Make some corrections and clean up.
Missing & ref on the the binary operator assignments.
Slight modification and includes comments.
Moved into namespace detail and corrected an error when calculating the distance between two iterators. It did not factor in the number of bits.  This class is still broken for images with < 8 bits per pixel.
Cleaned up some of the cruft and started preparing for doxygen by leaving doxygen style comments on most of the public interface.
Added several methods to create bitmaps from scratch.
Bitmaps can now be created from scratch using one of the libimg::bitmap constructors.  However this is still very alpha work and subject to A LOT of change.
Changed the bpp(pixel_format) method to supply a default bpp if not given one.  It is derived from the number of channels in format.  If the format is eq undefined the result will be zero which could cause some issues that arent currently being protected against.
Pixels now abide by the overflow rules for individual channels when being constructor or assigned by value.
Added to the growing list of formats, fixed some wording in comments.
Added some methods to support the creation of bitmaps from scratch. bmp implementation is working (though shall be reworked) png merely stubs the operation.
Update.
Update.
Resolved conflict between the pixel_format.hpp remote/local, the local one is the latest so merged.