Graphic Devices and Output Primitives

GRAPHICS DEVICES AND OUTPUT PRIMITIVES J.J. ADRI JOVIN Assistant Professor Department of Information Technology Sri Ramakrishna Institute of Technology

Raster Scan Displays

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Architecture

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Random Scan Displays

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Architecture

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Color CRT Monitor

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Flat Panel Displays

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Input Devices

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Trackball

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Space ball

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Joystick

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Image Scanner

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Touch Panel

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Light Pen

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Points and Lines • setpixel(x,y) – load a specified color point in the location specified by x and y

• getpixel(x,y) – retrieve the current frame buffer intensity

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Line drawing algorithms

y  m.x  c y 2  y1 m x 2  x1 y x  m

c  y1  m  x1

y  mx

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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DDA Algorithm • Digital Differential Analyzer • Consider positive slope and the slope is less than or equal to 1. • We sample at unit x interval yk 1  yk  m

• For lines with positive slope, greater than 1, the roles of x and y are reversed 1 xk 1  xk  m

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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DDA Algorithm (Contd..) • If the process start from right end point, we have x  1 • Therefore

yk 1  yk  m

• Similarly, for slope greater than 1, 1 xk 1  xk  m J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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DDA Algorithm (Contd..)

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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Bresenham Line Drawing Algorithm 1. Input the two line endpoints and store the left endpoint in ( x0 , y0 ) . 2. Load ( x0 , y0 ) into the frame buffer; that is, plot the first point. 3. Calculate constants x, y,2y, and 2y  2x and obtain the starting value for the decision parameter as

p0  2y  x 4. At each x k ,along the line, starting at k  0 ,perform the following test. If p k  0 , the next point to plot is ( xk  1, y k ) and

pk 1  pk  2y Otherwise, the next point to plot is ( xk  1, y k  1) and

pk 1  pk  2y  2x 5. Repeat step 4 x times.

J.J. ADRI JOVIN, Assistant Professor, Dept. of IT, SRIT

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