Graphics: Conceptual Graphics: Conceptual ModelModel

Real Object

Real Object

Human Eye

Human Eye

DisplayDevice

Graphics System

SyntheticModel

SyntheticCamera

Real Light

SyntheticLight Source

Raster Image Raster Image and Output and Output

DeviceDevice

Pixels and Frame BufferPixels and Frame Buffer

The image is made up of many small The image is made up of many small cellscells

The individual cells are called The individual cells are called PixelsPixels A raster image is stored in a computer as A raster image is stored in a computer as

an array of numerical values. The array is an array of numerical values. The array is called a called a Pixel Map. Pixel Map. If the value is only 0 If the value is only 0 and one, then it is called a and one, then it is called a bitmapbitmap

The memory that stores the pixels are The memory that stores the pixels are calledcalled Frame buffer. Frame buffer.

4Figures are extracted from Angel's book

(ISBN 0-201-38597-x)

Pixels and ImagePixels and Image

Gray-scale Raster ImagesGray-scale Raster Images

bi-level: one bit per pixelbi-level: one bit per pixel pixel depth: the number of bits for each pixelpixel depth: the number of bits for each pixel

2 produced 4 gray level, what about n?2 produced 4 gray level, what about n? Effect of Pixel depthEffect of Pixel depth

Color Raster ImageColor Raster Image

Ordered triple RGBOrdered triple RGB

The number of bits used to represent the color The number of bits used to represent the color of each pixel is called the of each pixel is called the color depthcolor depth 24 bits (true color), memory?24 bits (true color), memory?

Raster displaysRaster displays Display surfaceDisplay surface Frame bufferFrame buffer Scanning ProcessScanning Process

How Does Monitor Work?How Does Monitor Work?

http://il.youtube.com/watch?http://il.youtube.com/watch?v=Gnl1vuwjHto&feature=relatedv=Gnl1vuwjHto&feature=related

Video MonitorVideo Monitor

Cathode-ray tube CRTCathode-ray tube CRT RGB each 2 bits, total color?RGB each 2 bits, total color? Refresh rate, flicker Refresh rate, flicker

Indexed Color and Indexed Color and Lookup TableLookup Table

How many colors can a How many colors can a system displaysystem display

Color depth: b bitsColor depth: b bits LUT entry: w bitsLUT entry: w bits the system can display 2the system can display 2ww colors, 2 colors, 2bb

at one timeat one time Number of pixels in Frame buffer: MNumber of pixels in Frame buffer: M Frame Buffer size: M * b (bits)Frame Buffer size: M * b (bits) LUT size: w *2LUT size: w *2bb (bits) (bits)