/*

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

slouken@libsdl.org

*/

/* $Id$ */

/* 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*/

/* 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 */

}

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)

{

struct jpeg_decompress_struct cinfo;

JSAMPROW rowptr[1];

SDL_Surface *volatile surface = NULL;

struct my_error_mgr jerr;

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

cinfo.err = 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 */

jpeg_destroy_decompress(&cinfo);

IMG_SetError("JPEG loading error");

SDL_FreeSurface(surface);

return NULL;

}

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 */