an introduction to computer vision george j. grevera, ph.d
TRANSCRIPT
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An Introduction to An Introduction to Computer VisionComputer Vision
George J. Grevera, Ph.D.George J. Grevera, Ph.D.
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The science of analyzing images and videos in The science of analyzing images and videos in order to recognize or just model 3D objects, order to recognize or just model 3D objects, persons, and environments.persons, and environments.
Computer VisionComputer Vision
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How does the Sony AIBO dog find its way How does the Sony AIBO dog find its way “home” (to its charging stations)?“home” (to its charging stations)?
Computer VisionComputer Vision
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How does the yellow, virtual first-down line How does the yellow, virtual first-down line work?work?
Computer VisionComputer Vision
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How do cameras perform (digital) image How do cameras perform (digital) image stabilization?stabilization?
In this class, we study the underlying principles In this class, we study the underlying principles and produce working examples.and produce working examples.
Computer VisionComputer Vision
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Visualization includes…Visualization includes…
Computer graphicsComputer graphics
Computer / Machine Computer / Machine visionvision
Image understandingImage understanding
Database and Database and communicationscommunications
Computer gamesComputer games
Medical imagingMedical imaging
Image processingImage processing
Pattern recognitionPattern recognition
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Computer graphics/games vs. Computer graphics/games vs. computer visioncomputer vision
Computer graphics/games creates a 2D Computer graphics/games creates a 2D image from a 3D world/model.image from a 3D world/model.
3D to 2D3D to 2D
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Computer graphics/games vs. Computer graphics/games vs. computer visioncomputer vision
Computer vision estimates a 3D Computer vision estimates a 3D world/model from a 2D image.world/model from a 2D image.
2D to 3D2D to 3D
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ExamplesExamplesgray (b&w) and colorgray (b&w) and color
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Ansel Adams: El CapitanAnsel Adams: El Capitan
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Bill Brandt: Lambeth WalkBill Brandt: Lambeth Walk
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Lewis HineLewis Hine
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Lewis HineLewis Hine
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George Grevera: Horse FishingGeorge Grevera: Horse Fishing
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#1 Major problems in Computer #1 Major problems in Computer Vision: SegmentationVision: Segmentation
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SegmentationSegmentation
Recognition: Is a t-shirt present?Recognition: Is a t-shirt present? Delineation: Can you accurately outline the t-Delineation: Can you accurately outline the t-
shirt (what size is it)?shirt (what size is it)?
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Segmentation tasks:Segmentation tasks:
1.1. RecognitionRecognition Human is typically better.Human is typically better. more qualitativemore qualitative
2.2. DelineationDelineation Computer is typically better.Computer is typically better. more quantitativemore quantitative
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Model buildingModel building
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Models from CT (Computed Models from CT (Computed Tomography) head dataTomography) head data
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3D visualization of CT head data3D visualization of CT head data
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MRI Diffusion Tensor ImagingMRI Diffusion Tensor Imaging
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#2 Major problem in Computer #2 Major problem in Computer Vision: RegistrationVision: Registration
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RegistrationRegistration
A.K.A.:A.K.A.: alignmentalignment warpingwarping mosaicingmosaicing morphingmorphing fusionfusion
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Simple MRI Example (rigid)Simple MRI Example (rigid)
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DeformableDeformable
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Thirion’s “Demons” algorithm applied to Thirion’s “Demons” algorithm applied to pre- and post-contrast MRI of the breast.pre- and post-contrast MRI of the breast. excellent resultsexcellent results
Deformable registration Deformable registration exampleexample
pre
post (no reg)
post(after Thirion’s
Demons registration)
diff
diff (after reg)
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Thirion’s “Demons” algorithm applied to Thirion’s “Demons” algorithm applied to PET chest emission and transmission PET chest emission and transmission images.images. poor resultspoor results
PET transmission image
PET emission image
PET emission warped to match transmission
Deformable registration Deformable registration exampleexample
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NON-MEDICAL NON-MEDICAL VISUALIZATIONVISUALIZATION
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Red eye reductionRed eye reduction
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What is a distance transform?What is a distance transform?
Input:Input: a a binarybinary image image
Output:Output: a grey imagea grey image for all points . . .for all points . . .
assign the minimum distance from that particular point assign the minimum distance from that particular point to the nearest point on the border of an objectto the nearest point on the border of an object
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Applications of distance Applications of distance transforms:transforms:
skeletonization/medial axis transformskeletonization/medial axis transform interpolationinterpolation registrationregistration efficient ray tracingefficient ray tracing classification of plant cellsclassification of plant cells measuring cell wallsmeasuring cell walls characterize spinal cord atrophycharacterize spinal cord atrophy
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Experimental ResultsExperimental Results
binary input image distance transform result
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Application areas:
• Object recognition
• Tracking
• Registration
• Fusion
Intelligence, industrial and medical projects
• FBI Automatic Fingerprint Identification System
• FOCUS: Monitor change in satellite images
• FBI Facial Reconstruction
Software: Target Junior
Image UnderstandingImage Understanding
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Image UnderstandingImage Understanding
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Image UnderstandingImage Understanding
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Image UnderstandingImage Understanding
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Image UnderstandingImage Understanding
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TextbookTextbook
L.G. Shapiro, G.C. Stockman, Computer L.G. Shapiro, G.C. Stockman, Computer Vision, Prentice-Hall, 2001.Vision, Prentice-Hall, 2001.
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TopicsTopics
Imaging and image representationImaging and image representation SensorsSensors Problems (including noise)Problems (including noise) Image file formatsImage file formats
Color representation and shadingColor representation and shading Binary image analysisBinary image analysis
Connected componentsConnected components MorphologyMorphology Region propertiesRegion properties
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TopicsTopics
Pattern recognition conceptsPattern recognition concepts Classifiers and classificationClassifiers and classification
Filtering (enhancing) imagesFiltering (enhancing) images
SegmentationSegmentation
Registration (matching)Registration (matching)
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TopicsTopics
RegistrationRegistration
Texture representation and segmentationTexture representation and segmentation
Motion from sequences of 2D imagesMotion from sequences of 2D images
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Homework #1Homework #1
Read chapter 1.Read chapter 1.
Hand in 1.1, 1.2, and 1.3.Hand in 1.1, 1.2, and 1.3.
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Survey questions…Survey questions…
1. Do you have access to a digital camera?1. Do you have access to a digital camera?
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2. Write a function that, given a 2D array, returns a 2. Write a function that, given a 2D array, returns a 1D array where each entry is the sum of the 1D array where each entry is the sum of the corresponding row in the 2D array.corresponding row in the 2D array. (So result[0] (So result[0] contains the sum of values in m for row 0, result[1] contains the contains the sum of values in m for row 0, result[1] contains the sum of values in m for row 1, etc.)sum of values in m for row 1, etc.)
Java:Java:
int[] sumOfRows ( int m[][], int rows, int cols ) {int[] sumOfRows ( int m[][], int rows, int cols ) {
……
}}
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