[plug] Interactive generation of polygons from segments

[Cameron Patrick]

Cameron Patrick wrote:

> I'm also going to mention matplotlib http://matplotlib.sourceforge.net/ 
> which is a very handy plotting library for Python.  I don't think it's
> directly useful for what you're after, but then again things like
> drawing a scatter graph might have quite a bit in common with drawing
> nice polygons, and it allows you at least a little bit of interactivity
> in terms to doing stuff to your plots when they're clicked on and so on.

15 minutes looking at docs and less than 50 lines of code got me most
of what Jim wanted.  Source attached, do what you want with it.

Cameron


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#! /usr/bin/env python

from pylab import *
import sys

if len(sys.argv) != 2:
        print "usage: scatter.py input-file"
        sys.exit(1)

def add_point(event):
        if not event.inaxes:
                return
        click = array([event.xdata, event.ydata])
        best = None
        for p in points:
                dist = sum(pow(p-click,2))
                if best is None or dist < best[0]:
                        best = (dist, p[0], p[1])
        print best
        if best is None:
                return
        
        polyx.append(best[1])
        polyy.append(best[2])
        redraw()

def redraw():
        cla()
        scatter(x, y)
        plot(polyx, polyy)
        draw()

input_file = sys.argv[1]

lines = [line.strip().split() for line in file(input_file)]
points = array([[float(x) for x in y] for y in lines])
x = points[:, 0]
y = points[:, 1]

polyx = []
polyy = []

connect('button_press_event', add_point)
redraw()
show()