? Image Files

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Ch. 2 Image Files and MATLAB
? Image Files
Types of file formats BMP Microsoft
Bitmap Pattern GIF Graphics
Interchange Format JPEG Joint
Photo-graphics Experts Group TIFF
Tagged Image File Format PNG
Portable Network Graphics HDF
Hierarchical Data Format PCX PC
Paintbrush XWD X Window Dump
ICO ICOns CUR CURsor
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• BMP ( Microsoft Bitmap Pattern )
• without compression, need larger storage
• JPEG ( Joint Photographics Experts Group )
• lossy compression, need smaller storage

• GIF (Graphics Interchange Format )
• lossless compression
• PNG (Portable Network Graphics)

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Physically,

• An image file is a binary file, which can be
• shown in hexadecimal dump.

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An image file contains

• (a) Header Characteristics of image
• Image size, Color map, Compression
  method
• (b) Image data Pixel values, Index values

• BMP Format

Header
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Example
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How to read a BMP image?

• C/C programming
• Open CV

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C/C Program

• http//www.cs.ucsd.edu/classes/sp03/cse190-b/hw1/

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• Reading header information

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Open CV

• Download
• ftp//140.122.184.49876 ????? ????
• Setting
• http//iammic.pixnet.net/blog/post/34304039-visual
  
• studio-2010EFBC9Aopencv-2.3-
• E4BDBFE794A8-webcam

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// 0?????, 1?????
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Homework
1. Input a color image C(R,G,B) 2. Transform the
color image C into a grayscale image G by
G (RGB)/3 3. Show the input and output
images C and G.

• You may download the I/O program bmp_io.rar
• from
• http//www.cs.ucsd.edu/classes/sp03/cse190-b/hw1/

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GIF Format

• Header

Name Name Name Size Description
Signature Signature Signature 6 bytes GIF87a or GIF89a
Global Descriptor Global Descriptor Global Descriptor 7 bytes Global descriptor
Width Width 2 bytes Width in pixels
Height Height 2 bytes Height in pixels
Flags Flags Bit 7 Global descriptor flags
Global color map Bits 4-6
Color resolution bits Bit 3
Pixel bits Bit 2-0
Background color Background color 1 bytes 1color depth
Aspect Ratio Aspect Ratio 1 bytes
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• GIF Format

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Example
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• TIFF Format

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Steps of Compression

• JPEG Format

• (1) Splitting the image into blocks of
• 88 pixels
• (2) Applying DCT to each block
• (3) Storing the magnitudes of the low-
• frequency components

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Example http//en.wikipedia.org/wiki/JPEG
Shift values
Apply DCT
Quantization
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? MATLAB
1. Introduction ? MATLAB (a) A data
analysis and visualization tool (b)
Powerful for matrix operations,
graphics, and programming ? Toolbox a set of
programs designed to support a
particular task e.g., image-processing
toolbox
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• ? Function accepts parameters and
• produces output matrix,
• string, graph, or figure
• e.g., sin, imread, imclose
• ? Command
• e.g.,
• gtgt sin(pi/3)
• gtgt c imread(cameraman.tif)
• gtgt a imclose(b)
• Not display the result on the
  screen

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• Multiple commands can be put on a single line,
  which are separated by commas
• All data are considered to be matrices
• e.g.
• single value -- 11 matrix
• string -- 1n matrix of characters

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? Command window
2. Use of MATLAB
? prompt gtgt
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? Addition, subtraction, multiplication,
division, exponentiation
e.g., gtgt 22
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? Default format Internal double
precision Display 8 decimal places

• format

Entering format returns to the default
format
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sqrt, log, log10
pi built-in constant
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3. Variables and Workspace

• Variable for storing value

a and b are displayed in the short format
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Internally, MATLAB stores their full values
Further calculations
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3.1. Workspace

• -- contains all variables, their data types and
  sizes
• To open (1) use View menu, choose Workspace
• (2) use whos function

• Function who lists variables only

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4. Matrices

• Enter a matrix
• e.g.,

gtgt a4 -2 -4 7 1 5 -3 2 6 -8 -5 -6 -7 3
0 1
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4.1. Matrix Elements
m(i,j) corresponds to m(ir(j-1))
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Extract multiple values from a matrix

• gtgt 27 ans 2 3 4
  5 6 7

gtgt 2316 ans 2 5 8 11
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• gtgt a(2,13)
• ans
• 1 5 -3
• gtgt a(24,3)
• ans
• -3
• -5
• 0

gtgt a(23,34) ans -3 2
-5 -6 gtgt a(3,) ans 6
-8 -5 -6 gtgt a(,2) gtgt a()
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• 4.2. Matrix Operations
• -- add, subtract, multiply, invert power

gtgt b2 4 -7 -4 5 6 3 -2 1 -8 -5 -3 0 -6 7
-1 b 2 4 -7 -4 5 6
3 -2 1 -8 -5 -3 0 -
6 7 -1
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• ? Geometric operations

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? Dot operators

• Dot multiplication c(i,j) a(i,j) b(i,j)

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• Dot division

• gtgt a./b
• Warning Divide by zero.
• ans
• 2.0000 -0.5000 0.5714 -1.7500
• 0.2000 0.8333 -1.0000 -1.0000
• 6.0000 1.0000 1.0000 2.0000
• -Inf -0.5000 0 -1.0000

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• Dot power

• Dot reciprocal

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4.3. Constructing Matrices -- zeros, ones,
rand, randn, floor

• Zero matrices

gtgt zeros(5) ans 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
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• gtgt zeros(3,5)
• ans
• 0 0 0 0 0
• 0 0 0 0 0
• 0 0 0 0 0

zeros(m,n,o,p,) zero(a)
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• Random integer matrices

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A(i,j) ij-1
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4.4. Vectorization
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MATHLAB ??
1
2
3
4
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• 1 Current Directory
• -??????????
• 2 Workspace
• -?????????,?????????
• 3 Command Window
• -??????????
• 4 Command History
• -?????Command Window??????

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????

• Enter?????????
• ??()
• 1.????????,???????? ???
• ?,??????????
• 2.????????,??????(row)???
• ??A1,2,34,5,6
• ? ? ? ?(?-??)????????

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• ??()
• 1. ????
• ?? ?????? ? ????
• ?? A1210
• A1 3 5 7 9 10
• 2. for-loop iteration
• ?? for i110
• ???
• end

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• ????
• sin( ?? ) cos( ?? ) tan( ?? )
• csc( ?? ) sec( ?? ) cot( ?? )
• pi3.1416
• ????
• ??? plot ( x , y )
• ??? bar ( x , width )
• ?????? figure( number )
• ??title ( ?? ) -??figure ??

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• ????
• 1. ?????????(element)??0
• ?? A zeros( m , n , )
• ??m-by-n ???
• 2. ?????????(element)??1
• ?? A ones( m , n , )
• ??m-by-n ???
• ????
• 1. ???doubleAdouble(A) -???
• 2. ???uint8 Auint8(A) -?????

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????

• ??????(Matrix operation)
• 1.????() AB
• 2.????(-)A-B
• 3.????() AB
• 4.????() Ac (c is a constant)
• ???????(Array operation)
• 1. Array multiply(.) A.B
• ??A????????B???,??????
• 2. Array power(.) A.c
• ??A???????????

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• ??????(Matrix transpose)
• Binv(A)
• ?????(Matrix inverse)
• BA

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Example
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?????

• ???
• ??? ( for matlab )

A 4,52,1 b 102 x A\b
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??????

• ???? imread( )
• IMimread(c\example\pic1.bmp')
• ???? imread( '????' )
• ???? imwrite( )
• imwrite(TM , 'c\example\OM1.bmp' , 'bmp'
  )
• imwrite(????, '??' , '??')
• ???? imshow( )
• imshow(TM)
• imshow(????)

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• ????? rgb2gray()
• TMrgb2gray(IM)
• ???? rgb2gray ( RGB?? )
• mat2gray()??????gray scale 0-1
• mat2gray(IM)
• mat2gray(????)
• ?????? size()
• height width size ( IM )
• ??????imfinfo()
• info imfinfo ( '????' )

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• RGB to HSI?RGB????????HSI
• TM rgb2hsv ( IM )
• h s v rgb2hsv ( IM )
• HSI to RGB?HSI????????RGB
• TM2 hsv2rgb(TM)
• r g b hsv2rgb(TM)
• RGB to YCbCr?RGB????????YCbCr
• TM hsv2rgb(IM)
• YCbCr to RGB?YCbCr???RGB
• TM2 hsv2rgb(TM)

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• ?????
• OM imfilter (IM, Mask, option1, option2 )
• OM???????
• IM???????
• Mask??????mask(window)
• option???????????????
• ??Mask
• 1. ?????????,???????weight
• 2. Mask fspecial ( '??' , ?? )

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• Mask???

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• Order-statistic filter
• OM ordfilt2 ( TM, order, domain)
• domain??mask???
• order????n
• ?? 33 Median filter
• OM ordfilt2 (TM, 5, ones(3,3) )

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• Histogram of an image
• imhist (IM, bin)
• IM???????(gray-scale)
• bin???(???256)
• Histogram equalization
• OM histeq ( IM)
• OMhistogram equaliztion???
• IM???????

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• Edge detection
• OM edge ( TM, 'detector' , threshold , )
• detector????edge???
• threshold??edge??????
• edge????gray-scale???

detector
'prewitt'
'roberts'
'sobel'
'log'
'zerocross'
'canny'
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• Dilation
• OM imdilate ( TM, SE)
• SE?????structuring element (mask)
• Erosion
• OM imerode ( TM, SE)
• Closing
• OM imclose ( TM, SE)
• Opening
• OM imopen ( TM, SE)

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• Structuring element
• SE strel ( shape , ?? )
• shape??structuring element???