framebuffer应用程序测试 （一）

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  程序源代码是：   中提到的代码
   首先对 这个程序进行测试，看看效果，然后对它进行分析。

再次贴出代码 如下；
    Testing: Here's a short program that opens the frame buffer and draws a gradient-filled red square.

    画一个红色的矩形框

#include <unistd.h>
    #include <stdio.h>
    #include <fcntl.h>
    #include <linux/fb.h>
    #include <sys/mman.h>

    int main()
    {
        int fbfd = 0;
        struct fb_var_screeninfo vinfo;
        struct fb_fix_screeninfo finfo;
        long int screensize = 0;
        char *fbp = 0;
        int x = 0, y = 0;
        long int location = 0;

        // Open the file for reading and writing
        fbfd = open("/dev/fb0", O_RDWR);
        if (!fbfd) {
            printf("Error: cannot open framebuffer device.\n");
            exit(1);
        }
        printf("The framebuffer device was opened successfully.\n");

        // Get fixed screen information
        if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
            printf("Error reading fixed information.\n");
            exit(2);
        }

        // Get variable screen information
        if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
            printf("Error reading variable information.\n");
            exit(3);
        }

        printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );

        // Figure out the size of the screen in bytes
        screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

        // Map the device to memory
        fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
                           fbfd, 0);
        if ((int)fbp == -1) {
            printf("Error: failed to map framebuffer device to memory.\n");
            exit(4);
        }
        printf("The framebuffer device was mapped to memory successfully.\n");

        x = 100; y = 100; // Where we are going to put the pixel

        // Figure out where in memory to put the pixel
        for ( y = 100; y < 300; y++ )
            for ( x = 100; x < 300; x++ ) {

                location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
                           (y+vinfo.yoffset) * finfo.line_length;

                if ( vinfo.bits_per_pixel == 32 ) {
                    *(fbp + location) = 100; // Some blue
                    *(fbp + location + 1) = 15+(x-100)/2; // A little green
                    *(fbp + location + 2) = 200-(y-100)/5; // A lot of red
                    *(fbp + location + 3) = 0; // No transparency
                } else { //assume 16bpp
                    int b = 10;
                    int g = (x-100)/6; // A little green
                    int r = 31-(y-100)/16; // A lot of red
                    unsigned short int t = r<<11 | g << 5 | b;
                    *((unsigned short int*)(fbp + location)) = t;
                }

            }
        munmap(fbp, screensize);
        close(fbfd);
        return 0;
    }

然后通过 gsnap 截图工具，gsnap framer.jpg /dev/fb0 获取图片信息


操作过程如下：

[root@yuweixian yu]# ls
0.jpg          beijing.avi    framebuff      test-mmap.jpg  usb_camera
axu            capture        mmap.jpg       ts_test
[root@yuweixian yu]# ./framebuff
The framebuffer device was opened successfully.
320x240, 16bpp
The framebuffer device was mapped to memory successfully.
Segmentation fault
[root@yuweixian yu]# gsnap frammer.jpg /dev/fb0
---------------framebuffer---------------
/dev/fb0:
  width :      320
  height:      240
  bpp   :        2
  r(11,  5)    R G B  565   LCD 使用的模式
  g( 5,  6)
  b( 0,  5)
-----------------------------------------
[root@yuweixian yu]# sz frammer.jpg
rz
Starting zmodem transfer.  Press Ctrl+C to cancel.
Transferring frammer.jpg...
  100%      19 KB    9 KB/s 00:00:02       0 Errors

奜Osz 3.48 01-27-98 finished.
[root@yuweixian yu]#

背景 “hello测试程序” 是qt程序，开机时就开启了。

然后执行测试测试程序，就在 覆盖了 hello 测试程序，在其上面显示了 红色矩形框