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A Concise Introduction to Programming in Python by Mark J. Johnson

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Chapter 22

Image Synthesis

The Mandelbrot set is an interesting mathematical object that owes much of its popularity to the computer programs that create images of it.

Listing 22.1: Mandelbrot Set

 1 # mandelbrot.py
 2 from image import ImagePPM
 3
 4 def lerp(frac, low, high):
 5 return low + frac * (high − low)
 6
 7 def testpoint(c, maxreps):
 8 z = 0
 9 reps = 0
10 while abs(z) < 2 and reps < maxreps:
11   z = z ** 2 + c
12   reps += 1
13 frac = reps / maxreps
14 return (0, 0, int(lerp(frac, 0, 255)))
15
16 def mandelbrot(xint, yint, size, maxreps):
17 width, height = size
18 img = ImagePPM.new(size)
19 for i in range(width):
20  for j in range(height):
21    a = lerp(i / width, xint[0], xint[1])
22    b = lerp(1 − j / height, yint[0], yint[1])
23 ...

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