To: discussions about usage and development of dia <dia-list gnome org>
Subject: Re: Length of a PolyLine
Date: Tue, 25 Jan 2005 22:51:09 +0100
Chris Burkert wrote:
at first I would like to thank all of you developers of dia.
I'm using dia for drawing maps where I take some raster data like a
.png, put some lines and labels on it and export this as a .png again. I
have an example at .
Now I would like to measure the length of the red PolyLine at the
seaside in a defined unit. My first idea was to use pythagoras in the
python console and I wrote this little script which I load with
from math import sqrt
distance = 0
size = len(points.value)
for i in range(size):
a = points.value[i]
if i < size-1:
b = points.value[i+1]
distance += sqrt(pow(2,a.x-b.x) + pow(2,a.y-b.y))
Shouldn't the parameters to pow() be the other way around?
The problem is that the tuple points.value seems not to be ordered thus
points.value is not always the same.
What do you mean with "not always the same"? Looking just at the
Python bindings plug-ins/python/pydia-property.c(PyDia_get_PointArray)
you'll get the points in the same order as stored internally. And
that needs to be ordered to get the drawing right.
So what can I do to mesasure
the length of this PolyLine correct? Except parsing the .dia xml by hand
After fixing the bug from above it should work ;-)
-------- Hans "at" Breuer "dot" Org -----------
Tell me what you need, and I'll tell you how to
get along without it. -- Dilbert