EECS 487 Winter 2003

Homework #2

Due February 17th

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 circle using a Bezier curve. How many curve segments are necessary to get an accurate approximation of the circle?

a) Det ermine the control points for a 2 segment Bezier curve.

b) Plot the Bezier curve and compare it to the unit circle plotted in (a).

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