FreeType example. Load font file and export a specified glyph shape as a graphviz dot file.

glyph2dot.c

/*
gcc -I/usr/local/include/freetype2 -lfreetype glyph2dot.c -o glyph2dot
./glyph2dot hoge.ttf 0 A | dot -Kfdp -n -Tpng -o A.png
*/
#include <stdio.h>
#include <stdlib.h>

#include <ft2build.h>
#include FT_FREETYPE_H

const char* getErrorMessage(FT_Error err)
{
    #undef __FTERRORS_H__
    #define FT_ERRORDEF( e, v, s )  case e: return s;
    #define FT_ERROR_START_LIST
    #define FT_ERROR_END_LIST
    switch (err) {
        #include FT_ERRORS_H
    }
    return "(Unknown error)";
}

void exitOnError(FT_Error err)
{
    if (err)
    {
        printf("%s\n", getErrorMessage(err));
        exit(1);
    }
}

int main(int argc, char** args)
{
    // Initialize library
    FT_Library lib;
    exitOnError(FT_Init_FreeType(&lib));

    if (argc < 2) 
    {
        printf("Usage: ./glyph2dot font-path [index] [char]\n");
        return 1;
    }

    // Load font
    FT_Face face;
    int faceIndex = argc >= 3 ? atoi(args[2]) : 0;
    exitOnError(FT_New_Face(lib, args[1], faceIndex, &face));

    // Load glyph
    char ch = argc >= 4 ? args[3][0] : 'A';
    exitOnError(FT_Load_Char(face, ch, FT_LOAD_NO_SCALE));
    FT_Outline* outline = &face->glyph->outline;

    // Output outline as dot
    int start = 0;
    double scale = 0.002;
    printf("digraph {\n");
    printf("overlap=true;\n");
    for (int i = 0; i < outline->n_contours; i ++)
    {
        for (int j = start; j <= outline->contours[i]; j ++)
            printf("p%d [shape=point pos=\"%f,%f!\"]\n",
                   j, outline->points[j].x * scale, outline->points[j].y * scale);

        int onStart = start;
        while(!(outline->tags[onStart] & 1)) onStart ++;
        int before = onStart;
        for (int j = onStart + 1; j <= outline->contours[i]; j ++)
        {
            if (outline->tags[j] & 1)
            {
                printf("p%d -> p%d\n", before, j);
                before = j;
            }
        }
        printf("p%d -> p%d\n", before, onStart);

        start = outline->contours[i] + 1;
    }
    printf("}\n");

    // Release
    FT_Done_Face(face);
    FT_Done_FreeType(lib);
    return 0;
}