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/*

    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 JPEG image file loading framework */

#include 

#include 

#include "SDL_image.h"

#ifdef LOAD_JPG

#include 

/* Define this for fast loading and not as good image quality */

/*#define FAST_JPEG*/

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

int IMG_isJPG(SDL_RWops *src)

{

	int is_JPG;

	Uint8 magic[4];

	is_JPG = 0;

	if ( SDL_RWread(src, magic, 2, 1) ) {

		if ( (magic[0] == 0xFF) && (magic[1] == 0xD8) ) {

			SDL_RWread(src, magic, 4, 1);

			SDL_RWread(src, magic, 4, 1);

			if ( memcmp((char *)magic, "JFIF", 4) == 0 ) {

				is_JPG = 1;

			}

		}

	}

	return(is_JPG);

}

#define INPUT_BUFFER_SIZE	4096

typedef struct {

	struct jpeg_source_mgr pub;

	SDL_RWops *ctx;

	Uint8 buffer[INPUT_BUFFER_SIZE];

} my_source_mgr;

/*

 * Initialize source --- called by jpeg_read_header

 * before any data is actually read.

 */

static void init_source (j_decompress_ptr cinfo)

{

	/* We don't actually need to do anything */

	return;

}

/*

 * Fill the input buffer --- called whenever buffer is emptied.

 */

static int fill_input_buffer (j_decompress_ptr cinfo)

{

	my_source_mgr * src = (my_source_mgr *) cinfo->src;

	int nbytes;

	nbytes = SDL_RWread(src->ctx, src->buffer, 1, INPUT_BUFFER_SIZE);

	if (nbytes <= 0) {

		/* Insert a fake EOI marker */

		src->buffer[0] = (Uint8) 0xFF;

		src->buffer[1] = (Uint8) JPEG_EOI;

		nbytes = 2;

	}

	src->pub.next_input_byte = src->buffer;

	src->pub.bytes_in_buffer = nbytes;

	return TRUE;

}

/*

 * Skip data --- used to skip over a potentially large amount of

 * uninteresting data (such as an APPn marker).

 *

 * Writers of suspendable-input applications must note that skip_input_data

 * is not granted the right to give a suspension return.  If the skip extends

 * beyond the data currently in the buffer, the buffer can be marked empty so

 * that the next read will cause a fill_input_buffer call that can suspend.

 * Arranging for additional bytes to be discarded before reloading the input

 * buffer is the application writer's problem.

 */

static void skip_input_data (j_decompress_ptr cinfo, long num_bytes)

{

	my_source_mgr * src = (my_source_mgr *) cinfo->src;

	/* Just a dumb implementation for now.	Could use fseek() except

	 * it doesn't work on pipes.  Not clear that being smart is worth

	 * any trouble anyway --- large skips are infrequent.

	 */

	if (num_bytes > 0) {

		while (num_bytes > (long) src->pub.bytes_in_buffer) {

			num_bytes -= (long) src->pub.bytes_in_buffer;

			(void) src->pub.fill_input_buffer(cinfo);

			/* note we assume that fill_input_buffer will never

			 * return FALSE, so suspension need not be handled.

			 */

		}

		src->pub.next_input_byte += (size_t) num_bytes;

		src->pub.bytes_in_buffer -= (size_t) num_bytes;

	}

}

/*

 * Terminate source --- called by jpeg_finish_decompress

 * after all data has been read.

 */

static void term_source (j_decompress_ptr cinfo)

{

	/* We don't actually need to do anything */

	return;

}

/*

 * Prepare for input from a stdio stream.

 * The caller must have already opened the stream, and is responsible

 * for closing it after finishing decompression.

 */

static void jpeg_SDL_RW_src (j_decompress_ptr cinfo, SDL_RWops *ctx)

{

  my_source_mgr *src;

  /* The source object and input buffer are made permanent so that a series

   * of JPEG images can be read from the same file by calling jpeg_stdio_src

   * only before the first one.  (If we discarded the buffer at the end of

   * one image, we'd likely lose the start of the next one.)

   * This makes it unsafe to use this manager and a different source

   * manager serially with the same JPEG object.  Caveat programmer.

   */

  if (cinfo->src == NULL) {	/* first time for this JPEG object? */

    cinfo->src = (struct jpeg_source_mgr *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,

				  sizeof(my_source_mgr));

    src = (my_source_mgr *) cinfo->src;

  }

  src = (my_source_mgr *) cinfo->src;

  src->pub.init_source = init_source;

  src->pub.fill_input_buffer = fill_input_buffer;

  src->pub.skip_input_data = skip_input_data;

  src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */

  src->pub.term_source = term_source;

  src->ctx = ctx;

  src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */

  src->pub.next_input_byte = NULL; /* until buffer loaded */

}

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

SDL_Surface *IMG_LoadJPG_RW(SDL_RWops *src)

{

	struct jpeg_error_mgr errmgr;

	struct jpeg_decompress_struct cinfo;

	JSAMPROW rowptr[1];

	SDL_Surface *surface;

	/* Create a decompression structure and load the JPEG header */

	cinfo.err = jpeg_std_error(&errmgr);

	jpeg_create_decompress(&cinfo);

	jpeg_SDL_RW_src(&cinfo, src);

	jpeg_read_header(&cinfo, TRUE);

	/* Set 24-bit RGB output */

	cinfo.out_color_space = JCS_RGB;

	cinfo.quantize_colors = FALSE;

#ifdef FAST_JPEG

	cinfo.scale_num   = 1;

	cinfo.scale_denom = 1;

	cinfo.dct_method = JDCT_FASTEST;

	cinfo.do_fancy_upsampling = FALSE;

#endif

	jpeg_calc_output_dimensions(&cinfo);

	/* Allocate an output surface to hold the image */

	surface = SDL_AllocSurface(SDL_SWSURFACE,

	               cinfo.output_width, cinfo.output_height, 24,

#if SDL_BYTEORDER == SDL_LIL_ENDIAN

	                           0x0000FF, 0x00FF00, 0xFF0000,

#else

	                           0xFF0000, 0x00FF00, 0x0000FF,

#endif

				   0);

	if ( surface == NULL ) {

		IMG_SetError("Out of memory");

		goto done;

	}

	/* Decompress the image */

	jpeg_start_decompress(&cinfo);

	while ( cinfo.output_scanline < cinfo.output_height ) {

		rowptr[0] = (JSAMPROW)(Uint8 *)surface->pixels +

		                    cinfo.output_scanline * surface->pitch;

		jpeg_read_scanlines(&cinfo, rowptr, (JDIMENSION) 1);

	}

	jpeg_finish_decompress(&cinfo);

	/* Clean up and return */

done:

	jpeg_destroy_decompress(&cinfo);

	return(surface);

}

#else

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

int IMG_isJPG(SDL_RWops *src)

{

	return(0);

}

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

SDL_Surface *IMG_LoadJPG_RW(SDL_RWops *src)

{

	return(NULL);

}

#endif /* LOAD_JPG */