[boost] [gil] Indexed Images

From: Christian Henning (chhenning_at_[hidden])
Date: 2006-11-10 10:05:26

Hi there, I'm playing around with indexed images in GIL. My starting
point was an email from Lubomir during the review.

Here is what I have:

struct indexed_pixel_deref_fn
{
   typedef pixel_traits<rgb8_pixel_t>::reference       reference;
   typedef pixel_traits<rgb8_pixel_t>::const_reference const_reference;

   typedef const_reference const_t;
   typedef reference result_type;

   typedef rgb8_pixel_t value_type;
   static const bool is_mutable = false;

   indexed_pixel_deref_fn( rgb8_pixel_t* table ) : _table( table ) {}

   rgb8_pixel_t operator()( const gray8_pixel_t& index ) const
   {
      return _table[index[0]];
   }

   rgb8_pixel_t* _table;
};

typedef gray8_view_t::add_deref<indexed_pixel_deref_fn> indexed_factory_t;
typedef indexed_factory_t::type rgb8_indexed_view_t;

int _tmain(int argc, _TCHAR* argv[])
{
   // create color lookup table
   rgb8_pixel_t rgb_black( 0, 0, 0 );
   rgb8_pixel_t rgb_red( 255, 0, 0 );

   rgb8_pixel_t my_index_table[2];
   my_index_table[0] = rgb_red;
   my_index_table[1] = rgb_black;

   // create indexed image
   gray8_image_t indexed_img( 10,10 );
   fill_pixels( view( indexed_img ), unsigned char( 0 ) );

   rgb8_indexed_view_t indexed_view= indexed_factory_t::make( view(
indexed_img )
                                                            ,
indexed_pixel_deref_fn( &my_index_table[0] ));

   // color convert the indexed image into an rgb8 image
   rgb8_image_t rgb_img( indexed_img.dimensions() );
   copy_pixels( color_converted_view<rgb8_pixel_t>( view( indexed_img ))
               , view( rgb_img )                                         );

   // save image - it should be all red
   jpeg_write_view( "test.jpg", const_view( rgb_img ));

        return 0;
}

I'm not sure if all these typedefs in the deref functor class are
correct. Esspecially, I don't know what the const_t is for.

So, my problem is the operator() in my deref isn't called at all. That
shows me there is something wrong.

Anyone, any idea why?

Thanks,
Christian