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bresenham.py
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bresenham.py
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# He split it into octants...
#
class Coord:
x = 0;
y = 0;
def __init__(self, x,y):
self.x, self.y = x,y
def __str__(self):
return "<%d,%d>"%(self.x, self.y)
def categorise(start, end):
deltaX = end.x - start.x
deltaY = end.y - start.y
close_too_nothing = lambda val : abs(val) < 0.5
if close_too_nothing(deltaX):
return "vertical"
if close_too_nothing(deltaY):
return "horizontal"
# if the line is as much in the X axis as in the Y axis..
if abs(deltaX) < abs(deltaY):
return "Y Dominates"
else:
return "X Dominates"
def line0(start, end):
deltax = end.x-start.x
deltay = end.y-start.y
m = 1.0*deltay/deltax
x = start.x
y = start.y
for x in range(start.x, end.x):
yield x, y
yreal = m*(x-start.x)+start.y
if abs(y-yreal) >= 0.5:
y += 1
pt1 = Coord(10,0)
pt2 = Coord(300,100)
print pt1,pt2,'vs', list(line0(pt1, pt2))[-1]
print categorise(pt1,pt2)
# too steep
pt1 = Coord(10,20)
pt2 = Coord(200,300)
print pt1,pt2,'vs', list(line0(pt1, pt2))[-1]
print categorise(pt1,pt2)
# last coord incorrect.
def line1(start, end):
deltax = end.x-start.x
deltay = end.y-start.y
m = 1.0*deltay/deltax
x = start.x
y = start.y
for y in range(start.y, end.y):
yield x, y
xreal = (y-start.y)/m+start.x
if abs(x-xreal) >= 0.5:
x += 1
# too steep
pt1 = Coord(10,20)
pt2 = Coord(200,300)
print pt1,pt2,'vs', list(line1(pt1, pt2))[-1]
print categorise(pt1,pt2)
# Now, how about the other directions...
def line2(start, end):
deltax = end.x-start.x
deltay = end.y-start.y
m = 1.0*deltay/deltax
x = start.x
y = start.y
for y in range(start.y, end.y, -1):
yield x, y
xreal = (y-start.y)/m+start.x
if abs(x-xreal) >= 0.5:
x += 1
print 200*'--'
pt1 = Coord(200,300)
pt2 = Coord(300,10) # y decline is very steep!!
print pt1,pt2,'vs', list(line2(pt1, pt2))[-1]
print categorise(pt1,pt2)
print 200*'--'
pt1 = Coord(200,300)
pt2 = Coord(300,200) # y decline is not steep!!
print pt1,pt2,'vs', list(line2(pt1, pt2))[-1]
print categorise(pt1,pt2)
# combine line 1 and line 2:
def line_ydom(start, end):
incrementy = 1 if start.y < end.y else -1
incrementx = 1 if start.x < end.x else -1
deltax = end.x-start.x
deltay = end.y-start.y
m = 1.0*deltay/deltax
x = start.x
y = start.y
for y in range(start.y, end.y, incrementy):
yield x, y
xreal = (y-start.y)/m+start.x
if abs(x-xreal) >= 0.5:
x = x + incrementx
# and then deduce from line 0 and above:
def line_xdom(start, end ):
incrementy = 1 if start.y < end.y else -1
incrementx = 1 if start.x < end.x else -1
deltax = end.x-start.x
deltay = end.y-start.y
m = 1.0*deltay/deltax
x = start.x
y = start.y
for x in range(start.x, end.x, incrementx):
yield x, y
yreal = m*(x-start.x)+start.y
if abs(y-yreal) >= 0.5:
y = y + incrementy
def line(start,end):
#import pdb; pdb.set_trace()
pt_range = []
increment = lambda begin,end: 1 if end > begin else -1;
category = categorise(start,end)
if category == "X Dominates":
pt_range = line_xdom(start, end)
elif category == "Y Dominates":
pt_range = line_ydom(start, end)
elif category == "horizontal":
pt_range = [(x, start.y) for x in range(*([start.x, end.x, increment(start.x,end.x)]))]
else : # category == "vertical":
pt_range = [(start.x, y) for y in range(*([start.y, end.y, increment(start.y,end.y)]))]
return pt_range
print 200*'='
pt1 = Coord(200,300)
pt2 = Coord(300,10) # y decline is very steep!!
print pt1,pt2,'vs', list(line(pt1, pt2))[-1]
print categorise(pt1,pt2)
print 200*'=='
pt1 = Coord(200,300)
pt2 = Coord(300,200) # y decline is not steep!!
print pt1,pt2,'vs', list(line(pt1, pt2))[-1]
print categorise(pt1,pt2)
# Now let's try our older examples:
# too steep
pt1 = Coord(10,20)
pt2 = Coord(200,300)
print pt1,pt2,'vs', list(line(pt1, pt2))[-1]
print categorise(pt1,pt2)
print pt2,pt1,'vs', list(line(pt2, pt1))[-1]
print categorise(pt1,pt2)
pt1 = Coord(10,0)
pt2 = Coord(300,100)
print pt1,pt2,'vs', list(line(pt1, pt2))[-1]
print categorise(pt1,pt2)
print pt2,pt1,'vs', list(line(pt2, pt1))[-1]
print categorise(pt1,pt2)
print "horiz test"
pt1 = Coord(10,0)
pt2 = Coord(300,0)
print pt1,pt2,'vs'
print list(line(pt1, pt2))[-1]
print "Vert test"
pt1 = Coord(0,220)
pt2 = Coord(0,10)
print pt1,pt2,'vs', list(line(pt1, pt2))[-1]
XDIM,YDIM = 50,40
buffer = ['.' for i in range(XDIM*YDIM)]
def putchar(x,y,char):
global XDIM
buffer[x+y*YDIM] = char
pt1,pt2 = Coord(10,10), Coord(20,20)
def charline(pt1, pt2):
aline = list(line(pt1,pt2))
for i in aline:
x,y = i
putchar(x,y,'*')
putchar(pt1.x,pt1.y,'X')
putchar(pt2.x,pt2.y,'Q')
crds = [Coord(10,10),
Coord(10,20),
Coord(20,20),
Coord(20,10)]
# CLEN = len(crds)
# for i in range(0,CLEN):
# #print crds[i], crds[(i+1)%CLEN]
# charline(crds[i],crds[(i+1)%CLEN])
def regupoly(points):
number_of_pnts = len(points)
for i in range(0,number_of_pnts):
charline(points[i], points[(i+1)%number_of_pnts])
regupoly(crds)
#--------- random shape drawer
from math import pi, sin, cos
corners = 6
center = Coord(20,20)
radius = 10
angle = lambda num : num*2*pi/(1.0*corners)
output = []
for corner in range(0,corners):
a = angle(corner)
x,y = int(round(center.x+radius*cos(a))), int(round(center.y+radius*sin(a)))
putchar(x,y,'@')
output += [Coord(x,y)]
print output
regupoly(output)
#--------- print the "backbuffer" of chars
for y in range(0,YDIM):
for x in range(0,XDIM):
print buffer[x+y*YDIM],
print
# prints out an ugly pair of shapes:
'''
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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. . . . . . . . . . Q * * * * * * * * * X . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . * . . . . X * * * * * * * * * X . . . . . . . . . . . . . . . . . . . . . . . .
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. . . . . . . . . . * * . . . . . . . . * . . . . . . . * . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . * * . . . . . . . . * . . . . . . . * . . . . . . . . . . . . . . . . . . . . .
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. . . . . . . . . . X * * * * * * * * * X . . . . . . . . . Q . . . . . . . . . . . . . . . . . . .
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. . . . . . . . . . . . . . . X * * * * * * * * * X . . . . . . . . . . . . . . . . . . . . . . . .
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'''