Internet graphics
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Internet Graphics PowerPoint PPT Presentation


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Internet Graphics. Representing Images. Raster Image : Images consist of “dots” of color, not lines Pixel : Picture element-tiny rectangle Resolution : Number of pixels SVGA: 1280 x 1024 = 1,310,720 VGA: 640 x 480 Your monitor can be modified. Representing Images.

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Internet Graphics

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Internet graphics

Internet Graphics


Representing images

Representing Images

  • Raster Image: Images consist of “dots” of color, not lines

  • Pixel: Picture element-tiny rectangle

  • Resolution: Number of pixels

    • SVGA: 1280 x 1024 = 1,310,720

    • VGA: 640 x 480

    • Your monitor can be modified


Representing images1

Representing Images

  • RGB: monitor, each pixel

  • Intensity: 0 (dark) – 255 (bright)

  • Representing Color: # - # - #

    • 255-255-255 = white

    • 100-0-0 = scarlet

    • 16,777,216 = 16 million colors


Representing images2

Representing Images

  • Light media: RGB

  • Opaque media: paint

    • Red, blue, yellow

  • Printers

    • Cyan, yellow, magenta

    • Must have conversion software for translating monitor to printer


Storage of images

Storage of Images

  • 1 byte = 8 bits = 255 values

  • Images are memory hogs

  • Causes problems with transmission

  • e.g. Image: 5 million pixels = 14 Mb

  • Solutions

    • Less “accuracy”

    • Compression


Reducing color depth

Reducing Color Depth

  • Reduce the number of colors

  • Depth: measured by bits/pixel

  • True color = 3 bytes = 24 bits


8 bit color

8-bit Color

  • 1 byte = 8 bits = 256 colors

  • Color Palette – 256 colors

    • Multiple palettes are available

  • 8-bit number represents the particular color in the palette – not the mix of RGB

  • Uses 1/3 storage space + 768 bytes to define the palette


Other color depths

Other Color Depths

  • 1-bit - Black & White

  • 4-bit = 16 colors

    • Simple drawings, icons

    • Windows, but can change palette

    • Start; Settings; Control Panel; Display; Appearance; Scheme


Color depth tradeoff

Color Depth Tradeoff

  • Color depth vs. Resolution

  • Due to storage requirements, must reduce one

  • 1280 x 1024  256 colors

  • 16 M colors  640 x 480

  • Photos: need more than 256 colors


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