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Graphics / Multimedia

Graphics / Multimedia. CIS 110. Graphics Basics. Image versus Display (monitor or printer) Image composed of pixels -- short for picture element BITMAP – rows & columns More pixels = greater detail #pixels = Resolution Monitor /video card 1024x768 Printer/Scanner 1440dpi

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Graphics / Multimedia

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  1. Graphics / Multimedia CIS 110

  2. Graphics Basics • Image versus Display (monitor or printer) • Image composed of pixels -- short for picture element • BITMAP – rows & columns • More pixels = greater detail • #pixels = Resolution • Monitor /video card 1024x768 • Printer/Scanner 1440dpi • Digital Camera 5.0 megapixels

  3. Resolution • Higher resolution (more pixels)… • More detail • Larger file size • And slower downloads!! • But resolution isn’t everything…

  4. Color Depth • Also “bit depth” • Bits per pixel (bpp) • More bpp means more shades of color available • More bpp also means larger file size • Example: 24bpp = 224 = 16.7 MILLION colors Considered “True Color”, close to eye • Image & video colors RGB, printer CYMK

  5. Compression • With higher resolution and color depth files get BIG. • Compressed images are smaller, but must be uncompressed to display full detail. • Use formulas to reduce redundant data. • “Lossy” – smaller files but all original detail CANNOT be reconstructed. • “Loss-less” – all details CAN be reconstructed.

  6. Formats • GIF – lossless compression (.gif) • For logos with solid colors on web pages • Poor compression of photos with few blocks of identical colors • JPEG – lossy for photos (.jpg) • BMP – Windows native format, usually uncompressed (.bmp) • Example Images…

  7. Vector Graphics • Images stored as geometry information instead of raw pixels. • Ex. a circle stored as x,y of center plus radius • Actual pixels determined on the fly for display – allows zoom w/o jagged edges. • MS Paint versus Draw tool in MS Office • Files: WMF, EPS, Flash

  8. Animation • Most common Flash & Shockwave • Usually vector based on web pages (much less data to download). • Computer aids “tweening” in between frames.

  9. Digital Video • Bitmap rather than vector. • Each complete frame compressed. • Also, only changes from previous frame are sent. • MPEG2 (DVD), MPEG4 and DIVX (“ripped” movies)

  10. Digital Audio • Audio CDs are uncompressedPCM: 16bits @ 44.1kHz sample rate • Full CD, 660mb holds 72minutes sound • WAV files in PC also uncompressed • MP3: lossy compressed audio • Smaller files (greater compression) = lower quality • Common: 128bps (bits per second audio stream

  11. Streaming Video or Audio • Instead of having to download entire file before viewing/listening… • Can use “stream” on-the-fly if compressed enough and network connection fast enough.

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