JPH02127781A - Color changing method and device for color picture - Google Patents

Abstract

PURPOSE:To change the color of a color picture without damaging naturality by changing the three primary color values of the respective picture elements of an object in the color picture according to a fixed rule when the three primary color values of a light source color are changed. CONSTITUTION:When the light source color is changed, the color of the object is naturally changed. Namely, when the three primary color values of the light source color in the color picture are changed from (Rs, Gs, Bs) to (Rs', Gs', Bs'), three primary color values (R, G, B) of the respective picture elements of the object in the color picture are changed to (R', G', B') according to an expression I. Thus, a color scenary picture can be changed to the color scenary picture, which is irradiated with the light source of a color different from the original light source, and displayed. Then, a condition in the case that an industrial product is set under an environment to be different from the conventional environment can be checked without really executing the setting.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for changing the colors of a color image without impairing its naturalness.

(Prior Art) CAD (Computer Aided Design) is applied to the field of color design, and there is a need to change colors within it. Specifically, the object of design (
For example, when an image containing a car (for example, a car) is imported into a computer system using a scanner or a color camera, and then composited into another scene, the color of this object part is changed (for example, the body of a car that was originally red is changed to blue). or change the color of the light source (eg, from a daytime scene to a dusk scene). Regarding the former method of changing the color of a target object, the following method is already known (Japanese Patent Application No. 1982-072056).

The conventional method will be explained with reference to FIG. Light that hits the object 12 from the light source 11 and enters the camera 13 can be roughly divided into specularly reflected light 14 and diffusely reflected light 15. Specular reflected light is
Light is reflected from the surface of an object, and its spectral composition is the same as that of the light source, only the intensity changes. Diffuse reflected light is generated when light from a light source enters an object and undergoes spectral absorption unique to the object.
It is isotropically injected to the outside. The spectral composition of the diffusely reflected light is usually different from that of the light source. Therefore, the three color components (R, G, B) of each point on the target surface can be written as: Here, (RO2Go, Bo) are three components of the diffusely reflected light, and since they differ depending on the object, they are hereinafter referred to as "object colors" in this specification.

(Rs, Gs, B,) are the three components of specularly reflected light, and are equal to the color of the light source, so they are hereinafter referred to as [light source color] in this specification. α and p indicate the degree of contribution of diffuse reflected light and specular reflected light to the amount of emitted light, and are related to the surface material, direction, etc. This differs from pixel to pixel, so if the pixel position within a pixel is (x, y), then it is written as:

At this time, the appearance of objects with the same material but different colors can be changed by changing only the object color to (horse, GO-BO).
Each pixel value can be calculated as shown in equation (3).

Thinking similarly, when changing the color of the latter light source,
It is considered that by changing the light source color to (Rs', Gs', and Bs), each pixel value may be calculated as shown in equation (4).

(Problems to be Solved by the Present Invention) However, in reality, this method cannot naturally change the color of the scene. This is because, although it is natural that the object color also changes when the light source color changes, this model does not take into account whether the object color changes.

The present invention aims to solve this problem and provide a method and apparatus for changing the color of a scene by naturally changing the object color when the light source color changes.

(Means for solving the problem) The first invention is to change the three primary color values of the light source color in a color image from (Rs, G, B,) to desired (Rs', Gs', Bs
This is a method of changing the color of a color image, in which the three primary color values (R, G, B) of each pixel of an object in the color image are changed according to (R', α, B) when the object is changed to (R', α, B).

The second invention provides a color image storage means for storing a color image, and three primary color values ("s, Gs,
a first light source color storage means for storing the three primary color values (Rs', Gs', B) of the desired light source color; The values (R, G, B) are stored in the three primary color values (Rs, Gs, Bs) stored in the first light source color storage means and the three primary color values (Rs') stored in the second light source color storage means. , G.S.
', Bs') to create new primary color values (R', G',
This is a color changing device for a color image, comprising a changed image calculating means for changing the color according to the method (B).

(Function) Light source color displayed on the display (Rs, Gs, Bs)
, and the three primary colors of the object (Ma, Go, Bo) are determined by the spectral energy distribution S (λ) regarding the wavelength λ of the light source and the spectral reflectance distribution p (λ) of the object, as follows: Ma = JS (λ) 〒 (λ) dλ Gs=fS(λ) before (in) dλ (5
)Bs=fS(λ)b(λ)dλR=fSCλ)p(in)i:(λ)dλGo=fS(
λ) p(λ) g(λ) dλ (6) Bo=fS(λ
)p(λ)b(λ)dλ. Here, 〒 (in), i (λ), and stone (λ) are the spectral sensitivities of a three primary color sensor such as a camera.

Generally, the light source color changes from (Rs-Gs, Bs) to (L,',
Since it is not possible to obtain S(λ) even if p(λ) is constant when G8', B, and B change, it is not possible to predict how the object color will change. but,
Assuming that all spectral characteristics change smoothly with respect to wavelength, it is possible to approximate them with piecewise constant spectral characteristics as shown in FIG. That is, the light source is λ>λ2
Assuming that light has an intensity of G5 for λ1 x λ x 2, and B for λ x λ1, the reflectance of the object is pr for λ>λ2, pg for λ1 x λ x λ2, and pb for λ x λ1. I believe that. In this case, the object color (RO2Go, Bo) is the light source color (Rs,
GS, B, ) and reflectance (pr, pg, pb), "o = "s'9r, Go = Gs'Pg, Bo =
Since it is written as Bs・9b (7), the light source color is (
Rs', Gs', Bs'), the object color is expressed as (Ro', Go', Bo') as in equation (8).

5I Bo' = Bs'l)b = Bo'-Bs Therefore, in a scene containing the same object, the light source color is (
When the color changes from Rs, Gs, B,) to (L,', Gs', Bs), the color of each pixel is calculated using equation (8).
According to this method, formula (10) is easily established when compared with formula (2). It is possible to express it naturally.

(Example) An example of the present invention will be described with reference to FIG. In the color image memory 1, a full-color image including an object whose color is to be changed is stored, for example, in R, G, and B gradations of 8 bits each. This content is transferred to the CR via the D/A converter 2.
It is displayed as a color image on T3. The mask pixel memory 4 stores a mask of a color area to be changed in this image, with one bit for each pixel. This relationship is shown in FIG. In the scene at dusk, there is a car whose color is to be changed.

Originally, when an image of a car is synthesized from other daytime images, only this part is subject to color change. The mask image memory 4 is "1" only for the part of the car that is subject to this color change, and is "0" for the other parts.
Other parts have a mask image with a value of 110+1. A color image is usually created by cutting out an image part from another image and combining the mask image with a CRT.

The color specifying means 5 in FIG.
The original image including the inserted car is stored in the color image memory and displayed using the pointing device 6 and the light source color type R, G,
The B value (Rs, G8.Bs) is picked up and stored in the first light source color storage means 7, and can be realized by a microcomputer or the like.

To actually change the color, the user first stores an image in which the car is synthesized in the color image memory and displays it, and then, for example, uses the pointing device 6 to select a new light source color Cs instead of the light source color Cs from a twilight scene. 'R, G, B
Give the values ("s', Gs', Bs') to the color specifying means 5,
This is started by being stored in the second light source color storage means 8. The modified image calculation means 9 scans each pixel of the mask image memory 4, and calculates the value for the pixel whose value is "1".
For each pixel of color image memory 1, (R(x, y),
G(x, y), B(x, y)), and use the two R, G, and B values stored in the first light source color storage means 7 and the second light source color storage means 8 to form the formula (10) is calculated, and the changed pixel values (R'(x, y), G'(x, y
), B'(x,y)) are written into the color image memory again. When this is completed for all pixels, the scene image in the color image memory 1 has been naturally replaced with a scene image illuminated by the desired light source.

(Effects of the Invention) With the method and device described above, it becomes possible to change a color scene image into a scene image illuminated by a light source of a different color from the original light source and display it. According to the present invention, it is possible to check what happens when an industrial product is placed in an environment different from the conventional one without actually carrying out the test, and this has great industrial and economical effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the relationship between the color image memory and mask image memory in FIG. 1, and FIG. FIG. 4 is an explanatory diagram of the composition of reflected light, and is an explanatory diagram of piecewise constant spectral characteristics assumed in the operation of the present invention. In the figure, 1...color image memory, 2...-D/A converter, 3
... CRT, 4... Mask image memory, 5... Color specifying means, 6... Pointing device, 7...
First light source color storage means, 8... Second light source color storage means, 9... Changed image planning means.

Claims (1)

[Claims] 1. The three primary color values of the light source color in a color image are (R_s,
G_s, B_s) to the desired (R_s', G_s', B
_s'), the three primary color values (R, G, B) of each pixel of the object in the color image are changed to (R', G', B'), R'=(R_s'/R_s)R , G'=(G_s'/G
__s) A method of changing the color of a color image according to G, B'=(B_s'/B_s)B. 2. Color image storage means for storing a color image, and three primary color values (R_s, G_s, B_s) of the light source color of the color image.
), a second light source color storage means for storing the three primary color values (R_s', G_s', B_s') of the desired light source color, and the three primary colors of each pixel of the color pixels. The values (R, G, B) are stored in the three primary color values (R_s, G_s, B_s) stored in the first light source color storage means and the three primary color values (R_s) stored in the second light source color storage means.
__s', G_s', B_s') to new three primary color values (R', G', B'), R'=(R_s'/R_s)R, G'=(G_s'/G
_s) A change image calculation means for changing the color according to G, B'=(B_s'/B_s)B.