然后,< linux / fb.h>中的某些ioctl()有一些结构和常量.像许多内核头文件一样,您可以轻松学习浏览文件.

特别有趣的是ioctl FBIOGET_VSCREENINFO与struct fb_var_screeninfo.注意这里有xres,yres(resolution)和bits_per_pixel.那么有FBIOGET_FSCREENINFO和struct fb_fix_screeninfo,其中有更多的信息,如类型和line_length.

因此,(x,y)处的像素可能位于mmap_base_address x * bits_per_pixel / 8 y * line_length.像素的确切格式将取决于您通过ioctl检索的结构;这是你的工作,决定如何读/写它们.

已经有一段时间,因为我已经与这样做,所以我有点朦胧更多的细节..

这是一个快速而脏的代码示例,只是为了说明它的完成情况…我还没有测试过.

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
 
#include <linux/fb.h>
 
#include <unistd.h>
#include <fcntl.h>
 
#include <stdio.h>
 
int main()
{
   struct fb_var_screeninfo screen_info;
   struct fb_fix_screeninfo fixed_info;
   char *buffer = NULL;
   size_t buflen;
   int fd = -1;
   int r = 1;
 
   fd = open("/dev/fb0",O_RDWR);
   if (fd >= 0)
   {
      if (!ioctl(fd,FBIOGET_VSCREENINFO,&screen_info) &&
          !ioctl(fd,FBIOGET_FSCREENINFO,&fixed_info))
      {
         buflen = screen_info.yres_virtual * fixed_info.line_length;
         buffer = mmap(NULL,buflen,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
         if (buffer != MAP_Failed)
         {
            /*
             * TODO: something interesting here.
             * "buffer" now points to screen pixels.
             * Each individual pixel might be at:
             *    buffer + x * screen_info.bits_per_pixel/8
             *           + y * fixed_info.line_length
             * Then you can write pixels at locations such as that.
             */
 
             r = 0;   /* Indicate success */
         }
         else
         {
            perror("mmap");
         }
      }
      else
      {
         perror("ioctl");
      }
   }
   else
   {
      perror("open");
   }
 
   /*
    * Clean up
    */
   if (buffer && buffer != MAP_Failed)
      munmap(buffer,buflen);
   if (fd >= 0)
      close(fd);
 
   return r;
}