SDL_image: An example image loading library for use with SDL

Copyright (C) 1999, 2000, 2001 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

*/

/* $Id$ */

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

#include <stdlib.h>

#include <stdio.h>

#include "SDL_image.h"

#ifdef LOAD_PNG

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

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"

#ifdef macintosh

#define MACOS

#endif

#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)

{

/* 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)

{

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_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, or if partially transparent

entries exist, 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) {

/* Check if all tRNS entries are opaque except one */

int i, t = -1;

for(i = 0; i < num_trans; i++)

if(trans[i] == 0) {

if(t >= 0)

break;

t = i;

} else if(trans[i] != 255)

break;

if(i == num_trans) {

/* exactly one transparent index */

ckey = t;

} else {

/* more than one transparent index, or translucency */

} else

ckey = 0; /* actual value will be set later */

}

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)

/* FIXME: Should these be truncated or shifted down? */

ckey = SDL_MapRGB(surface->format,

(Uint8)transv->red,

(Uint8)transv->green,

(Uint8)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;

}

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);

}

#else

/* See if an image is contained in a data source */

int IMG_isPNG(SDL_RWops *src)

{

return(0);

}

/* Load a PNG type image from an SDL datasource */

SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)

{

return(NULL);

}

#endif /* LOAD_PNG */