpolation kernel is decomposed into row and column coefficient vectors, and interpolation in the vertical direction is performed after interpolation in the horizontal direction. In the following, the description will be limited to the one-dimensional case in the horizontal direction.

The electronic scaling means 68 performs scaling by interpolation by 2
In order to perform the division in the first time, a first interpolator 72 for performing the first magnification and a second interpolator 74 for performing the second magnification are provided. The first and second interpolators 72 and 74 include multipliers 76 and 78 and flip-flops 80 and 8 respectively.
2 are connected. The multiplier 76 connected to the first interpolator 72 is connected to the address generator 84. The multiplier 78 connected to the second interpolator 74 is connected to the address generator 84 via the multiplier 76.

The multiplier 76 receives the reciprocal 1 / α of the magnification α of the first scaling process. This reciprocal 1 / α represents the sampling interval of the first scaling process. The multiplier 76 multiplies this 1 / α in the first scaling process and outputs it by dividing it into an integer part N ₀ and a decimal part t ₀ . The integer part N ₀ is input to the address generator 84 and the decimal part t
₀ is input to the first interpolator 72.

Similarly, the reciprocal 1 / β of the magnification β of the second scaling process is input to the multiplier 78. The reciprocal 1 / β is
This represents the sampling interval of the second scaling process. Multiplier 7
8 outputs an integer part N ₁ and a decimal part t _{1 of} a value obtained by integrating 1 / β and adding 0.5 in the second scaling process. The multiplier 78 adds 0.5 in order to shift the start position of the scaling process by 画素 pixel period so that the phase is inverted from the first time in the second scaling process. .
Since the second scaling process uses the data after the first scaling process, it is necessary to specify the order of the data used by the second interpolator 74 as the data after the first scaling process. is there. Therefore, the integer part N ₁ is input to the multiplier 76, multiplied by 1 / α, and the integer part is input to the address generator 84. The decimal part t ₁ is input to the second interpolator 74.

The flip-flops 80 and 82 store the image data input to the interpolators 72 and 74 and the
This is for setting a timing between 6 and 78 and the scaling data input to the interpolators 72 and 74 for scaling processing. The address generator 84 determines the address of a pixel to be processed in the next scaling process.

Hereinafter, the scaling process of the present embodiment will be described in detail using a specific example. When the operator inputs the scaling ratio s from the keyboard 18a or the like, the key correction unit 60
In the first magnification change process α = (s + 1) / 2
And the magnification β = s / α of the second scaling process and their reciprocals 1 / α and 1 / β are calculated, and the parameter integration unit 62
Is sent to the image processing unit 54 via First magnification α
Is input to the multiplier 76, and the second magnification β
Is input to the multiplier 78. Here, assuming that the magnification is 110%, s = 1.1 and α = 1.0
5, β = 1.048, 1 / α = 0.95, 1 / β = 0.
95.

FIG. 5 schematically shows the first scaling process. In the first scaling process, the original image data I _i (i = 0, 1, 2,...) Is enlarged at a magnification α = 1.05, and the image data J _j (i = 0, 1, 2) is enlarged. , ………). For the first data J ₀ after the first scaling, the original image data I ₀ is used as it is. Pixel interval of original image is 1
, The pixel interval (1 / α) after scaling is 1 / α =
0.95. When 1 / α = 0.95 is input, the multiplier 76 outputs an integer part N ₀ = 0 and a decimal part t ₀ = 0.95. The address generator 84 receives the input of the integer part N ₀ and generates an address of data necessary for interpolation of the next data J ₁ . The first interpolator 72 receives the data _Ii whose address is specified, and performs interpolation according to the following equation (1). J ₁ = Σf _i (t ₀ ) * I _i (1)

Various interpolation coefficients f _i (t ₀ ) representing the interpolation kernel can be considered, but the simplest one is
The data on both sides of the position to be interpolated are added proportionally. Assuming that interpolation is performed in this manner, the integer part N
_{Since o} = 0, the data J ₁ to be interpolated are I ₀ and I ₁
, The address generator 84 generates 0 and 1 as addresses. Then, the two data I ₀ and I ₁ are input to the first interpolator 72, and interpolation is performed by the following equation (2). J ₁ = (1−0.95) * I ₀ + 0.95 * I ₁ (2)

To find the next data J ₂ , the multiplier 76
Thus, 1 / α = 0.95 is integrated as 2 * (1 / α) = 2 * 0.95 = 1.90, and an integer part N ₀ = 1 and a decimal part t ₀ = 0.90 are obtained. Is output. Address generator 8
4 generates 1 and 2 as addresses from the integer part N ₀ = 1. The first interpolator 72 interpolates the two data I ₁ and I _{2 according} to the following equation (3). J ₂ = (1−0.90) * I ₁ + 0.90 * I ₂ (3) Similarly, data J _j after the first scaling process is obtained.

FIG. 6 schematically shows the state of the second scaling process. The second scaling process of enlarging the image data I _i after the first round of scaling at a magnification beta = 1.048, the image data _{K k (k = 0,1,2, .........} ) to What you get. The second scaling process starts from a position shifted by １ ／ of the pixel period. Therefore, the multiplier 78 first adds 0.5. Therefore, the operation in the multiplier 78 is performed by the operation expression represented by the following expression (4). n * (1 / β) + 0.5 = n * 0.95 + 0.5 (4) Here, n is 0 or a natural number.

Assuming that n = 0 for the first data K ₀ , the operation result in the multiplier 78 is 0.5, and the integer part N ₁
= 0, decimal part t ₁ = 0.5 is output. The second scaling process is performed on the image data after the first scaling process, and the integer part N ₁ output from the multiplier 78 is output.
Is input to the multiplier 76 and multiplied by the pixel interval 1 / α after the first scaling process. The resulting integer part N ₀ is input to the address generator 84, and the source necessary for calculating the image data after the first scaling process required for the second scaling in the second interpolator 74. Generate the address of the image data.

The second interpolator 74 outputs the designated data J _j
In general, interpolation is performed according to the following equation (5) to obtain image data K _k after the second scaling process. K _k = Σf _j (t ₁ ) * J _j (5) Here, similarly to the first scaling process, the simplest interpolation method is to perform interpolation by proportional distribution from data on both sides of the position to be interpolated. 6, the first data K ₀ is obtained by the following equation (6) as an average of the first two data J ₀ and J ₁ after the first scaling process. Can be K ₀ = 0.5 * J ₀ + 0.5 * J ₁ (6)

To find the next data K ₁ , the multiplier 78
In the above, from n = 1, 1 * 0.95 + 0.5 = 1.4.
5 is obtained, and an integer part N ₁ = 1 and a decimal part t ₁ = 0.45 are output. And K ₁ is calculated by the following equation (7). K ₁ = (1−0.45) * J ₁ + 0.45 * J ₂ (7) Similarly, image data K after the second scaling process is performed.
_k is obtained. In this manner, the first magnification change processing with the magnification α = 1.05 and the second magnification processing with the magnification β = 1.048 are performed continuously, so that the magnification s = α * β = 1.
One-time scaled image data can be obtained.

At this time, the first data of the first scaling process uses the original image data as it is, and completely matches the original data. The doubling process is started with a shift of 1/2 pixel cycle.

Next, the electronic scaling unit 68 can perform the scaling process of the vertical magnification s in exactly the same manner as the scaling process of the horizontal scaling factor s, following the scaling process of the horizontal scaling factor s. In this way, the electronic scaling unit 68 can obtain image data that has been scaled at the magnification s, in which the occurrence of artifacts such as moire and beats is suppressed or prevented.

As described above, in this embodiment, artifacts can be easily suppressed with a simple device configuration, but the electronic scaling means 68 for performing scaling processing according to the present invention.
FIG. 4 shows an example, and the present invention is not limited to this, and various things can be considered. In both the horizontal and vertical scaling processes, the second
When performing the second scaling process, n × sampling interval + 0.
Interpolation processing may be performed right and left from the pixel position where 5 (n: natural number) is a natural number. By doing so, it is not necessary to perform an operation of shifting the start position of the second scaling in a half pixel cycle.

In the above-described example, the scaling process in the vertical direction is performed after the scaling process in the horizontal direction. However, the present invention is not limited to this. Conversely, the scaling process in the horizontal direction is performed after the scaling process in the vertical direction. The scaling process may be performed, or the scaling process may be performed simultaneously in both the horizontal and vertical directions. Further, in the above-described example, in the scaling processing in both the horizontal and vertical directions, the scaling processing with the same magnification s is performed. However, the present invention is not limited to this. May be different from the magnification of the scaling process. For example, when the scaling factor of the horizontal scaling process is s ₁ and the scaling factor of the vertical scaling process is s ₂ , the scaling factors α in the horizontal and vertical directions of the first scaling process are respectively set to α. = (S ₁ +1) / 2 and α = (s ₂
+1) / 2, the magnification β in the horizontal and vertical directions of the second scaling process is β = s ₁ / α = 2s ₁ /
(S ₁ +1) and β = s ₂ / α = 2s ₂ / (s ₂ +
It may be 1).

In the above example, when the magnification of the scaling process is s, the magnification of the first scaling process is α = (s +
1) / 2, and the magnification of the second scaling process is β = s
/ Α = 2s / (s + 1), but the present invention is not limited to this, and the magnification of the first scaling process is β = s / α = 2
s / (s + 1), and the magnification of the second scaling process is α
= (S + 1) / 2.

In the above example, the start position of the second scaling process is shifted by の of the pixel period from the start position of the first scaling process. The present invention is not limited to this, and the start position of the first scaling process may be shifted from the start position of the second scaling process by の of the pixel period. That is, in the first and second scaling processes, the start position of the first scaling process and the start position of the second scaling process are relatively set in the horizontal and vertical pixel periods. May be shifted by 1/2. Further, in the first and second scaling processes, the pixel period for relatively shifting the start position of the first scaling process and the start position of the second scaling process is also different from the first and second scaling processes. If the start positions of both scaling processes can be relatively shifted so that the phase of the second pixel position is inverted with respect to each other, it is not limited to 1/2 pixel (1/2 of the pixel period). Pixel period.

In the scaling process of the image processing method and apparatus of the present invention, compared to the suppression of artifacts such as moire and beats due to random noise disclosed in Japanese Patent Application No. 10-98612, the frequency of the image is reduced. Processing can be performed, and good frequency characteristics can be realized.
The effect of preventing artifacts such as moire and beats can be prevented or completely eliminated depending on the frequency of the image, and the effect is extremely large. For any image, appropriate artifact reduction according to the image The effect is extremely high, such as the effect can be obtained.

The image processing method and apparatus of the present invention have been described in detail with reference to various embodiments. However, the present invention is not limited to these embodiments, and does not depart from the gist of the present invention. Of course, various improvements and changes may be made.

[0057]

As described above in detail, according to the present invention, it is possible to suppress the artifacts generated in the image scaling (enlargement / reduction) processing. That is, according to the present invention, it is possible to perform processing according to the frequency of the image, achieve good frequency characteristics, prevent the occurrence of artifacts such as moire and beats according to the frequency of the image, or It is possible to provide an image processing method and apparatus which can obtain an appropriate effect of reducing an artifact corresponding to an image in any image, and an image processing method which has an extremely high reduction effect. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating an example of a digital photo printer to which an image processing apparatus that performs an image processing method according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram schematically illustrating an example of an image processing apparatus according to the embodiment.

FIG. 3 is a block diagram schematically showing an embodiment of an image processing unit in the fine scan data processing unit of the image processing apparatus shown in FIG.

FIG. 4 is a block diagram schematically showing an embodiment of an electronic scaling unit in the image processing unit shown in FIG.

FIG. 5 illustrates a first example of the image processing method according to the embodiment.
It is a schematic diagram which shows the outline of an example of the 2nd scaling process.

FIG. 6 is a schematic diagram schematically showing an example of a second scaling process in the image processing method according to the embodiment;

[Explanation of symbols]

Reference Signs List 10 digital photo printer 12 scanner (image reading device) 14 image processing device 16 image recording device 18 operation system 18a keyboard 18b mouse 20 monitor 22 light source 24 variable aperture 26 diffusion box 28 carrier 30 imaging lens unit 32 image sensor 33 amplifier 34A / D converter 36 Scanner correction unit 38 LOG converter 40 Prescan memory 42 Finescan memory 44 Prescan data processing unit 46 Finescan data processing unit 48 Condition setting unit 50 Image processing unit 52 (of prescan data processing unit) ( Image data conversion unit (of the pre-scan data processing unit) 54 Image processing unit (of the fine scan data processing unit) 56 Image data conversion unit (of the fine scan data processing unit) 58 Setup unit 60 Key complement Part 62 parameter coordinating subsection 64 color density gradation converting means 66 saturation conversion means 68 electronic zooming unit 70 image processing block 72 first interpolator 74 second interpolator 76, 78 multipliers 80, 82 flip-flop 84 address generator

Claims (10)

[Claims] 1. An image processing method for performing a scaling process at a predetermined magnification, wherein the scaling process at the predetermined magnification is divided into a first scaling process and a second scaling process. When the predetermined magnification is s1 in a _first direction and s2 in a _second direction orthogonal to the first direction, the first and second magnifications of the first scaling process are performed. Are (s ₁ +1) / 2 and (s ₂ +1) / 2, respectively.
The magnifications in the first and second directions in the second scaling process are 2s ₁ / (s ₁ +1) and 2s ₂ /, respectively.
(S ₂ +1), and in the first and second scaling processes, the start position of the first scaling process is set so that the phases of the first and second pixel positions are inverted with respect to each other. An image processing method, wherein a start position of the second scaling process is relatively shifted. 2. The image processing method according to claim ₁ , wherein the magnification s _{1 in} the first direction is equal to the magnification s _{2 in} the second direction. 3. In the first and second scaling processes,
The start position of the first scaling process and the start position of the second scaling process are relatively shifted by a half of a pixel period in the first direction and the second direction. The image processing method according to claim 1. 4. The method according to claim 1, wherein the start position of the second scaling process is set to a half of the pixel period in the first direction and the second direction with respect to the start position of the first scaling process. 4. The image processing method according to claim 3, wherein the image is shifted. 5. The image processing method according to claim 1, wherein the scaling processing of the predetermined magnification is performed on a multi-valued image. 6. A magnification in a first direction is s1, and said _first magnification is s1.
An image processing apparatus for performing a scaling process at a predetermined magnification wherein a magnification in a _second direction orthogonal to the direction of s is s ₂ , wherein the magnifications in the first and second directions are respectively (s ₁ +
Means for performing a first scaling process of 1) / 2 and (s ₂ +1) / 2, and a magnification in the first and second directions of 2s _1/2 , respectively.
Means for performing a second scaling process of (s ₁ +1) and 2s ₂ / (s ₂ +1); and a phase of a pixel position in the first scaling process and the second scaling process. An image processing apparatus comprising: means for relatively shifting a start position of the first scaling process and a start position of the second scaling process so as to be mutually inverted. 7. The image processing apparatus according to claim 6, wherein the magnification s _{1 in} the first direction is equal to the magnification s _{2 in} the second direction. 8. A means for shifting the start positions of the first and second scaling processes, the relative position between the start position of the first scaling process and the start position of the second scaling process. In the first direction and the second direction, one of the pixel periods
The image processing apparatus according to claim 6, wherein the image processing apparatus is a unit that shifts the image data by half. 9. A means for shifting the start positions of the first and second scaling processes, wherein the starting position of the second scaling process is shifted with respect to the starting position of the first scaling process. The first
The image processing apparatus according to claim 8, wherein the pixel cycle is shifted by の of the pixel period in the direction of the pixel and in the second direction. 10. The image processing apparatus according to claim 6, wherein the scaling processing at the predetermined magnification is performed on a multivalued image.