jpeg.c

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//
// $Id: jpeg.c,v 1.2 2000/08/29 08:05:33 weiym Exp $
// 
// jpg.c: Low-level JPEG file read/save routines.
// 
// Copyright (C) 2000, BluePoint Software.
// Copyright (C) 2000, Wei Yongming
//
// Current maintainer: Wei Yongming
//
// Create date: 2000/08/29

/*
**  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
**  Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
**  MA 02111-1307, USA
*/

/*
 * JPEG decompression routine
 *
 * JPEG support must be enabled (see README.txt in contrib/jpeg)
 *
 * SOME FINE POINTS: (from libjpeg)
 * In the below code, we ignored the return value of jpeg_read_scanlines,
 * which is the number of scanlines actually read.  We could get away with
 * this because we asked for only one line at a time and we weren't using
 * a suspending data source.  See libjpeg.doc for more info.
 *
 * We cheated a bit by calling alloc_sarray() after jpeg_start_decompress();
 * we should have done it beforehand to ensure that the space would be
 * counted against the JPEG max_memory setting.  In some systems the above
 * code would risk an out-of-memory error.  However, in general we don't
 * know the output image dimensions before jpeg_start_decompress(), unless we
 * call jpeg_calc_output_dimensions().  See libjpeg.doc for more about this.
 *
 * Scanlines are returned in the same order as they appear in the JPEG file,
 * which is standardly top-to-bottom.  If you must emit data bottom-to-top,
 * you can use one of the virtual arrays provided by the JPEG memory manager
 * to invert the data.  See wrbmp.c for an example.
 *
 * As with compression, some operating modes may require temporary files.
 * On some systems you may need to set up a signal handler to ensure that
 * temporary files are deleted if the program is interrupted.  See libjpeg.doc.
 */

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

#include "../image/jpeglib.h"
#include "common.h"
#include "gdi.h"
#include "readbmp.h"

int load_jpg (FILE *fp, MYBITMAP* bmp, RGB* pal)
{
    int i;
    int ret = ERR_BMP_LOAD;    /* image load error*/
    unsigned char magic[4];

    /* This struct contains the JPEG decompression parameters
     * and pointers to working space 
     * (which is allocated as needed by the JPEG library).
     */
    struct jpeg_decompress_struct cinfo;
    struct jpeg_error_mgr jerr;

    /* first determine if JPEG file since decoder will error if not*/
    fseek(fp, 0L, 0);
    if(!fread(magic, 2, 1, fp))
        return ERR_BMP_IMAGE_TYPE;        /* not JPEG image*/
    if (magic[0] != 0xFF || magic[1] != 0xD8)
        return ERR_BMP_IMAGE_TYPE;        /* not JPEG image*/
    fread(magic, 4, 1, fp);
    fread(magic, 4, 1, fp);
    if (strncmp(magic, "JFIF", 4) != 0)
        return ERR_BMP_IMAGE_TYPE;        /* not JPEG image*/

    fseek(fp, 0L, 0);

    /* Step 1: allocate and initialize JPEG decompression object */

    /* We set up the normal JPEG error routines. */
    cinfo.err = jpeg_std_error (&jerr);

    /* Now we can initialize the JPEG decompression object. */
    jpeg_create_decompress (&cinfo);

    /* Step 2: specify data source (eg, a file) */
    jpeg_stdio_src (&cinfo, fp);

    /* Step 3: read file parameters with jpeg_read_header() */
    jpeg_read_header (&cinfo, TRUE);

    /* Step 4: set parameters for decompression */
    cinfo.out_color_space = (bmp->flags & LOADBMP_FLAG_GRAYSCALE) ? JCS_GRAYSCALE: JCS_RGB;
    cinfo.quantize_colors = FALSE;

    if (!bmp->flags & LOADBMP_FLAG_GRAYSCALE)
    {
        if (bmp->depth <= 8)
        {
            cinfo.quantize_colors = TRUE;
    
            /* Get system palette */
            cinfo.actual_number_of_colors = 0x01 << bmp->depth;
    
            /* Allocate jpeg colormap space */
            cinfo.colormap = (*cinfo.mem->alloc_sarray)
                ((j_common_ptr) &cinfo, JPOOL_IMAGE,
                       (JDIMENSION)cinfo.actual_number_of_colors,
                (JDIMENSION)3);

            /* Set colormap from system palette */
            for(i = 0; i < cinfo.actual_number_of_colors; ++i)
            {
                cinfo.colormap[0][i] = pal[i].r >> 2;
                cinfo.colormap[1][i] = pal[i].g >> 2;
                cinfo.colormap[2][i] = pal[i].b >> 2;
            }
        }
    }
    else 
    {
        /* Grayscale output asked */
        cinfo.quantize_colors = TRUE;
        cinfo.out_color_space = JCS_GRAYSCALE;
        cinfo.desired_number_of_colors = 256;
        for (i = 0; i < 256; i++) {
            pal [i].r = i;
            pal [i].g = i;
            pal [i].b = i;
        }
    }
    jpeg_calc_output_dimensions (&cinfo);

    ret = ERR_BMP_MEM;

    bmp->w = cinfo.output_width;
    bmp->h = cinfo.output_height;
    bmp->frames = 1;
    bmp->depth = (bmp->flags & LOADBMP_FLAG_GRAYSCALE) ? 8 : cinfo.output_components * 8;
    bmpComputePitch (bmp->depth, bmp->w, &bmp->pitch, TRUE);
    bmp->rgb_order = RGB_ORDER_RGB;
    bmp->bits = malloc(bmp->pitch * bmp->h);
    if (!bmp->bits) goto err;

    /* Step 5: Start decompressor */
    jpeg_start_decompress (&cinfo);

    /* Step 6: while (scan lines remain to be read) */
    while (cinfo.output_scanline < cinfo.output_height) {
        JSAMPROW rowptr[1];
        BYTE* bits;
        bits = bmp->bits + cinfo.output_scanline * bmp->pitch;
        rowptr[0] = (JSAMPROW)(bits);
        jpeg_read_scanlines (&cinfo, rowptr, 1);
    }
    ret = ERR_BMP_OK;

err:
    /* Step 7: Finish decompression */
    jpeg_finish_decompress (&cinfo);

    /* Step 8: Release JPEG decompression object */
    jpeg_destroy_decompress (&cinfo);

    /* May want to check to see whether any corrupt-data
     * warnings occurred (test whether jerr.pub.num_warnings is nonzero).
     */
    return ret;
}