g1(h*ab) = 0.116|sin(​(h*ab-90)/​2)|+0.085

Please go through the code and tell me what is wrong.. Thankyou

% Lightness Correction
% **************************************************************************************
% L* for the lightness and a* and b* for the green–red and blue–yellow color components
[L,a,b] = RGB2Lab(IC); 

%RGB2LAB Convert an image from RGB to CIELAB
% Calculating CIELAB Coordinate
% C_ab=(((a.^2)+(b.^2)).^0.5); %Chroma (magnitude) :: C*ab = [a*2 + b*2]^2 
C_ab=sqrt((a.^2)+(b.^2));
% C_ab=(((a.^2)+(b.^2)).^0.5);

t_Hab=(b./a);
H_ab=atand(t_Hab);%Hue (angle):: h*ab = tan^-1(b*/a*)

% g2(L*) = 2.5 * 0.025L.
g2 = (2.5 -(0.025.*L));

** %g1(h*ab) = 0.116|sin((h*ab-90)/2)|+0.085,
g1_hab=((H_ab-90)./2);
g1=0.116.*(abs(sind(g1_hab)))+0.085;*

%L** = L* + g2(L*)g1(h*ab)C*ab,
tt=(g2.*g1.*C_ab);

Correct_Light=(L+tt);

figure,
imshow(Correct_Light);

[Steven Lord]

What makes you believe that something is wrong?

If you receive an error when you run the code, show us the full text (everything in red) of the error message.

If you receive a different answer than you expected, show us how you defined the variables needed to run the code, show the results you received when you ran the code using those variables, and explain what you expected to receive.

[cheppu mol]

the doubt is about one equation:: (h*ab) = 0.116|sin((h*ab-90)/2)|+0.085. what is this symbol|--|??? is it abs()? [|sin((h*ab-90)/2)|],,,

g1=0.116.*(abs(sind(g1_hab)))+0.085;

Answer 1

[Stephan]

Hi,

there are at least 2 things to do in your code:

• Get rid of the 2 * in beginning of line 18 and the * at the end of line 20
• use rgb2lab instead of 'RGB2Lab' in line 4 (or did you write your own RGB2Lab-function? Then ignore this hint)

Yes, you are right: the mathematical notation '|sin(x)|' is written with abs command in matlab:

>> y = |sin(1.5*pi)|
 y = |sin(1.5*pi)|
     ↑
Error: Unexpected MATLAB operator.

>> y = abs(sin(1.5*pi))

y =

       1

>> y = sin(1.5*pi)

y =

      -1

Best regards

Stephan