% simpleRGBimage.m manually specifies intensities in an image

I = ones(20,20);                     % a block of ones, double precision
Z = zeros(20,20);                    % a block of zeros, double precision
clear A                              % clear out A

clf
subplot(2,2,1)
                                     % A consists of 3 matrices
A(:,:,1) = [[I Z]; [Z Z]];           % The first tells red intensities
A(:,:,2) = [[Z I]; [Z Z]];           % The second tells green
A(:,:,3) = [[Z Z]; [I Z]];           % The third tells blue
imshow(A);                           % When A is double, 0<=A<=1
title('Only one color on in each block')

subplot(2,2,2)
A(:,:,1) = [[I I]; [Z Z]];           % Top of image has red intensity one
A(:,:,2) = [[Z I]; [Z I]];           % Right side has green intensity one
A(:,:,3) = [[Z Z]; [I I]];           % Bottom has blue intensity one
imshow(A);
title('Two colors on in the right blocks')

subplot(2,2,3)
A(:,:,1) = [[I I]; [I Z]];           % All intensities have high values
A(:,:,2) = [[Z I]; [I I]];           
A(:,:,3) = [[I Z]; [I I]];           
imshow(A);
title('Two or three colors on in each block')

subplot(2,2,4)
I        = I/2;                      % Cut intensities in half
A(:,:,1) = [[I Z]; [Z Z]];           % The first tells red intensities
A(:,:,2) = [[Z I]; [Z Z]];           % The second tells green
A(:,:,3) = [[Z Z]; [I Z]];           % The third tells blue
imshow(A);
title('Image at half intensity')