# Detection of geometric shapes based on contours
**URL:** https://forum.opencv.org/t/detection-of-geometric-shapes-based-on-contours/8501
**Category:** Python
**Tags:** object-detection
**Created:** [April 22, 2022, 12:23pm UTC](https://forum.opencv.org/t/detection-of-geometric-shapes-based-on-contours/8501 "2022-04-22T12:23:14Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Giacomo\_Zamprogno](https://forum.opencv.org/u/Giacomo_Zamprogno)
#### Post date: [April 22, 2022, 12:23pm UTC](https://forum.opencv.org/t/detection-of-geometric-shapes-based-on-contours/8501/1 "2022-04-22T12:23:14Z")
I am trying to implement a basic “greedy” heuristic for dissection puzzles like the tangram: given a geometric shape I would need to extract an area in a silhouette where such figure might fit, with a given degree of similarity, according to how much of its contour matches.
For example in the picture there I’ve highlighted 2 placement for the triangle (I show 2, but there are probably 5) but the blue matches more contour/perimeter. I am aware it is unlikely to be an ideal heuristic, but I am more interested in the problem per se.
I thought about using shape-based matching (something derived from Steger 2002), but I am not sure it is the ideal approach here, and was trying to understand whether there is something more appropriate. Unluckily I am not an expert on computer vision and thus I am writing to ask whether there is a class of similar problems I can look into.
Sorry if the question is a bit general an not code oriented, but after some googling I have realized I don’t know enough terminology to have proper searches.
Thank you in advance
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### Author:  [@crackwitz](https://forum.opencv.org/u/crackwitz)
#### Post date: [April 22, 2022, 3:39pm UTC](https://forum.opencv.org/t/detection-of-geometric-shapes-based-on-contours/8501/2 "2022-04-22T15:39:58Z")
probably related to bin packing, knapsack, “cutting stock”… problems known in computer science