% ee435 sample pseudocolor program
% Note: the image we will use here, is a grayscale image, but it is
% actually stored as if it were a color image, with a red, green and blue
% component to each pixel. In order for this to appear as only shades of
% gray, all components (r, g, and b) are the same value for each pixel.
a=imread('herndon.jpg');    % this is a grayscale image so 
r=a(:,:,1);     % matrix r is the red component
g=a(:,:,2);     % matrix g is the green component
b=a(:,:,3);     % matrix b is the blue component
gray=r;         % set aside a single component grayscale image to use in the following...

% define 2 thresholds for pseudocoloring
thresh1=240;
thresh2=120;

% find all gray levels > threshold 1 and set the color to red
loc=find(gray >thresh1);
r(loc)=gray(loc);     % set the red component at these locations to max value (255)
g(loc)=0;       % set the green component at these locations to 0
b(loc)=0;       % set the blue component at these locations to 0

% find all gray levels < threshold 2 and set the color to blue
loc=find(gray < thresh2);
r(loc)=0;       % set the red component at these locations to 0  
g(loc)=0;       % set the green component at these locations to 0
b(loc)=gray(loc);     % set the blue component at these locations to 255

% find all gray levels in between thresholds 1 and 2 and set the color that
% shade of green
loc=find(gray >= thresh2 & gray <=thresh1);
r(loc)=0;       % set the red component at these locations to 0
g(loc)=gray(loc);   % set the green component to be the gray level
b(loc)=0;       % set the blue component at these locations to 0

% put these component planes back together into new color image a1
a1=zeros(size(a));
a1(:,:,1)=r;
a1(:,:,2)=g;
a1(:,:,3)=b;
a1=uint8(a1);	% convert from double to uint8

% create a display for the original grayscale and the pseudocolor image
figure(1)
subplot(1,2,1)
imshow(a)
title('original grayscale')

subplot(1,2,2)
imshow(a1)         % image() needs color images to have values 0.0-1.0
title('pseudocolor')