fltk/src/Fl_PNG_Image.cxx

//
// "$Id$"
//
// Fl_PNG_Image routines.
//
// Copyright 1997-2011 by Easy Software Products.
// Image support by Matthias Melcher, Copyright 2000-2009.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
// USA.
//
// Please report all bugs and problems on the following page:
//
//     http://www.fltk.org/str.php
//
// Contents:

//
//   Fl_PNG_Image::Fl_PNG_Image() - Load a PNG image file.
//

//
// Include necessary header files...
//

#include <FL/Fl.H>
#include <FL/Fl_PNG_Image.H>
#include <FL/Fl_Shared_Image.H>
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <FL/fl_utf8.h>

#if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
extern "C"
{
#  include <zlib.h>
#  ifdef HAVE_PNG_H
#    include <png.h>
#  else
#    include <libpng/png.h>
#  endif // HAVE_PNG_H
}

typedef struct  {
  png_structp pp;
  const unsigned char *current;
  const unsigned char *last;
} fl_png_memory;

static void png_read_data_from_mem( png_structp png_ptr, //pointer to our data
				   png_bytep data,  // where to copy the image data for libpng computing
				   png_size_t length) // length of data to copy
{
  fl_png_memory *png_mem_data = (fl_png_memory*)png_get_io_ptr(png_ptr); // get the pointer to our struct
  if (png_mem_data->current + length > png_mem_data->last) {
    png_error(png_mem_data->pp, "Invalid attempt to read row data");
    return;
  }
  /* copy data from image buffer */
  memcpy (data, png_mem_data->current, length);
  /* advance in the memory data */
  png_mem_data->current += length;
}
#endif // HAVE_LIBPNG && HAVE_LIBZ


/**
  The constructor loads the named PNG image from the given png filename.

  The destructor frees all memory and server resources that are used by
  the image.

  \param[in] filename	Name of PNG file to read
*/
Fl_PNG_Image::Fl_PNG_Image (const char *filename): Fl_RGB_Image(0,0,0)
{
  load_png_(filename, NULL, 0);
}

/** 
 \brief Constructor that reads a PNG image from memory.

 Construct an image from a block of memory inside the application. Fluid offers
 "binary Data" chunks as a great way to add image data into the C++ source code.
 name_png can be NULL. If a name is given, the image is added to the list of 
 shared images (see: Fl_Shared_Image) and will be available by that name.
 
 \param name_png  A name given to this image or NULL
 \param buffer	  Pointer to the start of the PNG image in memory
 \param maxsize   Size in bytes of the memory buffer containing the PNG image
 */
Fl_PNG_Image::Fl_PNG_Image (
      const char *name_png, const unsigned char *buffer, int maxsize): Fl_RGB_Image(0,0,0)
{
  load_png_(name_png, buffer, maxsize);
}

void Fl_PNG_Image::load_png_(const char *name_png, const unsigned char *buffer_png, int maxsize)
{
#if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
  int i;	  // Looping var
  FILE *fp = NULL;	  // File pointer
  int channels;	  // Number of color channels
  png_structp pp; // PNG read pointer
  png_infop info; // PNG info pointers
  png_bytep *rows;// PNG row pointers
  fl_png_memory png_mem_data;
  int from_memory = (buffer_png != NULL); // true if reading image from memory

  if (!from_memory) {
    if ((fp = fl_fopen(name_png, "rb")) == NULL) return;
  }

  // Setup the PNG data structures...
  pp   = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
  info = png_create_info_struct(pp);

  if (setjmp(png_jmpbuf(pp)))
  {
    Fl::warning("PNG file \"%s\" contains errors!\n", name_png);
    return;
  }

  if (from_memory) {
    png_mem_data.current = buffer_png;
    png_mem_data.last = buffer_png + maxsize;
    png_mem_data.pp = pp;
    // Initialize the function pointer to the PNG read "engine"...
    png_set_read_fn (pp, (png_voidp) &png_mem_data, png_read_data_from_mem);
  } else {
    png_init_io(pp, fp); // Initialize the PNG file read "engine"...
  }  

  // Get the image dimensions and convert to grayscale or RGB...
  png_read_info(pp, info);

  if (png_get_color_type(pp, info) == PNG_COLOR_TYPE_PALETTE)
    png_set_expand(pp);

  if (png_get_color_type(pp, info) & PNG_COLOR_MASK_COLOR)
    channels = 3;
  else
    channels = 1;

  int num_trans = 0;
  png_get_tRNS(pp, info, 0, &num_trans, 0);
  if ((png_get_color_type(pp, info) & PNG_COLOR_MASK_ALPHA) || (num_trans != 0))
    channels ++;

  w((int)(png_get_image_width(pp, info)));
  h((int)(png_get_image_height(pp, info)));
  d(channels);

  if (png_get_bit_depth(pp, info) < 8)
  {
    png_set_packing(pp);
    png_set_expand(pp);
  }
  else if (png_get_bit_depth(pp, info) == 16)
    png_set_strip_16(pp);

#  if defined(HAVE_PNG_GET_VALID) && defined(HAVE_PNG_SET_TRNS_TO_ALPHA)
  // Handle transparency...
  if (png_get_valid(pp, info, PNG_INFO_tRNS))
    png_set_tRNS_to_alpha(pp);
#  endif // HAVE_PNG_GET_VALID && HAVE_PNG_SET_TRNS_TO_ALPHA

  array = new uchar[w() * h() * d()];
  alloc_array = 1;

  // Allocate pointers...
  rows = new png_bytep[h()];

  for (i = 0; i < h(); i ++)
    rows[i] = (png_bytep)(array + i * w() * d());

  // Read the image, handling interlacing as needed...
  for (i = png_set_interlace_handling(pp); i > 0; i --)
    png_read_rows(pp, rows, NULL, h());

#ifdef WIN32
  // Some Windows graphics drivers don't honor transparency when RGB == white
  if (channels == 4) {
    // Convert RGB to 0 when alpha == 0...
    uchar *ptr = (uchar *)array;
    for (i = w() * h(); i > 0; i --, ptr += 4)
      if (!ptr[3]) ptr[0] = ptr[1] = ptr[2] = 0;
  }
#endif // WIN32

  // Free memory and return...
  delete[] rows;

  png_read_end(pp, info);
  png_destroy_read_struct(&pp, &info, NULL);

  if (from_memory) {
    if (w() && h() && name_png) {
      Fl_Shared_Image *si = new Fl_Shared_Image(name_png, this);
      si->add();
    }
  } else {
    fclose(fp);
  }
#endif // HAVE_LIBPNG && HAVE_LIBZ
}


//
// End of "$Id$".
//