Transcript 2.2 jrowanFall2012SemesterOverview.ppt

Digital Media
Lecture 2: SemesterOverview
Georgia Gwinnett College
School of Science and Technology
Dr. Jim Rowan
Sampling
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The process used to convert continuous phenomena in the
real world to discrete numbers stored on a computer
But… this process makes an “alias” of the original; it’s an
approximation of the original that does have faults
These negative side effedts are called artifacts
Sampling artifact examples:
With audio, one artifact is
quantization hiss
 With video, one artifact is
retrograde motion; wheels look to
turn backwards
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http://wiki.ggc.edu/images/3/35/RetrogradeGMCarcadiaBroadbandHigh.mov
http://wiki.ggc.edu/images/8/85/JrowanSpring2012CroppedRetrogradeMotionClip.mov
Moving images: Film
With images one artifact is
posterization
http://wiki.ggc.edu/wiki/BitmappedImageDitheringPosterizationjrowanSummer2012
Images as piles of numbers: Bitmapped images: Dithering and posterization
Some sampling artifact causes
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One cause of quantization hiss is
undersampling
– Not storing enough different levels for each
sample taken
One cause of retrograde motion is
undersampling
– Taking too few images per second (too few
samples)
One cause of posterization is not having
enough quantization levels
– Not storing enough different levels for each
of the samples taken
Sampling artifacts
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More on this later in the class
How do you store sound?
Collect samples of the sound and
play them back
 Store it as numeric codes (midi)
and regenerated it from those
codes
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But we will only deal with
collecting samples in this class
How do you store images?
There are two techniques we will
discuss in this class
 Bitmapped images
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– Store the image as a collection of
spots of light known as pixels
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Vector graphics
– Store the image as a mathematical
description of the objects in the
image
Bitmapped image
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A collection of spots (pixels) of
light
Vector graphics
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A mathematical description of the
objects in the scene
This image could be
described like this:
(x1,y1) (x2,y2)
(255,0,0)
(x3,y3) (x4,y4)
(0,0,255)
Why are there two ways to
describe images?
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Bitmapped images
– The size of the file depends on how
many pixels there are in the image
– The content of the image does not
affect the file’s size
– But…. they do not scale well
Why are there two ways to
describe images?

Vector graphics
– The size of the file depends on how
many objects there are in the image
– So… the content of the image does
affect the file’s size
– But…. they are scalable
A brief look at the Internet
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–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet:
How to request stuff
•Uniform Resource Locator (URL)
•http://www.amazon.com/newStuff/index.html
•Has 3 parts
•Protocol
•HTTP://
•FTP://
•SMTP://
•Domain name
•Ends in .edu .com .gov .org
•Directory structure and the requested page
•/newStuff/index.html
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet:
How to request stuff
•Uniform Resource Locator (URL)
•http://www.amazon.com/newStuff/index.html
•Has 3 parts
•Protocol
•HTTP://
•FTP://
•SMTP://
•Domain name
•Ends in .edu .com .gov .org
•Directory structure and the requested page
•/newStuff/index.html
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet:
How to request stuff
•Uniform Resource Locator (URL)
•http://www.amazon.com/newStuff/index.html
•Has 3 parts
•Protocol
•HTTP://
•FTP://
•SMTP://
•Domain name
•Ends in .edu .com .gov .org
•Directory structure and the requested page
•/newStuff/index.html
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
A brief look at the Internet
–
–
http://wiki.ggc.edu/wiki/NetworkingIssues
Let’s get started: Networking issues
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