This is an adaptation of the Zhang-Suen thinning algorithm and related pre-processing and post-processing steps as presented in Algorithms for Image Processing and Computer Vision by JR Parker.
For only C++
For Python support
OpenCV, built with Python bindings.
$ cd zhang-suen-thinning
The library exposing the function that performs Zhang-Suen thinning can be
built in two ways. For use in C++ programs, the static llibrary
libzhangsuen.a can be produced by going into the toplevel directory for the
project and typing
This will produce
libzhangsuen.a in the current directory, which can then be
used to link with C++ programs using the library.
For use with Python, OpenCV must be installed, built with Python support. Then, the Python extension can be built by doing
$ make python
This will produce
python/, which is an extension directly
importable from Python:
$ cd python $ python Python 2.7.3 (default, Sep 9 2012, 17:41:34) [GCC 4.7.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import zhangsuen >>> zhangsuen.thin <Boost.Python.function object at 0x12f67e0> >>>
void thin(cv::Mat& img, bool need_boundary_smoothing=false, bool need_acute_angle_emphasis=false, bool destair=false)
zhangsuen.thin(img, need_boundary_smoothing, need_acute_angle_emphasis, destair) -> numpy.ndarray
img: The input grayscale(ideally binarized) image (A `numpy.ndarray` in Python). Thinning is performed in place in C++ and a new `numpy.ndarray` object holding the thinned image is returned in Python. need_boundary_smoothing: Whether or not to perform the Stentiford Boundary smoothing pre processing to reduce line fuzz. Line fuzz is the name given to spurious projections and extra lines on the skeleton boundaries. need_acute_angle_emphasis: Whether or not to perform acute-angle emphasis to reduce necking. Sometimes, a narrow point at the intersection of lines is stretched into a small line segment. This is called "necking". This type of artifacts can be reduced by setting all the black points that tend to choke an acute angle joint to white. This operation is known as acute-angle emphasis. destair: Whether to perform Holt's destairing pre processing operation. Sometimes, after thinning, there still are pixels that could be removed. Many of such removable pixels form staircases in oblique lines. Holt's post processing, called destairing, attempts to delete such points which, when removed, do not affect the connectivity or shape information of the skeleton.