Android拍摄视频流的格式转换（YUV --- RGB）

Android允许用户实时捕获摄像头的视频流，这在利用摄像头的AR应用中非常有用。可以利用摄像流实时做画面图像的分析，并做出许多有用的应用。比如 人脸识别，条码识别，特定图像替换等等，不过大多数图像处理软件在处理时是需要RGB格式的图像，而默认的视频流是压缩的YUV格式，Android下是 YUV420SP，这个格式，虽然可以在程序中修改，但是修改后好像不起作用，也就是说只能得到编码为YUV420SP的视频流，这就需要把 YUV420SP的视频流转换成RGB格式的图像，用于图像识别。特贴一个格式转换函数，方便大家使用。

  static public void decodeYUV420SP(byte[] rgbBuf, byte[] yuv420sp, int width, int height) {
    final int frameSize = width * height;
if (rgbBuf == null)
    throw new NullPointerException("buffer 'rgbBuf' is null");
if (rgbBuf.length < frameSize * 3)
    throw new IllegalArgumentException("buffer 'rgbBuf' size "
            + rgbBuf.length + " < minimum " + frameSize * 3);

if (yuv420sp == null)
    throw new NullPointerException("buffer 'yuv420sp' is null");

if (yuv420sp.length < frameSize * 3 / 2)
    throw new IllegalArgumentException("buffer 'yuv420sp' size " + yuv420sp.length
            + " < minimum " + frameSize * 3 / 2);

    int i = 0, y = 0;
    int uvp = 0, u = 0, v = 0;
    int y1192 = 0, r = 0, g = 0, b = 0;

    for (int j = 0, yp = 0; j < height; j++) {
        uvp = frameSize + (j >> 1) * width;
        u = 0;
        v = 0;
        for (i = 0; i < width; i++, yp++) {
            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;
            }

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

            rgbBuf[yp * 3] = (byte)(r >> 10);
            rgbBuf[yp * 3 + 1] = (byte)(g >> 10);
            rgbBuf[yp * 3 + 2] = (byte)(b >> 10);
        }
    }
  }