C ++对大小写敏感，opencv使用string作为其参数，但是使用String.我认为string和String是不同的东西.请参考下面的函数原型:

C++ is capital sensitive, opencv use string as its parameter, but you use String. I think string and String are different thing. Refer function prototype below:

static void*
imread_( const string& filename, int flags, int hdrtype, Mat* mat=0 )

Mat imread( const string& filename, int flags )