Re: [boost] [gil] [announcement] New IO lib

From: John Femiani (JOHN.FEMIANI_at_[hidden])
Date: 2008-04-30 00:41:25

> >  For hypothetical example, if the file would optimally 
> choose a gray16  
> > planar image, but I pass any_image<mpl::vector<rgb8_image_t,
> >  gray8_image_t> > to read_image, then I want the read_image 
> function 
> > to  create a gray8_image_t and convert the pixels to that.
> >
> >  I dont know how it would be done, but that would be a nice feature.
> 
> Yeah, sounds like a nice feature. I will make a mark in my todo list.
> Before I could tackle that I would need to overcome my 
> template instantiation issue. I cannot even compile with MSVC 
> 7.1. It's
> complaining:
> 
>  fatal error C1055: compiler limit : out of keys
> 
> I think I need to seriously rethink the design.

Hmmm...
 
> >
> >  I think the other thing would be for each image format to have its 
> > own  image_types typedef, to that I can read into an image variant 
> > that is  perfect for the reader.
> >
> 
> Not sure if I follow here.
> 

any_supported_image<jpeg_tag> result;
read_image(fname, result, jpeg_tag())

gil::apply_operation(result, my_operation)

On another note, I dont think you need filesystem to check the extension
of the images. You can use the boost string algorithms library (or just
use std::string operations).

bool can_read(std::string filename, jpeg_tag const& ){
    static const string extensions[] = {".jpg", ".jpeg" };
    return ::boost::algorithm::iends_with(filename, extensions[0]) 
        || ::boost::algorithm::iends_with(filename, extensions[1]);
}

Also, I beleive some of the image formats can peek at the first few
bytes of the file to determine if the format is appropriate. I dont know
about non-windows systems, but on some of them this might be the only
way to tell. If that is the way image formats are checked, then I dont
think filesystem (or string algs) is going to be important.

-- John