Usage: autotrace.exe [options] <input_name>.
Options:<input_name> should be a supported image.
  You can use `--' or `-' to start an option.
  You can use any unambiguous abbreviation for an option name.
  You can separate option names and values with `=' or ` '.
background-color <hexadecimal>: the color of the background that
  should be ignored, for example FFFFFF;
  default is no background color.
centerline: trace a character's centerline, rather than its outline.
color-count <unsigned>: number of colors a color bitmap is reduced to,
  it does not work on gray scale, allowed are 1..256;
  default is 0, that means not color reduction is done.
corner-always-threshold <angle-in-degrees>: if the angle at a pixel is
  less than this, it is considered a corner, even if it is within
  `corner-surround' pixels of another corner; default is 60.
corner-surround <unsigned>: number of pixels on either side of a
  point to consider when determining if that point is a corner;
  default is 4.
corner-threshold <angle-in-degrees>: if a pixel, its predecessor(s),
  and its successor(s) meet at an angle smaller than this, it's a
  corner; default is 100.
despeckle-level <unsigned>: 0..20; default is no despeckling.
despeckle-tightness <real>: 0.0..8.0; default is 2.0.
dpi <unsigned>: The dots per inch value in the input image, affects scaling
  of mif output image
error-threshold <real>: subdivide fitted curves that are off by
  more pixels than this; default is 2.0.
filter-iterations <unsigned>: smooth the curve this many times
  before fitting; default is 4.
input-format:  TGA, PBM, PNM, PGM, PPM or BMP.
help: print this message.
line-reversion-threshold <real>: if a spline is closer to a straight
  line than this, weighted by the square of the curve length, keep it a
  straight line even if it is a list with curves; default is .01.
line-threshold <real>: if the spline is not more than this far away
  from the straight line defined by its endpoints,
  then output a straight line; default is 1.
list-output-formats: print a list of support output formats to stderr.
list-input-formats:  print a list of support input formats to stderr.
log: write detailed progress reports to <input_name>.log.
output-file <filename>: write to <filename>
output-format <format>: use format <format> for the output file
output-format <format>: use format <format> for the output file
  eps, ai, p2e, sk, svg, fig, swf, emf, mif, er, dxf, epd, pdf, cgm or dr2d
  can be used.
preserve-width: whether to preserve line width prior to thinning.\n\
remove-adjacent-corners: remove corners that are adjacent.
tangent-surround <unsigned>: number of points on either side of a
  point to consider when computing the tangent at that point; default is 3.
report-progress: report tracing status in real time.
debug-arch: print the type of cpu.
debug-bitmap: dump loaded bitmap to <input_name>.bitmap.
version: print the version number of this program.
width-weight-factor: weight factor for fitting the line width.

gcc sample.c `pkg-config --libs autotrace` `pkg-config --cflags autotrace`

/* sample.c */
#include <autotrace/autotrace.h>

int main()
{
  char * fname = "img/triangle.png";
  at_fitting_opts_type * opts = at_fitting_opts_new();
  at_input_read_func rfunc = at_input_get_handler(fname);
  at_bitmap_type * bitmap ;
  at_splines_type * splines;
  at_output_write_func wfunc = at_output_get_handler_by_suffix("eps");

  bitmap = at_bitmap_read(rfunc, fname, NULL, NULL, NULL);
  splines = at_splines_new(bitmap, opts, NULL, NULL);
  at_splines_write(wfunc, stdout, "", NULL, splines, NULL, NULL);
  return 0;
}