BASICS

Q: WHAT IS IMAGE PROCESSING???

Accessing the data stored in an image and working with it is called Image Processing.

Q: WHAT IS AN IMAGE???

It’s a 2 dimensional array of pixels with each pixel having an unsigned value between 0 and 255.

SOME BASIC TERMINOLOGY USED IN Image Processing

Resolution: The resolution of an image defines how many pixels are there in the image, for example: if an image has the resolution of [ 800 X 600 ] it means that the image is a two dimensional array of size[800][600] that is 800 pixel in the horizontal direction for each of the 600 pixel in the vertical direction.

Pixel: Units which make up the image are called pixels. These contain some value depicting the shade of the particular cell.

Channel: It is the number of divisions in a particular pixel.

Eg: In a single channel image, the pixel has one value between 0 and 255. Eg: Grayscale

Image.

In a 3 channel image, each pixel will have 3 values between 0 and 255. The shade of that pixel will be the shade resulting from the combination of these 3 values. Eg: BGR image(Which is any coloured image we see) or and HSV Image.

Noise: Unwanted Part In an Image.

Binary Image: An Image which has only 2 shades (generally black and white).

Grayscale Image Binary Image

Threshold: Threshold in image processing is the value of a particular channel set by the programmer which is the border line between the wanted and the unwanted pixels. The image below shows an image thresholded into a binary image.

Histogram : A Graphical representation of the value of pixels versus the frequency of each pixel.

Q: HOW TO WORK WITH ALL THESE???

A Library called openCV contains Functions which helps us in accessing the image elements and working with them.

How to Start Working

Install Microsoft Visual Studio.

Install OpenCV .

Integrate OpenCV with Microsoft Visual Studio. (Procedure for linking given on our website : http://www.robotix.in/tutorials/ip ).

SAMPLE CODELOADING AN IMAGE STORED IN YOUR COMPUTER

#include "stdafx.h"#include <stdio.h>#include <cv.h>#include<iostream>#include"conio.h"#include <cxcore.h>#include <highgui.h>#include <stdlib.h>#include <windows.h>

int main( int argc, char **argv){cvNamedWindow("bgr image", CV_WINDOW_AUTOSIZE);//creating a window

for the image.cvMoveWindow("bgr image", 100, 100); //move it to 100, 100 position.

IplImage *frame=0;

frame = cvLoadImage("1.jpg");if( !frame ){printf("frame not captured properly");return 1;}

cvShowImage("bgr image", frame); // display the image

cvWaitKey(0);

cvReleaseImage(&frame);

return 0;}

LOADING AN IMAGE AND CONVERTING IT INTO A GRAYSCALE IMAGE.

int main( int argc, char **argv){cvNamedWindow("bgr image", CV_WINDOW_AUTOSIZE);//creating a window for the image.cvMoveWindow("bgr image", 100, 100); //move it to 100, 100 position.cvNamedWindow("grayscale img", CV_WINDOW_AUTOSIZE);//creating a window for the image.cvMoveWindow("grayscale img", 100, 100); //move it to 100, 100 position.

IplImage *frame=0;IplImage *grayscale=0;

frame = cvLoadImage("1.jpg");if( !frame ){printf("frame not captured properly");return 1;}

cvShowImage("bgr image", frame); // display the image

/* creating a single channel image of the same size as the original image*/grayscale = cvCreateImage( cvSize(frame->width, frame->height),

IPL_DEPTH_8U, 1 );

cvCvtColor(frame,grayscale,CV_RGB2GRAY);//for converting image into a grayscale image.

cvShowImage("grayscale img", grayscale); // display the imagecvWaitKey(0);cvReleaseImage(&frame);return 0;}

SOME USEFUL COMMANDSACCESSING THE VALUE OF PIXELS:

for(i=0;i<height;i++)//height is the image height{for(j=0;j<width;j++)//width is the image width{

k=image->imageData[i*height+j*nChannels]=0; printf(“The value of pixel [%d][%d] is %d”,I,j,k);}}The above commands prints the values of all the pixels in the

image oneby one

CLONING AN IMAGE

IplImage *img1=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1);

IplImage* img2;

img2=cvCloneImage(img1);// img2 is clone of img1

DO IT YOURSELF

Take a grayscale image and make its

histogram and display.

Sample Running Programs

• Histogram.

• Color Detection and Ball Following.

• Movement Detection.

ROBOTIX ’12 Image Processing EventNUKE-CLEAR

Problem Statement:

Build an autonomous image processing robot which can traverse around rooms, locate and disarm bombs.

HOW TO APPROACH THE PROBLEM STATEMENT?

ResourcesCodes can be found here.Image Processing Tutorial can be found hereNuke-Clear tutorial can be found here.

Hope You Enjoyed Learning Image Processing