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img_png.c

/*
    IMGLIB:  An example image loading library for use with SDL
    Copyright (C) 1999  Sam Lantinga

    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
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    5635-34 Springhouse Dr.
    Pleasanton, CA 94588 (USA)
    slouken@devolution.com
*/

/* This is a PNG image file loading framework */

#include <stdlib.h>
#include <stdio.h>

#include "IMG.h"


/*=============================================================================
        File: SDL_png.c
     Purpose: A PNG loader and saver for the SDL library      
    Revision: 
  Created by: Philippe Lavoie          (2 November 1998)
              lavoie@zeus.genie.uottawa.ca
 Modified by: 

 Copyright notice:
          Copyright (C) 1998 Philippe Lavoie
 
          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., 675 Mass Ave, Cambridge, MA 02139, USA.

    Comments: The load and save routine are basically the ones you can find
             in the example.c file from the libpng distribution.

  Changes:
    5/17/99 - Modified to use the new SDL data sources - Sam Lantinga

=============================================================================*/

#include "SDL_endian.h"

#include <png.h>

#define PNG_BYTES_TO_CHECK 4

/* See if an image is contained in a data source */
int IMG_isPNG(SDL_RWops *src)
{
   char buf[PNG_BYTES_TO_CHECK];

   /* Read in the signature bytes */
   if (SDL_RWread(src, buf, 1, PNG_BYTES_TO_CHECK) != PNG_BYTES_TO_CHECK)
      return 0;

   /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature. */
   return( !png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
}

/* Load a PNG type image from an SDL datasource */
static void png_read_data(png_structp ctx, png_bytep area, png_size_t size)
{
      SDL_RWops *src;

      src = (SDL_RWops *)png_get_io_ptr(ctx);
      SDL_RWread(src, area, size, 1);
}
SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
{
      SDL_Surface *surface;
      png_structp png_ptr;
      png_infop info_ptr;
      png_uint_32 width, height;
      int bit_depth, color_type, interlace_type;
      Uint32 Rmask;
      Uint32 Gmask;
      Uint32 Bmask;
      Uint32 Amask;
      SDL_Palette *palette;
      png_bytep *row_pointers;
      int row, i;
      int ckey = -1;
      png_color_16 *transv;

      /* Initialize the data we will clean up when we're done */
      png_ptr = NULL; info_ptr = NULL; row_pointers = NULL; surface = NULL;

      /* Check to make sure we have something to do */
      if ( ! src ) {
            goto done;
      }

      /* Create the PNG loading context structure */
      png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
                                NULL,NULL,NULL);
      if (png_ptr == NULL){
            IMG_SetError("Couldn't allocate memory for PNG file");
            goto done;
      }

       /* Allocate/initialize the memory for image information.  REQUIRED. */
      info_ptr = png_create_info_struct(png_ptr);
      if (info_ptr == NULL) {
            IMG_SetError("Couldn't create image information for PNG file");
            goto done;
      }

      /* Set error handling if you are using setjmp/longjmp method (this is
       * the normal method of doing things with libpng).  REQUIRED unless you
       * set up your own error handlers in png_create_read_struct() earlier.
       */
      if ( setjmp(png_ptr->jmpbuf) ) {
            IMG_SetError("Error reading the PNG file.");
            goto done;
      }

      /* Set up the input control */
      png_set_read_fn(png_ptr, src, png_read_data);

      /* Read PNG header info */
      png_read_info(png_ptr, info_ptr);
      png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth,
                  &color_type, &interlace_type, NULL, NULL);

      /* tell libpng to strip 16 bit/color files down to 8 bits/color */
      png_set_strip_16(png_ptr) ;

      /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
       * byte into separate bytes (useful for paletted and grayscale images).
       */
      png_set_packing(png_ptr);

      /* scale greyscale values to the range 0..255 */
      if(color_type == PNG_COLOR_TYPE_GRAY)
            png_set_expand(png_ptr);

      /* For images with a single "transparent colour", set colour key;
         if more than one index has transparency, use full alpha channel */
      if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
              int num_trans;
            Uint8 *trans;
            png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans,
                       &transv);
            if(color_type == PNG_COLOR_TYPE_PALETTE) {
                if(num_trans == 1) {
                  /* exactly one transparent value: set colour key */
                  ckey = trans[0];
                } else
                  png_set_expand(png_ptr);
            } else
                ckey = 0; /* actual value will be set later */
      }

      if ( color_type == PNG_COLOR_TYPE_GRAY_ALPHA )
            png_set_gray_to_rgb(png_ptr);

      png_read_update_info(png_ptr, info_ptr);

      png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth,
                  &color_type, &interlace_type, NULL, NULL);

      /* Allocate the SDL surface to hold the image */
      Rmask = Gmask = Bmask = Amask = 0 ; 
      if ( color_type != PNG_COLOR_TYPE_PALETTE ) {
            if ( SDL_BYTEORDER == SDL_LIL_ENDIAN ) {
                  Rmask = 0x000000FF;
                  Gmask = 0x0000FF00;
                  Bmask = 0x00FF0000;
                  Amask = (info_ptr->channels == 4) ? 0xFF000000 : 0;
            } else {
                    int s = (info_ptr->channels == 4) ? 0 : 8;
                  Rmask = 0xFF000000 >> s;
                  Gmask = 0x00FF0000 >> s;
                  Bmask = 0x0000FF00 >> s;
                  Amask = 0x000000FF >> s;
            }
      }
      surface = SDL_AllocSurface(SDL_SWSURFACE, width, height,
                  bit_depth*info_ptr->channels, Rmask,Gmask,Bmask,Amask);
      if ( surface == NULL ) {
            IMG_SetError("Out of memory");
            goto done;
      }

      if(ckey != -1) {
              if(color_type != PNG_COLOR_TYPE_PALETTE)
                    ckey = SDL_MapRGB(surface->format, transv->red,
                                transv->green, transv->blue);
              SDL_SetColorKey(surface, SDL_SRCCOLORKEY, ckey);
      }

      /* Create the array of pointers to image data */
      row_pointers = (png_bytep*) malloc(sizeof(png_bytep)*height);
      if ( (row_pointers == NULL) ) {
            IMG_SetError("Out of memory");
            SDL_FreeSurface(surface);
            surface = NULL;
            goto done;
      }
      for (row = 0; row < height; row++) {
            row_pointers[row] = (png_bytep)
                        (Uint8 *)surface->pixels + row*surface->pitch;
      }

      /* Read the entire image in one go */
      png_read_image(png_ptr, row_pointers);

      /* read rest of file, get additional chunks in info_ptr - REQUIRED */
      png_read_end(png_ptr, info_ptr);

      /* Load the palette, if any */
      palette = surface->format->palette;
      if ( palette ) {
          if(color_type == PNG_COLOR_TYPE_GRAY) {
            palette->ncolors = 256;
            for(i = 0; i < 256; i++) {
                palette->colors[i].r = i;
                palette->colors[i].g = i;
                palette->colors[i].b = i;
            }
          } else if (info_ptr->num_palette > 0 ) {
            palette->ncolors = info_ptr->num_palette; 
            for( i=0; i<info_ptr->num_palette; ++i ) {
                palette->colors[i].b = info_ptr->palette[i].blue;
                palette->colors[i].g = info_ptr->palette[i].green;
                palette->colors[i].r = info_ptr->palette[i].red;
            }
          }
      }

done: /* Clean up and return */
      png_destroy_read_struct(&png_ptr, info_ptr ? &info_ptr : (png_infopp)0,
                                                (png_infopp)0);
      if ( row_pointers ) {
            free(row_pointers);
      }
      return(surface); 
}


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