Both items taken together, what do you think about the following idea: model GIL's core functionality according to DataAccessor/Iterator, and provide an STL-style RandomAccessTraversalIterator as a wrapper on top of that?
Hi Thorsten, As a user of GIL I don't see why you should care if it internally uses DataAccessor/Iterator or STL-style iterators. All you should care about is how easy it is to use and extend GIL. In particular, if you have a DataAccessor+Iterator can you make easily from it a GIL iterator and image view? For immutable DataAccessors, it is trivial. You can think of GIL's PixelDereferenceAdaptor almost like a DataAccessor. It has an application operator that takes anything you want (for example a pixel reference) and must return something convertible to PixelValueConcept. To attach a PDA (PixelDereferenceAdaptor) to a given View, you simply do this: typename View::add_deref<PDA>::type newView = View::add_deref<PDA>::make(myView, myPDA); That's it! Now if you want to save the even pixels of the first channel of the view, and apply your custom transformation, you do this: jpeg_write_view("out.jpg", subsampled_view(nth_channel_view(newView, 0), 2,2)); With the DataAccessor/Iterator style, piping of views is not as nice. You will have to duplicate the piping chain for the accessor as well: jpeg_write_view("out.jpg", subsampled_view(nth_channel_view(newView, 0), 2,2), subsampled_accessor(nth_channel_accessor(newAcc, 0), 2,2)); Adapting a mutable DataAccessor requires a bit more work, and we can certainly add some utilities to make it easier, but I am having a hard time thinking of a practical example where you need this. Thorsten wrote:
From how it appears to me (and what you and others stated), GIL's selling points are currently pixel and image view abstractions, not so much the actual algorithms. As a user, I don't have too much use for that, I'm more interested in turn-key solutions like a Canny edge detector...
Ulli also wrote:
Yes, images alone are not of much use.
Please don't forget that computer vision is a niche domain. There is a much broader domain of basic image manipulation, like loading an image from file and converting it to a format that your window manager can display, or making a thumbnail out of an image. Far more people need basic utilities like the above. People like you who need a Canny edge detector, or even know what it means, are a minority. Lubomir