class ImageCollection
{
public:
     ...
     CV_WRAP size_t nimages() const;
     CV_WRAP ImageIterator begin() const;
     ImageIterator end() const;
     ...

     CV_WRAP static ImageCollection fromMultiPageImage(const std::string& img);
     CV_WRAP static ImageCollection fromDirectory(const std::string& dir);
}; 

class ImageIterator
{
public:
   Mat operator *() const;
   CV_WRAP Mat read() const; // operator * for Python/Java
   CV_WRAP size_t currentIndex() const;
   CV_WRAP bool next(); // operator ++() for Python/Java
   ImageIterator& operator ++();
   ImageIterator operator ++(int);
protected:
   Ptr<ImageIteratorImpl> pimpl;
}

// C+++
for(cv::Mat img: ImageCollection::fromMultiPageImage("big_tiff_file.tif")) {
    ...
}

# Python
image_col = cv2.ImageCollection.fromMultiPageImage("big_tiff_file.tif")
nimg = image_col.nimages()
it = image_col.begin()
i  = 0
while i < nimg:
   img = it.read()
   # process img ...
   it.next()
   i += 1

    ImageLoader imageloader;

    if( imageloader.open(filename, flags) )
        for (int i = 0; i < imageloader.getNumPages(); i++)
        {
            Mat page;
            if( imageloader.load(page) )
            {
                 // do something 
            }
            imageloader.nextPage();
        }

import cv2

il = cv2.ImageLoader()
il.open('D:/Github/opencv_extra/testdata/highgui/readwrite/multipage.tif', ,cv2.IMREAD_REDUCED_GRAYSCALE_2)

for i in range(il.getNumPages()):
    ret,img = il.load()
    cv2.imshow("pages", img)
    cv2.waitKey()
    il.nextPage()

cv2.destroyAllWindows()