rgb到xyz到lab色彩空间转换ppt

Substituting the above relation into the previous equation， we can have
Z can be computed as z= 1-x-y.
From the equation we have discussed ,We can get the conclusion that: given four pairs of corresponding chromaticity coordinates in both spaces, the transformation can be uniquely determined by solving a system of linear equations in eight unknowns.
the above equation can be expressed as
From the equation and the definition of chromaticity, we have X+Y+Z=(a11+a21+a31)R+(a12+a22+a32)G+(a13+a23+a33)B =(R+G+B)×[(a11+a21+a31)r+(a12+a22+a32)g+(a13+a23+a33)b]
Since r+g+b= 1 it is only necessary to specify any two of r , g, and b.
Transformation between two sets of primaries (RGB TO XYZ)
Let(R)(G)(B) and(X)(Y)(Z) be two sets of primaries. A color stimulus(C) can be expressed by the following two color matching relations: (C) ≡CR(R)+CG(G)+CB(B) (C) ≡CX(X)+CY(Y)+CZ(Z). If we determine the tristimulus values of(X),(Y), and(Z)using the primaries(R),(G), and (B), we have the following relations:
This algorithm is faster than the previous.
0.4124 A = 0.2126 0.0193
0.3576 0.7152 0.1192
0.1805 0.0722 0.9505
CIELAB color space
(Xn,Yn,Zn) are the tristimulus values of the reference (neutral) white point.
Built-in function of matlab
1. makecform() Create color transformation structure C = makecform(type) 2. applycform() Apply device-independent color space transformation B = applycform(A,C)
Realize the color space conversion CIERGB to CIEXYZ to CIELAB
Team members： 高雯菁 李佩佩 徐宁 李心雨
Colorimetry and its empirical foundations
Colorimetry is a scientific field in which the physical specifications of light stimuli that produce a given color sensation under restricted viewing conditions are studied. In particular ,it seeks to represent the spectral power distribution of any incident light with a much reduced number of parameters . It is mainly concerned with color matching and predicting small color differences when two stimuli do not match.
response functions.
The bipartite field used in color matching experiments.
1.“≡” means color matching. 2. (C), (R), (G), and(B), represent color stimuli or lights. 3. R,G, and B, represent scalar multipliers, meaning the amounts of light.
Then ,we can determine the parameters of matrix A.
Alternatively, we can solve the transformation by another Algorithm Let (x1,y1,z1), (x2,y2,z2), (x3,y3,z3), (x4,y4,z4) be four points in the chromaticity space of the primaries(X),(Y),(Z), and (r1,g1,b1), (r2,g2,b2), (r3,g3,b3), (r4,g4,b4)be their corresponding points in the chromaticity space of the primaries (R), (G), (B).
Let (x1,y1,z1), (x2,y2,z2), (x3,y3,z3), (x4,y4,z4) be four points in the chromaticity space of the primaries(X),(Y),(Z), and (r1,g1,b1), (r2,g2,b2), (r3,g3,b3), (r4,g4,b4)be their corresponding points in the chromaticity space of the primaries (R), (G), (B).
Let R, G, B be the tristimulus values for the (R), (G), (B) primaries and X, Y, Z be the tristimulus values for the (X), (Y), (Z) primaries. Their chromaticity coordinates are denoted by r,g,b and x,y,z . As we have just shown, the transformation from R, G, B to X, Y, Z can be done by a 3×3 matrix, A:
The receptor-level theory of color matching
One of the main goals of colorimetry is to derive a concise numerical representation of any given color stimulus from its spectral power distribution. But , A spectral power distribution may take more than 40 numbers to specify. Therefore, the main task of colorimetry is to determine the three cone
Color matchinBaidu Nhomakorabea experiments
chromaticity coordinates
Let R, G, and B be the tristimulus values of a given color, then its chromaticity coordinates (r,g,b) are defined as: