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8/13/2019 G52IIP Module Introduction
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G52IIPIntroduction to Image Processing
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! Introduces topics and techniques related to the useof computers to
!Acquire
! Store! Process/Manipulate! Model! Analyse/Interpret! Display
images
! Gives experience of implementing, applying andevaluating image processing methods
G52IIP
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Know Your Limitations
! Four terms are often used together, andsometimes interchanged
!Image Processing
! Image Analysis! Computer Vision! Computer Graphics
! All share representations, underlyingmathematics and some algorithms
! Their goals are very differentThis is an Image Processing module
Objects Images
Measurements
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Image Processing
! Mainly concerned with:! Image acquisition capture a low-level digital
representation of the viewed world! Image processing noise removal, smoothing,
sharpening, contrast enhancement, etc.
! Image compression efficient representation ofimage data for storage (minimise disk space) and
communication (minimise network bandwidth)! Display render the image data on
reproduction media (screens, printer paper)
Objects
Images
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Image Processing
! Image acquisition (low-level) digitalrepresentation of the viewed world
123 33 234 4567 90 12 134 3456 89 54 67 98111 56 67 90 6534 .
Pixel values represent the brightnessand colour of the viewed objects,
but give no indication of whatobject, e.g., books, monitors, these
numbers refer to hence low-level
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Image Processing
! Image acquisition (low-level) digitalrepresentation of the viewed world
123 33 234 4567 90 12 134 3456 89 54 67 98111 56 67 90 6534 .
What should these numbersrecord?
How big should the array be? What range (precision) of values
should be stored?
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Image Processing
! Image processing noise removal, smoothing,sharpening, contrast enhancement, changingthe appearance of an image
Noise reduction
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! Image processing noise removal, smoothing,sharpening, contrast enhancement, changingthe appearance of an image
Image Processing
Sharpening
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! Image processing noise removal, smoothing,sharpening, contrast enhancement, changingthe appearance of an image
Image Processing
Smoothing
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! Image processing noise removal, smoothing,sharpening, contrast enhancement, changingthe appearance of an image
Image Processing
10Contrast Enhancement
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! Image processing noise removal, smoothing,sharpening, contrast enhancement, changingthe appearance of an image
Image Processing
Changing image appearance
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Image Processing! Image compression efficiently represent image
data for storage (minimisedisk space) andcommunication (minimise network bandwidth)
245,760 bytes 69,632 bytes 5,951 bytes
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Image Processing! Display render the image data on reproduction
media (screens, printer paper)
123 33 234 4567 90 12 134 3456 89 54 67 98111 56 67 90 6534 .
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! Display render the image data on reproductionmedia (screens, printer paper)
123 33 234 4567 90 12 134 3456 89 54 67 98111 56 67 90 6534 .
Image Processing
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Image Analysis! Concerned with making quantitative
measurements on images:
!Image acquisition is constrained so that imagemeasurements are a proxy for some real world value
! Sits between image processing and computer vision! G52IIP covers methods widely used in image analysis
Objects Images Measurements
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Image Analysis! Many application areas:
! Document processing! Medical! Scientific! Industrial inspection:
Food, textiles, manufacturing,..
! Image processing pipelines and measurementmethods are application specific
! Uses generic operations where possible, andengineering, more than scientific approach
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Computer Vision! Each pixel value in a standard camera image is
a function of
! thereflectanceof the viewed object! theshapeof the viewed object! illuminationconditions! viewing geometry
! Biological vision inverts that function withapparent ease
! putting the toothpaste back in the tube! But the function is (usually) unknown, and very
complex....
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Computer Vision! Aims to invert image formation & recover
information about the viewed world
Objects MeasurementsObjects
Images
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Computer Vision! Those working in computer vision address issues in! Object detection and recognition!
Recovery of 3D shape! Tracking and motion analysis! Event recognition! .
! They work with naturally occurring images tosolve more general problems than are usuallyaddressed in Image Analysis
! See G54VIS: Computer Vision
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Computer Graphics! Focus is on creating images
from object models:
! Lighting and shading modeling! Volume modeling! Curve and surface modeling! Visibility modeling! Texture synthesis! Character animation! Modeling terrain, liquids, fire/smoke,
cloth, hair/fur, feathers, skin etc
! See G53GRA: Computer Graphics
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G52IIP - Content! Image formation, acquisition, colour
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G52IIP - Content! Image processing theory and practice
! How is this possible?! How is it achieved?! What problem is being solved?! What else can be done?
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G52IIP - Content! Spatial domain methods
(operating directly on the image)
! Point operations! Area operations
! Frequency domain methods! Compute the power spectrum of the
image
! Process the power spectrum! Reconstruct a new image from the
modified power spectrum
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G52IIP - Content! Image Compression! Types of redundancy! Exploiting redundancy! Huffman coding! LZW coding! Predictive coding! Quantisation-based methods
! DCT & JPEG
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G52IIP - Content! Edge detection and image segmentation
! A step towards imageanalysis & computer viison
! Underlying theory! Some useful algorithms
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G52IIP - Content! Selected Advanced Topics:
Content-based Image Retrieval
! Show me all the imageslike this
in here
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G52IIP - Content! Selected Advanced Topics:
IntroductiontoImageStitching
+ + .+
=
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G52IIP - Resources! Two lectures, one lab per week: exercises using
Matlab
! Moodle page with additional readings, links, etc! Some good books:
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G52IIP - Assessment! 2000 word programming assignment/report! Series of Matlab tasks! Explanation & evaluation of results! Out: soon! Deadline: soon after
! 1 hour exam! Answer each of 3 questions
im=imread('Atrium2.jpg');
im_grey=sum(im,3);im_grey=im_grey/max(im_grey(:));subplot(2,4,1);
imshow(im_grey);title('grey image');
thresh=0.5;
im_grey(im_greythresh)=1;subplot(2,4,2);
imshow(im_grey);title('binary image');