Framebuffer 画点，画线，画多边形，画圆，画抛物线 函数

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <asm/page.h>
#include <linux/fb.h>

#define TRUE    1
#define FALSE   0

#define MIN(x,y)        ((x)>(y)?(y):(x))
#define MAX(x,y)        ((x)>(y)?(x):(y))

typedef struct fbdev{
        int fb;
        unsigned long fb_mem_offset;
        unsigned long fb_mem;
        struct fb_fix_screeninfo fb_fix;
        struct fb_var_screeninfo fb_var;
        char dev[20];
} FBDEV, *PFBDEV;

typedef struct point{
        int x;
        int y;
        int z;
} POINT, *PPOINT;

/* These math function Writed by
* kf701 <[e-mail]>
* 2007-04-05 HeFei
*/
void draw_dot (PFBDEV pFbdev, POINT p, uint8_t r, uint8_t g, uint8_t b);
void draw_line(PFBDEV pFbdev, POINT p1, POINT p2, uint8_t r, uint8_t g, uint8_t b);
void draw_polygon(PFBDEV pFbdev, uint32_t num, PPOINT array, uint8_t r, uint8_t g, uint8_t b);
void draw_triangle(PFBDEV pFbdev, POINT p1, POINT p2, POINT p3, uint8_t r, uint8_t g, uint8_t b);
void draw_circle(PFBDEV pFbdev, POINT center, uint32_t radius, uint8_t r, uint8_t g, uint8_t b);
void draw_parabola_x(PFBDEV pFbdev, POINT center, int a, uint8_t r, uint8_t g, uint8_t b);
void draw_parabola_y(PFBDEV pFbdev, POINT center, int a, uint8_t r, uint8_t g, uint8_t b);

int fb_open(PFBDEV pFbdev)
{
        pFbdev->fb = open(pFbdev->dev, O_RDWR);
        if(pFbdev->fb < 0)
        {
                printf("Error opening %s: %m. Check kernel config\n", pFbdev->dev);
                return FALSE;
        }
        if (-1 == ioctl(pFbdev->fb,FBIOGET_VSCREENINFO,&(pFbdev->fb_var)))
        {
                printf("ioctl FBIOGET_VSCREENINFO\n");
                return FALSE;
        }
        if (-1 == ioctl(pFbdev->fb,FBIOGET_FSCREENINFO,&(pFbdev->fb_fix)))
        {
                printf("ioctl FBIOGET_FSCREENINFO\n");
                return FALSE;
        }

        pFbdev->fb_mem_offset = (unsigned long)(pFbdev->fb_fix.smem_start) & (~PAGE_MASK);
        pFbdev->fb_mem = (unsigned long int)mmap(NULL, pFbdev->fb_fix.smem_len +
                        pFbdev->fb_mem_offset,
                        PROT_READ | PROT_WRITE, MAP_SHARED, pFbdev->fb, 0);
        if (-1L == (long) pFbdev->fb_mem)
        {
                printf("mmap error! mem:%ld offset:%ld\n", pFbdev->fb_mem,
                                pFbdev->fb_mem_offset);
                return FALSE;
        }
/*
        printf("depth(bits per pixel) = %d\n",fb.fb_var.bits_per_pixel);
        printf("smemlen = %d\n",fb.fb_fix.smem_len);
        printf("fix_line(in byte) = %d\n",fb.fb_fix.line_length);
*/
        return TRUE;
}

void fb_close(PFBDEV pFbdev)
{
        close(pFbdev->fb);
        pFbdev->fb=-1;
}

void fb_memcpy(void *addr, void *color, size_t len)
{
        memcpy(addr, color, len);
}

void draw_dot (PFBDEV pFbdev, POINT p, uint8_t r, uint8_t g, uint8_t b)
{
        uint32_t offset;
        uint8_t color[4];
        color[0] = b;
        color[1] = g;
        color[2] = r;
        color[3] = 0x0;
        offset = p.y*pFbdev->fb_fix.line_length+4*p.x;
        fb_memcpy((void*)(pFbdev->fb_mem + pFbdev->fb_mem_offset + offset), color, 4);
}

void draw_line(PFBDEV pFbdev, POINT p1, POINT p2, uint8_t r, uint8_t g, uint8_t b)
{
        POINT p;
        int x,y;
        for( x=MIN(p1.x,p2.x); x<=MAX(p1.x,p2.x); x++ )
        {
                y = (p2.y-p1.y)*(x-p1.x)/(p2.x-p1.x) + p1.y;
                p.x = x;
                p.y = y;
                draw_dot(pFbdev, p, r, g, b);
        }
}

void draw_triangle(PFBDEV pFbdev, POINT p1, POINT p2, POINT p3, uint8_t r, uint8_t g, uint8_t b)
{
        POINT p[3];
        p[0] = p1;
        p[1] = p2;
        p[2] = p3;
        draw_polygon(pFbdev, 3, p, r, g, b);
}

void draw_polygon(PFBDEV pFbdev, uint32_t num, PPOINT array, uint8_t r, uint8_t g, uint8_t b)
{
        int i;
        for(i=0; i<num; i++)
        {
                draw_line(pFbdev, array[i], array[(i+1)%num], r, g, b);
        }
}

void draw_circle(PFBDEV pFbdev, POINT center, uint32_t radius, uint8_t r, uint8_t g, uint8_t b)
{
        POINT p;
        int x,y,tmp;
        for(x=center.x-radius; x<=center.x+radius; x++)
        {
                p.x = x;
                tmp = sqrt(radius*radius -(x-center.x)*(x-center.x));
                p.y = center.y + tmp;
                draw_dot(pFbdev, p, r, g, b);
                p.y = center.y - tmp;
                draw_dot(pFbdev, p, r, g, b);
        }
        for(y=center.y-radius; y<=center.y+radius; y++)
        {
                p.y = y;
                tmp = sqrt(radius*radius - (y-center.y)*(y-center.y));
                p.x = center.x + tmp;
                draw_dot(pFbdev, p, r, g, b);
                p.x = center.x - tmp;
                draw_dot(pFbdev, p, r, g, b);
        }
}

void draw_parabola_x(PFBDEV pFbdev, POINT center, int a, uint8_t r, uint8_t g, uint8_t b)
{
        int x;
        POINT p;
        for(x=center.x-100; x<center.x+100; x++)
        {
                p.x = x;
                p.y = (x-center.x)*(x-center.x)/a + center.y;
                draw_dot(pFbdev, p, r, g, b);
        }
}

void draw_parabola_y(PFBDEV pFbdev, POINT center, int a, uint8_t r, uint8_t g, uint8_t b)
{
        int y;
        POINT p;
        for(y=center.y-100; y<center.y+100; y++)
        {
                p.y = y;
                p.x = (y-center.y)*(y-center.y)/a + center.x;
                draw_dot(pFbdev, p, r, g, b);
        }
}

int main(void)
{
        FBDEV fb;
        memset(&fb, 0, sizeof(FBDEV));
        strcpy(fb.dev, "/dev/fb0");
        if(fb_open(&fb)==FALSE)
        {
                printf("open frame buffer error\n");
                return 0;
        }

        POINT p1, p2, p3;

        p1.x = 300;
        p1.y = 450;
        p2.x = 500;
        p2.y = 300;
        draw_line( &fb, p1, p2, 0x0, 0xff, 0x0 );

        p1.x = 200;
        p1.y = 200;
        p2.x = 300;
        p2.y = 400;
        p3.x = 500;
        p3.y = 250;
        draw_triangle(&fb, p1, p2, p3, 0x0, 0xff, 0x0);

        POINT center = { 600, 500, 0 };
        int radius = 100;
        draw_circle(&fb, center, radius, 0x0, 0xff, 0x0);
/*
        int i;
        for(i=radius-2; i>=0; i--)
        {
                draw_circle(&fb, center, i, 0xff, 0xff, 0x0);
        }
*/
        center.x = 700;
        center.y = 250;
        int a = -100;
        draw_parabola_x(&fb, center, a, 0x0, 0xff, 0x0);
        draw_parabola_x(&fb, center, -a, 0x0, 0xff, 0x0);
        draw_parabola_y(&fb, center, a, 0x0, 0xff, 0x0);
        draw_parabola_y(&fb, center, -a, 0x0, 0xff, 0x0);

        fb_close(&fb);
        return 0;
}

来源：http://hi.baidu.com/mikenoodle/blog/item/f0317ff0739d2cc57831aa55.html