1. Digital Image Processing using MATLAB
Introduction

2. What is Digital Image processing
Digital image processing refers to processing digital images by means of a digital computer .
It encompasses a wide and varied field of applications, which are computer vision, image analysis.
Three types of computerized processes – Low, mid, and high level.
It is used in exceptional social and economic value.

3. Background on MATLAB and Image Processing toolbox
MATLAB stands Matrix Laboratory.
Typical uses include the following
Math and computation
Algorithm development
Data acquisition
Modeling, simulation, and prototyping
Data analysis, exploration, and visualization
Scientific and engineering graphics
Application development, including building graphical user interfaces .
collection of MATLAB functions

4. The MATLAP Desktop

5. Digital Image Representation
Digital image is a representation of 2D image using binary value.
Digitizing the coordinates values is called sampling; Digitizing amplitude values is called quantization.
Coordinate conventions
Digital Image Processing using MATLAB

6. Images as Matrices

7. Reading images The syntax of reading image in MATLAB is
imread(‘file name’)
The function size gives the row & column dimensions of image
size(filename)
The whos function displays additional information about an array
whos file name

8. Writing images The syntax of writing image imwrite(f, ‘filename’)
Example
imwrite(f, ‘garden’, ‘tiff’)
imwrite(f, ‘garden.tif’)
The image file details of syntax
imfinfo filename

9. Classes in MATLAB Data types in MATLAB
Double (64-bit double-precision floating point)
Single (32-bit single-precision floating point)
Int32 (32-bit signed integer)
Int16 (16-bit signed integer)
Int8 (8-bit signed integer)
Uint32 (32-bit unsigned integer)
Uint16 (16-bit unsigned integer)
Uint8 (8-bit unsigned integer)
char (2 bytes per element).
Logical Values are 0 or 1 (1 byte per element).
Digital Image Processing using MATLAB

10. Image types The toolbox supports four types of images:
Intensity images : [0,1] or uint8, double etc.
Binary images : {0,1}
Indexed images : m-by-3 color map
RGB images : m-by-n-by-3

11. Image Types – Intensity Image
MATLAB stores an intensity image as a single matrix, with each element of the matrix corresponding to one image pixel.
The matrix can be of class double, in which case it contains values in the range [0,1], or of class uint8, in which case the data range is [0,255] (0 – black, 255 – white).

12. Image Types – Binary Images
In a binary image, each pixel assumes one of only two discrete values.
Essentially, these two values correspond to on and off.
A binary image is stored as a two-dimensional matrix of 0’s (off pixels) and 1’s (on pixels).
Example

13. Image Types - Indexed Images
The colormap is an m-by-3 matrix of class double. Each row of the colormap matrix specifies the red, green, and blue (RGB) values for a single color:
color = [R G B]
Example

14. Image Types – RGB Images
Like an indexed image, an RGB image represents each pixel color as a set of three values, representing the red, green, and blue intensities that make up the color.
Unlike an indexed image, however, these intensity values are stored directly in the image array, not indirectly in a colormap
Example
Digital Image Processing using MATLAB

15. Converting between Classes
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

16. Array Indexing
MATLAB supports a number of powerful indexing schemes that simplify array manipulation and improve the efficiency of programs
Two type of indexing –vectors and matrices
Indexing vectors
>> v=[ ]
Indexing matrices
>> m=[1 2 3;4 5 6;7 8 9]

17. Some Important Standard Arrays
Zeros(M, N) generates an M * N matrix of 0s of class double.
Ones(M, N) generates an M * N matrix of 1s of class double.
True(M, N) generates an M * N logical matrix of 1s.
False(M, N) generates an M * N logical matrix of 0s.
Magic(M) generates an M * M “magic square.” This is a square array in which the sum along any row, column, or main diagonal, is the same. Magic squares are useful arrays for testing purposes because they are easy to generate and their numbers are integers.
Eye(M) generates an M * M identity matrix.
Rand(M, N) generates an M * N matrix whose entries are uniformly distributed random numbers in the interval [0, 1].
Randn(M, N) generates an M * N matrix whose numbers are normally distributed (i.e., Gaussian) random numbers with mean 0 and variance 1.

18. Introduction to M-Function Programming
The components of a function M-file are
The function definition line
function [outputs] = name(inputs)
The H1 line
Help text
The function body
Comments

19. 0perators MATLAB operators are grouped into three main categories:
• Arithmetic operators that perform numeric computations
• Relational operators that compare operands quantitatively
• Logical operators that perform the functions AND, OR, and NOT

20. Arithmetic operators Operator Name Comments and Examples
+ Array and matrix addition a + b, A + B, or a + A.
− Array and matrix subtraction a − b, A − B, A − a, or a − A.
.* Array multiplication v= A.*B, C(I, J) = A(I, J)*B(I, J).
* Matrix multiplication A*B, standard matrix multiplication, or a*A, multiplication of a scalar times all elements of A.
./ Array right division C = A./B, C(I, J) = A(I, J)/B(I, J).
.\ Array left division C = A.\B, C(I, J) = B(I, J)/A(I, J).
/ Matrix right division A/B is the preferred way to compute A*inv(B).
\ Matrix left division A\B is the preferred way to compute inv(A)*B.
.^ Array power If C = A.^B, then C(I, J) = A(I, J)^B(I, J).
^ Matrix power See help for a discussion of this operator.
.' Vector and matrix transpose A.', standard vector and matrix transpose.
' Vector and matrix complex conjugate transpose A', standard vector and matrix conjugate transpose. When A is real A.' = A'.
+ Unary plus +A is the same as 0 + A.
− Unary minus −A is the same as 0 − A or −1*A.
: Colon

21. Logical Function

22. Logical Function(cont)

23. Flow Control

24. Interactive I/O
It used for display information and instructions to users and accept inputs from the keyboard.
Display syntax is
disp(argument)
Inputs syntax is
t=input(‘message’)