JP2002344733A - Image processing unit and processing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing unit and its processing method, that can conduct magnification processing in real time using a simple configuration. SOLUTION: A phase information revision processing section 703 decides phase information denoting a distance between a position of a target pixel after magnification processing and a pixel in the vicinity of the original image, depending on the magnification level for the magnification processing entered from a magnification entry section 701 and a coefficient-setting processing section 704 calculates in advance a plurality of filter coefficients in the filter processing, depending on the decided phase information and stores them to a coefficient register of the filter processing section. Then an N×1 filter processing section 705 and an 1×M filter processing section 706 apply convolution arithmetic processing to the input image data from the image storage section 604, while updating the filter coefficient according to the pixel position from an address arithmetic processing section 702.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for performing scaling processing on input image data and outputting the result, and a processing method therefor.

[0002]

2. Description of the Related Art In recent years, as a scaling process for scaling an image, a "nearest neighbor method" for selecting a pixel of original image data closest to a focused pixel after scaling has been known.

Also, processing such as "bicubic interpolation" is often used.

[0004]

However, since the above-described "nearest neighbor method" only uses the nearest pixel data, image deterioration such as occurrence of moiré or rough appearance of the pixel when enlarging the image is caused. There is a terrible problem.

On the other hand, the "bicubic interpolation method" has a better image quality than the "nearest neighbor method", but in order to maintain the resolution, it reads a document having periodicity at the time of reduction / magnification, for example, by reading a printed document document. During processing, there is a problem that moiré fringes occur and image quality deteriorates.

In the "bicubic interpolation method", it is necessary to change the coefficients of the filter in accordance with the position of each pixel after scaling, which requires time for interpolation processing and makes it difficult to implement hardware. There is also a problem that is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an image processing apparatus having a simple configuration and capable of real-time scaling processing and a processing method thereof.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an image processing apparatus for performing a scaling process on input image data and outputting the image data in accordance with a scaling factor of the scaling process. Determining means for determining phase information indicating the distance between the position of the pixel of interest after processing and neighboring pixels of the original image; and calculating and storing a plurality of filter coefficients in the filter processing in advance in accordance with the determined phase information. Storage means, and filter processing means for filtering input image data based on a plurality of stored filter coefficients.

According to another aspect of the present invention, there is provided a method of processing an image processing apparatus for performing a scaling process on input image data and outputting the image data. A determining step of determining phase information indicating a distance between the position of the target pixel after the doubling process and a neighboring pixel of the original image, and a plurality of filter coefficients in the filtering process calculated in advance in accordance with the determined phase information; And a filter processing step of filtering input image data based on the stored plurality of filter coefficients.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[Image Controller Uni
t)] FIG. 1 is a block diagram showing a configuration of the image control device according to the present embodiment. As shown, the image control apparatus 100 includes a scanner 2 as an example of an image input device.
00 and a printer 300, which is an example of an image output device, and a LAN 700 and a public line (WAN) 80.
0 is a controller for inputting and outputting image information and device information by connecting to 0.

In the image control apparatus 100, 101 is C
It is a PU and controls the entire system according to a program stored in a ROM described later. A RAM 102 is a memory in which a system work memory used when the CPU 101 executes processing and an image memory for temporarily storing image data are defined. A ROM 103 stores a system boot program, various processing programs, and control data. A hard disk drive (HDD) 104 stores system software and image data. An operation unit I / F 106 functions as an interface with the operation unit 160 and outputs image data to be displayed on the operation unit 160 to the operation unit 160. In addition, it plays a role of transmitting information input by the user from the operation unit 160 to the CPU 101. A network I / F 110 connects to a network (LAN) 700 and inputs and outputs information. 12
0 is a modem (Modem), and a public line (WAN) 80
0 to input / output information. The above devices are 1
07 on the system bus.

Reference numeral 105 denotes an image bus (Image Bus) I / F, which is a bus bridge that connects the above-described system bus 107 and an image bus 108 that transfers image data at high speed, and converts the data structure. The image bus 108 is a PC
It is composed of a high speed bus such as an I bus. The following devices are arranged on the image bus 108.

Reference numeral 150 denotes a raster image processor (R).
IP), and develops a page description language (PDL) code transmitted from a personal computer (personal computer) (not shown) or the like into a bitmap image. Reference numeral 600 denotes a device I / F, which is a scanner 20 which is an image input / output device.
0 and the printer 300 and the image control apparatus 100 are connected to perform synchronous / asynchronous conversion of image data. A scanner image processing unit 400 corrects, processes, and edits input image data. Reference numeral 500 denotes a printer image processing unit that performs smoothing processing and the like on the print output image data to smooth the edges of characters. 13
Reference numeral 0 denotes an image scaling processing unit, which is a characteristic processing module of the present embodiment, and details of the processing will be described later. An image compression unit 140 performs JPEG compression / expansion processing on multi-valued image data, and performs JBIG, MMR, MH compression / expansion processing on binary image data.

It is assumed that information indicating the image output speed, the installation position, and the like relating to the nodes connected to the network (LAN) 700 is stored in the HDD 104 for each address.

[Image Input Apparatus (Scanner)] FIG. 2 is an external perspective view showing an image input apparatus according to the present embodiment. As shown, a scanner 2 as an image input device
00 illuminates an image on paper as a document, and CC (not shown)
By scanning the D line sensor, it is converted into an electric signal as raster image data. Here, the original sheet is set on the tray 202 of the original feeder 201, and the user instructs the reading operation from the operation unit 160, and the CPU 101 of the image control apparatus 100 causes the device I / F
A start instruction is given to the scanner 200 via the scanner 600, and the feeder 201 of the scanner 200 feeds the document sheets one by one, and performs a reading operation of the document image.

[Image Output Apparatus (Printer)] FIG. 3 is an external perspective view showing an image output apparatus according to the present embodiment. As shown, a printer 3 as an image output device
Reference numeral 00 denotes a portion for converting raster image data into an image on paper, which includes an electrophotographic system using a photosensitive drum or a photosensitive belt, and a method in which ink is ejected from a minute nozzle array to directly print an image on the paper. And the like, but any method may be used. The print operation is started by the CPU 101 of the image control apparatus 100.
Is instructed via the device I / F 600. The printer 300 is provided with a plurality of paper feed stages so that different paper sizes or different paper orientations can be selected, and the corresponding paper cassettes 301, 302,
There are 303 and 304. The paper discharge tray 305 receives printed paper.

[Scanner Image Processing Unit] FIG. 4 is a diagram showing the configuration of the scanner image processing unit 400 shown in FIG. In the figure, reference numeral 401 denotes an image bus I / F controller, which is connected to the image bus 108 and controls the access sequence to the image bus 108, and generates control and timing of each device in the scanner image processing unit 400. Let it. A filter processing unit 402 performs a convolution operation using a spatial filter. An editing unit 403 recognizes a closed area surrounded by a marker pen from input image data and performs image processing such as shading, shading, and negative / positive inversion on the image data in the closed area. A table 405 is a table for converting image data, which is read luminance data, into density data. A binarizing unit 406 binarizes the multi-value grayscale image data by, for example, error diffusion processing or screen processing.

In the present embodiment, image processing can be performed irrespective of a binary image or a multi-valued image, and the binarization unit 406 performs the binarization processing only when a binary image is desired.
When handling multi-valued image data, the binarizing unit 406 outputs multi-valued image data without performing any processing. In particular, the image scaling unit 130, which is a feature of this embodiment,
Both the value image and the multi-value image can perform scaling processing with little image quality deterioration. In the present embodiment, a binarization unit 406 required when multi-valued image data input from the scanner processing unit is handled as binary image data is described in the present embodiment.
Needless to say, it is effective regardless of the multivalue.

The image data that has been subjected to the above-described image data processing is transferred to the image bus I / F controller 401 again.
Via the image bus 108.

[Printer Image Processing Unit] FIG. 5 is a diagram showing the configuration of the printer image processing unit 500 shown in FIG. In the figure, reference numeral 501 denotes an image bus I / F controller, which is connected to the image bus 108 and controls an access sequence to the image bus 108, and generates control and timing of each device in the printer image processing unit 500. Let it. A smoothing processing unit 503 performs a process of smoothing jaggies (roughness of an image appearing at a black-and-white boundary such as an oblique line) of image data.

[Image scaling unit] FIG. 6 is a simple block diagram for explaining the processing of the image scaling unit 130 shown in FIG. In the figure, reference numeral 601 denotes an image input unit;
02 is an image scaling unit, 603 is a CPU, 1104 is an image storage unit, and 605 is an image output unit. Each of the blocks is extracted from the blocks shown in FIG. 1 in order to explain the processing in an easy-to-understand manner, and represents a connection relationship. The image input unit 601 has a scanner 20 as a destination device.
0, image data may be input via the device I / F 600, image data may be input from the network I / F 110 or the modem 120 via the LAN 700 or WAN 800, or stored in a storage device such as the HDD 104 or the RAM 102. The input image data may be input.

The image scaling section 602 shown in FIG.
Is equivalent to the image scaling processing unit 130 shown in FIG. CP
U603 corresponds to the CPU 101, and the image storage unit 604 corresponds to a device for storing an image, such as the HDD 104 or the RAM 102, and may be any device that can read and write from the image scaling unit 602. The image output unit 605 is an image storage unit 60
4 shows the output, and if you want to print it,
If the print image processing unit 500 stores the image data in another storage device, the HDD 104 or the RA
If the image data is to be transferred to a storage device such as the M102 or by fax transmission or via a network, the image data is sent to the modem 120 or the network I / F 110, respectively.

In the configuration shown in FIG.
1 to the image data, and the CPU 603 to the image scaling unit 602 to input the scaling factor. The image scaling unit 60
Reference numeral 2 denotes a scaling unit that can independently control the scaling factor and the characteristics of the low-pass filter. In addition, the required characteristics of the low-pass filter change according to the magnification. In general, when the magnification is reduced, band limitation at a lower frequency is required. That is, the image scaling unit 602 is
Magnification is performed using a filter coefficient corresponding to the magnification from 3 and an image is output to the image storage unit 604 as image data.

FIG. 7 is a block diagram showing a detailed configuration of the image scaling section 602 shown in FIG. In FIG.
Reference numeral 1 denotes a magnification input unit for inputting a magnification from the CPU 603. Reference numeral 702 denotes an address calculation processing unit which receives a scaling ratio from a scaling ratio input unit 701 and an initial phase parameter from a phase information change processing unit, which will be described later, and moves the pixel position of an output image pixel by pixel to perform address calculation. Do. Specifically, which pixel position on the output image corresponds to the pixel of interest on the output image is calculated from the scaling factor, and a shift within one pixel from a neighboring pixel on the original image is calculated as phase information. , And outputs the phase information to a coefficient setting processing unit described later,
Based on the pixel position information of the original image, data of N × M pixels of the original image is read from the image storage unit 604 to an N × 1 filter processing unit described later. It is assumed that an original image to be processed is stored in the image storage unit 604 in advance.

Reference numeral 703 denotes a phase information change processing unit which outputs a phase information control parameter to a coefficient setting processing unit to be described later in accordance with a magnification from the magnification input unit 701 and an initial phase parameter in accordance with the magnification. Output to the address operation processing unit 702. 704 is a coefficient setting processing unit,
Using the phase information control parameters from the phase information change processing unit 703, N × 1 filter coefficients and 1 × M filter coefficients corresponding to the number of divided phases are calculated before the scaling process starts, respectively, N × 1 filter processing unit described later, 1 ×
The filter coefficients of all phases are stored in the coefficient registers of the M filter processing unit.

Reference numeral 705 denotes an N × 1 filter processing unit, which stores the filter coefficients received from the coefficient setting processing unit 704 in an internal coefficient register.
An Nx1 convolution operation is performed on the image data received from the image data unit 04 using the filter coefficient of the coefficient register. 7
Reference numeral 06 denotes a 1 × M filter processing unit, and a coefficient setting processing unit 7
04 is stored in an internal coefficient register, and 1 × M convolution is performed on the intermediate data normalized by the N × 1 filter processing unit 705 using the filter coefficient of the coefficient register during the scaling process. Perform the operation.

The N × 1 filter processing unit 705, 1 × M
Each of the filter processing units 706 includes N ×
One pixel one-dimensional filter processing unit, and one-dimensional filter processing unit of 1 × M pixels in the sub-scanning direction. Here, as shown in FIG. 7, the N × 1 filter processing unit 705 has M convolution processing units of N × 1 pixels in order to output M intermediate data for use in 1 × M. It is configured as follows. What is input to the M Nx1 convolution processing units is the original image data of the main scanning N pixels and the sub-scanning M lines near the target pixel position. In general, the target pixel after the scaling process is configured to be approximately at the center. The 1 × M filter processing unit 706 is configured to have one 1 × M pixel convolution operation processing unit, performs a convolution operation on the above-described M intermediate data, and outputs the result as output data of the pixel of interest.

In the configuration shown in FIG. 7, the N × 1 filter processing unit 705 stores N × M pixel data of the original image to be processed from the image storage unit 604 based on the pixel position information from the address operation processing unit 702. The convolution operation is performed on each of the M lines with N pixels × 1 line in the main scanning direction as one unit based on each filter coefficient. still,
If the N × 1 filter processing unit 705 is configured to output M normalized outputs, M N × 1 convolution operation processing units are arranged in parallel as shown in FIG.
Each of them may be configured to supply the original image data of N × 1 pixels from the 0th line to the M−1 line, and is different from the configuration shown in FIG. May be configured such that N × 1 data for M lines are processed in order and M outputs are made. The same set of N × 1 filter coefficients is used for each line.

Next, the 1 × M filter processing unit 706
The M calculation results output from the × 1 filter processing unit 705 and the filter coefficients calculated in the sub-scanning direction are received from the coefficient setting processing unit 704, the convolution operation is performed, and multi-value output is performed to the image output unit 605.

In this embodiment, first, pixels in the main scanning direction are processed by the N × 1 filter processing unit 705,
Although the pixels in the sub-scanning direction are processed by the x1 filter processing unit 706, the order of the main scanning direction and the sub-scanning direction can be reversed. In this case, the 1 × M filter outputs N outputs, and N × 1 outputs one image data after scaling from the N outputs.

In this embodiment, the description will be made with the filter size being 8 × 8. However, the size may be different between the main scanning and the sub-scanning, and the size is not limited to “8” but may be arbitrarily set. It is possible to set.

Next, the reduction / magnification processing performed by the magnification / magnification processing unit 602 will be described in more detail. Here, a description will be given of the fact that high-quality scaling processing using the phase information control parameter is possible, and since the method of obtaining the filter coefficient is complicated, a system configuration for performing this processing in real time, and specifically, I will continue to explain how to achieve this.

First, a description will be given of the fact that high-quality image scaling processing is possible. However, in order to simplify the explanation, the phase information control parameters, initial phase parameters, magnification, etc. Although the description will be made assuming that both are the same, it is needless to say that a configuration in which operation is performed using main and sub-parameters can be easily extended.

In the following, it is assumed that the magnification input from the magnification input unit 701 is 50% for both the main and the sub. Also, the phase information change processing unit 703 calculates a phase information control parameter LC (low-pass coefficient) according to the following scaling factor, for example.

LC = 1.5 + (100 / RPX (RP
Y) -1) × 0.5 Here, RPX (RPY) is a magnification in the main scanning (sub-scanning) direction. Since the main and auxiliary magnifications are 50%, LC = 2 this time.

The LC (low-pass coefficient) is used to control the frequency characteristics of the low-pass filter.
4 and used. In the present embodiment, the LC is changed according to the magnification based on the above equation, but it is needless to say that the LC is not limited to this. When changing the LC according to the magnification, the setting may be made so that the switching is continuously changed to such an extent that the switching does not affect the image. How to use LC will be described later.

The phase information change processing section 703 calculates an initial phase parameter according to the magnification. For example, in the case of a magnification ratio of 1 / integer, the initial phase parameter IX (I
In the present embodiment, a rule that Y) is set to 0.5 and others are set to zero. This rule will be further described later.

In this embodiment, the magnification is 1/2 = 50%.
Therefore, the initial phase parameter is IX = IY = 0.5
Is set. Also, 1/3 = about 33%, 1/4 = 25
The same is set for the magnification ratio of%.

When the magnification becomes an integral multiple at the time of enlargement / reduction, for example, 200% or 300%, the initial phase parameter is set by the following equation.

IX (IY) = 100 / RPX (RPY)
/ 2 Specifically, in the case of 200%, IX (IY) = 0.
In the case of 25 and 300%, IX (IY) = 0.16
7

The initial phase parameters IX and IY set in this way are output to the address arithmetic processing unit 702 and used.

Here, the address calculation processing section 702 calculates the scaling factor RPX (RPY) = 50 and the initial phase parameter IX
(IY) = 0.5, and operates as follows. For example, the pixel of interest is the 50th pixel in the main scan X = 50th pixel and the subscan Y = 1
In the case of the 0th pixel, the coordinates of the target pixel located in the original image can be calculated by the following equation.

Xo = X / (RPX / 100) + IX = 5
0 / (50/100) + 0.5 = 100.5 Yo = Y / (RPY / 100) + IY = 10 / (50 /
100) + 0.5 = 20.5 The initial phase parameter is used to be added at the time of address calculation as described above.

Here, the decimal part PIX of Xo, Yo = 0.
5 PIY = 0.5 (in the present embodiment, the fractional part of Xo and Yo is configured to have the same value, so the description will be continued with one parameter). The coefficient setting processing unit 704 is used as an initial phase parameter. And the integer parts OX = 100 and OY = 20 of Xo and Yo are output to the N × 1 filter processing unit 705 as pixel position information of the original image. When all the processing for the current target pixel is completed, the target pixel is moved by one pixel, and the processing is continued.

When the scaling factor RPX (RPY) is 50, it is always divided by 50/100 = 0.5, so that the decimal part PIX always remains unchanged as the initial phase IX. For example, when one pixel is updated by X = 51, Y = 10 and X,
Xo = 102.5 (the same is true when updating in the sub-scanning direction, so the description is omitted).
0.5. Xo even if X increases by one pixel
Increases by 2 and remains unchanged at PIX = 0.5.

However, this is an exception. In general, the value of PIX (PIY) changes every time the target pixel is moved by one pixel, and the value of the filter coefficient used in the interpolation calculation also changes for each pixel due to the change of PIX (PIY). For example, if the scaling factor RP is 80, as described above, the initial phase parameter is set to 0 and X = 50
When Xo = 50 / (80/100) + 0 = 62.5, PI
= 0.5, and when X = 51, Xo = 51 / (80/100) + 0 =
63.75, PI = 0.75, and when X = 52, Xo = 52 / (80/100) + 0 =
At 65.0, PI = 0, and when X (or Y) is updated, the value of PIX (PIY) is also updated.

Here, the description will be continued assuming that RPX = RPY = 50.

In the present embodiment, the next processing moves one pixel in the main scanning direction, and becomes X = 51st pixel and Y = 10th pixel. The maximum pixel value in the main scanning and sub-scanning changes depending on the size of the platen of the copier, the reading resolution, and the magnification. Here, if the maximum pixel value in the main scanning direction is 5000 pixels, this processing is performed in the main scanning direction. Starts from the 0th pixel, and when the pixel reaches the 4999th pixel, the next processing advances by one pixel in the sub-scanning direction. In the above example, X = 4999th pixel,
When the process proceeds to the Y = 10th pixel, the next process is configured such that the pixel of interest advances in the sub-scanning direction to the X = 0th pixel and the Y = 11th pixel, and reaches the maximum value in the sub-scanning direction. The processing will be continued until.

Next, the coefficient setting processing section 704 receives the phase information control parameter LC from the phase information change processing section 703,
The phase information PIX is received from the address arithmetic processing unit 702, and operates as follows.

FIG. 8 is a diagram showing a target pixel and pixels on the original image in the vicinity of the target pixel. In the figure, an X (cross) mark indicates a target pixel, and a ○ (circle) mark indicates a pixel on the original image. In this embodiment, since 8 × 8 filters are used, only 8 × 8 pixels on the original image near the target pixel are used. In addition, the target pixel X
(X) is always 3 ≦ the pixel on the original image near the pixel of interest.
It is set so that i <4 and 3 ≦ j <4. Also,
The position information OX, OY of the original image output from the address calculation processing unit 702 is set so that i = 3 and j = 3.

Here, the distance between the pixel on the original image near the pixel of interest and the pixel of interest is determined independently for main scanning and sub-scanning. FIG.
As shown in (1), projection is performed in the main scanning direction, and attention is paid to the distance in the main scanning direction. If AXi (i is an integer from 0 to 7) is the distance between the ith pixel and the pixel of interest, the following is obtained.

AX0 = 3 + PIX AX1 = 2 + PIX AX2 = 1 + PIX AX3 = PIX AX4 = 1-PIX AX5 = 2-PIX AX6 = 3-PIX AX7 = 4-PIX The calculation is performed by assuming that the distance between one pixel is 1. , 0 ≦
PIX (PIY) <1. AY0 to AY7 are calculated similarly in the sub-scanning direction.

Further, from the distance information of AX0 to AX7 and AY0 to AY7 and the phase information control parameter LC, the main scanning sub-independent i-th coefficient Ci and the sub-scanning j-th coefficient Cj are obtained independently. , The sub-scanning j-th coefficient Cij = Ci * Cj
The bicubic interpolation method will be described first in order to explain the effect of the present embodiment.

Here, a third-order polynomial approximation formula of a sinc function, which is well known as a bi-cubic interpolation method, is used as an arithmetic expression for obtaining a filter coefficient. However, this is an example for obtaining a filter coefficient, and the present invention is not limited to this.

The bicubic interpolation method is represented by the following equation, where the coefficient is C and the distance from the pixel of interest is d.

Coefficient C = 1−2 * d * d + d * d * d (0 ≦ d <1) 4-8 * d + 5 * d * d−d * d * d (1 ≦ d <2) (1) 0 (d ≧ 2) FIG. 10 is a diagram illustrating the relationship between the coefficient C of the bicubic interpolation method and the distance d. In the example shown in FIG. 10, how the distance information AXi or AYj of the present embodiment is arranged is indicated by △, and i (or j) corresponds to the numeral attached to △, and 0 to 7 Indicates the value. The distance d has the origin at X shown in FIG. 9 and is drawn so that one graduation is at a distance of 1 around the origin. Since the distance is a distance, it takes a positive value even if it is on the left of the origin. . Specifically, the position of # 3 is located PI from the origin, and AX3 (AY3) = PI. The distance between △ is 1. Therefore, AX0 is
0 and AX0 = 3 + PI. The curve drawn in FIG. 10 shows the value of the coefficient C according to the distance d,
When i is 2 to 5, coefficients are assigned,
In the case of 0, 1, 6, and 7, the coefficient is 0. That is, in the bicubic interpolation method, a filter of 4 × 4 pixels is always used.

FIG. 11 is a diagram showing frequency characteristics of the sinc function. The polynomial approximation formula used in the bicubic interpolation method is an approximation of the sinc function, and thus slightly differs from the frequency characteristic shown in FIG.
The following description is based on the assumption that these are equivalent to those shown in FIG. The sinc function is a band limiting filter as can be seen from FIG. The restricted band is a frequency band exceeding ± １ ／ (Nyquist frequency) of the frequency of the original image. Generally, an image having a frequency band exceeding the Nyquist frequency cannot be resolved, and the image quality deteriorates due to the occurrence of moire or the like.

For example, if the original image is 600 dpi, a frequency component exceeding 300 dpi is set to 0. When this arithmetic expression is used as it is at the time of reduction / magnification, the entire frequency band of the original image is preserved. When the original image contains a periodic image, if moire occurs, if the original image contains a frequency band,
It causes image quality degradation. For example, when a 50% reduction / magnification is performed, if a screen image of 200 dpi or a printed matter using halftone dots of 200 lines is included in the original image, the behavior is such that the apparent frequency is 400 dpi.
Therefore, the resolution exceeds the resolution limit of 300 dpi, and the image quality is degraded due to moiré fringes.

Therefore, in the present embodiment, the deterioration of the image quality due to the above-mentioned moiré fringes is prevented by changing the phase information according to the magnification.

Hereinafter, the processing of this embodiment for changing the phase information according to the magnification will be described. Since the distance d is originally a distance from the target pixel, dXi = AXi (dYj = AYj). However, the distance d is changed as follows using the phase control parameter LC.

DXi = AXi / LC (dYj = AYj / LC) LC is changed according to the magnification. For example, as described above, if LC = 100 / RP (magnification), LC
= 2.

When LC = 1, d = AX0 = 3.5 Ci = 0 d = AX1 = 2.5 Ci = 0 d = AX2 = 1.5 Ci = -0.125 d = AX3 = 0.5 Ci = 0.625 d = AX4 = 0.5 Ci = 0.625 d = AX5 = 1.5 Ci = -0.125 d = AX6 = 2.5 Ci = 0 d = AX7 = 3.5 Ci = 0 When LC = 2, d = AX0 = 3.5 / 2 = 1.75 Ci = -0.047 d = AX1 = 2.5 / 2 = 1.25 Ci = -0.141 d = AX2 = 1.5 / 2 = 0.75 Ci = 0.297 d = AX3 = 0.5 / 2 = 0.25 Ci = 0.891 d = AX4 = 0.5 / 2 = 0.25 Ci = 0.891 d = AX5 = 1.5 / 2 = 0.75 Ci = 0.297 d = AX6 = 2.5 / 2 = 1.25 Ci = −0.141 d = AX7 = 3.5 / 2 = 1.75 Ci = −0.047 For simplicity of explanation, the decimal point of the coefficient is 4th.
Rounded to the nearest place. The important thing here is that LC = 1
In the case of i, only the middle four coefficients from 2 to 5 are used (see FIG. 10), but when LC = 2, i is 0
To 7 are all assigned coefficients, and the band is limited to a lower frequency region.

FIG. 12 is a diagram showing the relationship between the coefficient C and the distance d when LC = 2. FIG. 13 is a diagram schematically showing the frequency characteristics of the filter when LC = 2.
In addition, as the actual frequency characteristics, the filter is not a sinc function itself but an approximation, and is truncated to a finite number, so that it does not become such a clean rectangle, but in the sense of the intended frequency characteristics. It has similar characteristics. As can be seen from FIG. 13, the band is limited to half the Nyquist frequency, and it is possible to reduce the image quality deterioration due to the occurrence of the moiré fringes as described above.

In the sub-scanning direction, Cj is obtained in the same manner as in the main scanning direction, and as a result, the coefficient Cij becomes Ci * Cj.
Is calculated as

Here, in order to perform these calculations in real time by a copying machine or the like, it is necessary to perform some floating point calculations for calculating the coefficient C from the distance d, but the number of gates increases, which is not preferable. .

Therefore, in the present embodiment, the above-described scaling processing is realized with a simpler operation, a hardware configuration, and a smaller scale. That is, the coefficient can be determined when the phase information control parameter and the phase are determined. for that reason,
When the scaling factor is specified and the phase information control parameter is determined, all possible phase value coefficients are calculated in advance by general-purpose processing means such as a CPU, and set in the coefficient register corresponding to each phase. When the image data starts to be input to the processing unit, a coefficient corresponding to the phase information of the pixel of interest is selected and set, and a convolution operation is performed so that a complicated operation for determining the coefficient is performed in real time. Such an operation is avoided and real-time calculation is easily realized.

The total number of registers for setting the coefficients in advance needs to be equal to the number of phases × the number of pixels to be convolved. It is necessary to keep the total number within a realistic number when hardening. The number of pixels to be convolved is 8
If × 8, the main and sub are eight, if N × M, the main is N
And the number of subs is M. The number of phases is the number of divisions per pixel. If the number of divisions is small, the range of the same phase is widened, and the image quality of the scaling process is deteriorated. If the number is too large, the total number of registers increases and costs increase.

In the present embodiment, in consideration of the above-described points, a configuration in which image quality and cost are well balanced is achieved by dividing one pixel into 32 pixels. Since it is 8 × 8 and is divided into 32, 8 × 32 = 256 registers are prepared in advance for both the main and the sub. When the scaling factor is set, the LC value is determined, and the image is started to be processed by the scaling process using 32 × 8 or 1 × 8 coefficients of 32 phases shifted by 1/32 pixel from 0 to 31. It must be calculated and set beforehand.

Next, when the phase information control parameter LC is 1.
A case where the number of phases is 32 and the number of phases is 32 will be described.
In addition, although the value of LC is chosen so that it may be easy to explain,
This is not the case.

The case where the phase is 0.5 pixels has been described above. However, 0.5 pixels = 16/32, which is equivalent to the case where the phase is 16. This is repeated from 0 to 31, that is, while the phase is shifted by 1/32 pixel, the distance between each pixel (line) and the phase value which is the shift from the pixel 3 which is the target pixel position after the magnification is changed. The coefficient obtained by dividing the value obtained by dividing LC by the equation (1) is defined as a distance in the equation (1).
FIG. 14 shows a result obtained by normalizing the sum to be 1 and then multiplying by 1024 and converting it to an integer.

In FIG. 14, the vertical axis represents phases 0 to 31.
, And the coefficient at that time is shown horizontally. Phase 0
In the case of, from the 0th pixel to the 7th pixel, referring to the column of phase 0 shown in FIG.

-63 -3 320 515 320 -3 -63 0 The rightmost column indicates the sum of the coefficients from the 0th pixel to the 7th pixel.

As shown in FIG. 14, for example, when the phase is 5, the first coefficient when the phase is set to 0 from the left is -36. This is, first, the position of the pixel of interest after scaling, 3 to 5 /
The distance from the position 32 pixels to the right to the first pixel is determined as shown in FIG.

Here, 2 pixels + 5/32 pixels = 69/3
Two pixels. This is referred to as a phase information control parameter L
Using C = 1.99, the distance used in equation (1) is 69 /
32 / 1.99 = about 1.084. In the equation (1), since the distance d is equal to or more than 1 and less than 2, using the second relational expression,
A coefficient C = about -0.0703 is obtained. This operation is repeated except for the first coefficient, that is, for the 0th to 7th coefficients. After normalizing so that the sum becomes 1, multiplying by 1024 gives -36.

Here, at the time of the convolution operation, by dividing by the sum of the convolution coefficients, the same luminance level is output when all the pixel values of the original image used for the convolution have the same luminance (or density) level. Need to guarantee.
Considering the hardware scale, it is preferable to divide by a power of 2 in division by bit shift, rather than by an arbitrary integer. In the present embodiment, it is normalized by 2 to the 10th power, 1024. However, in the above-described calculation, a quantization error occurs at the time of integer conversion, and there is a case where the sum of the rightmost column does not become 1024. Therefore, the sum is 1
The following operation is performed for the phase coefficient that does not reach 024.

That is, when the phase is from 0 to 15, the sum of the third coefficient among the 0th to 7th coefficients is 102
Adjust to 4 The sum of 1024 minus the sum is added to the third. If the phase is 17 to 31,
Since the phase is closer to the fourth phase than the third phase, the same operation is performed at the fourth phase. When the phase is 16, since the phase is exactly at the center, the value obtained by subtracting the sum from 1024 and dividing by 2 is added to the third and fourth values. Also, if the phase is 16
In the case of, the same coefficient is a pair of two each, such as the third and fourth, the second and the fifth, so the value obtained by subtracting the sum from 1024 is always an even number. It can be adjusted to 1024.

This can be confirmed by comparing FIG. 14 with no adjustment and FIG. 16 with the result of adjustment. That is, in the case of phase 16 in FIG. 14, the total sum is 1022, which is less than 1024 by 2. So the third and fourth
Third, the quantization error is corrected by adding 2/2 = 1 each. When the phase is 16, 0, 7, 1 and 6, 2 and 5, and 3 and 4 all have the same distance, the same coefficient is always calculated, and when an error occurs, it is always an even number. With an N × 1 filter, phases 0 through 15 are N /
Adjusted by the second coefficient, the phases 17 to 31 are N / 2 + 1
Adjusted by the second coefficient, phase 16 is N / 2 and N / 2 + 1
Will be adjusted. The same applies to the 1 × M filter. FIG. 16 shows the coefficients subjected to this operation.

In FIG. 16, the adjustment target pixels are represented by bold characters using the coefficients of the third and fourth pixels.

In the embodiment described above, the image scaling unit 6
Although the case has been described where hardware 02 is configured by hardware, it is also possible to perform processing by software.

FIG. 17 is a flowchart showing the processing procedure of the image scaling section in this embodiment. First, CPU
The phase information control parameter LC is determined before the image is subjected to the scaling process (step S101), and the filter coefficient for each pixel (line) in all phases is scaled based on the LC as shown in FIG. Before calculating,
The N × 1 filter processing module and the 1 × M filter processing module store in advance in a table that can be accessed in real time (step S102). Thereafter, during the scaling process, the N × 1 filter processing module performs an N × 1 convolution operation while changing the filter coefficient according to the phase information output for each pixel of interest after the scaling process (step S).
103), after normalizing the result of the N × 1 convolution operation (step S104), intermediate data for M lines is output, and 1 ×
An M-filtering module receives the intermediate data,
A 1 × M convolution operation is performed using the set filter coefficients (step S105), and the result of the 1 × M convolution operation is normalized (step S106), and then output as image data after scaling.

With such a configuration, during the scaling process, a complicated operation for finding the coefficient is not required.
A real-time easy configuration and high-quality image scaling processing can be realized.

Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), a device including one device (for example, a copying machine, a facsimile, etc.) Device).

Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (CPU or MP) of the system or apparatus.
It goes without saying that U) is achieved by reading and executing the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk,
Hard disk, optical disk, magneto-optical disk, CD-
A ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

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, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion 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.

[0089]

As described above, according to the present invention,
With a scaling process that can control the characteristics of the filter according to the scaling factor, a high-quality scaled image with a simple configuration can be created without unnecessary reduction in resolution and without the occurrence of periodic stripes such as moiré. In addition, it can be realized with a small amount of calculation.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image control device according to an embodiment.

FIG. 2 is an external perspective view illustrating the image input apparatus according to the embodiment.

FIG. 3 is an external perspective view illustrating the image output apparatus according to the embodiment.

FIG. 4 is a diagram showing a configuration of a scanner image processing unit 400 shown in FIG.

FIG. 5 is a diagram showing a configuration of a printer image processing unit 500 shown in FIG.

FIG. 6 is a simple block diagram for explaining processing of a binary image scaling processing section shown in FIG. 1;

FIG. 7 is a block diagram showing a detailed configuration of an image scaling unit 602 shown in FIG.

FIG. 8 is a diagram illustrating a pixel of interest and pixels on the original image near the pixel of interest.

FIG. 9 is a diagram for explaining a process of obtaining a distance in the main scanning direction.

FIG. 10 is a diagram illustrating a relationship between a coefficient C of the bicubic interpolation method and a distance d.

FIG. 11 is a diagram illustrating frequency characteristics of a sinc function.

FIG. 12 is a diagram illustrating a relationship between a coefficient C and a distance d when LC = 2.

FIG. 13 is a diagram schematically illustrating frequency characteristics of a filter when LC = 2.

FIG. 14 is a diagram illustrating a coefficient with respect to a phase when the total sum is not adjusted.

FIG. 15 is a diagram for explaining a process of obtaining a distance from a position 5/32 pixels to the right of the pixel of interest 3 after zooming to the first pixel.

FIG. 16 is a diagram illustrating a coefficient with respect to a phase when the sum is adjusted.

FIG. 17 is a flowchart illustrating a processing procedure of an image scaling unit according to the present embodiment.

Continuation of the front page F term (reference) 5B057 AA11 CA06 CA07 CA08 CA12 CA16 CB06 CB07 CB08 CB12 CB16 CC01 CD05 CE06 CE13 CG01 CH09 CH18 5C076 AA21 AA22 AA25 BA08 BB04 BB07 CB01

Claims (11)

[Claims] 1. An image processing apparatus for performing scaling processing on input image data and outputting the result, wherein a distance between a position of a target pixel after scaling processing and a neighboring pixel of an original image is determined according to a scaling rate of the scaling processing. Deciding means for deciding phase information indicating the following, storage means for preliminarily calculating and storing a plurality of filter coefficients in the filter processing according to the determined phase information, and based on the plurality of stored filter coefficients. And a filter processing means for filtering input image data. 2. The storage means stores filter coefficients independently for main scanning and sub-scanning, and the filter processing means performs a convolution operation in the main scanning direction based on the filter coefficients in the main scanning direction. The image processing apparatus according to claim 1, wherein a convolution operation in a sub-scanning direction is performed on a result of the convolution operation based on a filter coefficient in a scanning direction. 3. The storage means stores filter coefficients independently for main scanning and sub-scanning, and the filter processing means performs a convolution operation in the sub-scanning direction based on the filter coefficients in the sub-scanning direction. The image processing apparatus according to claim 1, wherein a convolution operation in a main scanning direction is performed on a result of the convolution operation based on a filter coefficient in a scanning direction. 4. The distance between the pixel position of the original image used for the convolution operation in the main scanning direction and the convolution operation in the sub-scanning direction and the position of the pixel of interest after scaling in the original image is defined as the pixel position of the original image and Based on the phase information, the distance projected in the main scanning direction (dx) and the distance projected in the sub-scanning direction (dy)
N and M distances are obtained respectively, and a filter coefficient for controlling the frequency characteristic of the filter processing is determined for each of the main scan and the sub-scan (LCx, LCy), and dx / LCx is a parameter. Using N filter coefficients in the main scanning direction and dy / LCy as parameters by the bicubic interpolation method
M filter coefficients in the sub-scanning direction are calculated by the next interpolation method, and the N coefficients and the M coefficients are previously calculated and stored for each set of the phase decomposition numbers. The image processing device according to claim 2. 5. The image processing apparatus according to claim 4, wherein the number of filter coefficients in each of the main scanning and sub-scanning directions is eight. 6. The image processing apparatus according to claim 4, wherein the number of sets of the phase decomposition numbers is 32 or less. 7. A processing method of an image processing apparatus that performs scaling processing on input image data and outputs the result, wherein a position of a pixel of interest after the scaling processing and a position of an original image are changed according to a scaling factor of the scaling processing. A determining step of determining phase information indicating a distance from a neighboring pixel; a storing step of calculating a plurality of filter coefficients in a filtering process in advance according to the determined phase information and storing the coefficient in a storage unit; A filtering step of filtering input image data based on a plurality of filter coefficients set. 8. The storage step stores filter coefficients independently for main scanning and sub-scanning. The filter processing step performs a convolution operation in the main scanning direction based on the filter coefficients in the main scanning direction. The method according to claim 7, wherein a convolution operation in a sub-scanning direction is performed on a result of the convolution operation based on a filter coefficient in a scanning direction. 9. The storage step stores filter coefficients independently for main scanning and sub-scanning, and the filtering processing step performs a convolution operation in the sub-scanning direction based on the filter coefficients in the sub-scanning direction. 8. The processing method according to claim 7, wherein a convolution operation in a main scanning direction is performed on a result of the convolution operation based on a filter coefficient in a scanning direction. 10. A program for a processing method in an image processing apparatus for performing scaling processing on input image data and outputting the result, wherein a position of a pixel of interest after scaling processing and an original A code of a determining step of determining phase information indicating a distance to a neighboring pixel of the image; A program comprising: a code; and a code of a filtering process for filtering input image data based on a plurality of stored filter coefficients. 11. A computer-readable storage medium storing the program according to claim 10.