based on
A. Wolin, B. Eoff, and T. Hammond, “ShortStraw: A Simple and Effective Corner Finder for Polylines.” in SBM, 2008, pp. 33–40.
and
Y. Xiong and J. J. LaViola Jr, “Revisiting shortstraw: improving corner finding in sketch-based interfaces,” in Proceedings of the 6th Eurographics Symposium on Sketch-Based Interfaces and Modeling, 2009, pp. 101– 108.
Use the function short_straw from shortstraw.py to calculate corner and curve points in a vector format image. A Jupyter notebook and a JSON file with an example dataset is included to demonstrate the functionality.
- paths : array_like
- expects an array in the form:
#Sketch array
[
#Path 1 array
[ #Points
[x0,x1,x2 ,...] # x positions
[y0,y1,y2 ,...] # y positions
],
#More paths
[...] , [...] , ...
]
- t1 : float, optional
- Threshold for first postprocessing iteration, should be between 0 and 1, default = 0.96
- t2max : float, optional
- Upper threshold for second postprocessing iteration, should be be between 0 and 1, default = 0.95
- t2min : float, optional
- Lower threshold for second postprocessing iteration, should be be between 0 and 1, default = 0.944
For a in depth description of the threshold, have a look at the Wolin et al. paper. If you just want to play around with the values, keep in mind that all values should be between 0 and 1 this should apply: t1 > t2max > t2min.
- all_corners: list
- the indices of the points that are determined to be corner points for each path, in the form:
#Feature point array
[
#Path 1 indices
[index0,index1,index2,...],
#More paths
[...],[...],...
]
- all_curves: list
- the indices of the points that are determined to be curve points for each path. Same format as all_corners
- feature_info: dict
- classifies angles and curve points and returns count. Have a look at the Xiong and LaViola paper for a definition of the curve angle.
| Key | Description |
|---|---|
| straight | number of corner points with angle ≥ 0.99 * PI |
| obtuse | number of corner points with 0.55 * PI < angle < 0.99 * PI |
| right | number of corner points with 0.45 * PI ≤ angle ≤ 0.55 * PI |
| obtuse | number of corner points with angle < 0.45 * PI |
| wide_curve | number of curve points with angle > 0.5 * PI |
| narrow_curve | number of curve points with angle ≤ 0.5 * PI |
- resampled_data: list
- resampled version of the input data
- all_raw_angles: list
- a list of floats representing the angle sizes for all corner points
- all_raw_curves: list
- a list of floats representing the angle sizes for all curve points