JPH0955881A - Picture shading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily make a shadow having gradation. SOLUTION: An initial outline IOL, which is used to form a shadow area of picture parts is prepared, and multiple outlines MUL at least partially crossing are formed by perturbation of the initial outline IOL. Gradation rates are assigned to plural closed areas formed by multiple outlines respectively, and picture data of picture elements in each closed area is corrected in accordance with the gradation rate to make the shadow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of casting a shadow on an image part in an image, and more particularly to a method of forming a shade having a gradation.

[0002]

2. Description of the Related Art As one of plate making processes, there is a process of attaching image parts. The pasting step is a task of sequentially pasting a plurality of image components onto the mount. At this time, a process of adding a shadow to the pasted image component may be performed.
For example, when a photograph of a product is pasted as an image component on a one-page image of a catalog or a leaflet, simply attaching the image component may give an unnatural impression that the product is floating in the air. In such a case, it is possible to give a sense of stability that the product is placed on the floor by adding a shadow to the image part, and to give the one-page image a naturalness.

As the shadow of the image part, a shadow accompanied by gradation (also called gradation) in which the density gradually changes, that is, a shadow having a gradation may be used.
In recent years, a shadow having a gradation is often formed using a computer system, but in this case, image processing called a so-called brush is used. In the brushing process, an image is displayed on the CRT screen, and the operator designates the position of each pixel by using coordinate value input means such as a mouse, and also designates the correction amount of the image data so that the image component is shaded. Attached.

[0004]

Conventionally, as described above, since an operator manually forms a shadow having a gradation, in order to form a shadow having a good shape and density change, There was a problem that it required considerable skill and long work. Further, when the desired shadow cannot be obtained, it is necessary to perform the same work again.

The present invention has been made to solve the above-mentioned problems in the prior art, and an object of the present invention is to provide a shadow-casting method capable of easily forming a shadow having gradation.

[0006]

Means for Solving the Problem and Its Action / Effect To solve at least a part of the above-mentioned problem, in the first invention, a method of casting a shadow on an image part in an image represented by image data is provided. At least: (a) preparing a first reference contour used to form a shadow area of the image part; and (b) at least one by perturbing the first reference contour. Forming a multi-contour line that partially intersects; (c) assigning a gradation rate to each of the plurality of closed regions formed by the multi-contour line; and (d) Image data of pixels
Correcting according to the gradation rate assigned in the step (c).

The "perturbation" in this specification means
It means a process of slightly deforming the reference contour line. According to the first aspect of the invention, a plurality of closed areas are formed by the multiple contour lines, and the image data is corrected according to the gradation rate assigned to each closed area. Therefore, it is possible to easily form a shadow having gradation. it can.

In the step (b), a step of obtaining a first affine transformation coefficient for mapping the first reference contour line on itself and a width of perturbing the first reference contour line are set. Setting a second affine transformation coefficient to be defined, obtaining a plurality of affine transformation coefficients by interpolating the first and second affine transformation coefficients, and using the plurality of affine transformation coefficients Forming the multiple contours by affine transforming the first reference contours.

According to this method, it is possible to easily obtain a plurality of affine transformation coefficients for creating a multiple contour line by interpolating the first and second affine transformation coefficients. Multiple contour lines can be easily formed from the first reference contour line.

Alternatively, the step (b) includes (e) a step of preparing a second reference contour line used for forming a shadow area of the image part, and (f) the first and second steps. Forming the multiple contour lines by interpolating the reference contour lines of.

Also by this method, multiple contour lines can be easily formed.

The step (f) is a step of obtaining a first affine transformation coefficient for mapping the first reference contour line to itself, and the first reference contour line is a second reference contour line. Determining a second affine transform coefficient for transforming into a plurality of affine transform coefficients, and interpolating the first and second affine transform coefficients to obtain a plurality of affine transform coefficients.
Forming the multiple contour lines by affine-transforming the first reference contour line using the plurality of affine transformation coefficients.

According to this method, by interpolating the first and second affine transformation coefficients, it is possible to easily obtain a plurality of affine transformation coefficients for creating a multi-contour line. Multiple contour lines can be easily created from one reference contour line.

In the step (a), a step of preparing a mask contour line representing a contour of an image part and a step of transforming the mask contour line by using a first affine transformation coefficient are performed. Obtaining a reference contour line, the step (b) obtaining a second affine transformation coefficient for converting the mask contour line into a second reference contour line; and the first and the second steps. Determining a plurality of affine transformation coefficients by interpolating two affine transformation coefficients, and forming the multiple contour lines by affine transforming the mask contour line using the plurality of affine transformation coefficients. Is preferably provided.

In this way, multiple contour lines can be obtained from the mask contour line.

The step of obtaining the plurality of affine transformation coefficients may include a step of obtaining the plurality of affine transformation coefficients by executing the interpolation using a predetermined function.

By executing interpolation using various functions representing straight lines, curved lines, etc., it is possible to adjust the shape of the shadow area constituted by multiple contour lines to various shapes.

Further, the step (c) may include a step of assigning a gradation rate according to a monotone function relating to the number of overlaps of the multiple contour lines.

In this way, since the gradation ratio can be assigned so as to change monotonously from the inside to the outside of the shadow area formed by the multiple contour lines, a natural shadow can be added.

The step (c) further includes a step of generating a plurality of gradation contour lines representing the contour lines of the closed areas to which the same gradation rate is assigned in the plurality of closed areas.
In the step (d), the value of the image data in the closed area is obtained by multiplying the value of the image data in the closed area represented by each gradation contour line by the gradation rate assigned to each gradation contour line. May be included.

In this way, it is possible to easily add a shade with gradation by modifying the value of the image data.

The step of perturbing in the step (b) includes a step of setting a part of the first reference contour line as a fixed contour portion fixed at the time of perturbation, and the first reference contour line. And a step of perturbing a portion other than the fixed contour portion.

In this way, it is possible to easily create a multiple contour line such that at least some of them intersect each other.

[0024]

Other Embodiments of the Invention The present invention includes the following other embodiments. In a first aspect, a storage medium that stores a software program that is executed by a computer to perform a process of casting a shadow on an image component in an image represented by image data, the shadow region of the image component By perturbing a first reference contour used to form a multi-contour, at least some of which intersect each other, and each of the plurality of closed regions formed by the multi-contour is a floor. A software program is stored that executes a process of assigning a tonality ratio and correcting image data of pixels in the plurality of closed regions according to the tone ratio.

By executing such a software program on a computer system, it is possible to easily add a shade having a gradation to an image part.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

A. Outline of the shadowing process: Next, an embodiment of the present invention will be described based on examples. FIG. 1 is an explanatory diagram showing a schematic procedure of a shadowing process in the embodiment of the present invention. FIG.
(A) shows a mask contour line of an image part of a quadrangle natural image (also referred to as “picture”) like a building. The mask contour line is the vertex p of the contour of the image component to be shadowed.
It is a closed loop vector in which 1 to p4 are sequentially connected by a straight line. Hereinafter, the contour line of the image component to be shaded will be referred to as “mask contour line MOL”. Incidentally, the image parts of the design are usually cut out by a cut-out mask and pasted in the one-page image. Therefore, with respect to the image part of the design, the cutout mask can be used as the mask outline of the shadowing.

In the process of FIG. 1B, two fixed points pf1 and pf2 and one moving origin pm are designated on the mask contour line MOL of the image part to be shaded by interactive processing. In the example of FIG. 1B, two fixed points pf
1 and pf2 are two end points p4 of the mask contour line MOL.
It matches p1. However, fixed points pf1 and pf2
Need only be on the mask contour line MOL and need not match the endpoints of the contour line. This also applies to the moving origin pm.

In the process of FIG. 1B, the first moving point pm0, which is the point after moving the moving origin pm, is designated by the interactive processing. A triangle composed of two fixed points pf1 and pf2 and a first moving point pm0 is referred to as "initial triangle T".
R0 ". The initial triangle TR0 has two fixed points pf
1, pf2 and a reference triangle BT composed of a moving origin pm
It can be considered that R is an affine transformation (linear transformation). The transformation coefficients a0 to f0 of this affine transformation are given by the following formula 1.

[0029]

[Equation 1]

Here, (x, y) is the coordinate of the moving origin pm, and (x0, y0) is the coordinate of the first moving point pm0.

When the mask contour line MOL is affine transformed using these affine transformation coefficients a0 to f0, FIG.
An initial contour line IOL shown in (B) is obtained. The initial contour line IOL is a contour line that is a source of the shadow area and corresponds to the first reference contour line in the present invention.

Instead of affine-transforming the mask contour line MOL to create the initial contour line IOL, each end point of the initial contour line IOL may be designated by interactive processing using a mouse or the like.

In the step of FIG. 1C, the second moving point pmn is designated by the interactive processing. Two fixed points pf1,
A triangle formed by pf2 and the second moving point pmn is called "final triangle TRn". The final triangle TRn can be regarded as an affine transformation of the initial triangle TR0. The transformation coefficients a to f of this affine transformation are given by the following Equation 2.

[0034]

[Equation 2]

Here, (xn, yn) is the second moving point p
is the coordinate of mn, and (x0, y0) is the first moving point pm
The coordinate is 0.

When the initial contour line IOL is affine-transformed using these affine transformation coefficients a to f, FIG.
The final contour line FOL shown in is obtained. The initial contour line IOL corresponds to the first reference contour line in the present invention, and the final contour line FOL corresponds to the second reference contour line.

In the process of FIG. 1D, the initial contour line IOL
And the final contour line FOL are interpolated to create a multiple contour line MUL. This multiple contour line MUL is
It includes an initial contour line IOL and a final contour line FOL.
If linear interpolation is performed so as to divide the initial contour line IOL and the final contour line FOL into three equal parts, as shown in FIG.
A multi-contour line MUL composed of book contour lines is obtained.
As will be described later, the affine transformation coefficient is interpolated without actually interpolating the contour line itself.

The steps of FIGS. 1C and 1D can also be regarded as a process of creating a multiple contour line MUL by perturbing the initial contour line IOL. In this embodiment, "perturbation" or "perturbation mapping" means a process of slightly deforming the initial contour line.

Further, as can be seen from FIG. 1D, in the perturbation mapping in this embodiment, a part of the initial contour line IOL is fixed at the time of perturbation (fixed points pf1 and pf2).
Between the contour lines) and the other part of the initial contour line IOL is perturbed to form a multi-contour line. By doing so, it is possible to create a multiple contour line MUL in which at least some of the portions intersect with each other in a portion other than the fixed contour portion.

In the process of FIG. 1E, the multiple contour line MUL
The gradation rate is automatically assigned to each of the plurality of closed areas formed by. Then, the value of the image data of the pixel in each closed region is converted according to the gradation rate assigned to each closed region, and thereby the image component is shaded. In FIG. 1E, for convenience of illustration, the multiple contour line MUL
Although it is drawn that other image parts do not exist in the closed area surrounded by, in reality, there are many cases where other image parts and background exist. In this case, the values of the other image parts and the image data of the background are converted by the processing of FIG.

In the step of FIG. 1E, a gradation contour line representing the contour of the closed area to which the same gradation ratio is assigned is obtained. FIG. 2 is an explanatory diagram showing the difference between the multiple contour line and the gradation contour line. In FIG. 2A, the multiple contour line M
1 to 4 gradation levels GL in each closed region formed by UL
Has been assigned. As will be described later, the gradation level GL is an index directly associated with the gradation rate. In the example of FIG. 2A, the gradation level GL is set to a value proportional to the number of overlapping closed regions represented by the multiple contour line MUL. In FIG. 2B, the gradation level GL is 3
Is a gradation contour line GOL (3) showing the contour of the closed region. The gradation contour line GOL (3) is represented by two point sequences [pf1, Q1, Q2] and [Q2, Q3, Q4, pf2, Q5] of the end points forming the closed region of GL = 3. As described above, the gradation contour line GOL means a contour line of a closed region to which the same gradation level GL is assigned.

As can be understood from FIG. 1E, the shadow area thus obtained has a natural gradation because it is dark in the area near the center of the shadow area and bright in the area near the periphery of the shadow area. It looks like a shadow.

B. Device Configuration: FIG. 3 is a block diagram showing the configuration of a plate-making processing system for applying an image shadowing process by applying an embodiment of the present invention. This plate making processing system includes an image input device 100 and an image processing device 200.
And an image output device 300. The image input device 100 is realized by an input unit of a drum type scanner that reads image data of a color image, a magnetic disk that stores image data, a communication line with another device, or the like. The image processing apparatus 200 is realized by a computer system such as a workstation or a personal computer. The image output device 300 is a display device such as a color CRT or a color liquid crystal display,
It is realized by an output unit of a drum type color scanner, a magnetic disk, a communication line and the like.

In the CPU 202 of the image processing apparatus 200,
The image memory 204, the initial contour line memory 205, the contour line memory 206, and the main memory 2 via the bus 203.
08 is connected. In addition, a keyboard 212, a mouse 214 as a pointing device, and a digitizer 216 are input via the input / output interface 210.
And a color CRT 218 as image display means are connected. The keyboard 212, the mouse 214, and the digitizer 216 are used as coordinate point inputting means for designating the coordinates of a fixed point or a moving point, and a parameter inputting means (designating means) for designating a change in the contents of a look-up table described later. Also used as). The image input device 100 and the image output device 300 are connected to the image input / output interface 220.

The main memory 208 includes an initial contour line creation unit 221, a multiple contour line creation unit 222, and a shadow area correction unit 2.
24, a graphic calculation unit 226, and a software program (application program) for realizing the functions of the pixel conversion unit 228. The functions of these units are realized by the CPU 202 executing software programs. The software programs that realize the functions of these units are stored in a portable storage medium (portable storage medium) such as a floppy disk or a CD-ROM, transferred from the portable storage medium to the image processing apparatus 200, and stored in the main memory. It is stored in the memory 208.

In the present embodiment, the image data of each pixel (also referred to as pixel data) has the reflectance or transmittance of the image of the three primary colors RGB of additive color mixture with a specific gradation number, for example, 256 gradation numbers. The value represented by the image data will be referred to as a gradation value hereinafter.

FIG. 4 is a block diagram showing the internal structure of the image memory 204. Image memory 20 shown in FIG.
4 includes a selector 230, an actual image memory 232, and a rough image memory 234. Coarse image memory 234
Stores the decimated image data for display on the color CRT 218. Note that the image memory 204 shown in FIG. 4B includes a coarse image conversion unit 236 instead of the coarse image memory 234, and the actual image memory 232.
Coarse image data is generated by thinning out the image data stored in. The image memory 204 shown in FIG. 4B can realize the same function as the image memory shown in FIG. 4A with a small memory.

FIG. 5 is a block diagram showing the contents of the initial contour line memory 205. The initial contour line memory 205 includes an initial contour point sequence coordinate memory 310 that stores the coordinates of the end points of the initial contour line IOL (FIG. 1C) of the shadow area, and a perturbation mapping parameter memory 312 that stores the parameters of the perturbation mapping.
And The perturbation mapping parameter includes a plurality of affine transformation coefficients for affine-transforming the initial contour line IOL to create the multiple contour line MUL.

FIG. 6 is a block showing the contents of the contour line memory 206. The contour line memory 206 includes a gradation contour line data memory 320 that stores data representing a gradation contour line GOL (FIG. 2B) for each gradation rate, and a control point memory 322. The control point memory 322 stores the coordinates of the control points when performing the affine transformation, that is, the fixed points pf1,
The coordinates of pf2 and the moving points pm, pm0 and pmn (FIG. 1 (C)) are stored. The gradation contour line data memory 320 stores a coordinate value memory 324 that stores the coordinate values of the end points of the gradation contour line GOL, and the relationship between the gradation level GL and the gradation rate assigned to each gradation contour line GOL. Attribute value memory 32
6 is included.

FIG. 7 is a block diagram showing the function of the initial contour line creating section 221. The initial contour line creation unit 221 uses 2
Two selectors 250 and 252, and shape contour line buffer OV
with _buf. Initial contour line IOL (Fig. 1 (B))
There are two methods for generating the mask contour line MOL, and a method in which the user directly specifies the end points of the initial contour line IOL by an interactive operation. In the method of affine transformation of the mask contour line MOL, the mask data transferred from the mask memory 244 is stored in the shape contour line buffer OV_buf, and the figure calculation unit 226 performs the affine transformation on this mask data to initialize the initial contour line IO.
L is created. On the other hand, in the method in which the user designates by an interactive operation, the data of the end point coordinates of the initial contour line IOL designated by the coordinate point input means (212, 214 or 216) is stored in the shape contour line buffer OV_buf.
The contour line data of the initial contour line IOL is transferred to the initial contour line memory 205 via the selector 252.

FIG. 8 is a block diagram showing the function of the multiple contour line creating section 222. The multiple contour line creation unit 222 includes a perturbation mapping parameter calculation unit 330 and a perturbation processing unit 332.
And the internal processing buffer 334 and the multiple contour line overlay unit 3
36 and a gradation contour extraction unit 338.

The perturbation mapping parameter calculation unit 330 has a function of interpolating perturbation mapping parameters for creating the multi-contour line MUL from the affine transformation coefficients a to f of the final contour line FOL given by the above-mentioned mathematical expression 2. . The perturbation mapping parameters are perturbations on the initial contour line IOL,
It is a parameter used when creating the multi-contour line MUL (FIG. 1D), and specifically, a plurality of sets of affine transformation coefficients. The contents of the interpolation calculation process for obtaining the perturbation mapping parameter will be described later.

The perturbation processing unit 332 generates a multiple contour line MUL by perturbing the initial contour line IOL according to the perturbation mapping parameter.

The multi-contour line overlapping unit 336 fills the insides of the respective contour lines of the multi-contour line MUL to form a binary image, and performs a process of superposing these binary images so that the multi-contour line is surrounded by the multi-contour line MUL. A process of assigning the gradation level GL to each closed region is realized. At this time, the value 1 is assigned to the pixels inside each contour and 0 is assigned to the pixels outside. Then, by adding the pixel values assigned by the respective contour lines, as shown in FIG.
L can be set.

FIG. 9 is a block diagram showing the function of the gradation contour line extracting section 338. The gradation contour line extraction unit 338 includes a uniform density region cutout unit 370 and a boundary contour extraction unit 372. The uniform density area cutout unit 370 extracts a closed area (uniform density area) to which the same gradation level is assigned for each value of the gradation level GL. The boundary contour extraction unit 372 extracts the contour line of this equal density area as the gradation contour line GOL (FIG. 2B) for the gradation level GL. The gradation contour line data generated by the gradation contour extraction unit 338 is transferred to the contour memory 206.

FIG. 10 is a block diagram showing the function of the shadow area correction unit 224. The shadow area correction unit 224 includes a contour line shape processing unit 380 for correcting the shape of the gradation contour line,
Gradation characteristic processing 382 for correcting the gradation rate assigned to each gradation contour line. The contour line shape processing unit 380 has a control buffer 390 and a contour line buffer 392. The contour shape processing unit 380
The data in these buffers is supplied to the graphic calculation unit 226, and the graphic calculation unit 226 performs graphic conversion such as affine transformation based on these data to correct the shape of the gradation contour line.

FIG. 11 is a block diagram showing the function of the graphic operation unit 226. The figure calculation unit 226 includes a control buffer Ctr_buf, a contour line buffer GV_buf, a coordinate conversion unit 270, and a selector 272. The control buffer Ctr_buf has the coordinates of the fixed points pf1 and pf2 input from the coordinate point input means and the moving points pm and pm.
The coordinates of 0 and pmn are stored. Contour line buffer GV_buf
Stores data representing various types of contour lines stored in the contour line memory 206. The coordinate transformation section 270 transforms or moves the contour line by performing affine transformation on the contour line stored in the contour line buffer GV_buf.

FIG. 12 is a block diagram showing the function of the pixel conversion section 228. The pixel conversion unit 228 uses the image memory 2
04, an image buffer 280 for storing the image data transferred from 04, a contour buffer 282 for storing the contour data transferred from the contour memory 206, a vector / raster conversion unit 286, a processing buffer 284, and a selector 2
And 88. The pixel conversion unit 222 performs vector-raster conversion of the gradation contour line GOL (FIG. 2B) for each gradation level GL, and the gradation value (image data value or pixel data value of the internal area of each gradation contour line. Also called)
A process of changing according to the gradation rate is performed. The processing content of the pixel conversion unit 228 will be described later.

C. Details of the shadowing process: FIG. 13 and FIG.
4 is a flowchart showing the procedure of the shadowing process.
15 to 21 are explanatory diagrams showing the processing contents of the main steps of the shadowing processing. The details of the shadowing process will be described below with reference to these flowcharts and explanatory diagrams.

In step S1 of FIG. 13, the user designates an image component to be a shadow-casting object from the image of one page displayed on the color CRT 218 (hereinafter referred to as "one-page image"). . It should be noted that the image data of the one-page image is previously input from the image input device 100 to the image processing device 20.
It is input to 0 and stored in the image memory 204.
FIG. 15A is a conceptual diagram showing an example of a one-page image. This one-page image includes a background image PC0 and three image components PC1, PC2, PC3. These image parts PC1 to PC3 are line drawings or patterns. Also,
The second image component PC2 is attached on the third image component PC3, and the first image component PC1 is attached on the second image component PC2. In this embodiment, the first image component PC1 is designated as the target image component for shadowing.

FIG. 15B shows the one-page image after the shadowing process. In the shadow area of the image component PC1, the image components PC2 and PC3 and the background image PC0 are provided with gradations corresponding to the respective gradation contour lines. As a result, on the image parts PC2, PC3 and the background image PC0,
An image in which the shadow of the image component PC1 is projected is generated.

The shadowing processing described below can be executed for both the image parts of the picture and the image parts of the line drawing. In this embodiment, the line drawing and the design are collectively referred to as "image", and the individual line drawing and the design attached to the one-page image are referred to as "image parts". Further, the image component that is the target of shadowing is simply referred to as "target image component".
The data representing an image is called "image data", but the image data of each pixel is sometimes called "pixel data".

In step S2 of FIG. 13, an initial contour line for forming a shadow area of the target image component PC1 is created. In this step S2, first, as shown in FIG. 16, the mask data representing the mask contour line MOL of the target image component is stored in the mask memory 244, and the shape contour in the initial contour line creation unit 221 is further stored from the mask memory 244. It is transferred to the line buffer OV_buf and stored (FIG. 7). Since the image part of the pattern is usually cut out by the cutout mask and attached to the one-page image, the cutout mask is used as the mask contour line MOL.
It should be noted that in the drawings after FIG. 16, a block in which a symbol (for example, p1, p2, etc.) indicating a point is described indicates that the coordinate value of the point is stored in the memory position.

Then, as shown in FIG. 17, two fixed points pf1 and pf are provided on the mask contour line MOL of the target image component.
2 and the movement origin pm are specified, and further, the first movement point pm
Specify 0. The initial contour line creation unit 221 (FIG. 7) transfers these coordinates to the control buffer Ctr_buf (FIG. 11) in the graphic calculation unit 226. The coordinate conversion unit 270 in the figure calculation unit 226 uses the above-described mathematical formula 1 to generate the coordinate shown in FIG.
Affine transformation coefficients a0 to f0 for mapping the standard triangle BTR shown in 7 onto the first reference triangle TR0 are calculated.

The coordinate transformation section 270 further uses these affine transformation coefficients a0 to f0 to mask contour MO.
By affine transforming the coordinates of the respective end points p1 to p4 of L, the end points pc1 to pc forming the initial contour line IOL
Find the coordinates of 4. As shown in FIG. 17, the initial contour line I
The coordinates of the end points pc1 to pc4 of the OL are stored in the contour line buffer GV_buf in the figure calculation unit 226, and further transferred from the contour line buffer GV_buf to the shape contour line buffer OV_buf in the initial contour line creation unit 221 (FIG. 7). It

When the mask data for the image part does not exist, the user designates the positions of the respective end points pc1 to pc4 constituting the initial contour line IOL by the interactive processing using the pointing device.

In step S3 of FIG. 13, the multiple contour lines are created by the multiple contour line creating section 222 (FIG. 8).
FIG. 14 is a flowchart showing the detailed procedure of step S3. First, in step S11, as shown in FIG. 18, three points pf1, pf2, and pf2 are located on the initial contour line IOL.
Specify pm0. When the initial contour line IOL is created from the mask contour line of the target image part, it is not necessary to execute step S11, and the fixed points pf1 and pf2 and the moving point pm0 specified when creating the initial contour line IOL are Three
Used as is as a dot.

In step S12, the final triangle TRn is designated as the most deformed shape when the initial triangle TR0 consisting of the three points designated in step S11 is perturbed. Specifically, the second moving point pmn shown in FIG.
Should be specified. As a result, the control buffer Ctr_buf in the graphic operation unit 226 has two fixed points pf.
1, pf2 and two moving points pm0 and pmn are registered.

Instead of designating the second moving point pmn, the user can also designate the moving direction and the moving amount from the first moving point pm0 to the second moving point pmn. . At this time, at least one of the moving direction and the moving amount may be predetermined.

In step S13 of FIG. 14, the affine transformation coefficients a to f for transforming the initial triangle TR0 into the final triangle TRn are calculated according to the above-mentioned formula 2.

In step S14, the multiple contour line creating unit 2
22 denotes the first affine transformation coefficient indicating the identity map of the initial triangle TR0, and the initial triangle TR0 to the final triangle TR.
The perturbation mapping parameter is calculated by linearly interpolating the second affine transformation coefficients a to f indicating the transformation to n. Here, the "identity map" is a map to itself, and the affine transformation showing the identity map of the moving point pm0 of the initial triangle TR0 is given by the following mathematical formula 3.

[0072]

(Equation 3)

Affine transformation coefficients ai to fi for obtaining the i-th triangle obtained by linear interpolation that divides the initial triangle TR0 and the final triangle TRn into n equal parts are given by the following formula 4.

[0074]

(Equation 4)

Affine transformation coefficient ai given by Equation 4
˜fi is a linear interpolation of the first affine transformation coefficient (equation 3) of the identity map and the second affine transformation coefficient (equation 2) indicating the transformation from the initial triangle TR0 to the final triangle TRn. It is the i-th conversion coefficient when

In step S15 of FIG. 14, the perturbation processing unit 332 transforms the initial contour line IOL using the affine transformation coefficient shown in Equation 4 to obtain n contour lines L1 to Ln shown in FIG. To be Note that the n-th contour line Ln is the final contour line F described in FIG.
OL. The multiple contour lines MUL are n contour lines L1 to
It is composed of (n + 1) contour lines including Ln and the initial contour line IOL. In the example of FIG. 19, n = 3,
In practice, it is preferable to set a value of about 256 as the number of divisions n. If the value is set to this level, the gradation ratio changes smoothly in the peripheral portion of the shadow area, and a natural shadow can be added.

The processing of steps S14 and S15 is as follows.
It is equivalent to performing linear interpolation between the initial contour line IOL and the final contour line FOL. However, as will be described later, the interpolation method is not limited to linear interpolation, and various interpolation methods can be applied.

When the multi-contour line MUL is obtained in this way,
In step S4 of FIG. 13, the multiple contour line overlapping portion 33
6 (FIG. 8) executes the coating process of the inner area of the multi-contour line MUL, thereby assigning the gradation level GL to each closed area constituted by the multi-contour line MUL. 20
The content of the coating process is shown. In FIG. 20, the value “1” is assigned to the pixel inside each contour line forming the multiple contour line MUL.
, And the value “0” is assigned to the external pixels to create (n + 1) binary images. Then, by adding the pixel values of these (n + 1) binary images for each pixel, the gradation level GL of each pixel is obtained. It can be seen that this gradation level GL has a value proportional to the number of overlaps of the internal regions of the multiple contour line MUL.

In step S5 of FIG. 13, the gradation contour extraction unit 338 (FIG. 8) obtains the gradation contour by extracting the contour of the uniform density area. As described with reference to FIG. 2, the gradation contour line is a contour line of a closed area (equal density area) to which the same gradation level GL is assigned. FIG. 21 shows the gradation contour line GOL for each gradation level GL.
(GL) is shown. The gradation contour line data representing the gradation contour line thus obtained is stored in the contour line memory 206.

In step S6, the one-page image is shaded using the gradation contour line GOL, and the one-page image after the shade is displayed on the color CRT 218. FIG.
3 is a flowchart showing the procedure of step S6.
In step S21, the rough image data for display is transferred from the image memory 204 to the image buffer 280 in the pixel conversion unit 228.
(FIG. 12). In step S22, the pixel conversion unit 228 executes pixel conversion processing to change the image gradation value in the shadow area (area surrounded by the gradation contour line) according to the gradation level GL.

FIG. 23 is a flow chart showing the procedure of pixel conversion processing. In step S31, the contour line data representing the gradation contour line is input from the contour line memory 206 to the contour line buffer 282 in the pixel conversion unit 228 (FIG. 12). In step S32, the vector / raster conversion unit 28
6 is the closed loop vector data representing the gradation contour line,
It is converted into raster data indicating a closed area formed by gradation contour lines. This raster data is 1-bit / pixel data which has a value "1" in the pixels in the closed area and "0" in the outside.

In the pixel value changing process of step S33, 1
The pixel data of the page image is read from the image buffer 280 for each pixel. If the pixel is within the closed region of the gradation contour line, the pixel data PD
The gradation rate GR is multiplied by (color data of each color of RGB),
The corrected pixel data PD ′ is obtained.

[0083]

(Equation 5)

FIG. 24 shows the gradation rate G used for pixel conversion.
7 is a graph showing the relationship between R and the gradation level GL assigned to each gradation contour line GOL. Gradation rate GR is 0
Takes a value in the range of to 1.0, and the gradation level GL is 1 to (n
Take a value in the range of +1). Here, (n + 1) is the number of contour lines forming the multiple contour line MUL. The relationship between the gradation level GL and the gradation rate GR (also referred to as “gradation characteristic” or “density attribute”) depends on the gradation level GL (that is, the number of overlaps of multiple contour lines). A characteristic represented by a monotone function in which the rate GR monotonically increases is preferable. However, it is possible to set the gradation characteristics to various relationships other than the example shown in FIG. The relationship between the gradation level GL and the gradation rate GR is stored in the attribute value memory 326 (FIG. 6) in the contour line memory 206 as a look-up table.

The converted pixel data P thus obtained
D ′ is overwritten in the image buffer 280. And
By repeating steps S31 to S34 of FIG. 23, the pixel conversion process for each gradation contour line is executed. As a result, a one-page image after the shadowing process as shown in FIG. 15B is obtained and displayed on the color CRT 218. In the shadow area (area surrounded by the multiple contour lines), the pixel data value is low and it is dark, so it appears that the target image component PC1 is shaded.

In step S7 of FIG. 13, the user observes the displayed one-page image after shadowing to determine whether or not the shadow area needs to be changed. When changing the shadow area, in step S8, the shadow area correction unit 224 (see FIG.
0) changes the shape of the gradation contour line and the density attribute (gradation characteristic). The density attribute is changed by displaying a graph as shown in FIG. 24 on the color CRT 218 and using the coordinate point input means to change the shape of the graph by the user.

FIG. 25 is an explanatory diagram showing the contents of the change processing of the shape of the gradation contour line. When changing the gradation contour line, the gradation contour line GOL having the lowest gradation level GL
(1) That is, the outermost gradation contour line is the color CRT
218 is displayed. The user selects this gradation contour line GOL
(1) Two fixed points pf1 and pf2 and a moving point pm1
And, and the moving point pm2 after the movement. The fixed points pf1 and pf2 may be the same as the fixed points when the multiple contour line is created, or different points may be designated. Next, two fixed points pf1 and pf2 and the first
From the first triangle TR1 composed of the moving points pm1 of
The conversion coefficient of the affine transformation to the second triangle TR2 composed of the two fixed points pf1 and pf2 and the second moving point pm2 is obtained. Then, using this affine transformation coefficient,
If the coordinates of the end points of all the gradation contours are affine-transformed, the shape of the gradation contours can be changed.

When the shadow area is corrected, the process returns to step S6 in FIG. 13 and the corrected shadow-added image is color CRT2.
It is displayed again on 18. When the desired one-page image is obtained in this way, a one-page image output process is executed in step S9. In the output process, the actual image data of the one-page image is transferred from the image memory 204 to the image buffer 280 (FIG. 12) of the pixel conversion unit 228 and the pixel conversion process is executed. As a result, the image buffer 280 is shaded by 1 Image data of the page image is generated. Then, the image data in the image buffer 280 is transferred to the image output device 300 (FIG. 1), and a one-page image is recorded.

According to the shadowing processing procedure of this embodiment, the initial contour line is perturbed to form a multi-contour line MUL that intersects at least a part of each other to form a shadow region. Makes it easy to create natural shadows that are dark and bright around.

D. Modified Example of Perturbation Map: FIG. 26 is an explanatory diagram showing a first modified example of the perturbation map. In FIG. 26, for convenience of illustration, the case where the initial contour line IOL is a triangle is shown. In this method, two moving points pm1 and pm2 are designated so as to sandwich the moving point pm0 on the initial contour line IOL, and perturbation is applied to the left and right from the initial contour line IOL. This perturbation is an affine transformation that performs the same linear interpolation as in the above embodiment. That is, the first to the left and right of the initial contour line IOL
And second final contour lines FOL1 and FOL2 are formed, and these final contour lines FOL1 and FOL2 and the initial contour line IO are formed.
Linear interpolation is performed between L and L to form a multiple contour line.

According to the method of FIG. 26, since the perturbation directions of the shadow area can be set to different directions on the left and right sides, a more natural shadow may be provided as compared with the above embodiment.

FIG. 27 is an explanatory diagram showing a second modification of the perturbation map. In this method, the initial contour line IOL and the final contour line FOL are interpolated according to a predetermined function yj = f (xj). This function yj = f (xj) is used for the moving point pm0 of the initial contour line IOL and the moving point p of the final contour line FOL.
It represents the locus traced by the j-th moving point pmj set between mn and mn. For example, when the area between the initial contour line IOL and the final contour line FOL is equally divided into n x-coordinates, the coordinates (xj, yj) of the j-th moving point pmj.
Is given by Equation 6 below.

[0093]

(Equation 6)

For each moving point pmj thus obtained, the affine transformation coefficient from the initial contour line IOL can be obtained. If the initial contour line IOL is affine-transformed using these affine transformation coefficient groups, a multi-contour map MUL obtained by perturbation mapping along a curved locus as shown in FIG. 27 can be obtained. The initial contour line IOL is 4
In the case of having more than one end point, interpolation can be performed according to an arbitrary function according to the same method.

The function indicating the trajectory of the perturbation map is not limited to the analytic function, but a parametric function such as a Bezier curve can be used.

FIG. 28 is an explanatory diagram showing an example of a shadow area formed according to the second modification of the perturbation map described above.
As shown in FIG. 28B, by perturbing the initial contour line to form a multiple contour line even for an initial contour line having relatively complicated unevenness as shown in FIG. You can create natural shadow areas. Further, according to this method, since a multiple contour line is formed by perturbing the initial contour line, a natural shadow area can be easily formed even when the shape of the initial contour line is complicated. it can. It should be noted that the same effect can be obtained when the perturbation is performed by linear interpolation instead of by curve interpolation.

FIG. 29 is an explanatory diagram showing a third modification of the perturbation map. In this method, a multiple contour line MUL is formed inside the initial contour line IOL by applying a perturbation that reduces the initial contour line IOL. In this case, the moving point pm0 on the initial contour line IOL and the final contour line F
When the moving point pmn on the OL is specified, the initial contour line IOL
A final contour line FOL having a reduced shape is obtained, and another contour line is interpolated between the initial contour line IOL and the final contour line FOL. The multi-contour lines MUL thus obtained differ from the other embodiments described above in that they do not intersect each other.

As a perturbation mapping method for reducing the initial contour line IOL, there are a method of creating a contour line similar to the initial contour line IOL and a method of contracting the circumference of the initial contour line IOL by an equal width. is there.

E. Other Modifications The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the scope of the invention. For example, the following modifications are also possible. It is possible.

(1) In the above embodiment, the pixel data is represented by the gradation values of the three additive primary colors RGB, but the pixel data is the gradation value of the three subtractive primary colors YMC, or YMCK (K The present invention can also be applied to the case where the gradation values of the four colors of black are represented. In this case, YMC or YMCK pixel data may be converted to RGB pixel data and then applied to the above-described embodiment.

(2) The data representing the shadow area includes vector data representing the gradation contour line and lookup data representing the density attribute (FIG. 24). However, instead of the vector data representing the gradation contour line, the vector data representing the initial contour line IOL and the graphic conversion parameter may be stored. As the figure conversion parameters, two fixed points pf1 and pf2 and two moving points p
It suffices to store m0, pmn and the division number n. Alternatively, the affine transformation coefficients a to f (Equation 2) corresponding to the final contour and the division number n may be stored as the figure transformation parameters. When the perturbation is applied by a predetermined function as in the second modification of the perturbation map described above,
Make sure to include this function in the figure conversion parameters. In this way, if the data representing the initial contour line and the graphic conversion parameter are stored, it is possible to add a shadow by a simple calculation if necessary. Further, if the initial contour line is replaced with the initial contour line of another image component, there is an advantage that a similar shadow can be easily added to the other image component.

(3) In the above embodiment, the multiple contour line MUL is formed by affine transforming each of the initial contour lines IOL using a plurality of affine transformation coefficients, but instead of this, the mask contour line MOL is used. It is also possible to form a multi-contour line MUL by affine transformation of. In this case, a first affine transformation coefficient for converting the mask contour line MOL into the initial contour line IOL and a second affine transformation coefficient for converting the mask contour line MUL into the final contour line FOL are obtained. By interpolating the first and second affine transformation coefficients, a plurality of affine transformation coefficients for transforming the mask contour line into the multiple contour line may be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a procedure of a shadowing process according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a difference between a multiple contour line and a gradation contour line.

FIG. 3 is a block diagram showing the configuration of a plate-making processing system that applies an image shadowing process by applying an embodiment of the present invention.

FIG. 4 is a block diagram showing an internal configuration of an image memory 204.

FIG. 5 is a block diagram showing the contents of an initial contour line memory 205.

FIG. 6 is a block diagram showing the contents of a contour line memory 206.

FIG. 7 is a block diagram showing the function of an initial contour line creation unit 221.

FIG. 8 is a block diagram showing the function of a multiple contour line creation unit 222.

FIG. 9 is a block diagram showing the function of a gradation contour line extraction unit 338.

FIG. 10 is a block diagram showing the function of a shadow area correction unit 224.

FIG. 11 is a block diagram showing the function of the graphic calculation unit 226.

FIG. 12 is a block diagram showing the function of a pixel conversion unit 228.

FIG. 13 is a flowchart showing the procedure of a shadowing process.

FIG. 14 is a flowchart showing the procedure of a shadowing process.

FIG. 15 is a conceptual diagram showing an example of a one-page image before and after a shadowing process.

FIG. 16 is an explanatory diagram showing the processing contents of each step of the shadowing processing.

FIG. 17 is an explanatory diagram showing the processing contents of each step of the shadowing processing.

FIG. 18 is an explanatory diagram showing the processing content of each step of the shadowing processing.

FIG. 19 is an explanatory diagram showing the processing contents of each step of the shadowing processing.

FIG. 20 is an explanatory diagram showing the processing contents of each step of the shadowing processing.

FIG. 21 is an explanatory diagram showing the processing contents of each step of the shadowing processing.

FIG. 22 is a flowchart showing the procedure of image display.

FIG. 23 is a flowchart showing the procedure of pixel conversion processing.

FIG. 24 is a graph showing the contents of a lookup table that gives the relationship between the gradation level GL and the gradation rate GR.

FIG. 25 is an explanatory diagram showing the contents of a process of changing the shape of a gradation contour line.

FIG. 26 is an explanatory diagram showing a first modification of the perturbation map.

FIG. 27 is an explanatory diagram showing a second modification of the perturbation map.

FIG. 28 is an explanatory diagram showing an example of a shadow area formed according to a second modification of the perturbation map.

FIG. 29 is an explanatory diagram showing a third modification of the perturbation map.

[Explanation of symbols]

 100 ... Image input device 200 ... Image processing device 202 ... CPU 203 ... Bus 204 ... Image memory 205 ... Initial contour line memory 206 ... Contour line memory 208 ... Main memory 210 ... Input / output interface 212 ... Keyboard 214 ... Mouse 216 ... Digitizer 218 ... Color CRT 220 ... Image input / output interface 221 ... Initial contour line creation unit 222 ... Pixel conversion unit 222 ... Multiple contour line creation unit 224 ... Shadow area correction unit 226 ... Graphic calculation unit 228 ... Pixel conversion unit 230 ... Selector 232 ... Actual image memory 234 ... Coarse image memory 236 ... Coarse image conversion unit 244 ... Mask memory 250, 252 ... Selector 270 ... Coordinate conversion unit 272 ... Selector 280 ... Image buffer 282 ... Contour line buffer 284 ... Processing buffer 286 ... Raster conversion unit Two 8 ... Selector 300 ... Image output device 310 ... Initial contour point sequence coordinate memory 312 ... Perturbation mapping parameter memory 320 ... Gradation contour line data memory 322 ... Control point memory 324 ... Coordinate value memory 326 ... Attribute value memory 330 ... Perturbation mapping parameter Calculation unit 332 ... Perturbation processing unit 334 ... Internal processing buffer 336 ... Multiple contour line overlapping unit 338 ... Gradation contour line extraction unit 370 ... Equal density region cutout unit 372 ... Boundary contour extraction unit 380 ... Contour line shape processing unit 382 ... Gradation characteristic processing 390 ... Control buffer 392 ... Contour line buffer

Claims (9)

[Claims] 1. A method of casting a shadow on an image part in an image represented by image data, comprising: (a) defining a first reference contour line used to form a shadow area of the image part. A step of preparing, (b) forming a multiple contour line at least partially intersecting each other by perturbing the first reference contour line, and (c) a plurality of contour lines formed by the multiple contour line. An image comprising: a step of assigning a gradation rate to each closed area; and (d) a step of correcting image data of pixels in the plurality of closed areas according to the gradation rate assigned in the step (c). Shadowing method. 2. The image shadowing method according to claim 1, wherein the step (b) comprises a first step for mapping the first reference contour line on itself.
By calculating a affine transformation coefficient of the first reference contour line, setting a second affine transformation coefficient that defines a width for perturbing the first reference contour line, and interpolating the first and second affine transformation coefficients. A method for obtaining a plurality of affine transformation coefficients, and a step of forming the multiple contour lines by affine transforming the first reference contour line using the plurality of affine transformation coefficients . 3. The image shadowing method according to claim 1, wherein the step (b) includes: (e) forming a second reference contour line used to form a shadow region of the image component. A method for shadowing an image, comprising the steps of: preparing, and (f) forming the multiple contours by interpolating the first and second reference contours. 4. The image shadowing method according to claim 3, wherein the step (f) comprises a first step for mapping the first reference contour line on itself.
To obtain a second affine transformation coefficient for converting the first reference contour line into a second reference contour line, and calculating the first and second affine transformation coefficients An image including a step of obtaining a plurality of affine transformation coefficients by interpolation, and a step of forming the multiple contour lines by affine-transforming the first reference contour line using the plurality of affine transformation coefficients Shadowing method. 5. The image shadowing method according to claim 3, wherein the step (a) uses a step of preparing a mask contour line representing a contour of an image component, and a first affine transformation coefficient. A step of obtaining the first reference contour line by converting the mask contour line; and the step (b) includes a second step for converting the mask contour line into a second reference contour line. Of the affine transformation coefficient, and a step of obtaining a plurality of affine transformation coefficients by interpolating the first and second affine transformation coefficients, and an affine transformation of the mask contour line using the plurality of affine transformation coefficients. Forming the multi-contour lines by transforming. 6. The image shadowing method according to claim 1, wherein the step of obtaining the plurality of affine transformation coefficients is performed by performing the interpolation using a predetermined function. And a method for obtaining the plurality of affine transformation coefficients, the method for shadowing an image. 7. The image shadowing method according to claim 1, wherein the step (c) assigns a gradation rate according to a monotonic function relating to the number of overlaps of the multiple contour lines. Image shadowing method including. 8. The image shadowing method according to claim 1, wherein the step (c) further assigns the same gradation rate to the plurality of closed regions. A step of generating a plurality of gradation contour lines that represent the contour lines of the closed region, and the step (d) includes the values of the image data in the closed region represented by the gradation contour lines and the gradation contour lines. A method for shadowing an image, comprising the step of correcting the value of the image data in the closed region by multiplying by the gradation rate assigned to. 9. The image shadowing method according to claim 1, wherein the step of perturbing in the step (b) comprises perturbing a part of the first reference contour line. An image shadowing method comprising: a step of setting as a fixed contour portion that is fixed at times; and a step of perturbing a portion of the first reference contour line other than the fixed contour portion.