I had been doing some image rotation using Pillow (PIL) in an application I am developing. Unfortunately I am not going to be able to get the performance I want rotating images. I am going back to the drawing board and going to attempt to just draw lines and rotate them instead. Last night I put this together based off of some code from the book Python 2.5 Graphics Cookbook. I am hoping someone can show me how to rotate this line not at it end point but at a designated point in the line. In this case the center of the circle Here is my code.
# rotate_line_1.py
#>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
from Tkinter import *
import math
class RotateLine(object):
def __init__(self, master):
self.cw = 430
self.ch = 480
self.chart_1 = Canvas(root, width=self.cw, height=self.ch, background='white' )
self.chart_1.grid(row=0, column=0)
self.counter = StringVar()
self.counter.set('0')
self.linewidth = 10
self.o1 = self.chart_1.create_oval(1, 1, 430, 430, width=2, fill='#555555')
self.o2 = self.chart_1.create_oval(15, 15, 420, 420, width=2, fill='black')
self.a = self.chart_1.create_line(215, 20, 215, 215, width=self.linewidth, fill='red')
self.p1_x = 214.9 # the pivot point
self.p1_y = 20.0 # the pivot point,
self.p2_x = 215.0 # the specific point to be rotated
self.p2_y = 215.0 # the specific point to be rotated.
self.a_radian = math.atan((self.p2_y - self.p1_y)/(self.p2_x - self.p1_x))
self.a_length = math.sqrt((self.p2_y - self.p1_y)*(self.p2_y - self.p1_y) + (self.p2_x - self.p1_x)*(self.p2_x - self.p1_x))
self.cycle_period = 0 # pause duration (milliseconds).
self.x = 0
self.buttonFw = Button(root, text="1 >>", command=lambda: self.rotate_line(1, 1))
self.buttonBk = Button(root, text="<< 1", command=lambda: self.rotate_line(-1, 1))
self.button45B = Button(root, text="<< 45", command=lambda: self.rotate_line(-1, 45))
self.button45F = Button(root, text="45 >>", command=lambda: self.rotate_line(1, 45))
self.button0 = Button(root, text="0", command=lambda: self.rotate_line(-1, 0))
self.buttonBk.place(x=10, y=440)
self.button45B.place(x=75, y=440)
self.button45F.place(x=290, y=440)
self.buttonFw.place(x=363, y=440)
self.button0.place(x=198, y=440)
self.clicks = 0
print self.a_radian
def rotate_line(self, direction, degree):
self.chart_1.delete(self.a)
if degree == 0:
print 'Hello zero'
self.chart_1.delete(self.a)
self.a = self.chart_1.create_line(215, 20, 215, 215, width=self.linewidth, fill='red')
self.a_radian = 1.57028350633
else:
self.a_radian += (.01747 * degree) * direction # incremental rotation with direction
print self.a_radian
self.p1_x = self.p2_x - self.a_length * math.cos(self.a_radian)
self.p1_y = self.p2_y - self.a_length * math.sin(self.a_radian)
self.i = self.chart_1.create_line(self.p1_x, self.p1_y, self.p2_x, self.p2_y, width=self.linewidth, fill='red')
self.chart_1.update()
self.chart_1.after(self.cycle_period)
self.chart_1.delete(self.i)
self.a = self.chart_1.create_line(self.p1_x, self.p1_y, self.p2_x, self.p2_y, width=self.linewidth, fill='red')
root = Tk()
root.title("Rotating line")
app = RotateLine(root)
root.mainloop()
If you run this you will get a line on a couple of circle backgrounds. Press the buttons to move the line around the center of the circles.
What I want to do it make the line longer but still rotate it at the circle center. Update the line cordinates in both of these lines in the code to 325.
self.a = self.chart_1.create_line(215, 20, 215, 325, width=self.linewidth,
fill='red')
Once the line is longer how can I keep the rotation point still at the center of the circle and redraw the line accordingly?
Thanks in advance and yes my trig skills stink.
