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Linux内核为显示提供的一套应用程序接口#xff08;驱动内核支持#xff09;
分辨率#xff1a;像素点的总和
像素点#xff1a;
显示屏#xff1a;800*600#xff08;横向有800个像素点#xff0c;纵向有600个像素点#x…framebuffer帧缓冲、帧缓存
Linux内核为显示提供的一套应用程序接口驱动内核支持
分辨率像素点的总和
像素点
显示屏800*600横向有800个像素点纵向有600个像素点
显卡显存保存像素点的值
RGB8个bitR8个bitG8个bitB
RGB888PC4412
RGB565S3C2440
原理
通过内存映射技术向显存空间写入RGB值
1.打开显示设备/dev/fb0
2.获取显示设备相关参数分辨率、位深度
3.建立内存映射
4.写入RGB颜色值
5.解除映射
6.关闭显
#include framebuffer.h
#include linux/fb.h
#include stdlib.h
#include sys/mman.h
#include sys/ioctl.h
#include unistd.h
#include fcntl.h
#include sys/types.h
#include sys/stat.h
#include stdio.h
#include math.hvoid* pmem;
struct fb_var_screeninfo vinf;
//初始化
int init_fb(char *devname)
{int fd open(devname, O_RDWR);if(-1 fd){perror(open fail);return -1;}int ret ioctl(fd, FBIOGET_VSCREENINFO, vinf);if(-1 ret){perror(ioctl fail);return -1;}size_t len vinf.xres_virtual * vinf.xres_virtual * vinf.bits_per_pixel/8;pmem mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);if ((void *)-1 pmem){perror(fail mmap);return -1;}return fd;}
//点
void draw_point(int x, int y, unsigned int col)
{if (x vinf.xres || y vinf.yres){return ;}if (vinf.bits_per_pixel RGB888_FMT){unsigned int *p (unsigned int*)pmem;*(p y * vinf.xres_virtual x) col;}else if (vinf.bits_per_pixel RGB565_FMT){unsigned short *p (unsigned short*)pmem;*(p y * vinf.xres_virtual x) col;}return ;
}
//横线
void draw_xline(int x, int y, int xlen, unsigned int col)
{if (x vinf.xres || y vinf.yres){return ;}int i 0;for(i 0; i xlen; i){if (vinf.bits_per_pixel RGB888_FMT){unsigned int *p (unsigned int*)pmem;*(p y * vinf.xres_virtual (x i)) col;}else if (vinf.bits_per_pixel RGB565_FMT){unsigned short *p (unsigned short*)pmem;*(p y * vinf.xres_virtual (x i)) col;}}return ;}
//竖线
void draw_yline(int x, int y, int ylen, unsigned int col)
{if (x vinf.xres || y vinf.yres){return ;}int i 0;for(i 0; i ylen; i){if (vinf.bits_per_pixel RGB888_FMT){unsigned int *p (unsigned int*)pmem;*(p (y i) * vinf.xres_virtual x) col;}else if (vinf.bits_per_pixel RGB565_FMT){unsigned short *p (unsigned short*)pmem;*(p (y i) * vinf.xres_virtual x) col;}}return ;}
//矩形
void draw_rectangle(int x, int y, int xlen, int ylen, unsigned int col)
{if (x vinf.xres || y vinf.yres){return ;}draw_xline(x,y,xlen,col);draw_xline(x,y ylen, xlen, col);draw_yline(x,y,ylen,col);draw_yline(x xlen, y, ylen, col);return ;
}
//清屏
void clear_scream_col(unsigned int col)
{int i 0, j 0;for(i 0; i vinf.xres; i){for(j 0; j vinf.yres; j){draw_point(i, j, col);}}}
//斜线
void draw_xyline(double x1, double y1, double x2, double y2, unsigned int col)
{double k (y2 - y1) / (x2 - x1);double b y1 - (k * x1);int i 0;for(i 0; i (x2 - x1); i){draw_point((int)x1 i, (int)(k * (x1 i) b), col);}return ;
}
//圆
void draw_circle(double x, double y, double r, unsigned int col)
{double a x, b y;int i 0;for (i 0; i 360; i) { float theta 2 * 3.14 * i / 360; float x1 r * cos(theta) x; float y1 r * sin(theta) y;draw_point(x1,y1,col);}return ;
}void uninit_fb(int fd)
{size_t len vinf.xres_virtual * vinf.yres_virtual * vinf.bits_per_pixel/8;munmap(pmem, len);close(fd);
}
示设备
