1.源码实现

#include <stdio.h>
#include <math.h>
#include <cairo.h>

#define CAIRO_HEIGHT 300
#define PI 3.141592654

void cairo_line_by_angle(cairo_t *cr, int x, int y, int r, int angle, int *a, int *b)
{
        double x1 = x;
        double y1 = CAIRO_HEIGHT - y;
        double x2 = x1 + r * cos(angle*PI/180.00);
        double y2 = y1 + r * sin(angle*PI/180.00);

        *a = x2;
        *b = CAIRO_HEIGHT - y2;

        cairo_line_to(cr, *a, *b);
}

int main()
{
        cairo_surface_t *surface;
        cairo_t *cr;                    //声明一支画笔
        int x = 100;
        int y = 240;
        double r = 100.00 / (2.00 * cos(36.0*PI/180.0));

        surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 300, CAIRO_HEIGHT);
        cr = cairo_create(surface);             //创建画笔
        cairo_set_source_rgb(cr,0,1,0); //设置画笔颜色，也就是红，绿，蓝，这里设置成绿色。
        cairo_move_to(cr, x, y);   //五角星
        cairo_line_by_angle(cr, x, y, r, 36, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 324, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 108, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 36, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 180, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 108, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 252, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 180, &x, &y);
        cairo_line_by_angle(cr, x, y, r, 324, &x, &y);
        cairo_close_path(cr);
        cairo_fill(cr);                 //填充，使用的颜色当然是上面设置的颜色。
        //cairo_stroke(cr);
        cairo_surface_write_to_png(surface, "h.png"); //写入png文件
        cairo_destroy(cr);              //销毁画笔

        return 0;
}

2.编译源码

$ gcc -I$HOME/local/include/cairo -o example example.c -L$HOME/local/lib -lcairo -lXrender -lfontconfig

3.运行结果

h.png