嵌入式学习--linux系统提供的显示接口”framebuffer“

1.利用framebuffer绘制图像

宏定义

1.#define RGB888_FMT 32
2.#define RGB565_FMT 16
3.#include"utf.h"

函数接口主体

void draw_bmp(int x, int y, char *picname, int w, int h)
{int fd = open(picname, O_RDONLY);if (-1 == fd){perror("fail open bmp");return ;}lseek(fd, 54, SEEK_SET);unsigned char r, g, b;unsigned char *buff = malloc(w*h*3);read(fd, buff, w*h*3);unsigned char *p = buff;for (int j = h-1; j >= 0; j--){for (int i = 0; i < w; i++){b = *p; p++;g = *p; p++;r = *p; p++;if (vinf.bits_per_pixel == RGB888_FMT){unsigned int col = (r << 16) | (g << 8) | (b << 0);draw_point(i+x, j+y, col);}else if (vinf.bits_per_pixel == RGB565_FMT){unsigned short col = ((r >> 3) << 11) | ((g >> 2) << 5) | ((b >> 3) << 0);draw_point(i+x, j+y, col);}}}free(buff);close(fd);
}

内部调用的函数接口

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 = pmem;
        *(p + y* vinf.xres_virtual + x)= col;
    }
    else if(vinf.bits_per_pixel == RGB565_FMT)
    {
        unsigned short *p = pmem;
        *(p + y *vinf.xres_virtual + x)= col;
    }
    return;
}

2.利用framebuffer实现输出一个字

函数主体

void draw_word(int x,int y,unsigned char *word,int w,int h,unsigned int col)
{
    for(int j =0;j<h;++j)
    {
        for(int i=0;i<w;++i)
        {
            unsigned char tmp = word[i+j*w];
            for(int k =0;k<8;++k)
            {
                if(tmp & 0x80)
                {
                    draw_point(i*8+k+x,j+y,col);
                }
                else
                {
                    //文字背景色
                }
                tmp = tmp << 1;
            }
        }
    }
}