Transcript Computer Concepts 8

信息处理技术
Chapter7:1:
4:Digital
File Management,
Computer,
Chapter
MediaInternet,Virus
Protection,
Web,
and E-Mail
and Backup
Basics
1
2
Chapter 7 Preview
After this chapter, you should be able to:
– Describe the advantages, disadvantages, and
uses for digital media, such as bitmap graphics,
vector graphics, 3-D graphics, 3-D animations,
desktop video, waveform audio, MIDI music,
speech synthesis, and speech recognition
– List the equipment and software that can be used
to work with various types of digital media
– Identify digital media files by their file extensions
– Understand the advantages and disadvantages
of using each type of digital media on the Web
Chapter 7: Digital Media
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Chapter 7 Preview
– Explain how resolution, image size, color depth,
and color palettes can be manipulated to adjust
the file size of a bitmap graphic
– Describe procedures required to convert bitmap
graphics into vectors and vector graphics into
bitmaps
– Explain how wireframes, rendering, and ray
tracing apply to 3-D graphics
– Define the differences between digital video and 3D animation
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Chapter 7 Preview
– Describe how to shoot, capture, edit, and process
digital video
– Explain how window size, frame rate, and
compression affect file size for a desktop video
– Describe the formats used for digital music
– Explain how to download music files and transfer
them to portable audio players
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Chapter 7 Outline
• Section A
– Bitmap Graphics 位图
• Section B
– Vector and 3-D Graphics矢量及三维图
• Section C
– Digital Video 数字视频
• Section D
– Digital Sound 数字音频
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Chapter 7
Digital Media
数字媒体
Section A: Bitmap Graphics
位图
Computer Concepts 8th Edition
Bitmap Basics: What is a
bitmap graphic?
• Bitmap graphic – “raster graphic”, consists
of a grid of dots
• The color of each dot is stored as a binary
number
• Example
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How do I create bitmap
images?
• Paint software – graphics software for
creating bitmap graphics
– Adobe Photoshop
– Jasc Paint Shop Pro
– Microsoft Paint
• Bit-by-bit editing
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How do I convert a printed
image into a bitmap?
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When should I use a digital
camera rather than a scanner?
• Digital camera – digitizes real objects
– Takes photo in digital format, which you can
then transfer directly to your computer
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How does a digital camera
store images?
• Some digital cameras store images on
floppy disks, CDs, mini-CDs, or
miniature hard disk drives
• Solid state storage – popular technology
for digital camera memory modules
– Holds data without consuming power
– Memory card
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How can I get the images out
of the camera?
•
•
•
•
•
•
Media transfer, e.g disk
Direct cable transfer
Infrared port
Card readers
Floppy disk adapters
E-mail
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Modifying Bitmap Graphics:
What characteristics of a
bitmap can I modify?
• You can use graphics software to
modify or edit bitmap graphics by
changing any individual pixels
– Retouch
– Repair
– Remove red eye or erase “rabbit ears”
• Bitmap graphics can require large
amounts of storage, and take a long
time to load
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Image Resolution: How does
resolution pertain to bitmap
graphics?
• Resolution – dimensions of the grid that
forms a bitmap graphic
– Number of horizontal and vertical pixels
that it contains
– 150 x 100 – 150 pixels across and 100
pixels high, 1600 x 1200
– 1.9 Megapixels (1600x1200)
– 3.5 Megapixels (2160x1440)
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Size of Graphics & Image
• Each pixel is 1 or more bits
• Enlarging an image pixelates it
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How do I specify the size of a
printed image?
• Most graphics software lets you specify
the size at which an image is printed
without changing the resolution of the
bitmap graphic
– Get better printout if an image meets or
exceeds the printers dpi (dots per inch)
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How does a bitmap’s resolution
relate to what I see on the
screen?
• Typically, one pixel on the graphic
corresponds to one pixel on the screen
• If image is larger than screen, you will
have to scroll
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Can I change a graphic’s file
size?
• Cropping – process of selecting part of an
image
• Resolution dependent – quality of the image
depends on its resolution
– Can reduce image quality
• Pixel interpolation – creates new pixels by
averaging the colors of nearby pixels
• Pixelated – undesirable jagged appearance
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Can I change a graphic’s file
size?
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Color Depth and Palettes:
What is color depth?
• The number of colors that are available
for use in an image
– Larger number, better quality and larger file
size. Why?
• 8-bit
• 24-bit or True Color
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How does a color palette
work?
8-bits
each
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How do I select a color
palette?
• Use color palette or color picker tool
• Grayscale palette – displays an image using
shades of gray (usually 256 shades of gray)
• System palette – selection of colors used by
the operating system
– Windows has 20 permanent colors and
236 that can be changed
• Web palette – standard set of colors used by
the Internet Web browsers
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What if a palette doesn’t
contain the colors needed for
an image?
• Dithering – uses
patterns composed
of two or more
colors to produce
the illusion of
additional colors
and shading, relying
on the human eye
to blend colors and
shapes
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Bitmap Graphics Formats:
Are there different kinds of
bitmap graphics?
• BMP – native bitmap graphic file format of
Microsoft Windows OS
• PCX – one of original personal computer bitmap
graphics file formats (8-bit – 256 color)
• TIFF (Tag Image File Format) – highly flexible
and platform-independent graphics file format
– Supports True Color
– Used by scanners and digital cameras
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Are there different kinds of
bitmap graphics?
• JPEG – graphics format with built-in
compression
– You control level of compression
– Uses True Color
• GIF – limited to 256 colors
• PNG – 48-bit True Color, compresses
without losing data
– Public domain format
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How do I know which
graphics format to use?
• BMP – Buttons and other controls
• PCX – Not used with much frequency
• TIFF – High-resolution images and
photos
• JPEG – Photographic or scanned
images
• GIF – Popular for Web graphics
• PNG – Alternative to GIF
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Chapter 7
Digital Media
Section B: Vector and 3-D Graphics
矢量及三维图
Computer Concepts 8th Edition
Vector Graphics Basics:
What is a vector graphic?
• Consists of set of instructions for recreating a picture
• Contains the instructions that the
computer needs to create the shape,
size, position, and color for each object
in an image
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What is a vector graphic?
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How do vector graphics
compare with bitmap
graphics?
• Vectors resize better than bitmaps
• Vector images usually require less storage
space than bitmaps
• It is easier to edit an object in a vector graphic
than an object in bitmap graphic
• Vector graphics are not usually as realistic as
bitmap images, simpler and more like a
cartoon or linedrawing
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What tools do I need to
create vector graphics?
• Digitizing tablet –
device that provides
a flat surface for a
paper-based
drawing
• AutoCAD for
architects
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What tools do I need to
create vector graphics?
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Vector-to-Bitmap Conversion:
Is it possible to convert a
vector graphic into a bitmap?
• Rasterization works by
superimposing a grid
over a vector image,
and determining the
color for each pixel
• Once converted, the
resulting graphic no
longer has the qualities
of a vector graphic
• Metafiles - bitmaps &
vectors
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How about converting a
bitmap graphic into a vector
graphic?
• This process is more difficult
• Tracing software locates the edges of
objects in a bitmap image and converts
the resulting shapes into vector
graphics objects
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Vector Graphics on the Web:
Do vector graphics work on
the Web?
• Browsers support a limited number of
graphics formats – GIF and JPEG
• Support for vector graphics has been
slow, but plug-ins and players are
currently available
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Which vector graphics
formats can be used on the
Web?
• SVG (Scalable Vector Graphics) – designed
for the Web
– Automatically resized when displayed on
different screens
– Uses <EMBED> tag
• Flash graphics – can be static or animated
and require less space than SVG graphics,
but require a browser plug-in to be viewed
• Animated GIFs much larger
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Advantages of Using Vector
Graphics on the Web
• Consistent Quality
– Looks the same on all screens
– Resizes
• Searchable
– Text in vector, e.g. labels
• Smaller than bitmaps
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3-D Graphics: How do vector
graphics relate to 3-D
graphics?
• 3-D graphics – stored as a set of
instructions
• Wireframe – framework for a 3-D graphic
• Rendering – process of covering a
wireframe with surface color and texture
• Ray tracing – technique for adding light
and shadows to a 3-D image
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How do vector graphics
relate to 3-D graphics?
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How do vector graphics
relate to 3-D graphics?
• Rotating the graphic
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What do I need to create 3-D
graphics?
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Is it possible to animate 3-D
graphics?
• 3-D graphics can be animated
– Pixar Animation Studios
– DreamWorks
– Toy Story, LOR, etc.
• Special effects can be created and
incorporated into final footage
• 3-D computer game animation happens in
“real-time,” rendered as you play
• Graphics cards
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VRML
•
•
•
•
Virtual Reality Markup Language
Similar to vector graphics
Interpreted by plug-ins
Allows you to “move thru” graphics
•
http://prt.fernuni-hagen.de/lehre/KURSE/PRT001/course_main/node19.html
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Chapter 7
Digital Media
Section C: Digital Video
数字视频
Computer Concepts 8th Edition
Desktop Video Basics: What
is digital video?
• Uses bits to store color and brightness data
for each video frame
– Stored on hard disks, CDs, DVDs, videotapes,
memory cards, or the Web
– Footage can be supplied by:
•
•
•
•
•
Video camera
Videotape
Television
DVD
Digital recording device
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What is digital video?
• Video is composed of a series of frames
• Each frame is essentially a still picture
(can be stored as bitmap graphic)
• Frame rate – number of frames per
second
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Are there different kinds of
digital videos?
•
•
•
•
Desktop video
Web-based video
DVD video
PDA video
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How do I create digital video?
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Is it necessary to use a digital
video camera for filming digital
video?
• You can use analog or digital video camera to
shoot footage
• Digital video camera – stores footage as a
series of bits
• Analog video camera –stores as continuous
track of magnetic patterns
– Must be digitized
• Videoconferencing cameras – attach
directly to a computer
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What are the advantages of a
digital video camera?
• Captures video data in digital format which
can then be directly transferred to a computer
for editing
• Produce higher quality video than analog or
videoconferencing cameras
• Images tend to be sharper and more colorful
• Higher quality of original video, the better the
final video will look
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How do I transfer video
footage to my computer?
• Send the data over a cable that
connects your camera to your computer
• Video capture device – converts
analog camera signal into digital data
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How do I transfer video
footage to my computer?
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How do I control the transfer
process?
• Video capture software – allows you to
start and stop the transfer, and select
the display size, frame rate, filename,
and file format for your video footage
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Video Editing: Do I need
special equipment for video
editing?
• Linear editing – recording segments
from one videotape onto another tape
• Non-linear editing – requires a
computer hard disk and video editing
software
– Can use random access devices to easily
edit and arrange footage
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How do I edit a video?
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How does video footage
become a digital video?
• You can save your digital video in a
variety of formats:
– AVI
– QuickTime Movie
– MPEG
– RealMedia
– WMV
– VOB
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Which compression
techniques should I use?
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How do Web-based videos
work?
• Streaming video – sends small
segment of the video to your computer
and begins to play it
– Web server sends next part of the file to
your computer, and so on, until the video
ends
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How do I add a video to a
Web page?
• 2 styles
– External video displays a link to a video file
• <A HREF = “ducks.avi”> 1.5 MB AVI Video
</A>
– Internal video (inline video) uses EMBED
tag, “in-place video”
– <EMBED SRC=“ducks.avi” width=145
height=60>
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How does Internet
connection speed affect Web
videos?
• Dial-up connections are slow
• High-speed Internet connections provide
much more bandwidth for streaming video
• Most Web sites provide one video file that’s
optimized for dial-up and one optimized for
high-speed (DSL, cable, and ISDN
connections)
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Can standalone DVD players
work with desktop and Web
video formats?
• Many DVD players are not able to read
desktop video or Web file formats
• Cannot read DVDs formatted for
computer data storage
• Commercial DVD movies are stored
using the industry-standard DVD-video
disk format
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Chapter 7
Digital Media
Section D: Digital Sound
数字音频
Computer Concepts 8th Edition
Waveform Audio: What is
waveform audio?
• Waveform audio is a digital
representation of sound.
– Music, voice, and sound effects can all be
recorded as waveforms
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Does sampling rate affect
sound quality?
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How does a computer
produce waveform audio?
• Sound card – contains a variety of
input and output jacks, plus audioprocessing circuitry
– Plugs into a PCI expansion slot inside the
system unit
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How does a computer
produce waveform audio?
• Digital signal processor – performs
three important tasks
– Transforms digital bits into analog waves
– Transforms analog waves into digital bits
– Handles compression and decompression,
if necessary
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What type of software is
required to record and play
waveform audio files?
• To play, you must use an audio player
– Microsoft Media Player
• To record, you may need another
software component
– Microsoft Sound Recorder
• Software may be part of your operating
system or purchased separately
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Can I add waveform audio
files to my Web pages?
• Yes, files can be embedded using
HTML
– <EMBED SRC = “daisy.wav”> or
<BGSOUND = “imagine.wav”>
– Use a streaming format to avoid lengthy
delays
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How can I listen to my digital
music collection when I’m away
from my computer?
• A portable audio player stores digital music
• You can transfer digital music from your
computer to your portable audio player
• MP3 is the most popular audio format for
digital audio
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MIDI Music: What is MIDI
music?
• Synthesized sound – artificially created
sound
• MIDI (Musical Instrument Digital Interface) –
specifies standard way to store music data
• MIDI sequence – encoded music stored as
.mid, .cmf, or .rol
• Most sound cards are equipped to capture
data from a MIDI instrument
• Wavetable – set of pre-recorded musical
instrument sounds
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When would I use MIDI
music?
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Speech Recognition and Synthesis:
What’s the difference between
speech synthesis and speech
recognition?
• Speech synthesis – process by which
machines produce sound that
resembles spoken words
• Speech recognition (or “voice
recognition”) – ability of machine to
“understand” spoken words
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How does speech synthesis
work?
• Phonemes – basic sound units strung
together by speech synthesizers
• Text-to-speech software – generates
sounds that are played through your
computer’s standard sound card
• Speech synthesis is a key technology in
wireless communication
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How does speech recognition
work?
• Speech recognition software – analyzes the
sounds of your voice and converts them to
phonemes
• Next, the software analyzes the content of your
speech; it compares the phonemes to the
words in a digital dictionary
• Can be integrated with word processing
software
• Windows XP includes speech recognition
software
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Conclusion
You should now be able to:
– Describe the advantages, disadvantages, and
uses for digital media, such as bitmap graphics,
vector graphics, 3-D graphics, 3-D animations,
desktop video, waveform audio, MIDI music,
speech synthesis, and speech recognition
– List the equipment and software that can be used
to work with various types of digital media
– Identify digital media files by their file extensions
– Understand the advantages and disadvantages
of using each type of digital media on the Web
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Conclusion
– Explain how resolution, image size, color depth,
and color palettes can be manipulated to adjust
the file size of a bitmap graphic
– Describe procedures required to convert bitmap
graphics into vectors and vector graphics into
bitmaps
– Explain how wireframes, rendering, and ray
tracing apply to 3-D graphics
– Define the differences between digital video and 3D animation
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Conclusion
– Describe how to shoot, capture, edit, and process
digital video
– Explain how window size, frame rate, and
compression affect file size for a desktop video
– Describe the formats used for digital music
– Explain how to download music files and transfer
them to portable audio players
Chapter 7: Digital Media
78