This tool converts from various formats of planar straight-line graphs used in our research groups to the GraphML format used by our straight skeleton codes monos and surfer2.
The specification can be found in the [GRAPH-ATTRIBUTES][./GRAPH-ATTRIBUTES.md] in this repository.
Just symlinking bin/ord-format to your ~/bin directory, if that is in your
PATH should suffice.
For a more pythonesque way, try pip3 install . or pip3 install -e . to install it
in your home directory, or a virtualenv if you set up and activated one.
The main interface is the ord-format script which reads from one file and
writes the resulting .graphml to a file or stdout. The -r option adds
random edge weights.
For testing purposes, some of the readers can also be run individually, as in `python3 ./ORD53/formats/Line.py ../test-data/st0000054.line st0000054.graphml'.
There is no formal specification for many of the formats in use here. Here we list the ones that format-converter is able to read, along with a brief description of how they look. All file formats, unless otherwise stated, are text formats and (text-) line based.
A .line file consists of one or more blocks of the following: A line with an
integer specifying the number of vertices in the following, then a list of that
many text-lines of x and y coordinates, and lastly an empty line. Coordinates
in a line are space seperated; there may be leading whitespace.
Each such block is considered a polygonal chain. For closed chains, the first vertex is repeated at the end (and also counted as a vertex).
For polygons, it is customary to have its boundary in positive (i.e., counter clockwise) orientation. Any holes would be subsequent blocks in negative orientation.
A .poly file is a .line file in which the line segments implicitly form a
closed chain. That is, unlike with .line, the first vertex in the list is
not repeated at the end.
Site files can represent line segments, (isolated) points, and circular arc pieces. The format is a sequence of line-pairs, the first specifying the type and the second providing data for the element. Element-type 0 for instance is a line segment, element-type 2 an isolated point. -1 and 1 are circular arc segments. The only element-type supported is 2, a line segment. Its data line consists of a 4-tuple (x0, y0, x1, y1) where (x0,y0) and (x1,y1) are the coordinates of the segments endpoints.
Wavefront OBJ files first specify a list of vertices, and then faces or polygonal chains that refer to these vertices by index (1-based).
Currently format converter can read chain based (l <idx> <idx> ...) and face
based (f <idx> <idx> <idx> ...) .obj files with only positive vertex
indices.
These files are also understood by blender which makes them a nice interchange format at times.
IPE is a popular drawing program in our community. It allows storing
drawings in .pdf files to be directly included in LaTeX documents while still
being able to edit them afterwards. The format converter can parse (simple)
.ipe files and extract line segments from it.
The pen width, when numerically assigned to segments in the drawing, is interpreted as edge weight.