A Brief Introduction to MATLAB Digital Image Processing 2014 Fall NTU

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

MATLAB NTU AppShare ( 臺大雲端軟體運算銀行 ) – Windows & IE

MATLAB interface

basic operation

variables English alphabet, number, underline – first word must be English alphabet – variable length <= 32 characters variables need not be previously declared (default double) comments – %

operators arithmetic operators – +, -, *, /, ^ relational operators – ==, ~=, >, >=, <, <= logical operators – &, |, ~ bitwise operators – bitand, bitor, bitxor

flow control conditional control – if-else – switch loop control – for – while – continue

script or type “edit filename.m” to create a script from command window Click to create a new script

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

matrix creation row vector – R = [ ]; – R = [7, 8, 9, 10]; column vector – C = [7; 8; 9; 10]; build vector fast – start:step:end – linspace(start, end, num);

extract sub-matrix A = [ ; ; ]; B = A(1, 2:4); C = A(2:3, 2:3); D = A([1 3], [1 2 3]);

Matrix operations add Scalar

Matrix operation(Cont’d) matrix multiplication array multiplication

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

2-D plotting

subplot Example 2 ： create figure with multiple graphs

Axis control Axis control example ：

histogram hist(data) ： histogram plot – data = randn(1000, 3); – hist(data, 20);

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

3-D plotting Example 1 ： mesh graph

3-D plotting (Cont’d) Example 2 ： surface graph

3-D plotting (Cont’d) Example 3 ： 3-d curve

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

overview Basic commands ： – img = imread(‘lena.jpg’, ‘jpg’); – imwrite(img, ‘my_lena.jpg’, ‘jpg’); – imfinfo(‘lena.jpg’) – image(img);

Image load and display

image scale imresize(img, scale) – resize image

image rotation I2 = imrotate(I, 60, ‘nearest’); I3 = imrotate(I, 60, ‘bilinear’); Nearest interpolationBilinear interpolation Original image

filter h1 = fspecial(‘laplacian’); f1 = filter2(h1, double(f)/255); h2 = fspecial(‘sobel’); f2 = filter2(h2, double(f)/255); laplacian filtersobel filter original image

edge detection f3 = egde(f, ‘sobel’); f4 = edge(f, ‘canny’); edge detection by sobel method edge detection by canny method original image

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

more about MATLAB more on, more off ： control paged output for command window help function_name ： help for functions in command window lookfor keyword ： search for keyword in all help entries

Outline MATLAB overview Matrix 2-D plotting 3-D plotting Image Processing more about MATLAB Reference

reference Mathworks document Mathworks forum Tutorial from Jyh-Shing Roger Jang