Re: how to use graphics???

* mohi:


You might use the Boost library.

However, the documentation and code seems to be the winner in a contest of
obfuscation and Bad Programming Habits.

I cooked up a usage example, shown below, and if this serves your needs then you
won't have to confront the full horror of that library! :-)

Disclaimer:

I haven't worked with the graphics part of Boost before, so it may very well be
that I'm using this in a non-idiomatic way!

<code>
// Visual C++ sillywarnings:
#ifdef _MSC_VER
# pragma warning( disable: 4100 ) // unreferenced argument
# pragma warning( disable: 4127 ) // constant conditional expression
# pragma warning( disable: 4512 ) // can't gen. assignment operator
#endif

#include <boost/gil/gil_all.hpp>
#include <boost/gil/extension/io/png_dynamic_io.hpp>

class ImageData: public boost::gil::rgb8_image_t
{
public:
     typedef boost::gil::rgb8_image_t Base;

     ImageData( size_t w, size_t h ): Base( w, h ) {}

     boost::gil::rgb8_view_t view()
     {
         return boost::gil::view( *this );
     }
};

class Image
     : protected ImageData // Image data, must be first (init)
     , protected boost::gil::rgb8_view_t // Image operations
{
private:
     typedef boost::gil::rgb8_view_t ImageOps;
     typedef boost::gil::rgb8c_view_t ConstImageOps;

     friend class ConstImageOps;

public:
     typedef ImageOps::reference PixelRef;

     Image( size_t w, size_t h )
         : ImageData( w, h )
         , ImageOps( ImageData::view() )
     {}

     PixelRef operator()( size_t x, size_t y )
     {
         return ImageOps::operator()( x, y );
     }

     ImageOps const& view() { return *this; }
     ConstImageOps view() const { return static_cast<ImageOps const&>( *this ); }
};

typedef boost::gil::rgb8_pixel_t ColorRGB;

int main()
{
     Image image( 42, 42 );

     for( int x = 0; x < 42; ++x )
     {
         image( x, x ) = ColorRGB( 0xff, 0, 0 );
     }
     boost::gil::png_write_view( "an_image.png", image.view() );
}
</code>

Note: the above doesn't compile cleanly with Visual C++. That's because the PNG
i/o is really really horrible code (adding a notch of horribility (whatever) to
the degree present in the main library). Looks like this:

<diagnostics>
c:\projects\lib\boost\boost_1_35_0\boost\gil\extension\io\png_io_private.hpp(157)
: warning C4611: interaction between '_setjmp' and C++ object destruction is
non-portable
c:\projects\lib\boost\boost_1_35_0\boost\gil\extension\io\png_io_private.hpp(319)
: warning C4611: interaction between '_setjmp' and C++ object destruction is
non-portable
c:\projects\lib\boost\boost_1_35_0\boost\gil\extension\io\png_io_private.hpp(340)
: warning C4244: 'argument' : conversion from
'boost::gil::image_view<Loc>::y_coord_t' to 'png_uint_32', possible loss of data
         with
         [
             Loc=boost::gil::rgb8_loc_t
         ]
 
c:\projects\lib\boost\boost_1_35_0\boost\gil\extension\io\png_io.hpp(202) : see
reference to function template instantiation 'void
boost::gil::detail::png_writer::apply<View>(const View &)' being compiled
         with
         [
             View=Image::ImageOps
         ]
         vc_project.cpp(65) : see reference to function template instantiation
'void boost::gil::png_write_view<Image::ImageOps>(const char *,const View &)'
being compiled
         with
         [
             View=Image::ImageOps
         ]
c:\projects\lib\boost\boost_1_35_0\boost\gil\extension\io\png_io_private.hpp(340)
: warning C4244: 'argument' : conversion from
'boost::gil::image_view<Loc>::x_coord_t' to 'png_uint_32', possible loss of data
         with
         [
             Loc=boost::gil::rgb8_loc_t
         ]
</diagnostics>

Especially the diagnostic about 'setjmp' makes alarm bells go off in my brain.
But hey, it's part of Boost. So even if it's not perfect yet, in fact very far
from perfect, it'll presumably be fixed, at least so it compiles cleanly with no
warnings.

Just disregard all those warnings -- if you get any with g++.

Cheers, & hth.,

- Alf

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