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From: Luca on 21 Jul 2010 10:26
"Sandeep " <sandeepdevasrii(a)gmail.com> wrote in message <hafchq$bl1$1(a)fred.mathworks.com>...
>
> Hi all,
>
> I am trying to implement a shadow removal algorithm in matlab. I follow the paper
> written by Mr.Graham.Finalyson i.e, "Shadow removal using Entropy minimization".
> First of all i am trying to get 1-D illuminant invariant image by assuming that we
> know the projection angle. I took some known images from the above mentioned
> paper so that i know the projection angle and there is no need of entropy calculation.
> The program which wrote works with some images and seems to be failed with some images. Please help me if some one has some experience with this algorithm. I am appending small part of my matlab code which is written to produce a 1-D illumination invariant image.
> ------------------------------------------------------------------------------------------------------------------
>
> I = imread('file1.tiff');
> J = im2double(I);
>
> R = J(:,:,1);
> G = J(:,:,2);
> B = J(:,:,3);
>
> [len,wid] = size(R);
>
> % Generation of 2-D Log Chromaticity Image.
> for i = 1:len
> for j = 1:wid
> if ((R(i,j)*G(i,j)*B(i,j))~= 0)
> c1(i,j) = R(i,j)/((R(i,j)*G(i,j)*B(i,j))^(1/3));
> c2(i,j) = G(i,j)/((R(i,j)*G(i,j)*B(i,j))^(1/3));
> c3(i,j) = B(i,j)/((R(i,j)*G(i,j)*B(i,j))^(1/3));
> else
> c1(i,j) = 1;
> c2(i,j) = 1;
> c3(i,j) = 1;
> end
> end
> end
>
> rho1 = mat2gray(log(c1));
> rho2 = mat2gray(log(c2));
> rho3 = mat2gray(log(c3));
>
> X1 = mat2gray(rho1*1/(sqrt(2)) - rho2*1/(sqrt(2))); %(1/sqrt(2); -1/sqrt(2); 0)
> X2 = mat2gray(rho1*1/(sqrt(6)) + rho2*1/(sqrt(6)) - rho3*2/(sqrt(6))); %(1/sqrt(6); 1/sqrt(6); -2/sqrt(6))
>
> theta = 120;
>
> InvariantImage = cos(theta*pi/180)*X1 + sin(theta*pi/180)*X2;
>
> -----------------------------------------------------------------------------------------------------
>
> Thank you all,
> Sandeep P

Hi,
at the end did you find the solution of this problem?

I'm as you with the same problem. I want to implement the algorithm to find the minimum entropy value....
From: casa on 24 Jul 2010 09:18
hi,i use this code to plot Entropy :

X1 = mat2gray(rho1*1/(sqrt(2)) - rho2*1/(sqrt(2)));
X2 = mat2gray(-rho1*sqrt(6)/4 + rho2*sqrt(6)/4 + rho3*(sqrt(6)/4));
for t=1:180

delta = t*pi/180;
img = cos(delta)*X1 + sin(delta)*X2 ;

logimg = -log(img);
r=img.*logimg;

n(t)=mean(abs(r(:)));
end;

plot(abs(n(:)), 'DisplayName', 'n', 'YDataSource', 'n'); figure(gcf)
[v,idx]=min(n(:));

result are inconsistent amongst the papers. may be the paper use some high precision
bmp.
From: casa on 24 Jul 2010 09:19
hi,i use this code to plot Entropy :

X1 = mat2gray(rho1*1/(sqrt(2)) - rho2*1/(sqrt(2)));
X2 = mat2gray(-rho1*sqrt(6)/4 + rho2*sqrt(6)/4 + rho3*(sqrt(6)/4));
for t=1:180

delta = t*pi/180;
img = cos(delta)*X1 + sin(delta)*X2 ;

logimg = -log(img);
r=img.*logimg;

n(t)=mean(abs(r(:)));
end;

plot(abs(n(:)), 'DisplayName', 'n', 'YDataSource', 'n'); figure(gcf)
[v,idx]=min(n(:));

result are inconsistent amongst the papers. may be the paper use some high precision
bmp.
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