% simpleRGBimage2.m manually specifies intensities as uint8

I = uint8(255*ones(20,20));          % a block of 255's, unsigned integers
Z = uint8(zeros(20,20));             % a block of zeros
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 uint8, 0<=A<=256

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);

subplot(2,2,3)
I = uint8(0.5*double(I));            % Convert to double, halve, convert back
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);

subplot(2,2,4)
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);