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1.1. Motivation1.2. Why is Computer Vision Difficult?1.3. Image Representation and Image Analysis1.4. Summary

Chapter 1 - Introduction

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1.1. Motivation

An image is worth thousands of words

Objectives of image processing: 1. Human perception 2. Machine interpretation

Two principal rolesof images: 1.Communication 2. Scene understanding

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Human Perception Before After

After

Before

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Before

After

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Before

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After

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For you, ...not much can be done!

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Machine Interpretation

AZ10• Optical Character Recognition (OCR)

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10

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• License Number IdentificationLocation

Recognition

GG4025

Input image

• Form Analysis• Documentation

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• Model-based Object Recognition

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Object Models

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Model Matching

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(ii) What are their spatial

relationships?

(i) How many people, adults, and children

are there in the picture?

(v) What are they doing?

(iii) Who are they?

(iv) Where are they?

• Image Understanding

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Machine interpretation of images requires diverse methods of

Mathematical Engineering Biological disciplines Psycho-physiological Intelligent Scientific

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Low-level processing: e.g., noise removal, deblurring, and contrast enhancement

Mid-level processing: e.g., edge, region, corner, and texture detections

High-level processing: e.g., object, function, relationship, event, and activity recognitions

Image Analysis

=====

CV

I P

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1.2. Why is Computer Vision Difficult?

(1) Loss of information in 3D 2D

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(2) Local window vs. global view

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(3) Sequential vs. parallel processing

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Sequential processing

(5) Noise(4) Too much data

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Image F(x,y): a 2-D continuous function

1.3. Image Representation

Origin

Scene G(x,y,z): a 3-D continuous function

Discrete image D(r,c): a 2-D discrete function

N

M

○

M × N : Image size

Digital image I(r,c): an array of discrete values

Dynamic range (or color depth) :

number of bits for a single pixel

(a) 1 - bit: black and white (binary image)

(b) 8 - bit: gray-scale (gray scale image)

(c) 24 - bit: true color (color image)

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An image file is a binary file, which can be dump.

• Physically,

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• Types of file formats:

BMP : Microsoft Bitmap formal JPEG : Joint Photographics Experts Group PNG : Portable Network Graphics TIFF : Tagged Image File Format GIF : Graphics Interchange Format HDF : Hierarchical Data Format PCX : PC Paintbrush XWD : X Window Dump ICO : ICOns CUR : CURsor

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(a) Header: Characteristics of image

Image size

Color map

Compression method

(b) Image data: Pixel values,

Index values

An image file contains

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Example: BMP header

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Example:

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C/C++ Programhttp://www.cs.ucsd.edu/classes/sp03/cse190-b/hw1/

Read header information

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Read image data

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• GIF header

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Example:

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• TIFF header

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Summary • Two major roles of images played: (i) Communication, (ii) scene understanding• Two main objectives of IP: (i) Human perception, (ii) machine interpretation• Three levels of IP: Low-, mid-, and high- levels

(1) Loss of information in 3D 2D

(2) Noise

(3) Too much data

(4) Local window vs. global view

(5) Sequential vs. parallel processing

• Difficulties of computer vision:

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Summary • Two main objectives of IP: Human perception, Machine interpretation

• Machine interpretation

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• Three levels of IP: Low-, mid-, and high- levels

(1) Loss of information in 3D 2D

(2) Noise

(3) Too much data

(4) Local window vs. global view

(5) Sequential vs. parallel processing

• Dynamic range (or color depth) : # bits per pixel

• Difficulties of computer vision:

OpenCV && Matlab

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Opencv 安裝

• 通常使用 Visual studio C++ 搭配 openCV

• 也可以使用 Dev C++搭配(http://yester-place.blogspot.tw/2008/06/

dev-copencv.html)

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Visual C++ 2010 Express• Visual express 下載

http://www.visualstudio.com/downloads/download-visual-studio-vs

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OpenCV 安裝• http://opencv.org/downloads.html

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安裝 OpenCV

• 這邊以 OpenCV 246為例• 將 opencv解壓縮至 C 槽 (C:\OpenCV246)

• 設定環境變數 (我的電腦右鍵 >內容 >進階系統設定 >環境變數

• 在環境變數 PATH加上• C:\OpenCV246\build;

• C:\OpenCV246\build\x86\vc10\bin;

切記!!!設定完環境變數要重新開機才會生效!!!

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設定 Visual C++

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• 對專案點右鍵 >屬性• VC++目錄 > Include目錄加上

– C:\OpenCV246\build\include– C:\OpenCV246\build\include\opencv

• 程式庫目錄加上– C:\OpenCV246\build\x86\vc10\lib

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• 連結器 >輸入 >其他相依性 >– opencv_core246d.lib

– opencv_calib3d246d.lib

– opencv_contrib246d.lib

– opencv_features2d246d.lib

– opencv_highgui246d.lib

– opencv_imgproc246d.lib

– opencv_ml246d.lib

– opencv_objdetect246d.lib

– opencv_video246d.lib

– opencv_videostab246d.lib

– opencv_nonfree246d.lib

– opencv_flann246d.lib

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OpenCV 範例 -讀取圖片 (Mat)

Include 函式庫

imread(檔案名稱 ,讀取參數 )參數” 1”為彩色影像

imshow(視窗名稱 ,變數名稱 )

imwrite(檔案名稱 ,變數名稱 )

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OpenCV 範例 -讀取圖片 (Iplimage)

cvLoadImage(檔案名稱 ,參數 )

cvNamedWindow(視窗名稱 ,參數 )參數 1為視窗自動縮放大小

cvShowImage(視窗名稱 ,變數名稱 )

cvSaveImage(檔案名稱 ,變數名稱 )

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OpenCV函式• 讀取圖片

– Imread()

– cvLoadImage()

• 輸出圖片– Imwrite()

– cvSaveImage()

• 讀取影片– VideoCapture

• 改變圖片大小– cvResize()

• 其餘的可以上 OpenCV官網查詢– http://docs.opencv.org/modules/refman.html

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Matlab 軟體安裝師大校園軟體服務 (http://www.itc.ntnu.edu.tw/sw/index.html)

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Matlab 安裝• 解開壓縮檔後，內有一份安裝說明文件，照著文件步驟安裝即可

• 記得啟動時必須要用校內 IP

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Matlab 讀圖範例• 讀取圖片• >> A = imread('C:\lena.bmp');

• 顯示圖片• >> imshow(A);

• 輸出圖片• >> imwrite(A,'C:\test.bmp');

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Matlab 好處• 方便監控變數狀態• 畫圖時很方便

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