Android -- 获取摄像头帧数据解码

由于Android下摄像头预览数据只能  ImageFormat.NV21 格式的，所以解码时要经过一翻周折.

Camera mCamera = Camera.open();

Camera.Parameters p = mCamera.getParameters();

p.setPreviewFormat(ImageFormat.NV21);

/*这是唯一值，也可以不设置。有些同学可能设置成 PixelFormat 下面的一个值，其实是不对的，具体的可以看官方文档*/

mCamera.setParameters(p);

mCamera.startPreview();

下面是解码核心部分：

@Override
  public void onPreviewFrame(byte[] data, Camera camera) {
      Size size = camera.getParameters().getPreviewSize();
      try{
          YuvImage image = new YuvImage(data, ImageFormat.NV21, size.width, size.height, null);
          if(image!=null){
              ByteArrayOutputStream stream = new ByteArrayOutputStream();
              image.compressToJpeg(new Rect(0, 0, size.width, size.height), 80, stream);
              Bitmap bmp = BitmapFactory.decodeByteArray(stream.toByteArray(), 0, stream.size());

                   stream.close();
          }
      }catch(Exception ex){
          Log.e("Sys","Error:"+ex.getMessage());
      }
  }

代码很简单。就是把YUV数据转成 Bitmap 就行了，系统提供 YuvImage 类。

yuv420sp转RGB                                                                       

/**
         * 解码
         *
         * @param rgb
         * @param yuv420sp
         * @param width
         * @param height
         */
        static public void decodeYUV420SP(int[] rgb, byte[] yuv420sp, int width, int height) {
                final int frameSize = width * height;

                for (int j = 0, yp = 0; j < height; j++) {
                        int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
                        for (int i = 0; i < width; i++, yp++) {
                                int y = (0xff & ((int) yuv420sp[yp])) - 16;
                                if (y < 0)
                                        y = 0;
                                if ((i & 1) == 0) {
                                        v = (0xff & yuv420sp[uvp++]) - 128;
                                        u = (0xff & yuv420sp[uvp++]) - 128;
                                }

                                int y1192 = 1192 * y;
                                int r = (y1192 + 1634 * v);
                                int g = (y1192 - 833 * v - 400 * u);
                                int b = (y1192 + 2066 * u);

                                if (r < 0)
                                        r = 0;
                                else if (r > 262143)
                                        r = 262143;
                                if (g < 0)
                                        g = 0;
                                else if (g > 262143)
                                        g = 262143;
                                if (b < 0)
                                        b = 0;
                                else if (b > 262143)
                                        b = 262143;

                                rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) & 0xff);
                        }
                }
        }

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