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/* jpg.c - Copyright (C) 2001-2002 Jacob Kroon, see COPYING for details */
/* JPG code originally by Sam Lantinga, slouken@libsdl.org */
#include <stdio.h>
#include <string.h>
#include <jpeglib.h>
#include <SDL_video.h>
#include <SDL_error.h>
#include <SDL_rwops.h>
#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 */
SDL_Surface *loadJPG(Uint8 * data, Uint32 * memcounter)
{
struct jpeg_error_mgr errmgr;
struct jpeg_decompress_struct cinfo;
JSAMPROW rowptr[1];
SDL_Surface *surface;
SDL_RWops *src = NULL;
Uint32 size;
memcpy(&size, data, sizeof(Uint32));
if (memcounter)
*memcounter += size + sizeof(Uint32);
data += sizeof(Uint32);
src = SDL_RWFromMem(data, size);
/* 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;
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) {
SDL_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:
if (src)
SDL_FreeRW(src);
jpeg_destroy_decompress(&cinfo);
return (surface);
}
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