影像處理應用之簡介
● 陳中亮
● 2017/12/12
簡介
What is Digital image processing ?
Digital image processing(數位影像處理) is the use of
computeralgorithmsto performimage processingondigital images.
As a subcategory or field ofdigital signal processing, digital image processing has many advantages overanalog image processing. It allows a much wider range of algorithms to be applied to the input data and can avoid problems such as the build-up of noise and signal distortion during processing. Since images are defined over two dimensions (perhaps more) digital image processing may be modeled in the form ofmultidimensional systems.
-- https://en.wikipedia.org/wiki/Digital_image_processing
Examples (Lena)
平滑化
影像幾何變換 伸縮、旋轉
影像幾何變換 伸縮、旋轉
Examples
Dilation(膨脹) ↔ Erosion(侵蝕)
Examples
邊緣偵測
其他(模糊、邊緣偵測…)
Examples
Hough line transform 霍夫線變換
透視變換(Perspective Transformation)
Examples
人臉偵測
Basic Concepts
影像即矩陣 0~255, 0 or 1
Basic Concepts
A colour image has 3 2-d matrices for R, G , B
Basic concepts
Example (0黑 ~ 255白)
Basic operations
Reading and displaying images
Writing images
Core module
個別像素
對比、亮度調整
g(x) = a f(x) + b
a = Contrast parameter b = Brightness parameter
Core module
Contrast and Brightness example
a =2.2 b=50
Core module
Drawing functions
Lines Circles Ellipses Polygon
Image Processing
平滑化(Smoothing) – Removes noise filters : Gaussian, Median, Bilateral,...
- medianBlur - GaussianBlur - bilateralFilter
Image Processing
Smoothing
Image Processing
Erosion and Dilation 用於減弱或突顯特徵
Erode + Dilate = Removal of stray marks
Erosion
Dilation
Image Processing
直方圖
Image Processing
直方圖均勻化 – 改進對比
Image Processing
邊緣偵測
Image Processing
Sobel Edge Detector
Image Processing
Laplace Edge Detector
Image Processing
Canny Edge Detector
Best edge detector available
Uses more advanced intensity gradient based methods
特徵偵測(Feature Detection)
The following 3 are considered to be keypoints in an image
1) Edges 邊緣
2) Corner 角點(also known as interest points) 3) Blobs (also known as regions of interest )
Once the features have been found, these features are
「described」.
Feature Detection
Feature Extraction: SURF, SIFT, BRIEF
Feature Descriptors: SURF, SIFT, BRIEF, STAR Matchers: FLANN, BruteForce
Template Matching
(圖樣比對,樣板比對,模板匹配)
Foreground Extraction(前景提取)
Corner Detection(角點偵測, 角點檢測)
Feature Match 特徵匹配
How we teach computers to understand pictures
李飛飛
https://www.youtube.com/watch?v=40riCqvRoMs
Image Processing v.s. Computer Vision
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Image Processing 影像處理
Computer Vision 電腦視覺
Low Level
High Level
Acquisition, representation, compression, transmission image enhancement edge/feature extraction Pattern matching image "understanding“
(Recognition, 3D)
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