如何画用C语言在framebuffer的图形..？ [英] How to draw the graph in framebuffer using c language..?

问题描述

我是新来的这本Linux的framebuffer所以不要任何人指导我绘制帧缓冲线路图。和我有code绘制在Turbo C的图形，但现在在Linux。所以，请帮助我。

i am new to this linux framebuffer so do anybody guide me to draw the line-graph in framebuffer. And i have the code to draw graph in turbo c but now in linux. So please help me out.

感谢您，
拉胡尔

Thank You, Rahul

推荐答案

使用 的open（） 在正确的文件的/ dev （如的/ dev / fb0设备），然后使用 mmap（）的 映射入存储器。联机手册将帮助这些系统调用，如果你不知道如何使用它们。

Use open() on the right file in /dev (eg. /dev/fb0), then use mmap() to map it into memory. Manpages will help for these syscalls if you do not know how to use them.

然后有一些 的ioctl（） S IN ＆LT; Linux的/ fb.h＆GT; 。像许多内核头文件，你可以学到很多简单的浏览文件。

Then there are some structures and constants for some ioctl()s in <linux/fb.h>. Like many kernel headers, you can learn a lot simply browsing the file.

特别有趣的是读写控制 FBIOGET_VSCREENINFO 与结构fb_var_screeninfo 。请注意，这有 XRES ， yres （分辨率）和 bits_per_pixel 。此外，还有 FBIOGET_FSCREENINFO 和结构fb_fix_screeninfo 里面有像更多信息键入和 line_length 。

Particularly interesting is the ioctl FBIOGET_VSCREENINFO with struct fb_var_screeninfo. Note this has xres, yres (resolution) and bits_per_pixel. Then there's FBIOGET_FSCREENINFO and struct fb_fix_screeninfo which has further information like type and line_length.

因此​​，在（X，Y）的像素可能会在 mmap_base_address + X * bits_per_pixel / 8 + Y * line_length 。像素将取决于你通过ioctl检索结构的具体格式;这是你的工作，以决定如何读/写。

So a pixel at (x, y) might be at mmap_base_address + x * bits_per_pixel/8 + y * line_length. The exact format of the pixels will depend on the structures you retrieve via ioctl; it's your job to decide how to read/write them.

这是一段时间，因为我跟这个工作，所以我的更多细节几分朦胧..

It's been a while since I've worked with this so I'm a bit hazy on more details..

下面是一个快速和肮脏的code样品只是为了说明它是如何做......我没有测试过这一点。

Here's a quick and dirty code sample just to illustrate how it's done... I haven't tested this.

#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;
}

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