Patent ID: 11962949
Assignee: NATIONAL CHUNG HSING UNIVERSITY
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 10:
11. The method of claim 10, the reference color image being in the form of an 8-bit color image expressed using a standard red, green, blue (sRGB) color space, wherein the converting operation includes:
obtaining the converted reference image using the equations:, [
     
      
       
        
         X
         C
        
       
      
      
       
        
         Y
         C
        
       
      
      
       
        
         Z
         C
        
       
      
     
     ]
    
    =
    
     
      
       
        [
        
         M
         A
        
        ]
       
       [
       T
       ]
      
      [
      
       
        
         
          f
          ⁡
          (
          
           R
           sRGB
          
          )
         
        
       
       
        
         
          f
          ⁡
          (
          
           G
           sRGB
          
          )
         
        
       
       
        
         
          f
          ⁡
          (
          
           B
           sRGB
          
          )
         
        
       
      
      ]
     
     ×
     100
    
   
   ,
   
    
     
      
       
        R
        sRGB
       
      
     
     
      
       
        0
        ≤
        
         G
         sRGB
        
        ≤
        1
       
      
     
     
      
       
        B
        sRGB
       
      
     
    
    ;
   
  
  ⁢
  

  
   
    T
    =
    
     [
     
      
       
        0.4104
       
       
        0.3576
       
       
        0.1805
       
      
      
       
        0.2126
       
       
        0.7152
       
       
        0.0722
       
      
      
       
        0.0193
       
       
        0.1192
       
       
        0.9505
       
      
     
     ]
    
   
   ;
  
  ⁢
  

  
   
    f
    ⁡
    (
    n
    )
   
   =
   
    {
    
     
      
       
        
         
          
           
            (
            
             
              n
              +
              0.055
             
             1.055
            
            )
           
           2.4
          
          ,
          
           n
           >
           0.04045
          
         
        
       
       
        
         
          
           (
           
            n
            12.92
           
           )
          
          ,
            
          otherwise
         
        
       
      
      ;
      

      
       
        and
        

        [
        
         M
         A
        
        ]
       
       =
       
        [
        
         
          
           
            
             X
             SW
            
            /
            
             X
             CW
            
           
          
          
           0
          
          
           0
          
         
         
          
           0
          
          
           
            
             Y
             SW
            
            /
            
             Y
             CW
            
           
          
          
           0
          
         
         
          
           0
          
          
           0
          
          
           
            
             Z
             SW
            
            /
            
             Z
             CW
            
           
          
         
        
        ]
       
      
     
     ,, where XC, YC and ZC represent an X value, a Y value and a Z value of a pixel of the converted reference image in the CIE 1931 XYZ color space, RsRGB, GsRGB and BsRGB represent a red value, a green value and a blue value of a pixel of the reference color image in the sRGB color space corresponding to the pixel of the converted reference image, XCW, YCW and ZCW represent a white point defining the white color in the sRGB color space, XSW, YSW and ZSW represent a white point for an environmental illuminant under which the reference color image was captured, and [MA] represents a chromatic adaptation matrix; and
obtaining the converted spectral dataset using the equations:

XS=k∫380nm780nmS(λ)R(λ)x(λ)dλ; 

YS=k∫380nm780nmS(λ)R(λ)y(λ)dλ; 

ZS=k∫380nm780nmS(λ)R(λ)z(λ)dλ; and

k=100/∫380nm780nmS(λ)y(λ)dλ,, where, for each wavelength λ of the spectrum of the reflection spectral dataset, XS, YS and ZS represent an X value, a Y value and a Z value of the converted spectral dataset in the CIE 1931 XYZ color space for the spectral value corresponding to the wavelength λ of the spectrum of the reflection spectral dataset, S(λ) represents a spectral value corresponding to the wavelength λ in a spectrum of the environmental illuminant under which the reference color image was captured, R (λ) represents the spectral value corresponding to the wavelength λ of the spectrum of the reflection spectral dataset of the reference object, and x, y and z represent color matching functions of the CIE 1931 XYZ color space.