%% Integer Arithmetic Examples
% This gives examples of performing arithmetic on signal
% and image integer data.

% Copyright 1984-2004 The MathWorks, Inc. 
% $Revision: 1.1.4.2 $  $Date: 2004/04/06 21:52:56 $

%% Load integer signal data
% Load measurement datasets comprising signals from four  instruments using
% 8 and 16-bit A-to-D's resulting in data saved as |int8|, |int16| and
% |uint16|. Time is stored as |uint16|.

load integersignal

% Look at variables
whos Signal1 Signal2 Signal3 Signal4 Time1

%% Plot data
% First we will plot two of the signals to see the signal ranges.
plot(Time1, Signal1, Time1, Signal2);
grid;
legend('Signal1','Signal2');

%%
% Here we see the values are in the range -128 and 127, which is as we
% would expect for |int8|. It is likely that these values would need to be
% scaled to calculate the actual physical value that the signal represents
% e.g. Volts.

%% Process data
% We can perform standard arithmetic on integers such as |+|, |-|, |*|, and
% |/|. Let's say we wished to find the sum of Signal1 and Signal2.

SumSig = Signal1 + Signal2; % Here we sum the integer signals.

%%
% We can turn on warnings to tell us if the arithmetic saturates. In the
% case of |int8|, this will ocurr if the result of an operation is outside
% the range -128 to 127. We will turn these warnings on with the
% |intwarning| command and re-execute.

intwarning('on')
SumSig = Signal1 + Signal2; % Here we subtract the integer signals again.

%%
% However, performing this checking greatly slows down execution. It is
% best to turn it on during algorithm development and back off for final
% execution. Now let's plot the sum signal and see where it
% saturates. 

intwarning('off')

%%
cla;
plot(Time1, SumSig);
hold on;
Saturated = (SumSig == intmin('int8')) | (SumSig == intmax('int8')); % Find where it has saturated
plot(Time1(Saturated),SumSig(Saturated),'rd');grid;
hold off;

%%
% The markers show where ths signal has saturated. 

%% Load integer image data
% Next we will look at arithemtic on some image data.
street1=imread('street1.jpg'); % Load image data
street2=imread('street2.jpg');
whos street1 street2
%% 
% Here we see the images are 24-bit color, stored as three planes of |uint8| data.

%% Display images
% Display first image.
cla;
image(street1); % Display image
axis equal; axis off

%%
% Display second image
image(street2); % Display image
axis equal; axis off

%% Scale an image
% We can scale the image by a double precision constant but keep the image
% stored as integers. For example,

duller = 0.5 * street2; % Scale image with a double constant but create an integer
whos duller

%%
subplot(1,2,1);
image(street2); 
axis off equal tight
title('Original');  % Display image

subplot(1,2,2);
image(duller);
axis off equal tight
title('Duller');    % Display image


%% Add the images
% We can add the two street images together and plot the ghostly result.
combined = street1 + duller; % Add |uint8| images
subplot(1,1,1)
cla;
image(combined); % Display image
title('Combined');
axis equal; axis off