YUV420旋转执行代码（JAVA版）

旋转都是顺时针，镜像都是左右镜像；

YUV420_ROTATE_90：

    private byte[] YUV420_ROTATE_90(byte[] buffer, int pixel_w, int pixel_h) {
        byte[] buffer_new = new byte[buffer.length];
        int k = 0;
        //Y
        for (int i = 0; i < pixel_w; i++) {
            for (int j = pixel_h - 1; j >= 0; j--) {
                buffer_new[k] = buffer[j * pixel_w + i];
                k++;
            }
        }
        //U
        for (int i = 0; i < pixel_w / 2; i++) {
            for (int j = pixel_h / 2 - 1; j >= 0; j--) {
                buffer_new[k] = buffer[pixel_w * pixel_h + j * pixel_w / 2 + i];
                k++;
            }
        }
        //V
        for (int i = 0; i < pixel_w / 2; i++) {
            for (int j = pixe