Image Processing - Code to filter color in MATLAB

In this post we will learn to how filter color in Matlab. Matlab provide very good Image processing tool box with many ready made functions. Here I have illustrated a very basic method to filter color in Matlab. The concept is- in the 3D matrix of RGB color space, if the value at a particular pixel have more value in Red space than blue or Green, and if it is within a tolerance value then consider that pixel Red.
eg -


  elseif im(i,j,1)>200 & im(i,j,2)<50 & im(i,j,3)<50
            white(i,j)=0;
            green(i,j)=0;
            blue(i,j)=0;
            red(i,j)=1;


Copy this code an save as .m file. then run this file.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% ------------------------@author:-  RITESH RANJAN

% -------- visit:-  http://programing-tutorial.blogspot.com/

% ------I have used a simple method. There are many more complex

%--------------- methods too that I will discuss Later

% ------------Just copy it save a .m file run in MATLAB 7 or higher
% ----------------Don't forget to change the name of Image file

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clear;
im=imread('image.jpg'); %put image name here
imtool(im);
sz=size(im);

for i=1:sz(1)
    for j=1:sz(2)
        if im(i,j,1)>200 & im(i,j,2)>200 & im(i,j,3)>200
            white(i,j)=1;
            green(i,j)=0;
            blue(i,j)=0;
            red(i,j)=0;
        elseif im(i,j,1)>200 & im(i,j,2)<50 & im(i,j,3)<50
            white(i,j)=0;
            green(i,j)=0;
            blue(i,j)=0;
            red(i,j)=1;
        elseif im(i,j,1)<50 & im(i,j,2)>200 & im(i,j,3)<50
            white(i,j)=0;
            green(i,j)=1;
            blue(i,j)=0;
            red(i,j)=0;
        elseif im(i,j,1)<50 & im(i,j,2)<50 & im(i,j,3)>200
            white(i,j)=0;
            green(i,j)=0;
            blue(i,j)=1;
            red(i,j)=0;
        else 
            white(i,j)=0;
            green(i,j)=0;
            blue(i,j)=0;
            red(i,j)=0;
       end
             end
end


imtool(white);
imtool(green);
imtool(blue);
imtool(red);

How to access parallel port in MATLAB

Have you ever wondered how you can use and access parallel port using Matlab. This post give a very easy and basic method of accessing and using Parallel port using Matlab. But first of all lets learn a bit about Parallel port.

Parallel port configuration

A typical Parallel port

This is a typical type of port you usually find in the back of your PC. Other external port such as USB or serial port requires more complex sending and data receiving algorithms. But by using 8 data pins in parallel port you can easily send a byte of data. That's why  Parallel Port is the most commonly used port for interfacing home made projects. Here is a good tutorial about parallel port configurations.

Now lets learn to access Parallel port using Matlab for your project.

You can easily access parallel port in Matlab

paraport=digitalio('parallel','LPT1');

by this u create a digital i/o object


line1=addline(paraport,0:3,'out');

this tells matlab to use first 4 data pins as output pin


pval=[0 0 0 1];

putvalue(paraport,pval);
this sends 1 value 2 pinno- 2.