View Full Version : contour path generation for spectrogram

10th November 2008, 08:36
Hi list,

Qwt now can only generate line segments for contour plot. I came across this article, implementing the vector generation based on CONREC algorithm, http://apptree.net/conrec.htm. Unfortunately it is a Cocoa Object-C program and I can not directly test.

While I have made an naive try and found the following problems:
1. the generated paths often aren't closed. And the situation is better when zoomed in.
2. this algorithms does not include boundary conditions.

Since my Qwt knowledge is very limited. Uwe, are you interested? This would open more options in contour plot, such as filled contour, labeling contour lines.

10th November 2008, 10:35
Qwt already uses the CONREC algo. So what exactly is your suggestion ?


10th November 2008, 11:01
The original CONREC algorithm generates the contour line segments randomly. And it does not give contour vectors. The one algorithm I refer to would allow the generation of contour lines as vectors, corresponding to Painter Path in Qt. As said, this is necessary for filled contour plot or contour lines labeling.
This may be what you called "vectorizer" in another thread,

10th November 2008, 12:14
This sound like a substantial improvement and yes I'm interested to have the advanced CONREC algorithm in Qwt. Let me know ( by email ), if you need support for the implemention.