Computer Vision – Overview

Computer Vision – Computer Vision – OverviewOverview

Hanyang University

Jong-Il Park

Department of Computer Science and Engineering, Hanyang University

Digital Image ProcessingDigital Image Processing

Sampling & Quantization

Image Enhancement

Image Restoration

Image Coding( or Image Data Compression)

Image Understanding( or Computer Vision)


Image formationImage formation


Sampling & QuantizationSampling & Quantization



Subsampling & aliasingSubsampling & aliasing

aliasing


Sub-Nyquist samplingSub-Nyquist sampling

H ½, v ½ Org.

Circular Zone Plate

aliasing


Image EnhancementImage Enhancement

Goal to accentuate certain image features for subsequent

analysis or for image display

Input : image Output : image




Image EnhancementImage Enhancement

Techniques contrast/edge enhancement histogram equalization pseudo coloring noise filtering edge sharpening smoothing

Applications processing of remote-sensed image via satellite radar, SAR, Ultrasonic image processing


Image RestorationImage Restoration

Goal to remove or minimize known/unknown degradations in

image



Blur modelBlur model

estimate or recover f(x,y) from g(x,y)

deconvolution problem

modeldiscrete;or

),(),(),;,(),(

nHfg

yxnddfyxhyxg

),( yxn


Enhancement by integrationEnhancement by integration


Image RestorationImage Restoration

Techniques deblurring noise filtering correction of geometric distortion inverse filtering Least mean square(Wiener) filtering

Applications remote-sensed image processing noise cancellation


Image Data CompressionImage Data Compression Goal

to reduce the amount of data required to represent images

Input : image Output : bit-stream data

“010100101100110101001 . . . .”

moving image:1,0001,0008(bits/sample)330 frame/sec = 72107 bit/sec


2-2-D Image Compression, JPEGD Image Compression, JPEG

(a) 27.9 dB at 0.125 bpp (b) 31.5 dB at 0.25 bpp (c) 34.8 dB at 0.5 bpp

Image quality by JPEG




33D Mesh CompressionD Mesh Compression

Original ‘Bunny’

12 bpc 8 bpc10 bpc

Model # of Vertex

# of Triangle

Original (byte)

Compressed (byte)

12 bpc 10 bpc 8 bpc

Bunny 34835 69473 2,879,786 57,952 37,642 24,842

Compression ratio 50 : 1 77 : 1 116 : 1


Image Data CompressionImage Data Compression Techniques

Error-free coding( or lossless coding) Lossy compression Image Compression Standard

JPEG, H.261, H.263, MPEG-1,2,4 etc Applications

Transmission teleconferencing ,TV system, remote sensing via

satellite Storage

VOD(video on demand), Video CD, DVD(digital video disk), medical imaging, educational and business documents


Standard Application Bit rate

JPEG Still-image Variable

H.261 Visual telephony and video conferencing p64 kbps

H.263 < 64 kbps

MPEG-1 Full motion video on digital storage media 1.5 Mbps

MPEG-2 Higher resolution video than MPEG-1 2 Mbps

HDTV Terrestrial broad cast 20 Mbps

Image Coding StandardsImage Coding Standards


MPEGMPEG

MPEG-1 1992 Video CD Includes Audio Layer III (MP3)

MPEG-4 Part 1: 1998 Part 2: 1999 (addition still under development) Audio visual object Mobile telephony (IMT-2000) Interactivity Content –Based Interactivity


MPEG-7 2001 (addition still under development) Content Description Interface Metadata language and schemes for search & retrieval


Content-based Image RetrievalContent-based Image Retrieval

Image retrieval

Find similar images from

image database

Used features

Color

Texture

Shape

Query

Retrieved


Query Image

Image Data List

Retrieval Results

Texture Option


Video retrieval Scene change detection and key frame extraction Extracted key frame from a movie clip

Content-based Video RetrievalContent-based Video Retrieval


Video retrieval Automatic indexing Index from a news sequence

Content-based Video RetrievalContent-based Video Retrieval


Media Framework Tech.Media Framework Tech.

MPEG-21 All electronic creation, delivery and trade of digital

multimedia content Transparent usage of various content types on various

devices connected through various network


WatermarkingWatermarking

the process of embedding information into a host signal without changing perceived characteristics of the host

WatermarkEmbedding

Image/Document

* Filtering* Lossy Compression* Forgery* Cropping & Scaling* Geometric Distortion

WatermarkInformation

WatermarkGeneration

Key

WatermarkDetection

* Copy Protection* Fingerprinting* Authentification

Key

DecodedWatermark


Image UnderstandingImage Understanding

Goal to interpret or describe the meaning contained in the

image

Input : image Output : interpretation(description)

““KAISION”KAISION”

““circle”circle”




Stereo Vision (disparity map)Stereo Vision (disparity map)

기준 영상 ( 좌 ) 기준 영상 ( 우 )

변위 참 값 ( 붉은색 : 가리워짐 )

구한 변위 지도 ( 검은색 : 가리워짐 )


ModelModel image

Input scene

Scene matching result

Scene Matching (1)Scene Matching (1)


Model

Input image Edge image

Scene matching result

Scene Matching (2)Scene Matching (2)


– 크기 , 반지름

Fruit ClassifierFruit Classifier

Apple Orange Water Mellon


– color


Edge Detection

256)(256 Image Original Lena (a) 10) high 5, low 2,(Operator Canny (b)


Segmentation

(a) Aerial Original Image (b) Segmented Image



There are a lot of interesting topics to explore in image processing and computer vision.

Documents

Computer Vision – Overview