path: root/converter/other/jpeg2000/libjasper/jp2/jp2_dec.c

/*
 * Copyright (c) 1999-2000 Image Power, Inc. and the University of
 *   British Columbia.
 * Copyright (c) 2001-2002 Michael David Adams.
 * All rights reserved.
 */

/* __START_OF_JASPER_LICENSE__
 *
 * JasPer Software License
 *
 * IMAGE POWER JPEG-2000 PUBLIC LICENSE
 * ************************************
 *
 * GRANT:
 *
 * Permission is hereby granted, free of charge, to any person (the "User")
 * obtaining a copy of this software and associated documentation, to deal
 * in the JasPer Software without restriction, including without limitation
 * the right to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the JasPer Software (in source and binary forms),
 * and to permit persons to whom the JasPer Software is furnished to do so,
 * provided further that the License Conditions below are met.
 *
 * License Conditions
 * ******************
 *
 * A.  Redistributions of source code must retain the above copyright notice,
 * and this list of conditions, and the following disclaimer.
 *
 * B.  Redistributions in binary form must reproduce the above copyright
 * notice, and this list of conditions, and the following disclaimer in
 * the documentation and/or other materials provided with the distribution.
 *
 * C.  Neither the name of Image Power, Inc. nor any other contributor
 * (including, but not limited to, the University of British Columbia and
 * Michael David Adams) may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 *
 * D.  User agrees that it shall not commence any action against Image Power,
 * Inc., the University of British Columbia, Michael David Adams, or any
 * other contributors (collectively "Licensors") for infringement of any
 * intellectual property rights ("IPR") held by the User in respect of any
 * technology that User owns or has a right to license or sublicense and
 * which is an element required in order to claim compliance with ISO/IEC
 * 15444-1 (i.e., JPEG-2000 Part 1).  "IPR" means all intellectual property
 * rights worldwide arising under statutory or common law, and whether
 * or not perfected, including, without limitation, all (i) patents and
 * patent applications owned or licensable by User; (ii) rights associated
 * with works of authorship including copyrights, copyright applications,
 * copyright registrations, mask work rights, mask work applications,
 * mask work registrations; (iii) rights relating to the protection of
 * trade secrets and confidential information; (iv) any right analogous
 * to those set forth in subsections (i), (ii), or (iii) and any other
 * proprietary rights relating to intangible property (other than trademark,
 * trade dress, or service mark rights); and (v) divisions, continuations,
 * renewals, reissues and extensions of the foregoing (as and to the extent
 * applicable) now existing, hereafter filed, issued or acquired.
 *
 * E.  If User commences an infringement action against any Licensor(s) then
 * such Licensor(s) shall have the right to terminate User's license and
 * all sublicenses that have been granted hereunder by User to other parties.
 *
 * F.  This software is for use only in hardware or software products that
 * are compliant with ISO/IEC 15444-1 (i.e., JPEG-2000 Part 1).  No license
 * or right to this Software is granted for products that do not comply
 * with ISO/IEC 15444-1.  The JPEG-2000 Part 1 standard can be purchased
 * from the ISO.
 *
 * THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE.
 * NO USE OF THE JASPER SOFTWARE IS AUTHORIZED HEREUNDER EXCEPT UNDER
 * THIS DISCLAIMER.  THE JASPER SOFTWARE IS PROVIDED BY THE LICENSORS AND
 * CONTRIBUTORS UNDER THIS LICENSE ON AN ``AS-IS'' BASIS, WITHOUT WARRANTY
 * OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION,
 * WARRANTIES THAT THE JASPER SOFTWARE IS FREE OF DEFECTS, IS MERCHANTABLE,
 * IS FIT FOR A PARTICULAR PURPOSE OR IS NON-INFRINGING.  THOSE INTENDING
 * TO USE THE JASPER SOFTWARE OR MODIFICATIONS THEREOF FOR USE IN HARDWARE
 * OR SOFTWARE PRODUCTS ARE ADVISED THAT THEIR USE MAY INFRINGE EXISTING
 * PATENTS, COPYRIGHTS, TRADEMARKS, OR OTHER INTELLECTUAL PROPERTY RIGHTS.
 * THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE JASPER SOFTWARE
 * IS WITH THE USER.  SHOULD ANY PART OF THE JASPER SOFTWARE PROVE DEFECTIVE
 * IN ANY RESPECT, THE USER (AND NOT THE INITIAL DEVELOPERS, THE UNIVERSITY
 * OF BRITISH COLUMBIA, IMAGE POWER, INC., MICHAEL DAVID ADAMS, OR ANY
 * OTHER CONTRIBUTOR) SHALL ASSUME THE COST OF ANY NECESSARY SERVICING,
 * REPAIR OR CORRECTION.  UNDER NO CIRCUMSTANCES AND UNDER NO LEGAL THEORY,
 * WHETHER TORT (INCLUDING NEGLIGENCE), CONTRACT, OR OTHERWISE, SHALL THE
 * INITIAL DEVELOPER, THE UNIVERSITY OF BRITISH COLUMBIA, IMAGE POWER, INC.,
 * MICHAEL DAVID ADAMS, ANY OTHER CONTRIBUTOR, OR ANY DISTRIBUTOR OF THE
 * JASPER SOFTWARE, OR ANY SUPPLIER OF ANY OF SUCH PARTIES, BE LIABLE TO
 * THE USER OR ANY OTHER PERSON FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR
 * CONSEQUENTIAL DAMAGES OF ANY CHARACTER INCLUDING, WITHOUT LIMITATION,
 * DAMAGES FOR LOSS OF GOODWILL, WORK STOPPAGE, COMPUTER FAILURE OR
 * MALFUNCTION, OR ANY AND ALL OTHER COMMERCIAL DAMAGES OR LOSSES, EVEN IF
 * SUCH PARTY HAD BEEN INFORMED, OR OUGHT TO HAVE KNOWN, OF THE POSSIBILITY
 * OF SUCH DAMAGES.  THE JASPER SOFTWARE AND UNDERLYING TECHNOLOGY ARE NOT
 * FAULT-TOLERANT AND ARE NOT DESIGNED, MANUFACTURED OR INTENDED FOR USE OR
 * RESALE AS ON-LINE CONTROL EQUIPMENT IN HAZARDOUS ENVIRONMENTS REQUIRING
 * FAIL-SAFE PERFORMANCE, SUCH AS IN THE OPERATION OF NUCLEAR FACILITIES,
 * AIRCRAFT NAVIGATION OR COMMUNICATION SYSTEMS, AIR TRAFFIC CONTROL, DIRECT
 * LIFE SUPPORT MACHINES, OR WEAPONS SYSTEMS, IN WHICH THE FAILURE OF THE
 * JASPER SOFTWARE OR UNDERLYING TECHNOLOGY OR PRODUCT COULD LEAD DIRECTLY
 * TO DEATH, PERSONAL INJURY, OR SEVERE PHYSICAL OR ENVIRONMENTAL DAMAGE
 * ("HIGH RISK ACTIVITIES").  LICENSOR SPECIFICALLY DISCLAIMS ANY EXPRESS
 * OR IMPLIED WARRANTY OF FITNESS FOR HIGH RISK ACTIVITIES.  USER WILL NOT
 * KNOWINGLY USE, DISTRIBUTE OR RESELL THE JASPER SOFTWARE OR UNDERLYING
 * TECHNOLOGY OR PRODUCTS FOR HIGH RISK ACTIVITIES AND WILL ENSURE THAT ITS
 * CUSTOMERS AND END-USERS OF ITS PRODUCTS ARE PROVIDED WITH A COPY OF THE
 * NOTICE SPECIFIED IN THIS SECTION.
 *
 * __END_OF_JASPER_LICENSE__
 */

#include "jasper/jas_image.h"
#include "jasper/jas_stream.h"
#include "jasper/jas_math.h"
#include "jasper/jas_debug.h"
#include "jasper/jas_malloc.h"
#include "jasper/jas_version.h"

#include "netpbm/nstring.h"

#include "jp2_cod.h"
#include "jp2_dec.h"

#define JP2_VALIDATELEN (JAS_MIN(JP2_JP_LEN + 16, JAS_STREAM_MAXPUTBACK))



static jp2_dec_t *
jp2_dec_create(void) {

    jp2_dec_t *dec;

    dec = jas_malloc(sizeof(jp2_dec_t));
    if (dec) {
        dec->ihdr = 0;
        dec->bpcc = 0;
        dec->cdef = 0;
        dec->pclr = 0;
        dec->image = 0;
        dec->chantocmptlut = 0;
        dec->cmap = 0;
        dec->colr = 0;
    }
    return dec;
}



static void
jp2_dec_destroy(jp2_dec_t *dec) {

    if (dec->ihdr)
        jp2_box_destroy(dec->ihdr);

    if (dec->bpcc)
        jp2_box_destroy(dec->bpcc);

    if (dec->cdef)
        jp2_box_destroy(dec->cdef);

    if (dec->pclr)
        jp2_box_destroy(dec->pclr);

    if (dec->image)
        jas_image_destroy(dec->image);

    if (dec->cmap)
        jp2_box_destroy(dec->cmap);

    if (dec->colr)
        jp2_box_destroy(dec->colr);

    if (dec->chantocmptlut)
        jas_free(dec->chantocmptlut);

    jas_free(dec);
}



static int
jp2_getct(int colorspace, int type, int assoc) {

    if (type == 1 && assoc == 0)
        return JAS_IMAGE_CT_OPACITY;

    if (type == 0 && assoc >= 1 && assoc <= 65534) {
        switch (colorspace) {
        case JAS_IMAGE_CS_RGB:
            switch (assoc) {
            case JP2_CDEF_RGB_R:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_RGB_R);
                break;
            case JP2_CDEF_RGB_G:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_RGB_G);
                break;
            case JP2_CDEF_RGB_B:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_RGB_B);
                break;
            }
            break;
        case JAS_IMAGE_CS_YCBCR:
            switch (assoc) {
            case JP2_CDEF_YCBCR_Y:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_YCBCR_Y);
                break;
            case JP2_CDEF_YCBCR_CB:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_YCBCR_CB);
                break;
            case JP2_CDEF_YCBCR_CR:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_YCBCR_CR);
                break;
            }
            break;
        case JAS_IMAGE_CS_GRAY:
            switch (assoc) {
            case JP2_CDEF_GRAY_Y:
                return JAS_IMAGE_CT_COLOR(JAS_IMAGE_CT_GRAY_Y);
                break;
            }
            break;
#if 0
        case JAS_IMAGE_CS_ICC:
#endif
        default:
            return JAS_IMAGE_CT_COLOR(assoc - 1);
            break;
        }
    }
    return JAS_IMAGE_CT_UNKNOWN;
}



static int
jp2_getcs(jp2_colr_t *colr) {

    if (colr->method == JP2_COLR_ENUM) {
        switch (colr->csid) {
        case JP2_COLR_SRGB:
            return JAS_IMAGE_CS_RGB;
            break;
        case JP2_COLR_SYCC:
            return JAS_IMAGE_CS_YCBCR;
            break;
        case JP2_COLR_SGRAY:
            return JAS_IMAGE_CS_GRAY;
            break;
        }
    }
    return JAS_IMAGE_CS_UNKNOWN;
}



static int
fromiccpcs(int cs) {
   
    switch (cs) {
    case ICC_CS_RGB:
        return JAS_IMAGE_CS_RGB;
        break;
    case ICC_CS_YCBCR:
        return JAS_IMAGE_CS_YCBCR;
        break;
    case ICC_CS_GRAY:
        return JAS_IMAGE_CS_GRAY;
        break;
    }
    return JAS_IMAGE_CS_UNKNOWN;
}



void
jp2_decode(jas_stream_t * const in,
           const char *   const optstr,
           jas_image_t ** const imagePP,
           const char **  const errorP) {

    jp2_box_t *box;
    int found;
    jas_image_t *image;
    jp2_dec_t *dec;
    bool samedtype;
    int dtype;
    int i;
    jp2_cmap_t *cmapd;
    jp2_pclr_t *pclrd;
    int channo;
    int newcmptno;
    int_fast32_t *lutents;
    jp2_cmapent_t *cmapent;
    unsigned char *iccp;
    int cs;

    dec = 0;
    box = 0;
    image = 0;

    if (!(dec = jp2_dec_create())) {
        pm_asprintf(errorP, "jp2_dec_create failed");
        goto cleanup;
    }

    /* Get the first box.  This should be a JP box. */
    if (!(box = jp2_box_get(in))) {
        pm_asprintf(errorP, "cannot get box");
        goto cleanup;
    }
    if (box->type != JP2_BOX_JP) {
        pm_asprintf(errorP, "expecting signature box");
        goto cleanup;
    }
    if (box->data.jp.magic != JP2_JP_MAGIC) {
        pm_asprintf(errorP, "incorrect magic number");
        goto cleanup;
    }
    jp2_box_destroy(box);
    box = 0;

    /* Get the second box.  This should be a FTYP box. */
    if (!(box = jp2_box_get(in))) {
        pm_asprintf(errorP, "cannot get second box");
        goto cleanup;
    }
    if (box->type != JP2_BOX_FTYP) {
        pm_asprintf(errorP, "expecting file type box");
        goto cleanup;
    }
    jp2_box_destroy(box);
    box = 0;

    /* Get more boxes... */
    found = 0;
    while ((box = jp2_box_get(in))) {
        if (jas_getdbglevel() >= 1) {
            jas_eprintf("box type '%s'\n", box->info->name);
        }
        switch (box->type) {
        case JP2_BOX_JP2C:
            found = 1;
            break;
        case JP2_BOX_IHDR:
            if (!dec->ihdr) {
                dec->ihdr = box;
                box = 0;
            }
            break;
        case JP2_BOX_BPCC:
            if (!dec->bpcc) {
                dec->bpcc = box;
                box = 0;
            }
            break;
        case JP2_BOX_CDEF:
            if (!dec->cdef) {
                dec->cdef = box;
                box = 0;
            }
            break;
        case JP2_BOX_PCLR:
            if (!dec->pclr) {
                dec->pclr = box;
                box = 0;
            }
            break;
        case JP2_BOX_CMAP:
            if (!dec->cmap) {
                dec->cmap = box;
                box = 0;
            }
            break;
        case JP2_BOX_COLR:
            if (!dec->colr) {
                dec->colr = box;
                box = 0;
            }
            break;
        }
        if (box) {
            jp2_box_destroy(box);
            box = 0;
        }
        if (found) {
            break;
        }
    }

    if (!found) {
        pm_asprintf(errorP, "no code stream found");
        goto cleanup;
    }

    {
        const char * decodeError;
        jpc_decode(in, optstr, &dec->image, &decodeError);
        if (decodeError) {
            pm_asprintf(errorP, "cannot decode code stream.  %s", decodeError);
            pm_strfree(decodeError);
            goto cleanup;
        }
    }

    /* An IHDR box must be present. */
    if (!dec->ihdr) {
        pm_asprintf(errorP, "missing IHDR box");
        goto cleanup;
    }

    /* Does the number of components indicated in the IHDR box match
      the value specified in the code stream? */
    if (dec->ihdr->data.ihdr.numcmpts != jas_image_numcmpts(dec->image)) {
        jas_eprintf("warning: number of components mismatch\n");
    }

    /* At least one component must be present. */
    if (!jas_image_numcmpts(dec->image)) {
        pm_asprintf(errorP, "no components");
        goto cleanup;
    }

    /* Determine if all components have the same data type. */
    samedtype = true;
    dtype = jas_image_cmptdtype(dec->image, 0);
    for (i = 1; i < jas_image_numcmpts(dec->image); ++i) {
        if (jas_image_cmptdtype(dec->image, i) != dtype) {
            samedtype = false;
            break;
        }
    }

    /* Is the component data type indicated in the IHDR box consistent
      with the data in the code stream? */
    if ((samedtype && dec->ihdr->data.ihdr.bpc != JP2_DTYPETOBPC(dtype)) ||
      (!samedtype && dec->ihdr->data.ihdr.bpc != JP2_IHDR_BPCNULL)) {
        jas_eprintf("warning: component data type mismatch\n");
    }

    /* Can we handle the compression type? */
    if (dec->ihdr->data.ihdr.comptype != JP2_IHDR_COMPTYPE) {
        pm_asprintf(errorP, "not capable of this compression type");
        goto cleanup;
    }

    if (dec->bpcc) {
        /* Is the number of components indicated in the BPCC box
          consistent with the code stream data? */
        if (dec->bpcc->data.bpcc.numcmpts != jas_image_numcmpts(
                dec->image)) {
            jas_eprintf("warning: number of components mismatch\n");
        }
        /* Is the component data type information indicated in the BPCC
          box consistent with the code stream data? */
        if (!samedtype) {
            for (i = 0; i < jas_image_numcmpts(dec->image); ++i) {
                if (jas_image_cmptdtype(dec->image, i) !=
                    JP2_BPCTODTYPE(dec->bpcc->data.bpcc.bpcs[i])) {
                    jas_eprintf("warning: component data type mismatch\n");
                }
            }
        } else {
            jas_eprintf("warning: superfluous BPCC box\n");
        }
    }

    /* A COLR box must be present. */
    if (!dec->colr) {
        pm_asprintf(errorP, "no COLR box");
        goto cleanup;
    }

    switch (dec->colr->data.colr.method) {
    case JP2_COLR_ENUM:
        jas_image_setcolorspace(dec->image, jp2_getcs(&dec->colr->data.colr));
        break;
    case JP2_COLR_ICC:
        if (dec->colr->data.colr.iccplen < 128) {
            abort();
        }
        iccp = dec->colr->data.colr.iccp;
        cs = (iccp[16] << 24) | (iccp[17] << 16) | (iccp[18] << 8) |
          iccp[19];
        if (jas_getdbglevel() > 1)
            jas_eprintf("ICC Profile CS %08x\n", cs);
        jas_image_setcolorspace(dec->image, fromiccpcs(cs));
        break;
    }

    /* If a CMAP box is present, a PCLR box must also be present. */
    if (dec->cmap && !dec->pclr) {
        jas_eprintf("warning: missing PCLR box or superfluous CMAP box\n");
        jp2_box_destroy(dec->cmap);
        dec->cmap = 0;
    }

    /* If a CMAP box is not present, a PCLR box must not be present. */
    if (!dec->cmap && dec->pclr) {
        jas_eprintf("warning: missing CMAP box or superfluous PCLR box\n");
        jp2_box_destroy(dec->pclr);
        dec->pclr = 0;
    }

    /* Determine the number of channels (which is essentially the number
      of components after any palette mappings have been applied). */
    dec->numchans = dec->cmap ?
        dec->cmap->data.cmap.numchans :
        jas_image_numcmpts(dec->image);

    /* Perform a basic sanity check on the CMAP box if present. */
    if (dec->cmap) {
        for (i = 0; i < dec->numchans; ++i) {
            /* Is the component number reasonable? */
            if (dec->cmap->data.cmap.ents[i].cmptno >=
                jas_image_numcmpts(dec->image)) {
                pm_asprintf(errorP, "invalid component number in CMAP box");
                goto cleanup;
            }
            /* Is the LUT index reasonable? */
            if (dec->cmap->data.cmap.ents[i].pcol >=
                dec->pclr->data.pclr.numchans) {
                pm_asprintf(errorP, "invalid CMAP LUT index");
                goto cleanup;
            }
        }
    }

    /* Allocate space for the channel-number to component-number LUT. */
    dec->chantocmptlut = jas_malloc(dec->numchans * sizeof(uint_fast16_t));
    if (!dec->chantocmptlut) {
        pm_asprintf(errorP, "no memory");
        goto cleanup;
    }

    if (!dec->cmap) {
        for (i = 0; i < dec->numchans; ++i) {
            dec->chantocmptlut[i] = i;
        }
    } else {
        cmapd = &dec->cmap->data.cmap;
        pclrd = &dec->pclr->data.pclr;
        for (channo = 0; channo < cmapd->numchans; ++channo) {
            cmapent = &cmapd->ents[channo];
            if (cmapent->map == JP2_CMAP_DIRECT) {
                dec->chantocmptlut[channo] = channo;
            } else if (cmapent->map == JP2_CMAP_PALETTE) {
                lutents = jas_malloc(pclrd->numlutents * sizeof(int_fast32_t));
                for (i = 0; i < pclrd->numlutents; ++i) {
                    lutents[i] =
                        pclrd->lutdata[cmapent->pcol + i * pclrd->numchans];
                }
                newcmptno = jas_image_numcmpts(dec->image);
                jas_image_depalettize(
                    dec->image, cmapent->cmptno, pclrd->numlutents, lutents,
                    JP2_BPCTODTYPE(pclrd->bpc[cmapent->pcol]), newcmptno);
                dec->chantocmptlut[channo] = newcmptno;
                jas_free(lutents);
#if 0
                if (dec->cdef) {
                    jp2_cdef_t * const cdefd = &dec->cdef->data.cdef;
                    cdefent = jp2_cdef_lookup(cdefd, channo);
                    if (!cdefent) {
                        abort();
                    }
                jas_image_setcmpttype(
                    dec->image, newcmptno,
                    jp2_getct(jas_image_colorspace(dec->image),
                              cdefent->type, cdefent->assoc));
                } else {
                    jas_image_setcmpttype(
                        dec->image, newcmptno,
                        jp2_getct(jas_image_colorspace(dec->image),
                                  0,
                                  channo + 1));
                }
#endif
            } else {
                pm_asprintf(errorP, "invalid MTYP in CMAP box");
                goto cleanup;
            }
        }
    }

    /* Mark all components as being of unknown type. */

    for (i = 0; i < jas_image_numcmpts(dec->image); ++i) {
        jas_image_setcmpttype(dec->image, i, JAS_IMAGE_CT_UNKNOWN);
    }

    /* Determine the type of each component. */
    if (dec->cdef) {
        unsigned int i;
        for (i = 0; i < dec->numchans; ++i) {
            jas_image_setcmpttype(
                dec->image,
                dec->chantocmptlut[dec->cdef->data.cdef.ents[i].channo],
                jp2_getct(jas_image_colorspace(dec->image),
                          dec->cdef->data.cdef.ents[i].type,
                          dec->cdef->data.cdef.ents[i].assoc));
        }
    } else {
        unsigned int i;
        for (i = 0; i < dec->numchans; ++i) {
            jas_image_setcmpttype(dec->image, dec->chantocmptlut[i],
              jp2_getct(jas_image_colorspace(dec->image), 0, i + 1));
        }
    }

    /* Delete any components that are not of interest. */
    for (i = jas_image_numcmpts(dec->image) - 1; i >= 0; --i) {
        if (jas_image_cmpttype(dec->image, i) == JAS_IMAGE_CT_UNKNOWN) {
            jas_image_delcmpt(dec->image, i);
        }
    }

    /* Ensure that some components survived. */
    if (!jas_image_numcmpts(dec->image)) {
        pm_asprintf(errorP, "no components");
        goto cleanup;
    }

    /* Prevent the image from being destroyed later. */
    image = dec->image;
    dec->image = 0;

    jp2_dec_destroy(dec);

    *imagePP = image;
    *errorP = NULL;
    return;

cleanup:
    if (box) {
        jp2_box_destroy(box);
    }
    if (dec) {
        jp2_dec_destroy(dec);
    }
}



int
jp2_validate(jas_stream_t *in) {

    char buf[JP2_VALIDATELEN];
    int i;
    int n;

    assert(JAS_STREAM_MAXPUTBACK >= JP2_VALIDATELEN);

    /* Read the validation data (i.e., the data used for detecting
      the format). */
    if ((n = jas_stream_read(in, buf, JP2_VALIDATELEN)) < 0) {
        return -1;
    }

    /* Put the validation data back onto the stream, so that the
      stream position will not be changed. */
    for (i = n - 1; i >= 0; --i) {
        if (jas_stream_ungetc(in, buf[i]) == EOF) {
            return -1;
        }
    }

    /* Did we read enough data? */
    if (n < JP2_VALIDATELEN) {
        return -1;
    }

    /* Is the box type correct? */
    if (((buf[4] << 24) | (buf[5] << 16) | (buf[6] << 8) | buf[7]) !=
      JP2_BOX_JP)
    {
        return -1;
    }

    return 0;
}