This class write an image in a png file. More...

#include <png.hpp>

Classes
struct	options
	Parameters of the writing algorithm. More...
struct	target_manager
	Target manager that allow us to write in a std::ostream. More...
Public Member Functions
	writer (const image &img)
	Constructor.
	writer (const image &img, std::ostream &f, const options &opt=options())
	Constructor.
void	save (std::ostream &f, const options &opt=options()) const
	Save the image in a PNG file.
Private Member Functions
void	set_options (png_structp png_ptr, png_infop info_ptr, const options &opt) const
	Set the parameters of the PNG saving structures.
void	save_image (png_structp png_ptr, png_infop info_ptr) const
	Save the image in a configured PNG file.
void	copy_pixel_line (png_bytep data, unsigned int y) const
	Copy the pixels from the image to an array of bytes.
void	create_write_structures (png_structp &png_ptr, png_infop &info_ptr) const
	Initialize the png write structures.
Private Attributes
const image &	m_image
	The image from which we thake the data to save.
Static Private Attributes
static const unsigned int	s_rgba_pixel_size = 4
	Size, in bytes, of a red/green/blue/alpha pixel in a png file.

Detailed Description

This class write an image in a png file.

Author:: Julien Jorge

Definition at line 113 of file png.hpp.

Constructor & Destructor Documentation

claw::graphic::png::writer::writer ( const image & img )

Constructor.

Parameters:

img

The image in which the data will be stored.

Definition at line 136 of file png_writer.cpp.

  : m_image( img )
{

} // png::writer::writer()

claw::graphic::png::writer::writer	(	const image &	img,
		std::ostream &	f,
		const options &	opt = `options()`
	)

Constructor.

Parameters:

	img	The image to save.
	f	The file in which we write the data.
	opt	Saving options.

Definition at line 150 of file png_writer.cpp.

References claw::graphic::png::save().

  : m_image( img )
{
  save(f, opt);
} // png::writer::writer()

Member Function Documentation

void claw::graphic::png::writer::copy_pixel_line	(	png_bytep	data,
		unsigned int	y
	)			const `[private]`

Copy the pixels from the image to an array of bytes.

Parameters:

	data	(out) The pixels for the PNG image.
	y	Index of the line of the image from which we read the pixels.

Precondition:: The memory pointed by data is long enough to store the pixels.

Definition at line 268 of file png_writer.cpp.

References CLAW_PRECOND.

{
  CLAW_PRECOND( data );
  CLAW_PRECOND( y < m_image.height() );

  // four bytes for each pixel in the line
  for (unsigned int x=0; x!=m_image.width(); ++x, data+=s_rgba_pixel_size)
    {
      data[0] = m_image[y][x].components.red;
      data[1] = m_image[y][x].components.green;
      data[2] = m_image[y][x].components.blue;
      data[3] = m_image[y][x].components.alpha;
    }
} // png::writer::copy_pixel_line()

void claw::graphic::png::writer::create_write_structures	(	png_structp &	png_ptr,
		png_infop &	info_ptr
	)			const `[private]`

Initialize the png write structures.

Parameters:

	png_ptr	PNG file description.
	info_ptr	PNG file informations.

Definition at line 290 of file png_writer.cpp.

References CLAW_EXCEPTION.

Referenced by save().

{
  png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);

  if (png_ptr)
    {
      info_ptr = png_create_info_struct(png_ptr);

      if (!info_ptr)
        png_destroy_write_struct(&png_ptr, png_infopp_NULL);
    }

  if (!png_ptr || !info_ptr)
    throw CLAW_EXCEPTION("Can't create PNG write structures.");
} // png::writer::create_write_structures()

void claw::graphic::png::writer::save	(	std::ostream &	f,
		const options &	opt = `options()`
	)			const

Save the image in a PNG file.

Parameters:

	f	PNG file.
	opt	Saving options.

Definition at line 163 of file png_writer.cpp.

References claw__graphic__png__target_manager__flush(), claw__graphic__png__target_manager__write(), CLAW_EXCEPTION, CLAW_PRECOND, create_write_structures(), save_image(), and set_options().

{
  CLAW_PRECOND( !!f );

  target_manager outfile(f);
  png_structp png_ptr;
  png_infop info_ptr;

  create_write_structures(png_ptr, info_ptr);

  if (setjmp(png_jmpbuf(png_ptr)))
    {
      /* If we get here, we had a problem reading the file */
      /* Free all of the memory associated with the png_ptr and info_ptr */
      png_destroy_write_struct(&png_ptr, &info_ptr);
      throw CLAW_EXCEPTION("Invalid PNG file.");
    }
      
  png_set_write_fn( png_ptr, (void *)&outfile,
                    claw__graphic__png__target_manager__write,
                    claw__graphic__png__target_manager__flush );

  set_options( png_ptr, info_ptr, opt );
  save_image( png_ptr, info_ptr );
      
  png_destroy_write_struct(&png_ptr, &info_ptr);
} // png::writer::save()

void claw::graphic::png::writer::save_image	(	png_structp	png_ptr,
		png_infop	info_ptr
	)			const `[private]`

Save the image in a configured PNG file.

Parameters:

	png_ptr	PNG file description.
	info_ptr	PNG file informations.

Definition at line 220 of file png_writer.cpp.

References CLAW_PRECOND.

Referenced by save().

{
  CLAW_PRECOND( png_ptr );
  CLAW_PRECOND( info_ptr );

  const unsigned int row_length = s_rgba_pixel_size * m_image.width();
  png_bytepp data =
    (png_bytepp)png_malloc( png_ptr, sizeof(png_bytep) * m_image.height() );
  unsigned int i=0;

  try
    {
      for (i=0; i!=m_image.height(); ++i)
        {
          data[i] = (png_bytep)png_malloc( png_ptr, row_length );

          if (!data[i])
            throw std::bad_alloc();

          copy_pixel_line( data[i], i );
        }

      png_set_rows(png_ptr, info_ptr, data);
      png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
    }
  catch(...)
    {
      for(unsigned int j=0; j!=i; ++j)
        png_free(png_ptr, data[j]);

      png_free(png_ptr, data);
      throw;
    }

  for(i=0; i!=m_image.height(); ++i)
    png_free(png_ptr, data[i]);

  png_free(png_ptr, data);
} // png::writer::save_image()

void claw::graphic::png::writer::set_options	(	png_structp	png_ptr,
		png_infop	info_ptr,
		const options &	opt
	)			const `[private]`

Set the parameters of the PNG saving structures.

Parameters:

	png_ptr	PNG file description.
	info_ptr	PNG file informations.
	opt	Compression options.

Definition at line 199 of file png_writer.cpp.

References CLAW_PRECOND, claw::graphic::png::writer::options::compression, and claw::graphic::png::writer::options::interlace.

Referenced by save().

{
  CLAW_PRECOND( png_ptr );
  CLAW_PRECOND( info_ptr );

  png_set_compression_level( png_ptr, opt.compression );

  png_set_IHDR( png_ptr, info_ptr, m_image.width(), m_image.height(),
                sizeof(pixel_type::component_type) * 8, /* 8 bits per byte */
                PNG_COLOR_TYPE_RGB_ALPHA,
                opt.interlace, PNG_COMPRESSION_TYPE_DEFAULT,
                PNG_FILTER_TYPE_DEFAULT );
} // png::writer::set_options()