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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 <stdio.h> |
| #include <string.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 */ |
| } |
| |
| /* 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 */ |