imcount function
Returns the number of images inside the give file.
The function imcount will return the number of pages in a multi-page image, or 1 for single-page images
https://docs.opencv.org/4.10.0/d4/da8/group__imgcodecs.html#ga02237b2aad2d4ae41c9489a83781f202
Implementation
int imcount(String filename, {int flags = IMREAD_ANYCOLOR}) {
final cname = filename.toNativeUtf8().cast<ffi.Char>();
final rval = cimgcodecs.cv_imcount(cname, flags);
calloc.free(cname);
return rval;
}