Question

I just started learning the opencv library for c++. In my previous c++ experience (which isn’t much) I’ve never encountered the following syntax

IplImage* dopPyrDown (
            IplImage * in,
            int filter = IPL_GAUSSIAN_5x5
    ) {
        assert(in->width%2 == 0 && i->height%2 == 0);
        IplImage* out = cvCreteImage(
         cvSize(in->width/2, in->height/2),
         in->depth,
         in->nChannels
        );
        cvPyrDown(in, out);
        return(out);
    };

More specifically, I mean the “IplImage* dopPurDown (*argument*){*code*};” Could someone explain what It means?

Answer 1

More specifically, I mean the “IplImage* dopPurDown
(argument){code};” Could someone explain what It means?

It’s declaring a function called dopPurDown which returns a pointer to a IplImage and accepts some arguments (in this case, two arguments called in and filter). The code in between the brackets define the function.

Before you go on, please pick up a good introductory C++ book as functions are fundamental to pretty much every high-level programming language in existence. Quite frankly, if you can’t recognize a function definition in C++ you need to step back and learn C++ properly first before trying to tackle on OpenCV, which is an entirely different beast.