image processing using matlab

Workshop on “Image processing using MATLAB”

Presented byAmarjeetsingh ThakurAsst. ProfessorDept. of Electronics & Communication

Engg. S.G.B.I.T. Belgaum

Outline What is MATLAB? Image Processing tool box Image formats How to read an image? Image conversion Arithmetic operations on images Conversion of an image into different formats Image rotation Image blurring and deblurring Fill in ROI in grayscale image References

What is MATLAB?• MATLAB = MATrix LABoratory

• “MATLAB is a high-level language and interactive environment that enables us to perform computationally intensive tasks faster than with traditional programming languages such as C, C++ and Fortran.”

• MATLAB is an interactive, interpreted language that is designed for fast numerical matrix calculations.

Who uses MATLAB?

Key Industries

Aerospace and defense Automotive Biotech and pharmaceutical Communications Computers Education Electronics and semiconductors Energy production Industrial automation and machinery Medical devices

The MATLAB Environment MATLAB window

components:Workspace

> Displays all the defined variables

Command Window > To execute

commands in the MATLAB environment

Command History> Displays record of

the commands usedFile Editor Window

> Define functions

MATLAB Help• MATLAB Help is an

extremely powerful assistance to learning MATLAB

• Help not only contains the theoretical background, but also shows demos for implementation

• MATLAB Help can be opened by using the HELP pull-down menu

MATLAB Help (cont.)• Any command

description can be found by typing the command in the search field

• As shown above, the command to take square root (sqrt) is searched

• We can also utilize MATLAB Help from the command window as shown

What is the Image Processing Toolbox?

• The Image Processing Toolbox is a collection of functions that extend the capabilities of the MATLAB’s numeric computing environment. The toolbox supports a wide range of image processing operations, including:– Geometric operations– Linear filtering and filter design– Transforms– Image analysis and enhancement– Binary image operations– Region of interest operations

Images in MATLAB• MATLAB can

import/export several image formats:– BMP (Microsoft

Windows Bitmap)– GIF (Graphics

Interchange Files)– HDF (Hierarchical Data

Format)– JPEG (Joint

Photographic Experts Group)

– PCX (Paintbrush)– PNG (Portable Network

Graphics)– TIFF (Tagged Image

File Format)– XWD (X Window

Dump)– raw-data and other

types of image data

• Data types in MATLAB– Double (64-bit double-

precision floating point)

– Single (32-bit single-precision floating point)

– Int32 (32-bit signed integer)



– Uint32 (32-bit unsigned integer)



Images in MATLAB• Binary images : {0,1}• Intensity images : [0,1] or uint8, double etc. • RGB images : m × n × 3• Multidimensional images: m × n × p (p is the number of layers)

Binary ImagesThey are also called “ Black & White ”

images , containing ‘1’ for white and ‘0’(zero) for black

MATLAB code

Intensity ImagesThey are also called ‘ Gray Scale images ’ ,

containging numbers in the range of 0 to 255

Indexed ImagesThese are the color images and also

represented as ‘RGB image’. In RGB Images there exist three indexed

images.First image contains all the red portion of the

image, second green and third contains the blue portion.

How to read an image??I=imread(‘steve.jpg’)figureImshow(I)size(I) % 295 171 3

Images and Matrices

Column 1 to 256

Row 1 to 256

o

[0, 0]

o

[256, 256]

How to build a matrix

(or image)?Intensity Image:

row = 256;col = 256;img = zeros(row, col);img(100:105, :) = 0.5;img(:, 100:105) = 1;figure;imshow(img);

Image Conversion• gray2ind - intensity image to index image• im2bw - image to binary• im2double - image to double precision• im2uint8 - image to 8-bit unsigned

integers• im2uint16 - image to 16-bit unsigned

integers• ind2gray - indexed image to intensity

image• mat2gray - matrix to intensity image• rgb2gray - RGB image to grayscale• rgb2ind - RGB image to indexed image

Arithmetic operations on images1. Imadd Syntax : Z = imadd(X,Y) Description: Z = imadd(X,Y) adds

each element in array X with the corresponding element in array Y and returns the sum in the corresponding element of the output array Z.

Figure window shows addition of two different images

Contd..2. imsubtractSyntax : Z = imsubtract(X,Y)Description: Z = imsubtract(X,Y) subtracts

each element in array Y from the corresponding element in array X and returns the difference in the corresponding element of the output array Z

Figure window shows Subtraction of two different images

Contd..3. immultiplySyntax : Z = immultiply(X,Y)Description: Z = immultiply(X,Y)

multiplies each element in array X by the corresponding element in array Y and returns the product in the corresponding element of the output array Z.

Figure window shows Multiplication of two different images

Contd..4. imdivideSyntax : Z = immultiply(X,Y)Description: Z = imdivide(X,Y) divides

each element in the array X by the corresponding element in array Y and returns the result in the corresponding element of the output array Z.

Figure window shows Division of two different images

Converting RGB image to gray formatI=imread(‘Sachin.jpg'); % Read

an imageI=rgb2gray(I); % RGB to gray

conversionfigure % Figure windowimshow(I) % Display figure

on figure window

Figure window displaying Gray image

RGB to BW image conversion commandsi=imread('Sachin.jpg');I=im2bw(I);imshow(I)

Figure window shows BW image

Image rotation by some angleI=imread('steve.jpg');J=imrotate(I,45); % Rotate

image anticlockwise by an angle 45

K=imrotate(I,-45); % Rotate image clockwise by

an angle 45 imshow(J)Imshow(K)

Deblurring operation on an blurred image using wiener filterI=imread(‘Sachin.jpg');figureimshow(I)

Commands for blurring the imagePSF=fspecial('motion');Blurred=imfilter(I,PSF,'circula

r','conv');figure, imshow(Blurred)

Blurred image

Commands for deblurring the imagewnr1=deconvwnr(Blurred,PS

F); figure, imshow(wnr1);title('Restored image');

Recovered image

Fill in specified region of interest (ROI) polygon in grayscale image

I = imread('eight.tif');J = roifill(I);figure, imshow(J)

ROI fillI=imread('C:\Documents and

Settings\All Users.WINDOWS\Documents\My Pictures\Sample Pictures\avataar.jpg');

figureimshow(I)J=rgb2gray(I);figureimshow(J)

ROI fill (contd..)K = roifill(J);figureimshow(K)

ROI fill (contd..)

Applications of image processingBIOLOGICAL: automated systems for analysis of

samples.DEFENSE/INTELLIGENCE: enhancement and

interpretation of images to find and track targets.DOCUMENT PROCESSING: scanning, archiving,

transmission.FACTORY AUTOMATION: visual inspection of products.• MATERIALS TESTING: detection and quantification of

cracks, impurities, etc. MEDICAL: disease detection and monitoring,

therapy/surgery planning

ANY QUERRIES????????

Referenceswww.mathworks.com “Digital Image Processing using

MATLAB” by Rafael C. Gonzalez, Richard E. Woods, Steven L. Eddins.

http://www.mathworks.com/

THANK YOU