JPH07113964B2 - Image fusion synthesizing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is intended for synthesizing two images different from each other and creating a post-synthesis image in which the image smoothly changes from one image to the other. The present invention relates to an image melting and synthesizing method.

(Prior Art) When two images are combined to create one combined image, the same graphic area to be combined is set for each of the two images, and the outline of the graphic area is set. A so-called "image fusion" process is performed so that the image smoothly changes from one image to the other in the vicinity. To satisfactorily perform such image fusion, an area in which the image composition ratio changes smoothly (hereinafter referred to as "composite area") is formed so as to have a constant width from the contour line. Need to

(Problems to be Solved by the Invention) However, conventionally, it is only possible to perform image fusion processing on a graphic region having a simple contour line that can be represented by a mathematical expression such as a circle or a square, and it is possible to perform a process of blending an arbitrary shape. Since it is difficult to form a synthetic area having a constant width in the graphic area, there is a problem that the image fusion processing cannot be performed. In addition, since a large capacity memory is required to perform the melting process for a large graphic area,
There is a problem that the size of the graphic area that can be processed is also limited.

(Object of the Invention) This invention intends to solve the above-mentioned problems in the prior art, and melts an image in which a graphic region of an arbitrary size and shape can be easily melted and synthesized. It is intended to provide a synthetic method.

(Means for Achieving the Purpose) In order to achieve the above-mentioned object, in the present invention, the same graphic area surrounded by the same contour line is set for each of different first and second images, and the graphic area is set. Determining a composition ratio of the first and second image data representing the first and second images for each pixel in the image, and combining the first and second image data using the composition ratio. Thus, in the image fusion synthesizing method for merging the first and second images with each other, (a) the graphic region is divided into a plurality of divided regions, and (b) the divided regions are vertically divided. Obtaining a reference contour line including the portions of the contour line respectively corresponding to the directional coordinate range and the lateral coordinate range,
(C) For each pixel in the divided area, a point closest to the pixel on the reference contour line is determined as a reference point, and (d) a predetermined combination ratio in which the distance between the reference point and the pixel is a variable. The combination ratio of the pixel is determined based on the function.

In addition, in order to reduce the processing time, each of the divided areas is further divided into a plurality of small divided areas, and the inside of each of the small divided areas is divided into a plurality of pieces that are circumferentially divided from the outer peripheral side toward the central side. In order to determine the composition ratio of each pixel in the step (d),
(D-1) selecting the outermost pixel layer in the subdivided area, and (d-2) calculating the composite ratio using a composite ratio function for each of the pixels forming the selected pixel layer. And (d-3) when the composition ratio is constant for all the pixels included in the selected pixel layer, the selected pixel layer and the center of the selected pixel layer The composition ratio of all the pixel layers existing on the side is determined to be the same as the composition ratio of the selected pixel layer, and (d-
4) If the composition ratio of the pixels included in the selected pixel layer is not constant, the composition ratio calculated in step (d-2) for each of the pixels included in the selected pixel layer remains unchanged. By adopting, and further selecting a pixel layer on the center side adjacent to the selected pixel layer, (d-5) repeating steps (d-2) to (d-4) above, Determine the composite ratio of each of the pixels.

(Operation) In the first means, the image is divided into a plurality of divided areas, so that it is possible to process a graphic area having an arbitrary size. Further, only the point on the reference contour line corresponding to the coordinate range of each divided area is selected as the closest point from each pixel as a reference point, and the composition ratio of the pixel is determined based on the distance between the reference point and the pixel. Therefore, a graphic region having an arbitrary shape can be processed by the same processing procedure.

In the second means, each divided area is further divided into a plurality of small divided areas, and when the combined ratio of the selected pixel layers in each small divided area is constant, the pixel layer located closer to the center than that is. Since the same combination ratio is determined without calculating the combination ratio of, the calculation of the combination ratio in the pixel layer closer to the center than the selected pixel layer can be omitted.

(Embodiment) A. Overall Configuration of Apparatus FIG. 1 is a schematic configuration diagram of an image processing apparatus which applies an embodiment of the present invention to perform image fusion processing. In this figure, this device is an image operation control device 1, an image disk control device 2, an image disk memory 3, an image scanner 4, a digitizer control device 5, a digitizer 6, and a host computer (hereinafter referred to as "host CPU") 7 It comprises a disk memory 8 and an image fusion synthesizing device 10. The image melting and synthesizing device 10 is a unique device for the embodiment of the present invention, and includes a bus line 11 connected to the image arithmetic and control unit 1, an image memory 12 and an image display connected to the bus line 11, respectively. A control device 13, a flat screen generator 14, an image synthesizing device 15, a fusion blending ratio calculating device (hereinafter simply referred to as “combining ratio calculating device”) 16, and a RAM 17 are provided. Further, the image display control device 13 further includes an image display device.
18 connected.

B. Operation of Embodiment B-1. First Method FIG. 2A is a flowchart showing the procedure of the embodiment of the present invention. FIG. 3 is an explanatory diagram showing the processing contents of the embodiment of the present invention.

In step S1, the original image input from the image scanner 4 and stored in advance in the image disk 3 is written in the image memory 12 according to the instruction of the operator and simultaneously displayed on the image display device 18. When the image memory 12 has a small capacity and cannot store all the image data of the original image, only a small amount of thinned image data is stored, so that a rough original image is displayed. As the original image, as will be described later, there are a combined image to be an image inside the graphic area to be combined and a combined image to be an image outside the same graphic area. Only one of the images is written in the image memory 12. However, the correspondence relationship between the combined image and the combined image on the image plane is designated in advance by the operator.

In step S2, the operator moves the stylus pen 6a or the cursor (not shown) of the digitizer 6 which is interlocked with the image display device 18 while observing the display of the original image, so that the contour line S of the desired graphic region F is formed. Enter (3A
Figure). Based on the contour line S, the host CPU 7 obtains a rectangular outer peripheral frame SF circumscribing the graphic region F, and also obtains vertical raster data D _y and horizontal raster data D _x (first
(Figure 3B). The vertical direction raster data D _y is data indicating the y-direction vector B _y inside the graphic region F that passes through each pixel P on the contour line S, and includes a start point PI _y (= P) and an end point PE _y existing on the contour line. Data represented as a combination of coordinate values of. Similarly, the horizontal raster data D _x is also data indicating the x-direction vector B _x . These raster data
D _x and D _y are obtained for all the pixels P on the contour line S, and are stored in the disk memory 8 as graphic data together with the data indicating the outer peripheral frame SF.

In step S3, the operator uses the digitizer 6, a keyboard (not shown), or the like to create a composite area width L described later.
Input the parameters required for setting the and composite ratio function f (d _min ). These parameter inputs are stored in the host CPU 7. With the above, input by the operator is completed, and in the following steps, arithmetic processing is performed in the image processing apparatus.

In step S4, the size of the image area IA that can be stored in the image memory 12 is obtained by the image calculation control device 1 based on the capacity of the image memory 12, and the number N ₁ of divisions of the outer peripheral frame SF is calculated.
Is determined (Fig. 3C).

In step S5, the image area IA in the N ₁ divided outer peripheral frame SF is divided.
2, the image data of the two original images (composite image and composite image) are taken into the image memory 12 from the image disk 3 as image area data I ₁ and I ₂ , respectively.

In step S6, the image processing apparatus 1 determines the size of an image that can be processed at one time from the limit of the number of raster data that can be stored in the RAM 17, and the image area IA is further divided into N ₂ divided areas DA ( (Figure 3D).

In step S7, the reference contour line data corresponding to one divided area DA is selected by the host CPU 7 from the graphic data stored in the disk memory 8 and transferred to the RAM 17. As shown in FIG. 3E, the reference contour line data in the first method includes vertical raster data D _y and horizontal raster data D _y that pass through the respective x-direction and y-direction coordinate ranges Δx and Δy of the divided area DA. It includes data D _x , and further includes horizontal raster data D _x that passes through the range of the combined area width L on both sides of the y-direction coordinate range Δy. That is, for the divided area DA, the contour line portion SR ₁ corresponding to each of the x-direction coordinate range Δx and the y-direction coordinate range (Δy + 2L).
To SR ₄ are the reference contour, the reference outline data is constituted by the raster data of the pixel on the reference contour SR ₁ to SR ₄ as a starting point or end point. Reference contour lines SR _{1 to} SR ₄
Is the contour line S from each pixel in the divided area DA as described later.
This is the contour line portion that is referred to when the shortest distance d _min to is obtained. On the other hand, the synthetic area in which the two original images are fused is the shortest distance d _min between the pixel in the divided area DA and the contour line S.
Is only a portion smaller than the combined area width L. Therefore,
When a certain pixel is in the composite area, a part of the contour line S (this is referred to as a “reference contour element”) is included in a circle having the pixel as the center and a radius of the composite area width L. It should be. Therefore, if the coordinates of the pixel are (x ₀ , y ₀ ), the end point of the horizontal raster data D _x passing through the range of coordinates (x ₀ , y ₀ −L) to (x ₀ , y ₀ + L) The reference contour element is necessarily included in the set. The above-described reference contour lines SR _{1 to} SR ₄ are obtained by adding the combined area width L to both sides of the y-direction coordinate range Δy based on this idea. The combination area width L is added to the y-direction coordinate range because the horizontal raster data D _x is mainly referred to in the calculation of the shortest distance d _min as described later. Of course, the combined area width L may be added to both sides of the x-direction coordinate range Δx, and if added in only one direction, a reference contour line including all reference contour elements of each pixel can be obtained.

In step S8, the composite area width L is set as the host CP as a command for causing the image fusion composition apparatus 10 to execute the process.
It is given from U7 to the image calculation control device 1 and further transmitted to the composition ratio calculation device 16.

FIG. 2B is a flowchart showing a detailed procedure of the synthesis ratio calculation performed by the synthesis ratio calculation device 16 in step S9. In step S91, as shown in FIG.
The intersections PC _{1 to} PC ₄ of the straight line drawn in the x direction and the y direction from one pixel P _{0 in} A and the contour line S are obtained. Then, a distance l ₁ to l ₄ between the intersections PC ₁ to PC ₄ and the pixel P _0, respectively, obtain the minimum value l _min. In the example of FIG. 3F, l _min = l ₃ .

In steps S92 to S97, the shortest distance between the contour line S and the pixel P ₀
d _min is required (Fig. 3G). That is, first, the minimum value l _min is set as the temporary minimum distance d _m . (Step S92).
Then, the coordinates of the pixel _{P 0 (x 0, y 0} ), lateral raster data in the coordinate range of the y-direction from the (y ₀ -l _min +1) to (y ₀ + l _min -1) RAM17 for each coordinate value
From the composite ratio calculation device 16 (step S9
3). The target horizontal raster data is limited to this range, because the shortest distance d _min smaller than the minimum value l _min can be obtained only at the end points of the horizontal raster data in this range. . Here, the coordinate value is 1 pixel
The unit is used. Then, a distance d (not shown in FIG. 3) between each of the end points (start point PI and end point PE) of each horizontal raster data and the pixel P ₀ is obtained, and the value is smaller than the temporary minimum distance d _m. When the distance is small, the distance d is set as the temporary shortest distance d _m . Then, the loop of steps S93 to S96 is repeated, and the finally obtained provisional shortest distance d _m is set as the true shortest distance d _min (step S97). In Fig. 3G, y above
Coordinate range (y ₀ -l _min +1) ~ and three transverse raster data B ₁ .about.B ₃ at each end of _{(y 0 + l min -1)} , these end points PI ₁ ~PI ₃ and PE ₁ -PE ₃ , And examples of distances d _{1 to} d ₆ are shown.

As a result, as shown in FIG. 3H, the distance (shortest distance) d _min between the pixel P ₀ and the pixel p _min on the contour line S closest to the pixel P ₀ is obtained. At this time, the pixel P ₀ is on the normal line of the contour line S at the pixel P _min .

Since the horizontal raster data stored in the RAM 17 is only in the y coordinate range of (Δy + 2L) shown in FIG. 3E, the y coordinate range of the horizontal raster data used in steps S92 to S96 (y ₀ − l _min +1) to (y ₀ ＋ l _min −
If 1) is wider than this, the distance is checked for the raster data in the range stored in the RAM 17.
Furthermore, during the repetition of the loop of steps S93 to S96, rather than the minimum value l _min obtained in step S91,
When the provisional shortest distance d _m has a small value, the reference horizontal raster data is from (y ₀ −l _min +1) to (y ₀ + d _m
It is limited to the range up to -1). That is, the y-coordinate y portion of ₀ to + y direction from of the pixel P ₀ is (y ₀ + d _m
Only lateral raster data up to -1) is examined. This is because a smaller value cannot be obtained as the temporary shortest distance d _m even if a wider range is examined.

FIG. 4 is a conceptual diagram showing a method of calculating the composition ratio of the pixel P ₀ in step S98. For convenience of illustration, the divided area DA
Only a part of the graphic region F including "" is rotated from FIG. 3 and shown in FIG. 4 (a). FIG. 4 (b) is a composite ratio function
f (d _min ) is shown, and the composition ratio R in the pixel P ₀ is given by the following equation.

If d _min <L: For _{L ≦ d min R = f (} d min) = r e ... (2) where, r _s: outline synthesis ratio r on S _e: figure F inside away from the contour line S synthesis region width L or more For example, the composition ratio in r is _s = 0 and r _e = 1.0.

In this way, when the composition ratio R of the pixel P ₀ is obtained, the coordinate values (x ₀ , y ₀ ) of the pixel P ₀ and the composition ratio R are transferred from the composition ratio calculation device 16 to the image composition device 15 in step S10. It

The image synthesizing device 15 fetches the image data I ₁ (P ₀ ) and I ₂ (P ₀ ) of the synthesized image and the synthesized image at the pixel P ₀ from the image memory 12 in step S11.

In step S12, the image data I (P ₀ ) after composition of the pixel P ₀ is obtained by the following equation.

I (P ₀ ) = R × I ₁ (P ₀ ) + (1−R) × I ₂ (P ₀ ) ... (3) Then, the image data I (P ₀ ) after combination is the image combining device 15
From the image memory 12 to the combined image data I ₂
It is stored while being replaced with (P ₀ ).

As described above, in the loop of steps S7 to S12, the image area IA
The image data is combined for all the pixels included in each of the N ₂ divided areas DA in.

In step S13, the combined image data created for the entire image area IA is transferred from the image memory 12 to the image disk 3 and stored in a corresponding portion of the image area IA. Then, in the loop of steps S5 to S13, N in the outer peripheral frame SF is
Image synthesis is performed on _one of the image areas IA.

FIG. 3I is a conceptual diagram showing the distribution of image data after melted and synthesized. In the image inside the outer peripheral frame SF, the combined image I ₂ is maintained as it is in the region between the contour line S and the outer peripheral frame SF. In the combined area CS formed inside the contour line S with a constant combined area width L, the image smoothly changes from the combined image I ₂ to the combined image I ₁ according to the above equation (3). The composite image I ₁ is maintained as it is inside the composite area CS.

As described above, according to the first method, the area of the image to be combined, that is, the inside of the outer peripheral frame SF is divided into the divided areas DA to be processed, so that even if the capacity of the image memory 12 or the RAM 17 is small, it is arbitrary. It is possible to perform image fusion and composition for a figure F having a size of. Further, for each pixel P ₀ in the divided area DA, when the shortest distance d _min to the contour line S is obtained, it is necessary to perform the calculation only based on the predetermined reference contour line data, which is advantageous in that the processing time is relatively short. is there. Further, in the first method, since the fusion synthesizing can be performed with the same synthetic region width L over the entire circumference of the contour line S,
There is an advantage that a good combined image can be obtained. Since the operator can set the combined area width L to a desired value, it is possible to perform the melted combination with an arbitrary width.

B-2. Second Method The second method in the embodiment of the present invention is almost the same as the above-mentioned first method, and is transferred to the RAM 17 in step S7 of FIG. 2A (see FIG. 3E). The only difference is the content of the contour line data and the method of calculating the shortest distance d _min in steps S93 to S97 in FIG. 2B.

FIG. 5A is an explanatory diagram showing reference contour lines corresponding to divided areas DA in the second method. The reference contour is a divided area
A contour line portion SR _{1a to} SR _4a existing in one of the x-direction coordinate range Δx and the y-direction coordinate range Δy of DA, and a line segment SL that successively connects these contour line portions SR _{1a to} SR _4a to form a closed curve.
_It consists of _{1 to} SL ₄ . Of these, the outline parts SR _1a and SR
Longitudinal raster data D _y for _3a is also achieves the content transverse raster data D _x to constitute a reference outline data, respectively for contour portions SR _2a and SR _4a. Further, regarding the line segments SL _{1 to} SL ₄ , the equation of the straight line representing these constitutes the reference contour line data.

FIG. 5B is an explanatory diagram showing a method of obtaining the shortest distance d _mina for the pixel P _0a . In the second method, the steps of Figure 2B
In S94, not only the distance between the contour line portions SR _2a and SR _4a and the pixel P _0a , but also the distance between the pixel P _0a and the line segments SL _{1 to} SL ₄ is examined. Of these distances, pixel P
_When the distance d _mina between _0a and the line segment SL ₁ is the shortest, this is assumed to be the shortest distance to the contour line S, and the subsequent processing is performed. Such shortest distance d _mina is
It can be easily calculated from the linear equation of L _{1 to} SL ₄ and the coordinate value of the pixel P _0a .

As described above, in the second method, the number of points on the reference contour line to obtain the distance to each pixel in the divided area DA is smaller than that in the first method, so that the processing can be performed at higher speed. There is an advantage. On the other hand, as can be seen from FIG. 5B, the shortest distance d _mina between the pixel P _0a and the contour line S is an approximate value. Therefore, as compared with the first method, the width in which the melt-melting synthesis is actually performed tends to vary to some extent. However, with respect to a convex figure that is close to a circle or an ellipse, the second method can be used to perform a very good combining process.

B-3. Speed-up Method of Processing FIG. 6 is an explanatory diagram showing a method of speeding up the calculation of the composition ratio in the above-mentioned first and second methods.

First, the divided area DA is further divided into a plurality of small divided areas DS. This is because there are many parts where the composition ratio R is a constant value (R = r _e ) in the central portion of the graphic region F, etc. Therefore, the calculation of the composition ratio will be described later in the small divided regions corresponding to these parts. This is because it is omitted in the procedure. Then, each small divided area DS is divided into peripheral pixel area layers PL _i (i = 1, 2, ...) From the outer circumference toward the center. The width of the pixel region layer PL _i is equal to one pixel.

The composition ratio is first obtained for all the pixels in the outermost pixel region layer PL ₁ . Within the pixel area layer PL ₁ , the composition ratio is a constant value R
If it is ₀ , the composition ratio of the pixel region layers PL ₂ on the center side of this is also equal to R ₀ . Pixel area layer in this case
The area from PL ₂ to the center of the small divided area DS is called a “uniform area”, and its composition ratio is called a “uniform composition ratio”. If the composition ratio in the pixel region layer PL ₁ is not constant, the composition ratio obtained for each pixel is directly adopted in the pixel region layer PL ₁ and the next pixel region layer PL ₂ on the one center side is adopted.
The composition ratio is calculated for.

After that, by repeating the same processing, the small divided area DS
It is possible to obtain the composition ratio of all the pixels in.

Fig. 2C shows Fig. 2B when this speedup method is adopted.
It is a flowchart which shows the procedure corresponding to step S9 of a figure. Step S9a in FIG. 2C is only steps S90 and S99 added to step S9 in FIG. 2B. Step S90
Then, it is determined whether or not the target pixel is in the uniform area. If it is a uniform region, the combination ratio R is made equal to the uniform combination ratio R ₀ in step S99. If it is not a uniform region, the combination ratio R is calculated in the procedure of steps S91 to S98 described above.

By using this speed-up method, it is not necessary to calculate the composition ratio (steps S91 to S98) for all pixels, and the processing can be performed at high speed.

C. Other image fusion synthesizing methods Two other more simplified methods (third and fourth methods) will be described below in relation to the image fusion method according to the embodiment of the present invention described above.

C-1. Third Method FIG. 7 shows a pixel P _0b in the graphic area F in the third method.
It is explanatory drawing which shows the method of calculating | requiring the shortest distance between the contour line and the contour line. First, the intersections PC _{1b to} PC _4b of the straight line drawn in the x direction and the y direction from the pixel P _0b in the figure area F and the contour line S are obtained, and the distances between these intersections PC _{1b to} PC _4b and the pixel P _0b. Calculate l _{1b to} l _4b respectively. Then, the minimum value l _1b is regarded as the shortest distance d _minb . Then, the combination ratio of the pixel P _0b is _calculated by the equations (1) and (2).

In this third method, the second B in the first and second methods is used.
Since the operations of steps S92 to S96 in the figure are not required, the processing is performed at extremely high speed. In the third method, there is no need to divide into divided areas DA, so step S6 in FIG. 2A is performed.
Is also unnecessary. However, due to the limitation of the capacity of the image memory 12, the division in step S4 is necessary.

C-2. Fourth Method FIG. 8 is an explanatory diagram showing a fourth method for obtaining the shortest distance between the pixel P _0b and the contour line S.

First, similar to the third method, the intersection points PC _{1b to} PC _4b and the distances l _{1b to} l
_Ask for _4b . Then, three intersections (points PC _1b , PC _2b and PC _{3b in} the example of FIG. 8) are selected in the ascending order of the distances l _{1b to} l _4b , and a circle C passing through these intersections is drawn. Then, on the radius passing through the center O of the circle C and the pixel P _0b , the distance between the pixel P _0b and the circular arc
_Consider d _minc as the shortest distance. The other processing is the same as the third method.

The fourth method can also perform high-speed processing similarly to the third method. However, the third and fourth methods have the property that the width in which the welding is performed is likely to change to some extent according to the shape of the contour line S, as compared with the first and second methods, but practically it is almost the same. It does not hinder.

D. Modified Example In the above embodiment, the composition ratio function f (d _min ) is linear as shown in FIG. 4 (b), but it is also possible to use one having other functional form such as polynomial. It goes without saying that it is good. FIG. 9 is a graph showing a composite ratio function g (d _min ) having an S shape as an example. The horizontal axis of the graph shows the shortest distance d _min from the contour line, and the vertical axis shows the composition ratio R. The composite ratio function g (d _min ) is obtained by using two point-symmetrical quadratic curves g ₁ (d _min ) and g at a distance L / 2 which is half the composite area width L.
_It has a shape that continues ₂ (d _min ). If the composite ratio function g (d _min ) having such an S-shape is used, the composition is performed so that the image changes more smoothly at the boundary of the composite area, that is, the part where d _min = O and d _min = L. be able to.

Both the composite image as the original image and the composite image are taken into the image disc 3 from the image scanner 4. For example, a flat screen image (constant color image) generated from the flat screen generator 14 as a composite image is used. You may use. This can be used, for example, to create a shadow image by blending a black halftone screen image with a region to be a shaded part of the combined image.

(Effects of the Invention) As described above, according to the first means of the present invention,
Since the image to be combined is divided into a plurality of divided areas and processed, it is possible to easily and quickly combine the images with each other in a short time in a graphic area having an arbitrary size. Further, a reference contour line is determined for each divided area, a point on the reference contour line closest to the pixel in the divided area is used as a reference point, and the synthesis ratio is determined based on the distance between the reference point and the pixel. , It is possible to perform fusion-synthesis with respect to a graphic region having an arbitrary shape. Further, since the composition is carried out based on a predetermined composition ratio function, it is possible to carry out the melt composition by setting desired conditions with respect to changes in the composition width and composition ratio.

According to the second means of the present invention, the divided area is further divided into a plurality of small divided areas, and the composition ratio is calculated for each pixel layer in the small divided area. In this case, the calculation of the composition ratio of the pixel layer located on the center side can be omitted, and the processing time can be further shortened.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus to which an embodiment of the present invention is applied, FIG. 2 is a flow chart showing a procedure of an embodiment of the present invention, and FIGS. 3 to 6 are embodiments of the present invention. 7 and 8 are explanatory diagrams showing another processing method, and FIG. 9 is a diagram showing a composite ratio function in the embodiment of the present invention. 10 ... Image merging / synthesizing device, F ... Graphic, S ... Contour line,
SR ₁ to SR ₄ ... reference contour, DA ... divided region, DS ... subdivided regions, PL _1, PL ₂ ... pixel region _{layer, f (d min), g} (d min) ... synthesis ratio function, L ... synthetic Region width, R ... Composite ratio

Claims (2)

[Claims] 1. A same graphic area surrounded by the same contour line is set for each of first and second images different from each other,
The composition ratio of the first and second image data representing the first and second images is determined for each pixel in the graphic region, and the first and second image data are combined using the composition ratio. An image fusion synthesizing method for merging the first and second images by synthesizing, wherein (a) the graphic region is divided into a plurality of divided regions, and (b) each of the divided regions, A reference contour line including a portion of the contour line corresponding respectively to the vertical coordinate range and the horizontal coordinate range of the divided area is obtained, and (c) for each pixel in the divided area, the pixel on the reference contour line. An image characterized in that a point closest to the reference point is determined as a reference point, and (d) a combination ratio of the pixel is determined based on a predetermined combination ratio function having a distance between the reference point and the pixel as a variable. Melted in Only synthetic method. 2. Each of the divided areas is further divided into a plurality of small divided areas, and the inside of the small divided areas is divided into a plurality of pixel layers circumferentially divided from the outer peripheral side toward the central side. Then, in determining the composition ratio of each pixel in the step (d), (d-1) the outermost pixel layer in the small divided region is selected, and (d-2) the selected pixel pixel For each of the pixels forming the layer, the combination ratio is calculated using a combination ratio function, and (d-3) for all pixels included in the selected pixel layer, the combination ratio is constant. Determines that the composite ratio of the selected pixel layer and all the pixel layers existing on the center side of the selected pixel layer is the same as the composite ratio of the selected pixel layer, and (d-4 ) For the pixels included in the selected pixel layer When have the synthetic ratios is not constant for each step of the pixels included in the selected pixel layer (d-
The composition ratio calculated in 2) is used as is, and
A pixel layer on the center side adjacent to the selected pixel layer is selected, and (d-5) the steps (d-2) to (d-4) are repeated to synthesize each pixel. The method according to claim 1, wherein the ratio is determined.