lxw_workbook *workbook_new_from_template(const char *filename, const char *template);
To use - just add
#include "libxlsxwriter_open_template.h"
#include "libxlsxwriter_open_template.h"
int main(int argc, char* argv[])
{
lxw_workbook *wb =
workbook_new_from_template("out.xlsx", "template.xlsx");
//do your magic
workbook_close(wb);
return 0;
}