JP2701961B2 - Image processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method, and more particularly to an image processing method for emphasizing image edges and performing image processing.

[Conventional technology]

2. Description of the Related Art An image processing apparatus such as a reader printer irradiates an image recorded on a microfilm or the like with a light beam, scans the image with an optical sensor such as a CCD, and detects the amount of light transmitted or reflected from the image. The amount of light transmitted or reflected from the image changes according to the density pattern of the image (a pattern having a different density for each pixel). Therefore, an image signal corresponding to the density pattern of the image is output from the optical sensor,
An image is recorded on a recording material based on the image signal.

However, when detecting the amount of light transmitted or reflected through the image, the amount of light input to the optical sensor may not accurately correspond to the density pattern of the image due to the influence of an optical system or the like. For example, as shown in FIG. 6 (A), a so-called image edge in which the density of an adjacent pixel in an image suddenly changes from high density to low density, or rapidly changes from low density to high density. In the portion, it is preferable that the change in the amount of light input to the optical sensor accurately corresponds to the change in the density, as indicated by the dashed line in FIG. 6 (B). However, in practice, the light intensity of the light input to the optical sensor changes gradually as shown by the solid line due to the influence of diffraction. Therefore, when an image is recorded on a recording material using the image signal output from the optical sensor as it is, the recorded image is not sharp in the edge portion,
So-called blurring will occur. Therefore, it is necessary to perform image processing for processing so that the image signal output from the optical sensor has an appropriate value.

A Laplacian method is generally used as an image processing method for processing an image signal so that an edge portion is emphasized. Hereinafter, Laplacian will be described.

In FIG. 7, the density value of the central pixel is D ₀ ,
D ₁ The density value in the vicinity of the _{pixel, D 2, D 3, D} 4, D 5, D 6, D 7, D 8
Then, the density value D ₀ of the central pixel is defined as follows in Laplacian.

Therefore, the value added to the density value of the center pixel is proportional to the sum of the differences between the density value of the center pixel and the density values of the neighboring pixels as shown in FIG. Accordingly, for example, when the density value of the central pixel is higher than the density value of the neighboring pixels, the sign of (K · X) in the equation becomes plus, and the expression is emphasized so as to have a higher density. Is lower than the density value of a neighboring pixel, the sign of (K · X) in the expression becomes negative, and the density is emphasized to be lower. The edge of the image can be emphasized by performing the above-described processing on all the pixels constituting the image.

[Problems to be solved by the invention]

However, in the Laplacian case, there is a difference between the density value of the central pixel and the density value of the neighboring pixels (X ≠ in the above expression).
In the case of 0), emphasis is performed regardless of the difference. For this reason, when edge enhancement of an image is performed by Laplacian, unevenness of density values in a background portion in the image is enhanced, resulting in an image with much noise, or conversely, sufficient enhancement to suppress noise cannot be obtained. There was something.

In order to solve this, there is an image processing method that emphasizes only when the difference between the density value of the central pixel and the density value of the neighboring pixels is equal to or more than a predetermined value. Is required, the processing becomes complicated. Further, there is an image processing method in which an image is divided into small regions and the degree of emphasis is changed for each small region, for example, the degree of emphasis of the background portion is reduced to suppress noise in the background portion. In addition to this, there is a problem that a new process is required and an image becomes unnatural near the boundary between the small areas.

The present invention has been made in view of the above facts, and provides an image processing method which can sufficiently enhance an edge portion of an image, can suppress generation of noise, and can easily perform processing. Is the purpose.

[Means for solving the problem]

In order to achieve the above object, an image processing method according to the present invention obtains a total sum X of a difference between a pixel value of a specific pixel and a pixel value of a pixel near the specific pixel, and obtains a predetermined value K1, a total sum X, and a total sum X The product Y of the difference obtained by subtracting the predetermined value K2 from the absolute value | X | of the target pixel is calculated, and the image processing is performed using the sum of the product Y and the pixel value of the specific pixel as the pixel value of the specific pixel.

[Action]

In the present invention, the emphasis of a specific pixel is determined by summing a difference X between a pixel value (density value or luminance value) of a specific pixel and a pixel value of a pixel near the specific pixel, a predetermined value K1, and an absolute value | X of the sum. It is obtained by multiplying the difference obtained by subtracting the predetermined value K2 from |. The pixel value of a specific pixel is A _0, the pixel values of the pixels in the vicinity of the specific pixel A _1, ..., a pixel value A of a particular pixel in the case of the A _{n 0}
Is obtained by the following equation.

Therefore, the value added to the pixel value of the specific pixel becomes a quadratic function of the sum X of the difference between the pixel value of the specific pixel and the pixel value of the neighboring pixel as shown in FIG. , The sign of Y (see equation) is reversed at the boundary of K2, and similarly, in the region of X <0, the sign of Y is reversed at the boundary of -K2.

Thereby, when the difference between the pixel value of the specific pixel and the neighboring pixel value is small (| X | <| K2 |), the difference is further reduced, so that the density unevenness of the background portion of the image is reduced. The image is not emphasized and noisy. Also,
When the difference between the pixel of the specific pixel and the number of neighboring pixels is large (| X |> | K2 |), 2 is set so that the difference becomes larger.
Since the image is emphasized in the form of a curve, sufficient enhancement can be obtained for the edge portion of the image. The edge of the image can be emphasized by performing the above processing on all the images constituting the image.

Further, since the image processing method of the present invention does not need to divide an image into small areas, the processing is simplified, and the image does not become unnatural at boundaries of the small areas.

〔Example〕

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

FIG. 1 shows a reader printer 10 to which the image processing method of the present invention can be applied. This reader printer 10
Is a screen 16 for projecting an image recorded on the microfilm 14 on the front surface (the right side surface in FIG. 1) of the casing 12.
Is arranged. A line sensor 17 is provided on the back side of the screen 16 along the longitudinal direction of the screen 16. Both ends in the longitudinal direction of the line sensor 17 are
The guide shaft 19 is inserted through a guide shaft 19 extending in the lateral direction of the screen 16. As a result, the line sensor 17 is moved in the axial direction of the guide shaft 19 by the driving force of a driving unit (not shown), and can scan the image projected on the screen 16 for photometry.

A cartridge 18 in which the microfilm 14 is wound and stored in a layered manner is loaded in a loading section 20 provided slightly below the screen 16.
The leading end of the microfilm 24 inside is wound around the take-up reel 22 inside the apparatus. Cartridge 18 and take-up reel
The light source 14 is provided between the light source 22 and the microfilm 14. The light beam emitted from the light source 24 passes through the image frame arranged on the optical axis L, and passes through a screen through an optical system including a lens 26 and a plurality of reflection mirrors 28.
Guided in 16 directions. Thereby, the image recorded on the microfilm 14 can be enlarged and projected on the screen 16.

The reader printer 10 includes a digital printer 32. This digital printer 32 has a screen 16
Has the role of recording the image projected on the. That is, the analog image signal output from the line sensor 17 by the scanning is transmitted to the control device 38 (FIG. 2B).
), The image is converted into digital image data and subjected to image processing, and an image is recorded on a recording material (not shown) based on the processed image data.

2 (A) and 2 (B) show details of the loading section 20. FIG. The cartridge 18 has a supply-side reel 34 (hereinafter simply referred to as a reel 34) connected to a rotation shaft 42 of a supply motor 40 connected to a control device 38 via a torque control unit 36. The supply motor 40 is rotated in a direction of winding the microfilm 14 onto the reel 34 with a constant weak torque (the direction of arrow A in FIGS. 2A and 2B). The leading end of the microfilm 14 wound in a layer on the reel 34 is pulled out from an opening 44 provided in the cartridge 18 by the driving force of a loading roller of a loading mechanism (not shown), and guide rollers 46 and 48 are provided.
And then wound on a take-up reel 22.
Film detection sensors 49 and 51 for detecting the presence or absence of the microfilm 14 are disposed near the guide rollers 46 and 48, respectively.

The outer periphery of the endless transport belt 52 is in contact with the shaft 50 of the take-up reel 22. The transport belt 52 has an elastic force, and is wound around guide rollers 54, 56, and 58.
The transport belt 52 is wound around a drive reel 66 attached to a rotating shaft 64 of a take-up motor 62 connected to the control device 38 via a speed controller 60. Therefore, the transport belt 52 is moved to the second position in accordance with the rotation of the drive reel 66.
It is designed to be moved in the direction of arrow B in FIGS. (A) and (B) and in the opposite direction.

The microfilm 14 is sandwiched between the conveyor belt 52 and the shaft 50, and the shaft 50 is moved in accordance with the movement of the conveyor belt 52.
, Or pulled out from the shaft 50.

A driven roller 68 is in contact with the conveyor belt 50. The driven roller 68 is attached to the rotating shaft 72 of the encoder 70, so that the driving state of the transport belt 52 can be detected by the encoder 70 as the number of pulses. The encoder 70 is connected to the control device 38.

A slit plate 74 is provided slightly closer to the guide roller 46 than the optical axis L between the guide roller 46 and the guide roller 48, and a pair of light receiving elements 76 are provided corresponding to both widthwise ends of the microfilm 14. Installed. In correspondence with the light receiving element 76, the LED 7 is provided on the opposite side of the microfilm 14.
8 mounted, illuminated from LED78, microfilm
The light transmitted through 14 is received by the light receiving element 76. The light receiving element 76 and the LED 78 are connected to the control device 38, respectively.

At both ends of the microfilm 14, a blip mark 80
The presence or absence of the clip mark 80 can be detected based on a change in the amount of light received by the light receiving element 76.

The distance dimension M between the light receiving element 76 and the optical axis L is fixed (75 mm in this embodiment). Therefore, after detecting the image frame 14A specified by the light receiving element 76, it is moved by the dimension M. , The position of the optical axis L.

The control device 38 includes a conversion unit 39, an image storage unit 41, and an image processing unit 42. The conversion unit 39 converts the analog image signal (photometric value) output from the line sensor 17 into digital image data corresponding to the pixel of the image, and outputs the digital image data to the image storage unit 41. The image storage unit 41 is configured by a storage device such as a plurality of image memories, and stores the image data output from the conversion unit 39 and the image data after the image processing in association with the pixels. The image processing unit 42 reads out the image data stored in the image storage unit 41, performs various image processing including an image edge enhancement process according to the image processing method of the present invention, and writes the image data into the image storage unit 41. .

 Next, the operation of the present embodiment will be described.

First, an image search operation by the reader printer 10 will be described.

When the cartridge 18 is loaded (for example, it is determined based on the on / off state of the microswitch or the like), the loading mechanism operates, and the loading roller comes into contact with the outer periphery of the microfilm 14 to pull out the tip. The drawn-out microfilm 14 reaches the take-up reel 22 via the guide rollers 46 and 48, and is held between the transport belt 52 and the shaft 50. As a result, when the microfilm 14 is wound around the shaft 50 by a predetermined amount, the movement of the transport belt 52 is stopped, and a standby state is set.

Here, when an image frame is designated by the keyboard 92,
The take-up motor 62 is driven, the transport belt 52 is moved, and the microfilm 14 is wound around the shaft 50 at the same time.

When the microfilm 14 is transported, the LED 7
Each blip mark 80 passing between 8 and the light receiving element 76 is counted. When a predetermined number of counts are made, the light is conveyed by the distance between the detection point by the light receiving element 76 and the optical axis L,
The drive of the take-up motor 62 is stopped. Thereby, the positioning of the designated frame on the optical axis L is completed, and the light source 24
Can be projected on the screen 16.

Next, a process of performing image processing according to the present invention on an image projected on the screen 16 and outputting image data to the digital printer 32 will be described with reference to a flowchart of FIG.

In step 100, the screen 1 is detected by the line sensor 17.
The photometry of the image projected on 6 is performed. This is screen 1
This is performed by moving the line sensor 17 in the axial direction of the guide shaft 19 while the image is projected on 6. In step 102, the analog image signal (photometric value) input from the line sensor 17 into the control device 38 is logarithmically converted by the conversion unit 39, and then converted to digital image data (density value). In step 104, the image data converted in step 102 is stored in the image memory of the image storage unit 41.

Hereinafter, in steps 106 to 112, edge enhancement processing of an image is performed by the image processing method of the present invention. That is, in step 106, the density value D ₀ of the specific pixel and the density values D _{1 of} the eight pixels near the specific pixel, so-called eight neighboring pixels, are calculated from the image data (density value) stored in the image storage unit 41.
D ₂ , D ₃ , D ₄ , D ₅ , D ₆ , D ₇ , D ₈ are read out and the image processing unit 42 is read out.
Take in. In step 108, the density value of a specific pixel to be emphasized is calculated based on the image data captured in step 106. This calculation is performed based on the following equation.

Accordingly, when the density value of the specific pixel is higher than the density value of the pixel near 8 and the difference between the density value of the specific pixel and the density value of the pixel near 8 is small (| X | <| K2 |). Since the sign of Y (see the equation) added to the density value D ₀ of the specific pixel is minus, the density value is reduced, and the difference from the density value of pixels near 8 is further reduced. The density value of the specific pixel is 8
The density value is lower than the density value of the neighboring pixels, and the difference between the density value of the specific pixel and the density value of the eight neighboring pixels is small (| X | <| K2 |).
Similarly, in this case, the sign of Y added to the density value D ₀ of the specific pixel is positive, so that the density value is increased, and the difference from the density value of the pixels near eight is further reduced. For this reason, small variations in density such as uneven density in the background portion of the image are reduced.

When the density value of the specific pixel is higher than the density value of the pixel in the vicinity of 8 and the difference between the density value of the specific pixel and the density value of the pixel in the vicinity of 8 is large (| X |> | K2 |), Since the sign of Y added to the density value D ₀ of the specific pixel is positive, the density value is increased, and the difference from the density value of the pixels near 8 is further increased. Similarly, when the density value of the specific pixel is lower than the density value of the pixel near 8 and the difference between the density value of the specific pixel and the density value of the pixel near 8 is large (| X |> | K2 |). Since the sign of Y added to the density value D ₀ of the specific pixel is minus, the density value is increased, and the difference from the density value of the pixels near 8 is further increased. Therefore, sufficient emphasis can be obtained for a portion where the density difference between adjacent pixels is large, such as an edge portion of an image.

The density value D ₀ of a particular pixel as determined by equation in step 110, and stores in a different image memory the image memories was read in step 106. At step 112, it is determined whether or not the edge enhancement processing of the image has been completed. As shown in FIG. 4, in the present embodiment, the edge enhancement processing is performed in correspondence with the scan line of the image 82 (in the direction of arrow C in FIG. 4).
After the process for one scan line is completed, the next scan line is moved (in the direction of arrow D in FIG. 4) and the same process is performed. If the processing has not been completed for all scan lines, the process returns to step 106, and the processing is repeated by repeating steps 106 to 112 according to the processing order.

When processing for all scan lines is completed,
At step 114, the image data stored at step 110 is output to the digital printer 32. As a result, the digital printer 32 can record a blur-free image in which edges are emphasized on recording paper.

As described above, in the present embodiment, the sum X of the difference between the density value of the specific pixel and the density values of the eight pixels near the specific pixel is obtained, and the predetermined value K1, the total X, and the absolute value | X | Since the product Y of the difference obtained by subtracting the predetermined value K2 and the difference is obtained, and the sum of the product Y and the density value of the specific pixel is used as the density value of the specific pixel, the image processing is performed. Sufficient emphasis on the portion can be obtained, and the occurrence of noise can be suppressed, so that the processing can be easily performed.

In the present embodiment, the pixels in the vicinity of the specific pixel are eight pixels in the vicinity of the specific pixel. However, the present invention is not limited to this.
A nearby pixel, a pixel adjacent to a specific pixel in a direction along a scan line, a pixel adjacent to a specific pixel in a direction orthogonal to the scan line, or the like may be adopted as a nearby pixel.

In the present embodiment, the photometric value output from the line sensor 17 is converted into a density value, but it is also possible to convert the photometric value into a luminance value and perform processing.

Further, in the present embodiment, the image data subjected to the edge enhancement processing is output to the digital printer 32 and recorded on the recording paper. However, after the image processing such as smoothing and binarization is performed, The data may be output to the digital printer 32 and recorded on recording paper.

In the above description, the enhancement is performed using the quadratic function. However, the enhancement may be performed using the cubic function.

〔The invention's effect〕

As described above, in the present invention, the predetermined value K2 is subtracted from the total value X of the difference between the pixel value of the specific pixel and the pixel value of the pixel near the specific pixel, the predetermined value K1, and the absolute value | X | Since the image processing is performed by calculating the product of the difference and the obtained difference, sufficient enhancement of the edge portion of the image can be obtained, noise can be suppressed, and the processing can be easily performed.
An excellent effect is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a reader printer according to the present embodiment,
FIG. 2 (A) is a perspective view of the vicinity of the cartridge loading portion, and FIG.
FIG. (B) is a schematic block diagram of the vicinity of the cartridge loading section,
FIG. 3 is a flow chart for explaining the operation of the present embodiment, FIG. 4 is a conceptual diagram for explaining the processing sequence, FIG. 5 is a diagram showing the operation of the present invention, and FIG. FIG. 7 is a conceptual diagram showing the concept of the neighborhood, and FIG. 8 is a diagram showing the degree of enhancement in Laplacian. 10 ... Reader printer, 17 ... Line sensor, 32 ... Digital printer, 38 ... Control device, 39 ... Converter, 41 ... Image storage unit, 42 ... Image processing unit.

Claims (1)

(57) [Claims] 1. A method for calculating a sum X of a difference between a pixel value of a specific pixel and a pixel value of a pixel in the vicinity of the specific pixel, and obtaining a predetermined value K1 and a total X
Image processing method for obtaining a product Y of the difference between the absolute value | X | of the sum and the predetermined value K2, and performing image processing on the sum of the product Y and the pixel value of the specific pixel as the pixel value of the specific pixel .