How to read directory with images by VideoCapture?

edit

I had a similar need as you did, I solved the problem with boost filesystem library.

For file scanning with boost, it would look something like this:

int scanFiles( const path & directory, string filterFileType)
{   
    int fileCount=0;
    if( exists( directory ) )
    {
        directory_iterator end ;
        for( directory_iterator iter(directory) ; iter != end ; ++iter )
            if ( (is_regular_file( *iter ) && iter->path().extension().string() == filterFileType))
        {                               
            cout << iter->path().filename().string() << endl ; //this is the one of scanned file names
            fileCount++;
        }
    }   
    return fileCount;
}

Basically what that function does (at least in my app), returns the count of files with a specified extension. So scanFiles("labels", "png"); will return me the number of png files in directory labels.

While scanning you can return or update global Mat variable and use it to do your stuff.

But I don't think that OpenCV can scan through files natively.

If your images have different size, be sure to capture the largest first (by naming it 001 e.g.), otherwise you may get a memory access fault. Further the step size is not adapted by VideoCapture (opencv 2.4.2.). After

 cap >> Img;

you may need

 // correct false step size for images of different size
 Img.step = Img.elemSize()*Img.cols;

If you are working in Windows and don't want to use boost you can do it like that (include Windows.h beforehand):

WIN32_FIND_DATA found;
HANDLE hfind;

vector<Mat> images;
int fileCount=0; 

hfind=FindFirstFile("C:\\path\\baseFilename???.jpg",&found);
if(hfind!=INVALID_HANDLE_VALUE)
    do
    {
        fileCount++;
        images.push_back(imread(found.cFileName)); 
    }while(FindNextFile(hfind,&found));

Hope someone will find it useful. I wish VideoCapture worked like that. I mean, it would use wildcards and load all the files in the directory in alphabetical order even if some consecutive files are missing.