JP2613095B2 - Image enlargement apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Overview Industrial application Field of technology Background (Figs. 11 and 12) Conventional technology (Figs. 10 and 13) Problems to be solved by the invention (Fig. 13) Means for Solving the Problems (FIGS. 1 and 2) Operation (FIGS. 1 and 2) Embodiment (FIGS. 3 to 9) Effects of the Invention [Overview] Setting a Divided Area on a Plane on Which Pixels to be Converted are Arranged In addition, the present invention relates to an image enlarging method for determining the density of a converted pixel from the density of a pixel to be converted in accordance with a logical expression corresponding to a divided region, An object of the present invention is to provide an image enlarging apparatus and method for enlarging, and designate a segmented area where a transformed pixel is located among segmented areas set on a plane and determined based on a conversion magnification, and convert pixels based on the segmented area. Of a given group of pixels to be converted Data is sequentially input, and a diagonal pattern and a tilt angle having a predetermined tilt angle formed by the density data of the pixel group to be converted are detected based on the area, and a corresponding boundary line is determined based on at least the tilt pattern and the tilt angle. While dividing into divided regions by, the divided region where the conversion pixel is located is determined based on the conversion magnification,
The density of the converted pixel is calculated based on the determined divided area and the density of the pixel to be converted.

[Industrial applications]

The present invention relates to an image enlarging apparatus and method in pixel density conversion or image processing from low density to high density such as G3 to G4 facsimile, particularly, setting a divided area on a plane where pixels to be converted are arranged, The present invention relates to an image enlargement device that determines the density of each converted pixel from the density of a neighboring pixel to be converted according to a logical expression corresponding to a divided area where a converted pixel projected on a plane is located.

[Technological background]

As a conventional image enlargement method, SPC (Selective Process
ing Conversion) method, OR method, nine-division method, high-speed projection method (Japanese Patent Application Laid-Open No. 58-97958, Journal of the Institute of Image Electronics Engineers of Japan, Vol. 11, No. 2,
2-83 (1982)) and the like, all of which are methods for determining the density of a converted pixel from four neighboring pixels to be converted.

In the SPC method, diagonal lines tend to be more conspicuous as the enlargement magnification is larger.

On the other hand, in the high-speed projection method, the collapse at the time of enlargement is small, and the adaptation of the oblique lines reduces the unevenness of the oblique lines.

The high-speed projection method realizes the high-speed projection method by replacing the arithmetic conversion when determining the density of the converted pixel with a logical operation. In the high-speed projection method, as shown in FIG. 12, a logical area for setting a divided area according to the conversion magnification in the plane of the converted image and determining the density of the converted pixel from the converted pixel in the divided area. Is prepared in advance, and the density of the converted pixel is determined based on the logical expression assigned to the divided area where the converted pixel is located.

FIG. 11 shows the principle of a general projection method, and Table 1 shows divided regions and logical expressions of the high-speed projection method.

As shown in FIG. 11, first, a converted image plane including four neighboring pixels A, B, C, and D is divided into four equal parts. The pixel density of four neighboring pixels
I _A , I _B , I _C , and I _D, and when the converted pixel R is projected on the conversion target pixel surface, the area ratio projected to each of the four divided areas is W _A , W _B , W _C , W _D In the projection method, the density of the transformed pixel R is set to I
_{Since R} = ΣIi * Wi, i = A, B, C, D, the binarization is performed, so that I _R ≧ 0.5 → I _R = 1 (black) and I _R <0.5 → I _R = 0 (white) become. Note that p and q in FIG. 11 are conversion magnifications in the X-axis and Y-axis directions.

However, in the projection method, high-speed processing cannot be performed because an arithmetic operation is required to obtain the density of the converted pixel R. Therefore, in the high-speed projection method, the arithmetic operation is replaced with a logical operation to increase the speed.

The straight line in FIG. 12 indicates one of four pixels based on the projection method.
The boundary where the density of the conversion pixel R can be determined only by the pixel is shown. For example, a curve separating the G ₃ and G ₇ is given by the following equation.

px + qy = 0.5 Note that this straight line is an equation for smoothing diagonal lines at the time of enlargement.
The calculation is performed with the conversion magnification p = 1 and q = 1 and fixed regardless of the conversion magnification. The reason for this is that, when the linear equation is determined according to the conversion magnification, the area for determining the density of the converted pixel by one pixel increases, and as a result, it is not different from the SPC method, and the oblique line cannot be smoothed. .

[Conventional technology]

In the case of enlarging an image by using the conventional high-speed projection method, as shown in FIG. 10, a converted pixel which sequentially inputs each density data of the converted pixel groups A to L located near the converted pixel is used. An input unit 21, a divided region determining unit 24 that determines which divided region a converted pixel belongs to based on a desired conversion magnification, density data of the converted pixel group input by the converted pixel input unit 21, and Conversion pixel density calculation means for calculating the density of the conversion pixel based on the divided area to which the conversion pixel belongs
The image has been enlarged using an image enlargement device having 25.

As shown in Table 1, the logical expressions of the high-speed projection method are the regions G _{1 to} G ₄
In one pixel only, it has a binding and logical expression from the surrounding 2 pixels considering distinguish adaptive smoothing hatched perpendicular portion between the other three pixels in area G ₅ ~G _8.

[Problems to be solved by the invention]

By the way, in the conventional image enlarging apparatus, when enlarging, it is good only when the angle of the oblique line pattern in the converted image is 45 degrees, and when the angle of the pattern is other, the oblique line smoothing is unnatural. Shape.

For example, consider a case in which three oblique line patterns as shown in FIG. 13 are tripled by a conventional high-speed projection method.

The oblique line pattern (a) in FIG. 13 has an angle of 45 degrees, so that the entire oblique line is smoothed.

However, the oblique line patterns (b) and (c) have a problem that the oblique line smoothing is performed only in the step-like portion, and the entire surface is not smoothed.

In addition, there is a problem that as the conversion magnification increases, the stepped shape of the oblique line tends to be more noticeable.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-described problems, and to provide an image enlargement capable of performing natural diagonal line smoothing so as not to make the diagonal step shape conspicuous. It is intended to provide an apparatus and a method.

[Means for solving the problem]

In the first invention, as shown in FIG. 1, a divided area is set in accordance with a conversion magnification on a plane on which pixels to be converted are arranged, and a divided area in which the converted pixel is projected on the plane is set. An image enlarging device that determines the density of each converted pixel from the density of a neighboring pixel to be converted according to a corresponding logical expression, wherein a section in which the converted pixel is located among the divided areas set on the plane and determined based on a conversion magnification. A divided area designating means 2 for designating an area, and a reference pixel pattern indicating a group of pixels to be converted which are located in the vicinity of the converted pixel and in the quasi-neighborhood of the converted pixel necessary for determining the angle of the oblique line are determined for each divided area. A converted pixel input 1 for sequentially inputting density data of a converted pixel group of a converted pixel pattern of a corresponding reference pixel pattern based on the segmented region, and a density of the converted pixel group based on the segmented region. A diagonal line pattern having a predetermined inclination angle formed by the degree data and a diagonal line pattern detecting means 3 for detecting the diagonal angle, and dividing the region into divided regions by at least a corresponding boundary line based on the diagonal line pattern and the diagonal line angle; Area division determining means 4 for determining the divided area where the converted pixel is located based on the conversion magnification, and a converted pixel for calculating the density of the converted pixel based on the determined density of the divided area and the pixel to be converted And a density calculating means 5.

On the other hand, in the second invention, as shown in FIG. 2, a divided area is set on a plane on which pixels to be converted are arranged according to a conversion magnification, and a divided area where the converted pixel projected on the plane is located. In an image enlarging method for determining the density of a conversion pixel from the density of a pixel to be converted in accordance with a logical expression corresponding to the following, a division in which the conversion pixel is located in a division area set on the plane and determined based on a conversion magnification In addition to specifying the area, a reference pixel pattern indicating a group of pixels to be converted located in the vicinity of the conversion pixel and near the conversion pixel necessary for determining the angle of the oblique line is determined for each section area, and based on the specified section area Sequentially inputting the density data of the converted pixel group of the corresponding reference pixel pattern (S1), and determining a predetermined inclination angle formed by the density data of the converted pixel group based on the area. Detecting the oblique line pattern and the inclination angle to be performed (S2), and dividing the image into the divided areas by at least the corresponding boundary line based on the oblique line pattern and the inclination angle, and determining the position of the conversion pixel based on the conversion magnification. Step of determining divided area (S3)
And calculating the density of the converted pixel based on the determined density of the divided area and the converted pixel (S4).

[Action]

 The operation of the present invention (first and second inventions) will be described.

In the case of enlarging an image according to the present invention, for a conversion pixel for which the density is to be determined at the present time, in step S1, the division area specified by the division area specifying means 2 based on the conversion magnification is determined. Of these, the divided area in which the converted pixel is located is designated, and density data of a predetermined group of pixels to be converted located near the converted pixel is sequentially input by the converted pixel input means 1 based on the divided area.

Here, the designation of the segmented region is performed in order to select and limit a reference pixel necessary for the next step from among the pixels to be converted and to perform processing at high speed.

Further, “predetermined” is a group of pixels to be converted that influences the determination of the density of the converted pixel, and is, for example, within a certain distance from the converted pixel when projected onto the plane of the converted pixel. The pixel to be converted.

In step S2, the oblique line pattern detecting means 3 detects an oblique line pattern having a predetermined angle and an oblique angle based on the oblique line pattern and the oblique angle detected based on the limited density of the pixel to be converted.

In step S3, the area division determination means 4 determines a boundary line of the divided area necessary for calculating the density of the conversion pixel based on the oblique line pattern and the inclination angle detected by the oblique line pattern detection means 3.

Here, the boundary line of the divided region is determined based on the oblique line pattern and the inclination angle of the pixel to be converted, because the shape of the oblique line of the enlarged converted pixel greatly depends on the shape of the boundary line separating each divided region. This is for smoothing oblique lines by determining each divided area based on the oblique line pattern and the inclination angle of the pixel to be converted.

Further, the area division determining unit 4 determines the divided area where the converted pixel projected is located based on the conversion magnification.

In step S4, the conversion pixel density calculating means 5
Based on the density data of the group of pixels to be converted located in the vicinity of the divided area and the converted pixel determined in step S3, the density of the converted pixel at the present time is calculated by a corresponding logical expression.

 The above procedure is sequentially repeated for each conversion pixel.

〔Example〕

 An embodiment of the present invention will be described.

FIG. 3 shows an image enlargement apparatus according to an embodiment of the present invention.

The apparatus includes a two-dimensional image memory 10 storing an original image composed of pixels to be converted, and a group of pixels to be converted selected based on a segmented area designated by a control unit 12 as a segmented area designating means 2 to be described later. Pixel data input means 11 for sequentially inputting the density data of the pixels, and a diagonal line pattern having a predetermined tilt angle formed by the density data of the pixel to be converted input by the input means 11 and a tilt angle based on the designated area. A logic circuit 13 for oblique line pattern detection as the oblique line pattern detecting means 3 for detecting an object by dividing the image into at least one of divided regions based on at least the oblique line pattern and the inclination angle, and dividing the conversion magnification based on the conversion magnification. The conversion pixel input means includes an area division determination means 4 for determining an area and a division area designation means 2 for designating a quadrant area in which the conversion pixel is located. 11 and the two-dimensional image memory
A control unit 12 for controlling an access command or the like to the control unit 10; and a conversion pixel density calculation unit 5 for calculating the density of the conversion pixel based on the determined divided area and the input conversion target pixel group. And a logic circuit 15.

As shown in FIG. 3, the converted pixel input means 11
It has eight shift registers 11a to 11h. The shift registers 11a and 11b hold the pixels to be converted on the first image line.

Similarly, the shift registers 11c and 11d are on the second image line,
The shift registers 11e, f sequentially move and hold the pixels to be converted on the third image line, and the shift registers 11g, h sequentially move and hold the pixels to be converted on the fourth image line.

When detecting the oblique line pattern and the inclination angle, the control unit 12 as the segmented area designating means 2 divides a grid formed by four pixels to be converted located near the current conversion pixel into four equal parts. It is necessary to test the density of the converted pixel by dividing into the equally divided areas and specifying the four equally divided areas where the converted pixels are located and limiting the converted pixels to be referred from the group of converted pixels. The number of pixels to be converted is reduced.

FIG. 4 shows quaternary divided areas R1, R2, R3, R4 applied by the control unit 12 as the divided area designating means 2. This is obtained by dividing a region in the grid defined by the four conversion pixels A to D located closest to the conversion pixel into four equal parts.

According to this four-level division area, 11 converted pixels necessary for determining the oblique line pattern and the inclination angle are extracted from the group of 24 converted pixels (A to X) located in the vicinity of the converted pixel. .

The larger the number of converted pixels to be referred, the better. However, if the number is too large, it takes too much processing time, but if the number is 11, the oblique line pattern and the inclined angle can be determined with high accuracy.

The oblique line pattern detection logic circuit 13 detects an oblique line pattern based on the quaternary regions R1 to R4 specified by the control unit 12, and as shown in FIG. For each of the 11 converted pixels located in a predetermined vicinity of the current converted pixel for each, P1-No. 1 to 8, P2
−No.1 to 4, P3−No.1 to 4.

Here, as the type of the oblique line pattern, a slant pattern of P1-No.1,2: tan θ = 1 (θ = 45 °) with respect to the slant angle θ P1-No.3,4: Non-oblique line pattern corresponding to a right angle portion P1-No.5,6: Oblique line pattern of tanθ = 2 (center part of oblique line) P1-No.7,8: Oblique line pattern of tanθ = 0.5 (center part of oblique line) P2-No.1,2: tanθ = 2 diagonal pattern (diagonal end) P2-No.3,4: diagonal pattern with tanθ = 1 (diagonal end) P3-No.1,2: diagonal pattern with tanθ = 0.5 (diagonal end) P3-No.3,4: The oblique line pattern (end portion of the oblique line) of tanθ = 1 is shown.
= 1, 2, and 0.5 are detected.

As shown in FIG. 6, the control unit 12 describes the boundary line of each divided area based on the oblique line pattern and the inclination angle of each divided area outputted from the oblique line pattern detection logic circuit tan> 1: tan θ * X + y = tan θ / 2 tan ≦ 1: x + y / tan θ = 1 / (2 * tan θ) (when x> 0, y> 0) it is to determine the divided regions G ₁ ~G ₁₂ located.

Further, the density of the converted pixel is calculated based on the logical expression described in Table 2 corresponding to each of the divided areas.

Hereinafter, the operation of the image enlargement device according to the present embodiment will be described.

The control unit 12 issues an access command to the two-dimensional image memory 10 in which the original image to be enlarged by the present apparatus is stored, for each fixed word length unit (for example, 4 bits).

The read converted pixel group for the four lines located near the current converted pixel is sequentially shifted one pixel at a time for each line by line for the shift registers 11a, c, e, g, as the converted pixel input means 11. The control unit 12 moves each pixel to the shift register 11b, d, f, h at a predetermined timing, and causes the shift register 11b, d, f, and h to input the pixel to the logic circuit 13 for oblique line pattern in parallel.

On the other hand, the control unit 12 specifies the four-segment areas R1 to R4 where the current conversion pixel is located based on the conversion magnifications p and q, and outputs a 2-bit signal (signal for distinguishing R1 to R4). It is sent to the oblique line pattern detection logic circuit 13.

Then, the oblique line pattern detection logic circuit 13 divides the converted pixel into each divided region by a boundary line as shown in FIG. 6 corresponding to the oblique line pattern for each of the four divided regions where the converted pixel is located. The divided areas G _{1 to} G ₁₂ located are determined, and a 4-bit signal is output to the conversion pixel density determination logic circuit 15.

The conversion pixel determination logic circuit 15 outputs the density of the conversion pixel from a logical expression as shown in Table 2 according to the division.

FIG. 7 shows an example of a three-fold enlargement according to this embodiment. FIG. 7 (a) is a diagonal pattern with an inclination angle θ and tan θ = 1, FIG. 7 (a) is tan θ = 2, and FIG.
This is a diagonal line pattern corresponding to 0.5, and is distinguished from FIGS.
The image can be enlarged as an image having an inclination angle of nθ = 1.

FIGS. 8 and 9 show the inclination determination results of FIGS. 7 (d) and 7 (e).

According to the present embodiment, by first designating the quaternary area, it is possible to detect the oblique line pattern limited to 11 pixels to be converted. Since the boundary of each divided area can be uniquely defined, the division and determination of the area can be performed at high speed.

In addition, by referring to the pixel to be converted of 11 pixels (4 lines of data), it is possible to obtain an enlarged image not only at the center of the oblique line but also at the end, according to the inclination angle of the contour.

In order to perform this in the conventional example, it is necessary to refer to a pixel to be converted of 24 pixels (data of 6 lines).

〔The invention's effect〕

As described above, the present invention is directed to the problem of the original image,
By detecting a predetermined oblique line pattern and an inclination angle, a boundary line of each divided area is determined based on the oblique line pattern and the inclination angle.

Therefore, by setting a diagonal line greatly affected by the shape of the boundary line according to the inclination of the diagonal line, an enlarged converted image having a naturally smoothed diagonal line can be obtained by high-speed projection. Therefore, it is possible to provide a highly reliable image enlargement apparatus and method.

[Brief description of the drawings]

FIG. 1 is a block diagram of the principle of the first invention, FIG. 2 is a flowchart of the principle of the second invention, FIG. 3 is a circuit block diagram of the image enlargement apparatus according to the embodiment, and FIG. FIG. 5 is a diagram showing a conversion pixel and a divided region, FIG. 5 is a diagram showing a diagonal pattern according to the embodiment, FIG. 6 is a diagram showing a boundary line of a divided region corresponding to the diagonal pattern according to the embodiment, and FIG. FIG. 8 is a diagram showing a region determination result (three times enlarged) in the case of FIG. 7 (d), and FIG. 9 is a region in the case of FIG. 7 (e). The figure showing the judgment result (3 times magnification), FIG.
FIG. 10 is a block diagram according to a conventional example, FIG. 11 is a diagram showing the principle of the projection method, FIG.
FIG. 13 is a diagram showing an example of a three-fold enlargement of a diagonal line pattern according to a conventional example. 1, 11: Converted pixel input means 2 (12): Segmented area designating means (control unit) 3 (13): Oblique pattern detecting means (logic circuit for oblique pattern detection) 4 (12): Area division Determination means (control unit) 5 (15)... Conversion pixel density calculation means (conversion pixel density determination logic circuit)

Claims (2)

(57) [Claims] 1. A divided area is set on a plane on which pixels to be converted are arranged in accordance with a conversion magnification, and a neighborhood to be converted according to a logical expression corresponding to the divided area where the converted pixels projected on the plane are located. An image enlarging device that determines the density of each conversion pixel from the pixel density, wherein a division area designating unit that designates a division area where the conversion pixel is located among division areas set on the plane and determined based on a conversion magnification. (2) A reference pixel pattern indicating a group of pixels to be converted, which is located in the vicinity of the conversion pixel and in the quasi-neighborhood of the conversion pixel required for determining the angle of the oblique line, is determined for each of the divided areas, and based on the specified divided area,
A converted pixel input means (1) for sequentially inputting the density data of the converted pixel group of the corresponding reference pixel pattern; and a predetermined inclination angle formed by the density data of the converted pixel group based on the divided area. A diagonal pattern detection means (3) for detecting a diagonal pattern and an inclination angle thereof, and dividing the image into divided regions at least by a corresponding boundary line based on the diagonal pattern and the inclination angle, and performing the conversion based on the conversion magnification. Area division determining means (4) for determining the divided area where the pixel is located; and converted pixel density calculating means (5) for calculating the density of the converted pixel based on the determined divided area and the density of the pixel to be converted. An image enlarging device comprising: 2. A divided area is set in accordance with a conversion magnification on a plane on which pixels to be converted are arranged, and a neighboring pixel to be converted is determined according to a logical expression corresponding to the divided area where the converted pixel projected on the plane is located. In the image enlarging method for determining the density of the conversion pixel from the density of, the partition area where the conversion pixel is located among the partition areas set on the plane and determined based on the conversion magnification, and the neighborhood of the conversion pixel A reference pixel pattern indicating a group of pixels to be converted, which is located in the vicinity of the conversion pixel necessary for determining the angle of the oblique line, is determined for each of the divided areas, and based on the specified divided area, the converted pixel of the corresponding reference pixel pattern is determined. A step (S1) of sequentially inputting the density data of a group; a diagonal pattern and a tilt angle having a predetermined tilt angle formed by the density data of the pixel group to be converted based on the area; Detecting the degree (S2); and dividing the divided area into divided areas based on at least the corresponding boundary line based on the oblique line pattern and the inclination angle, and determining the divided area where the conversion pixel is located based on the conversion magnification. (S3) and a step (S4) of calculating the density of the converted pixel based on the determined density of the divided area and the pixel to be converted.