dashing - a library for autocad-style hatch patterns

License: permissive (zlib); see source files for additional details.

On a i5-3320M in benchmark mode, it runs at over 175 million dashes per second:

$ time ./dashing -b -s .01 data/HWOOD6E1.pat  data/sf.seg
111430525
user    0m0.616s

xyhatch(const HatchPattern&, It start, It end, Cb cb, Wr wr): Iterators start..end define a range of segments, which must define a set of closed contours. The winding rule wr defines which regions are in the interior of the contours. For each dash or dot in the resulting hatch, cb is called with the output segment.

xyhatch(const HatchPattern&, const C &segments, Cb cb, Wr wr): The container C holds segments which must define a set of closed contours. The winding rule wr defines which regions are in the interior of the contours. For each dash or dot in the resulting hatch, cb is called with the output segment.

parse_numbers(std::string line): Read a comma and/or space-separated sequence of numbers into a vector

Useful winding rules include:

• [](int i) { return i % 2 != 0; }, the even-odd winding rule
• [](int i) { return i != 0;}, the non-zero winding rule
• [](int i) { return i > 0;}, the greater-than-zero winding rule but any predicate of a single integer may be used.

Other items in the header files are implementation details.

Demo program

The demo program, which compiles to dashing with make, reads a dash pattern file and a segment list file and produces a svg file on the output which visualizes the result of the hatch operation.

A segment list file consists of a closed contour on each line specified as a series of x,y coordinates. For instance, this segment list is a simple box:

-100 -100 100 -100 100 100 -100 100

The first point is -100 -100.

It accepts several commandline parameters:

-b: Benchmark mode: print only the number of dashes that would have been
    generated

-j: Apply a jitter to all coordinaes in the segment list file

-s: scale the dash pattern file by a given factor

-r rulename: select the given rulename, one of the following: odd nonzero positive negative abs_geq_two