Raster Scan Graphics, Line Drawing Algorithm and Circle Drawing Algorithm
- 1. Raster Scan Graphics Presented by Asst. Prof. Aparna Joshi
- 2. Rasterization • The process of determining which pixel will provide the best approximation to the desired line is known as ‘Rasterization’.
- 3. Characteristics of Line Drawing Algorithm • The line should appear straight. • Displayed line should have constant brightness along their length. • The line should be start and end accurately. • Lines should have constant density,. • Line density should be independent of line length and angle. • Lines should be drawn rapidly.
- 4. DDA Line Drawing Algorithm 1. Read the line end points (x1, y1) & (x2, y2) such that they are not equal. (If equal then plot that single point and exit) . 2. Approximate the line length, If absolute (x2-x1) >= absolute (y2-y1) then length = absolute (x2-x1) else length = absolute (y2-y1) 3.
- 5. DDA Line Drawing Algorithm 4. Using the sign function, make the algorithm work in all quadrant x = x1+0.5 * sign ( ∆x) y = y1 + 0.5 * sign (y) Here, x1 & y1 are initial values. 5. Begin main loop i = 1 while (i < = length) { plot (integer (x), Integer (y)) x= x+x y = y+y i = i + 1 } end while 6. Finish / Stop
- 6. DDA Line Drawing Algorithm Advantages: • It is the simplest algorithm & it does not require special skills for implementation. • It is a faster method for calculating pixel positions than the direct use of equation y = m.x + b • It eliminates the multiplication in the equation by making use of raster characteristics, so that appropriate increments are applied in the x or y direction to find the pixel positions along the line path. • It is very easy to understand and implement. Disadvantages: • Floating point arithmetic in DDA algorithm is still time-consuming. • The algorithm is orientation dependent. Hence end point accuracy is poor. • It drifts away from the actual line path because of rounding off float values into integer.
- 7. Bresenham’s Line Drawing Algorithm
- 9. Eight-way Symmetry of a Circle
- 10. Bresenham’s Circle Drawing Algorithm
- 12. Thank You