EECS 487 Fall 2003

Homework #2

Due October 15th

1. Use the table in "Compositing Digital Images", Thomas Porter & Tom Duff and find the output pixel value for each operation in the table.

Argb	Aa
255,255,255 128,128,128 64,64,64	1.0 0.5 .25

Brgb	Ba
128,128,128 128,128,128 128,128,128	1.0 0.5 0.25

Fa

Fb

AoverB =

BoverA =

A in B =

B in A =

A out B =

B out A =

A atop B =

B atop A =

A xor B =

2. Up till now we talked about the output color value. What if we wanted to know the output alpha for A over B. How would you solve it and what is your answer.

3. Suppose we want to draw a unit circle using a Bezier curve. How many curve segments are necessary to get an accurate approximation of the circle?

a) Determine the control points for a 2 segment Bezier curve. (You Only need to do one segment)

b) Plot the Bezier curve and compare it to the unit circle.  What is the maximum error?

c) Repeat (a) and (b) for a four segment Bezier curve.