IMG_jpg.c
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IMG_jpg.c
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	/*
	SDL_image: An example image loading library for use with SDL
	Copyright (C) 1997-2009 Sam Lantinga

	This library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public
	License as published by the Free Software Foundation; either
	version 2.1 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
	Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public
	License along with this library; if not, write to the Free Software
	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

	Sam Lantinga
	slouken@libsdl.org
	*/

	#if !defined(__APPLE__) \|\| defined(SDL_IMAGE_USE_COMMON_BACKEND)

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

	#include <stdio.h>
	#include <string.h>
	#include <setjmp.h>

	#include "SDL_image.h"

	#ifdef LOAD_JPG

	#include <jpeglib.h>

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

	/* Define this for quicker (but less perfect) JPEG identification */
	#define FAST_IS_JPEG

	static struct {
	int loaded;
	void *handle;
	void (*jpeg_calc_output_dimensions) (j_decompress_ptr cinfo);
	void (*jpeg_CreateDecompress) (j_decompress_ptr cinfo, int version, size_t structsize);
	void (*jpeg_destroy_decompress) (j_decompress_ptr cinfo);
	boolean (*jpeg_finish_decompress) (j_decompress_ptr cinfo);
	int (*jpeg_read_header) (j_decompress_ptr cinfo, boolean require_image);
	JDIMENSION (*jpeg_read_scanlines) (j_decompress_ptr cinfo, JSAMPARRAY scanlines, JDIMENSION max_lines);
	boolean (*jpeg_resync_to_restart) (j_decompress_ptr cinfo, int desired);
	boolean (*jpeg_start_decompress) (j_decompress_ptr cinfo);
	struct jpeg_error_mgr * (jpeg_std_error) (struct jpeg_error_mgr err);
	} lib;

	#ifdef LOAD_JPG_DYNAMIC
	int IMG_InitJPG()
	{
	if ( lib.loaded == 0 ) {
	lib.handle = SDL_LoadObject(LOAD_JPG_DYNAMIC);
	if ( lib.handle == NULL ) {
	return -1;
	}
	lib.jpeg_calc_output_dimensions =
	(void (*) (j_decompress_ptr))
	SDL_LoadFunction(lib.handle, "jpeg_calc_output_dimensions");
	if ( lib.jpeg_calc_output_dimensions == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_CreateDecompress =
	(void (*) (j_decompress_ptr, int, size_t))
	SDL_LoadFunction(lib.handle, "jpeg_CreateDecompress");
	if ( lib.jpeg_CreateDecompress == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_destroy_decompress =
	(void (*) (j_decompress_ptr))
	SDL_LoadFunction(lib.handle, "jpeg_destroy_decompress");
	if ( lib.jpeg_destroy_decompress == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_finish_decompress =
	(boolean (*) (j_decompress_ptr))
	SDL_LoadFunction(lib.handle, "jpeg_finish_decompress");
	if ( lib.jpeg_finish_decompress == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_read_header =
	(int (*) (j_decompress_ptr, boolean))
	SDL_LoadFunction(lib.handle, "jpeg_read_header");
	if ( lib.jpeg_read_header == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_read_scanlines =
	(JDIMENSION (*) (j_decompress_ptr, JSAMPARRAY, JDIMENSION))
	SDL_LoadFunction(lib.handle, "jpeg_read_scanlines");
	if ( lib.jpeg_read_scanlines == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_resync_to_restart =
	(boolean (*) (j_decompress_ptr, int))
	SDL_LoadFunction(lib.handle, "jpeg_resync_to_restart");
	if ( lib.jpeg_resync_to_restart == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_start_decompress =
	(boolean (*) (j_decompress_ptr))
	SDL_LoadFunction(lib.handle, "jpeg_start_decompress");
	if ( lib.jpeg_start_decompress == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	lib.jpeg_std_error =
	(struct jpeg_error_mgr * () (struct jpeg_error_mgr ))
	SDL_LoadFunction(lib.handle, "jpeg_std_error");
	if ( lib.jpeg_std_error == NULL ) {
	SDL_UnloadObject(lib.handle);
	return -1;
	}
	}
	++lib.loaded;

	return 0;
	}
	void IMG_QuitJPG()
	{
	if ( lib.loaded == 0 ) {
	return;
	}
	if ( lib.loaded == 1 ) {
	SDL_UnloadObject(lib.handle);
	}
	--lib.loaded;
	}
	#else
	int IMG_InitJPG()
	{
	if ( lib.loaded == 0 ) {
	lib.jpeg_calc_output_dimensions = jpeg_calc_output_dimensions;
	lib.jpeg_CreateDecompress = jpeg_CreateDecompress;
	lib.jpeg_destroy_decompress = jpeg_destroy_decompress;
	lib.jpeg_finish_decompress = jpeg_finish_decompress;
	lib.jpeg_read_header = jpeg_read_header;
	lib.jpeg_read_scanlines = jpeg_read_scanlines;
	lib.jpeg_resync_to_restart = jpeg_resync_to_restart;
	lib.jpeg_start_decompress = jpeg_start_decompress;
	lib.jpeg_std_error = jpeg_std_error;
	}
	++lib.loaded;

	return 0;
	}
	void IMG_QuitJPG()
	{
	if ( lib.loaded == 0 ) {
	return;
	}
	if ( lib.loaded == 1 ) {
	}
	--lib.loaded;
	}
	#endif /* LOAD_JPG_DYNAMIC */

	/* See if an image is contained in a data source */
	int IMG_isJPG(SDL_RWops *src)
	{
	int start;
	int is_JPG;
	int in_scan;
	Uint8 magic[4];

	/* This detection code is by Steaphan Greene <stea@cs.binghamton.edu> */
	/* Blame me, not Sam, if this doesn't work right. */
	/* And don't forget to report the problem to the the sdl list too! */

	if ( !src )
	return 0;
	start = SDL_RWtell(src);
	is_JPG = 0;
	in_scan = 0;
	if ( SDL_RWread(src, magic, 2, 1) ) {
	if ( (magic[0] == 0xFF) && (magic[1] == 0xD8) ) {
	is_JPG = 1;
	while (is_JPG == 1) {
	if(SDL_RWread(src, magic, 1, 2) != 2) {
	is_JPG = 0;
	} else if( (magic[0] != 0xFF) && (in_scan == 0) ) {
	is_JPG = 0;
	} else if( (magic[0] != 0xFF) \|\| (magic[1] == 0xFF) ) {
	/* Extra padding in JPEG (legal) */
	/* or this is data and we are scanning */
	SDL_RWseek(src, -1, RW_SEEK_CUR);
	} else if(magic[1] == 0xD9) {
	/* Got to end of good JPEG */
	break;
	} else if( (in_scan == 1) && (magic[1] == 0x00) ) {
	/* This is an encoded 0xFF within the data */
	} else if( (magic[1] >= 0xD0) && (magic[1] < 0xD9) ) {
	/* These have nothing else */
	} else if(SDL_RWread(src, magic+2, 1, 2) != 2) {
	is_JPG = 0;
	} else {
	/* Yes, it's big-endian */
	Uint32 start;
	Uint32 size;
	Uint32 end;
	start = SDL_RWtell(src);
	size = (magic[2] << 8) + magic[3];
	end = SDL_RWseek(src, size-2, RW_SEEK_CUR);
	if ( end != start + size - 2 ) is_JPG = 0;
	if ( magic[1] == 0xDA ) {
	/* Now comes the actual JPEG meat */
	#ifdef FAST_IS_JPEG
	/* Ok, I'm convinced. It is a JPEG. */
	break;
	#else
	/* I'm not convinced. Prove it! */
	in_scan = 1;
	#endif
	}
	}
	}
	}
	}
	SDL_RWseek(src, start, RW_SEEK_SET);
	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 = lib.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 */
	}

	struct my_error_mgr {
	struct jpeg_error_mgr errmgr;
	jmp_buf escape;
	};

	static void my_error_exit(j_common_ptr cinfo)
	{
	struct my_error_mgr err = (struct my_error_mgr )cinfo->err;
	longjmp(err->escape, 1);
	}

	static void output_no_message(j_common_ptr cinfo)
	{
	/* do nothing */
	}

	/* Load a JPEG type image from an SDL datasource */
	SDL_Surface IMG_LoadJPG_RW(SDL_RWops src)
	{
	int start;
	struct jpeg_decompress_struct cinfo;
	JSAMPROW rowptr[1];
	SDL_Surface *volatile surface = NULL;
	struct my_error_mgr jerr;

	if ( !src ) {
	/* The error message has been set in SDL_RWFromFile */
	return NULL;
	}
	start = SDL_RWtell(src);

	if ( !IMG_Init(IMG_INIT_JPG) ) {
	return NULL;
	}

	/* Create a decompression structure and load the JPEG header */
	cinfo.err = lib.jpeg_std_error(&jerr.errmgr);
	jerr.errmgr.error_exit = my_error_exit;
	jerr.errmgr.output_message = output_no_message;
	if(setjmp(jerr.escape)) {
	/* If we get here, libjpeg found an error */
	lib.jpeg_destroy_decompress(&cinfo);
	if ( surface != NULL ) {
	SDL_FreeSurface(surface);
	}
	SDL_RWseek(src, start, RW_SEEK_SET);
	IMG_SetError("JPEG loading error");
	return NULL;
	}

	lib.jpeg_create_decompress(&cinfo);
	jpeg_SDL_RW_src(&cinfo, src);
	lib.jpeg_read_header(&cinfo, TRUE);

	if(cinfo.num_components == 4) {
	/* Set 32-bit Raw output */
	cinfo.out_color_space = JCS_CMYK;
	cinfo.quantize_colors = FALSE;
	lib.jpeg_calc_output_dimensions(&cinfo);

	/* Allocate an output surface to hold the image */
	surface = SDL_AllocSurface(SDL_SWSURFACE,
	cinfo.output_width, cinfo.output_height, 32,
	#if SDL_BYTEORDER == SDL_LIL_ENDIAN
	0x00FF0000, 0x0000FF00, 0x000000FF, 0xFF000000);
	#else
	0x0000FF00, 0x00FF0000, 0xFF000000, 0x000000FF);
	#endif
	} else {
	/* 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
	lib.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 ) {
	lib.jpeg_destroy_decompress(&cinfo);
	SDL_RWseek(src, start, RW_SEEK_SET);
	IMG_SetError("Out of memory");
	return NULL;
	}

	/* Decompress the image */
	lib.jpeg_start_decompress(&cinfo);
	while ( cinfo.output_scanline < cinfo.output_height ) {
	rowptr[0] = (JSAMPROW)(Uint8 *)surface->pixels +
	cinfo.output_scanline * surface->pitch;
	lib.jpeg_read_scanlines(&cinfo, rowptr, (JDIMENSION) 1);
	}
	lib.jpeg_finish_decompress(&cinfo);
	lib.jpeg_destroy_decompress(&cinfo);

	return(surface);
	}

	#else

	int IMG_InitJPG()
	{
	IMG_SetError("JPEG images are not supported");
	return(-1);
	}

	void IMG_QuitJPG()
	{
	}

	/* 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 */

	#endif /* !defined(__APPLE__) \|\| defined(SDL_IMAGE_USE_COMMON_BACKEND) */

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