如何通过编程确定android屏幕的bpp和像素颜色格式

Question

我正在尝试将压缩的原始framebuffer数据流式传输到PC上的客户端应用程序，从Android上的服务器服务。在PC上，我想在我的客户端视图中显示这些原始数据作为流视频，提供Android设备屏幕的实时视图。我知道如何获得屏幕的分辨率，但不是比特每像素(BPP)也不是像素的颜色格式在Android(服务器)端编程的原始数据。请帮助。

我能在网上找到的都是本地代码。但是我真的希望尽可能保持Java定义的应用程序。

从FBIOGET_VSCREENINFO over ioctl获取BPP(bit -per-pixel)，如下所示

int main () {
    int fbfd;
    struct fb_var_screeninfo variable_info;
    fbfd=open("/dev/fb0", O_RDWR);
    //in real life, check every ioctl if it returns -1
    ioctl (fbfd, FBIOGET_VSCREENINFO, &variable_info);
    //This is the required BPP value
    switch(variable_info.bits_per_pixel) {
        case 16: //pixel format is RGB_565
            break;
        case 24: //pixel format is RGB_888
            break;
        case 32: //pixel format is RGBX_8888
            break;
    }
}

Answer 1

终于弄明白了如何判定

• BPP(bit -per-pixel)帧
• 像素的实际RGB字节方向

• framebuffer的大小&单个帧

  int main() {
      //Structs defined in "linux/fb.h"
      struct fb_var_screeninfo vscreeninfo;
      struct fb_fix_screeninfo fscreeninfo;
      //Open the framebuffer
      fbfd=open("/dev/graphics/fb0",O_RDONLY);
      if(fbfd==-1) {
          __android_log_print(ANDROID_LOG_ERROR,ERR,
                  "Could not open framebuffer fbfd=%d errno=%d",fbfd,errno);
          return errno;
      }
      //Fetch variable screen info
      ioct=ioctl(fbfd,FBIOGET_VSCREENINFO,&vscreeninfo);
      if(ioct==-1) {
          __android_log_print(ANDROID_LOG_ERROR,ERR,
                  "VSCREEN-IOCTL failed ioct=%d errno=%d",ioct,errno);
          return errno;
      }
      //Fetch fixed screen info
      ioct=ioctl(fbfd,FBIOGET_FSCREENINFO,&fscreeninfo);
      if(ioct==-1) {
          __android_log_print(ANDROID_LOG_ERROR,ERR,
                  "FSCREEN-IOCTL failed ioct=%d errno=%d",ioct,errno);
          return errno;
      }
      close(ioct);
      /**********************************VSCREEN DATA************************************/
      printf("nVscreen Info:-n");
      printf(" Xres   = %4ld | Yres   = %4ldn",vscreeninfo.xres,vscreeninfo.yres);
      printf(" BPP    = %4ld | Height = %4ld | Width = %4ldn",vscreeninfo.bits_per_pixel,
                                                               vscreeninfo.height,
                                                               vscreeninfo.width);
      printf(" Xres_V = %4ld | Yres_V = %4ldn",vscreeninfo.height,vscreeninfo.width);
      printf(" Pixel format : RGBX_%ld%ld%ld%ldn",vscreeninfo.red.length,
                                                   vscreeninfo.green.length,
                                                   vscreeninfo.blue.length,
                                                   vscreeninfo.transp.length);
      printf(" Begin of bitfields(Byte ordering):-n");     //In my case :
      printf("  Red    : %ldn",vscreeninfo.red.offset);    //Red    : 16
      printf("  Blue   : %ldn",vscreeninfo.blue.offset);   //Blue   : 0
      printf("  Green  : %ldn",vscreeninfo.green.offset);  //Green  : 8
      printf("  Transp : %ldn",vscreeninfo.transp.offset); //Transp : 24
                //Hence orientation is : BGRT => (BGR4)RGB32 packed format
      /********************************~VSCREEN DATA************************************/
      /*********************************FSCREEN DATA************************************/
      printf("nFscreen Info:-n");
      printf(" Device ID : %sn",fscreeninfo.id);
      printf(" Start of FB physical address : %ldn",fscreeninfo.smem_start);
      printf(" Length of FB : %ldn",fscreeninfo.smem_len); //Size of framebuffer in bytes
      printf(" Length of Line : %ldn",fscreeninfo.line_length);
      printf(" Start of MMIO physical address : %ldn",fscreeninfo.mmio_start);
      printf(" Length of MMIO : %ldn",fscreeninfo.mmio_len);
      /********************************~FSCREEN DATA************************************/
      close(fbfd);
      return 0;
  }
  

引用

: -

• Framebuffer数据http://www.ummon.eu/Linux/API/Devices/framebuffer.html
• 打包的RGB格式http://linuxtv.org/downloads/v4l-dvb-apis/packed-rgb.html V4L2-PIX-FMT-RGB565