Created
April 10, 2013 20:02
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Rotate a polygon in Tkinter using complex numbers.
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from Tkinter import * | |
import math | |
c = Canvas(width=200, height=200) | |
c.pack() | |
# a square | |
xy = [(50, 50), (150, 50), (150, 150), (50, 150)] | |
polygon_item = c.create_polygon(xy) | |
center = 100, 100 | |
def getangle(event): | |
dx = c.canvasx(event.x) - center[0] | |
dy = c.canvasy(event.y) - center[1] | |
try: | |
return complex(dx, dy) / abs(complex(dx, dy)) | |
except ZeroDivisionError: | |
return 0.0 # cannot determine angle | |
def press(event): | |
# calculate angle at start point | |
global start | |
start = getangle(event) | |
def motion(event): | |
# calculate current angle relative to initial angle | |
global start | |
angle = getangle(event) / start | |
offset = complex(center[0], center[1]) | |
newxy = [] | |
for x, y in xy: | |
v = angle * (complex(x, y) - offset) + offset | |
newxy.append(v.real) | |
newxy.append(v.imag) | |
c.coords(polygon_item, *newxy) | |
c.bind("<Button-1>", press) | |
c.bind("<B1-Motion>", motion) | |
mainloop() |
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