Antialiasing jaggies digitized Analog line Digital line aliasing

Antialiasing jaggies digitized Analog line Digital line: aliasing occurs Aliased 'W ' Antialiased 'W ' 168 471 Computer Graphics, KKU. Lecture 9 1

Antialiasing What anti-aliasing attempts to do is, using mathematics, fill in some of the digital system with colors that are in-between the two adjoining colors. In this case a medium gray would be between the black and the white. Some gray squares placed in the grid might help soften up the "jaggies " 168 471 Computer Graphics, KKU. Lecture 9 2

Antialiasing 168 471 Computer Graphics, KKU. Lecture 9 3

Unweighted Area Sampling • Intensity is proportional to the amount of area covered. • Defining the box weighting function which has volume of 1 (I max. ( • Determine the overlap volume Ws [0, 1. [ • 168 471 Computer Graphics, KKU. Lecture 9 4

Weighted Area Sampling 168 471 Computer Graphics, KKU. Lecture 9 5

Antialiasing in Practice • Use of low pass filter by summing products between the mask coefficients and the intensities of the pixels under the mask. • For w which is a 3 x 3 mask, the response R at the center of the mask is R = w 1 z 1 + w 2 z 2 + … + w 9 z 9 mask R mask 168 471 Computer Graphics, KKU. Lecture 9 R 6

Antialiasing in Practice )a( 168 471 Computer Graphics, KKU. Lecture 9 )b( 7