android camera yuv帧水平翻转实例

Camera预览时需要对yuv帧做水平翻转处理，直接在onPreviewFrame(byte[] data, Camera camera)里调用Mirror函数，处理完后的图片和预览效果成水平翻转关系。

nv21的镜像算法：

  private void Mirror(byte[] src, int w, int h) { //src是原始yuv数组
    int i;
    int index;
    byte temp;
    int a, b;
    //mirror y
    for (i = 0; i < h; i++) {
      a = i * w;
      b = (i + 1) * w - 1;
      while (a < b) {
        temp = src[a];
        src[a] = src[b];
        src[b] = temp;
        a++;
        b--;
      }
    }

    // mirror u and v
    index = w * h;
    for (i = 0; i < h / 2; i++) {
      a = i * w;
      b = (i + 1) * w - 2;
      while (a < b) {
        temp = src[a + index];
        src[a + index] = src[b + index];
        src[b + index] = temp;

        temp = src[a + index + 1];
        src[a + index + 1] = src[b + index + 1];
        src[b + index + 1] = temp;
        a+=2;
        b-=2;
      }
    }
  }

i420的镜像算法：

private void Mirror(byte[] src, int w, int h) { //src是原始yuv数组
    int i;
    int index;
    byte temp;
    int a, b;
    //mirror y
    for (i = 0; i < h; i++) {
      a = i * w;
      b = (i + 1) * w - 1;
      while (a < b) {
        temp = src[a];
        src[a] = src[b];
        src[b] = temp;
        a++;
        b--;
      }
    }
    //mirror u
    index = w * h;//U起始位置
    for (i = 0; i < h / 2; i++) {
      a = i * w / 2;
      b = (i + 1) * w / 2 - 1;
      while (a < b) {
        temp = src[a + index];
        src[a + index] = src[b + index];
        src[b + index] = temp;
        a++;
        b--;
      }
    }
    //mirror v
    index = w * h / 4 * 5;//V起始位置
    for (i = 0; i < h / 2; i++) {
      a = i * w / 2;
      b = (i + 1) * w / 2 - 1;
      while (a < b) {
        temp = src[a + index];
        src[a + index] = src[b + index];
        src[b + index] = temp;
        a++;
        b--;
      }
    }

I420，YV12，NV12，NV21均属于YUV420，以下为四种格式的排列顺序：

I420: YYYYYYYY UUVV =>YUV420P
YV12: YYYYYYYY VVUU =>YUV420P
NV12: YYYYYYYY UVUV =>YUV420SP
NV21: YYYYYYYY VUVU =>YUV420SP

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