Use wxGtkString here to clean up code, and not leak in debug builds

[wxWidgets.git] / src / tiff / tif_jpeg.c

/* $Header$ */

/*
 * Copyright (c) 1994-1997 Sam Leffler
 * Copyright (c) 1994-1997 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and 
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the names of
 * Sam Leffler and Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Sam Leffler and Silicon Graphics.
 * 
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
 * 
 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 */

#include "tiffiop.h"
#ifdef JPEG_SUPPORT
/*
 * TIFF Library
 *
 * JPEG Compression support per TIFF Technical Note #2
 * (*not* per the original TIFF 6.0 spec).
 *
 * This file is simply an interface to the libjpeg library written by
 * the Independent JPEG Group.  You need release 5 or later of the IJG
 * code, which you can find on the Internet at ftp.uu.net:/graphics/jpeg/.
 *
 * Contributed by Tom Lane <tgl@sss.pgh.pa.us>.
 */
#include <assert.h>
#include <stdio.h>
#include <setjmp.h>

int TIFFFillStrip(TIFF*, tstrip_t);
int TIFFFillTile(TIFF*, ttile_t);

/* We undefine FAR to avoid conflict with JPEG definition */

#ifdef FAR
#undef FAR
#endif

/*
   The windows RPCNDR.H file defines boolean, but defines it with the
   wrong size.  So we declare HAVE_BOOLEAN so that the jpeg include file
   won't try to typedef boolean, but #define it to override the rpcndr.h
   definition.

   http://bugzilla.remotesensing.org/show_bug.cgi?id=188
*/
#if defined(__RPCNDR_H__)
#define HAVE_BOOLEAN
#define boolean unsigned int
#endif

#include "jpeglib.h"
#include "jerror.h"

/*
 * On some machines it may be worthwhile to use _setjmp or sigsetjmp
 * in place of plain setjmp.  These macros will make it easier.
 */
#define SETJMP(jbuf)            setjmp(jbuf)
#define LONGJMP(jbuf,code)      longjmp(jbuf,code)
#define JMP_BUF                 jmp_buf

typedef struct jpeg_destination_mgr jpeg_destination_mgr;
typedef struct jpeg_source_mgr jpeg_source_mgr;
typedef struct jpeg_error_mgr jpeg_error_mgr;

/*
 * State block for each open TIFF file using
 * libjpeg to do JPEG compression/decompression.
 *
 * libjpeg's visible state is either a jpeg_compress_struct
 * or jpeg_decompress_struct depending on which way we
 * are going.  comm can be used to refer to the fields
 * which are common to both.
 *
 * NB: cinfo is required to be the first member of JPEGState,
 *     so we can safely cast JPEGState* -> jpeg_xxx_struct*
 *     and vice versa!
 */
typedef struct {
        union {
                struct jpeg_compress_struct c;
                struct jpeg_decompress_struct d;
                struct jpeg_common_struct comm;
        } cinfo;                        /* NB: must be first */
        int             cinfo_initialized;

        jpeg_error_mgr  err;            /* libjpeg error manager */
        JMP_BUF         exit_jmpbuf;    /* for catching libjpeg failures */
        /*
         * The following two members could be a union, but
         * they're small enough that it's not worth the effort.
         */
        jpeg_destination_mgr dest;      /* data dest for compression */
        jpeg_source_mgr src;            /* data source for decompression */
                                        /* private state */
        TIFF*           tif;            /* back link needed by some code */
        uint16          photometric;    /* copy of PhotometricInterpretation */
        uint16          h_sampling;     /* luminance sampling factors */
        uint16          v_sampling;
        tsize_t         bytesperline;   /* decompressed bytes per scanline */
        /* pointers to intermediate buffers when processing downsampled data */
        JSAMPARRAY      ds_buffer[MAX_COMPONENTS];
        int             scancount;      /* number of "scanlines" accumulated */
        int             samplesperclump;

        TIFFVGetMethod  vgetparent;     /* super-class method */
        TIFFVSetMethod  vsetparent;     /* super-class method */
        TIFFStripMethod defsparent;     /* super-class method */
        TIFFTileMethod  deftparent;     /* super-class method */
                                        /* pseudo-tag fields */
        void*           jpegtables;     /* JPEGTables tag value, or NULL */
        uint32          jpegtables_length; /* number of bytes in same */
        int             jpegquality;    /* Compression quality level */
        int             jpegcolormode;  /* Auto RGB<=>YCbCr convert? */
        int             jpegtablesmode; /* What to put in JPEGTables */

        int             ycbcrsampling_fetched;
} JPEGState;

#define JState(tif)     ((JPEGState*)(tif)->tif_data)

static  int JPEGDecode(TIFF*, tidata_t, tsize_t, tsample_t);
static  int JPEGDecodeRaw(TIFF*, tidata_t, tsize_t, tsample_t);
static  int JPEGEncode(TIFF*, tidata_t, tsize_t, tsample_t);
static  int JPEGEncodeRaw(TIFF*, tidata_t, tsize_t, tsample_t);
static  int JPEGInitializeLibJPEG( TIFF * tif );

#define FIELD_JPEGTABLES        (FIELD_CODEC+0)

static const TIFFFieldInfo jpegFieldInfo[] = {
    { TIFFTAG_JPEGTABLES,        -1,-1, TIFF_UNDEFINED, FIELD_JPEGTABLES,
      FALSE,    TRUE,   "JPEGTables" },
    { TIFFTAG_JPEGQUALITY,       0, 0,  TIFF_ANY,       FIELD_PSEUDO,
      TRUE,     FALSE,  "" },
    { TIFFTAG_JPEGCOLORMODE,     0, 0,  TIFF_ANY,       FIELD_PSEUDO,
      FALSE,    FALSE,  "" },
    { TIFFTAG_JPEGTABLESMODE,    0, 0,  TIFF_ANY,       FIELD_PSEUDO,
      FALSE,    FALSE,  "" },
};
#define N(a)    (sizeof (a) / sizeof (a[0]))

/*
 * libjpeg interface layer.
 *
 * We use setjmp/longjmp to return control to libtiff
 * when a fatal error is encountered within the JPEG
 * library.  We also direct libjpeg error and warning
 * messages through the appropriate libtiff handlers.
 */

/*
 * Error handling routines (these replace corresponding
 * IJG routines from jerror.c).  These are used for both
 * compression and decompression.
 */
static void
TIFFjpeg_error_exit(j_common_ptr cinfo)
{
        JPEGState *sp = (JPEGState *) cinfo;    /* NB: cinfo assumed first */
        char buffer[JMSG_LENGTH_MAX];

        (*cinfo->err->format_message) (cinfo, buffer);
        TIFFError("JPEGLib", buffer);           /* display the error message */
        jpeg_abort(cinfo);                      /* clean up libjpeg state */
        LONGJMP(sp->exit_jmpbuf, 1);            /* return to libtiff caller */
}

/*
 * This routine is invoked only for warning messages,
 * since error_exit does its own thing and trace_level
 * is never set > 0.
 */
static void
TIFFjpeg_output_message(j_common_ptr cinfo)
{
        char buffer[JMSG_LENGTH_MAX];

        (*cinfo->err->format_message) (cinfo, buffer);
        TIFFWarning("JPEGLib", buffer);
}

/*
 * Interface routines.  This layer of routines exists
 * primarily to limit side-effects from using setjmp.
 * Also, normal/error returns are converted into return
 * values per libtiff practice.
 */
#define CALLJPEG(sp, fail, op)  (SETJMP((sp)->exit_jmpbuf) ? (fail) : (op))
#define CALLVJPEG(sp, op)       CALLJPEG(sp, 0, ((op),1))

static int
TIFFjpeg_create_compress(JPEGState* sp)
{
        /* initialize JPEG error handling */
        sp->cinfo.c.err = jpeg_std_error(&sp->err);
        sp->err.error_exit = TIFFjpeg_error_exit;
        sp->err.output_message = TIFFjpeg_output_message;

        return CALLVJPEG(sp, jpeg_create_compress(&sp->cinfo.c));
}

static int
TIFFjpeg_create_decompress(JPEGState* sp)
{
        /* initialize JPEG error handling */
        sp->cinfo.d.err = jpeg_std_error(&sp->err);
        sp->err.error_exit = TIFFjpeg_error_exit;
        sp->err.output_message = TIFFjpeg_output_message;

        return CALLVJPEG(sp, jpeg_create_decompress(&sp->cinfo.d));
}

static int
TIFFjpeg_set_defaults(JPEGState* sp)
{
        return CALLVJPEG(sp, jpeg_set_defaults(&sp->cinfo.c));
}

static int
TIFFjpeg_set_colorspace(JPEGState* sp, J_COLOR_SPACE colorspace)
{
        return CALLVJPEG(sp, jpeg_set_colorspace(&sp->cinfo.c, colorspace));
}

static int
TIFFjpeg_set_quality(JPEGState* sp, int quality, boolean force_baseline)
{
        return CALLVJPEG(sp,
            jpeg_set_quality(&sp->cinfo.c, quality, force_baseline));
}

static int
TIFFjpeg_suppress_tables(JPEGState* sp, boolean suppress)
{
        return CALLVJPEG(sp, jpeg_suppress_tables(&sp->cinfo.c, suppress));
}

static int
TIFFjpeg_start_compress(JPEGState* sp, boolean write_all_tables)
{
        return CALLVJPEG(sp,
            jpeg_start_compress(&sp->cinfo.c, write_all_tables));
}

static int
TIFFjpeg_write_scanlines(JPEGState* sp, JSAMPARRAY scanlines, int num_lines)
{
        return CALLJPEG(sp, -1, (int) jpeg_write_scanlines(&sp->cinfo.c,
            scanlines, (JDIMENSION) num_lines));
}

static int
TIFFjpeg_write_raw_data(JPEGState* sp, JSAMPIMAGE data, int num_lines)
{
        return CALLJPEG(sp, -1, (int) jpeg_write_raw_data(&sp->cinfo.c,
            data, (JDIMENSION) num_lines));
}

static int
TIFFjpeg_finish_compress(JPEGState* sp)
{
        return CALLVJPEG(sp, jpeg_finish_compress(&sp->cinfo.c));
}

static int
TIFFjpeg_write_tables(JPEGState* sp)
{
        return CALLVJPEG(sp, jpeg_write_tables(&sp->cinfo.c));
}

static int
TIFFjpeg_read_header(JPEGState* sp, boolean require_image)
{
        return CALLJPEG(sp, -1, jpeg_read_header(&sp->cinfo.d, require_image));
}

static int
TIFFjpeg_start_decompress(JPEGState* sp)
{
        return CALLVJPEG(sp, jpeg_start_decompress(&sp->cinfo.d));
}

static int
TIFFjpeg_read_scanlines(JPEGState* sp, JSAMPARRAY scanlines, int max_lines)
{
        return CALLJPEG(sp, -1, (int) jpeg_read_scanlines(&sp->cinfo.d,
            scanlines, (JDIMENSION) max_lines));
}

static int
TIFFjpeg_read_raw_data(JPEGState* sp, JSAMPIMAGE data, int max_lines)
{
        return CALLJPEG(sp, -1, (int) jpeg_read_raw_data(&sp->cinfo.d,
            data, (JDIMENSION) max_lines));
}

static int
TIFFjpeg_finish_decompress(JPEGState* sp)
{
        return CALLJPEG(sp, -1, (int) jpeg_finish_decompress(&sp->cinfo.d));
}

static int
TIFFjpeg_abort(JPEGState* sp)
{
        return CALLVJPEG(sp, jpeg_abort(&sp->cinfo.comm));
}

static int
TIFFjpeg_destroy(JPEGState* sp)
{
        return CALLVJPEG(sp, jpeg_destroy(&sp->cinfo.comm));
}

static JSAMPARRAY
TIFFjpeg_alloc_sarray(JPEGState* sp, int pool_id,
                      JDIMENSION samplesperrow, JDIMENSION numrows)
{
        return CALLJPEG(sp, (JSAMPARRAY) NULL,
            (*sp->cinfo.comm.mem->alloc_sarray)
                (&sp->cinfo.comm, pool_id, samplesperrow, numrows));
}

/*
 * JPEG library destination data manager.
 * These routines direct compressed data from libjpeg into the
 * libtiff output buffer.
 */

static void
std_init_destination(j_compress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;
        TIFF* tif = sp->tif;

        sp->dest.next_output_byte = (JOCTET*) tif->tif_rawdata;
        sp->dest.free_in_buffer = (size_t) tif->tif_rawdatasize;
}

static boolean
std_empty_output_buffer(j_compress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;
        TIFF* tif = sp->tif;

        /* the entire buffer has been filled */
        tif->tif_rawcc = tif->tif_rawdatasize;
        TIFFFlushData1(tif);
        sp->dest.next_output_byte = (JOCTET*) tif->tif_rawdata;
        sp->dest.free_in_buffer = (size_t) tif->tif_rawdatasize;

        return (TRUE);
}

static void
std_term_destination(j_compress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;
        TIFF* tif = sp->tif;

        tif->tif_rawcp = (tidata_t) sp->dest.next_output_byte;
        tif->tif_rawcc =
            tif->tif_rawdatasize - (tsize_t) sp->dest.free_in_buffer;
        /* NB: libtiff does the final buffer flush */
}

static void
TIFFjpeg_data_dest(JPEGState* sp, TIFF* tif)
{
        (void) tif;
        sp->cinfo.c.dest = &sp->dest;
        sp->dest.init_destination = std_init_destination;
        sp->dest.empty_output_buffer = std_empty_output_buffer;
        sp->dest.term_destination = std_term_destination;
}

/*
 * Alternate destination manager for outputting to JPEGTables field.
 */

static void
tables_init_destination(j_compress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;

        /* while building, jpegtables_length is allocated buffer size */
        sp->dest.next_output_byte = (JOCTET*) sp->jpegtables;
        sp->dest.free_in_buffer = (size_t) sp->jpegtables_length;
}

static boolean
tables_empty_output_buffer(j_compress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;
        void* newbuf;

        /* the entire buffer has been filled; enlarge it by 1000 bytes */
        newbuf = _TIFFrealloc((tdata_t) sp->jpegtables,
                              (tsize_t) (sp->jpegtables_length + 1000));
        if (newbuf == NULL)
                ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 100);
        sp->dest.next_output_byte = (JOCTET*) newbuf + sp->jpegtables_length;
        sp->dest.free_in_buffer = (size_t) 1000;
        sp->jpegtables = newbuf;
        sp->jpegtables_length += 1000;
        return (TRUE);
}

static void
tables_term_destination(j_compress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;

        /* set tables length to number of bytes actually emitted */
        sp->jpegtables_length -= sp->dest.free_in_buffer;
}

static int
TIFFjpeg_tables_dest(JPEGState* sp, TIFF* tif)
{
        (void) tif;
        /*
         * Allocate a working buffer for building tables.
         * Initial size is 1000 bytes, which is usually adequate.
         */
        if (sp->jpegtables)
                _TIFFfree(sp->jpegtables);
        sp->jpegtables_length = 1000;
        sp->jpegtables = (void*) _TIFFmalloc((tsize_t) sp->jpegtables_length);
        if (sp->jpegtables == NULL) {
                sp->jpegtables_length = 0;
                TIFFError("TIFFjpeg_tables_dest", "No space for JPEGTables");
                return (0);
        }
        sp->cinfo.c.dest = &sp->dest;
        sp->dest.init_destination = tables_init_destination;
        sp->dest.empty_output_buffer = tables_empty_output_buffer;
        sp->dest.term_destination = tables_term_destination;
        return (1);
}

/*
 * JPEG library source data manager.
 * These routines supply compressed data to libjpeg.
 */

static void
std_init_source(j_decompress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;
        TIFF* tif = sp->tif;

        sp->src.next_input_byte = (const JOCTET*) tif->tif_rawdata;
        sp->src.bytes_in_buffer = (size_t) tif->tif_rawcc;
}

static boolean
std_fill_input_buffer(j_decompress_ptr cinfo)
{
        JPEGState* sp = (JPEGState* ) cinfo;
        static const JOCTET dummy_EOI[2] = { 0xFF, JPEG_EOI };

        /*
         * Should never get here since entire strip/tile is
         * read into memory before the decompressor is called,
         * and thus was supplied by init_source.
         */
        WARNMS(cinfo, JWRN_JPEG_EOF);
        /* insert a fake EOI marker */
        sp->src.next_input_byte = dummy_EOI;
        sp->src.bytes_in_buffer = 2;
        return (TRUE);
}

static void
std_skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
        JPEGState* sp = (JPEGState*) cinfo;

        if (num_bytes > 0) {
                if (num_bytes > (long) sp->src.bytes_in_buffer) {
                        /* oops, buffer overrun */
                        (void) std_fill_input_buffer(cinfo);
                } else {
                        sp->src.next_input_byte += (size_t) num_bytes;
                        sp->src.bytes_in_buffer -= (size_t) num_bytes;
                }
        }
}

static void
std_term_source(j_decompress_ptr cinfo)
{
        /* No work necessary here */
        /* Or must we update tif->tif_rawcp, tif->tif_rawcc ??? */
        /* (if so, need empty tables_term_source!) */
        (void) cinfo;
}

static void
TIFFjpeg_data_src(JPEGState* sp, TIFF* tif)
{
        (void) tif;
        sp->cinfo.d.src = &sp->src;
        sp->src.init_source = std_init_source;
        sp->src.fill_input_buffer = std_fill_input_buffer;
        sp->src.skip_input_data = std_skip_input_data;
        sp->src.resync_to_restart = jpeg_resync_to_restart;
        sp->src.term_source = std_term_source;
        sp->src.bytes_in_buffer = 0;            /* for safety */
        sp->src.next_input_byte = NULL;
}

/*
 * Alternate source manager for reading from JPEGTables.
 * We can share all the code except for the init routine.
 */

static void
tables_init_source(j_decompress_ptr cinfo)
{
        JPEGState* sp = (JPEGState*) cinfo;

        sp->src.next_input_byte = (const JOCTET*) sp->jpegtables;
        sp->src.bytes_in_buffer = (size_t) sp->jpegtables_length;
}

static void
TIFFjpeg_tables_src(JPEGState* sp, TIFF* tif)
{
        TIFFjpeg_data_src(sp, tif);
        sp->src.init_source = tables_init_source;
}

/*
 * Allocate downsampled-data buffers needed for downsampled I/O.
 * We use values computed in jpeg_start_compress or jpeg_start_decompress.
 * We use libjpeg's allocator so that buffers will be released automatically
 * when done with strip/tile.
 * This is also a handy place to compute samplesperclump, bytesperline.
 */
static int
alloc_downsampled_buffers(TIFF* tif, jpeg_component_info* comp_info,
                          int num_components)
{
        JPEGState* sp = JState(tif);
        int ci;
        jpeg_component_info* compptr;
        JSAMPARRAY buf;
        int samples_per_clump = 0;

        for (ci = 0, compptr = comp_info; ci < num_components;
             ci++, compptr++) {
                samples_per_clump += compptr->h_samp_factor *
                        compptr->v_samp_factor;
                buf = TIFFjpeg_alloc_sarray(sp, JPOOL_IMAGE,
                                compptr->width_in_blocks * DCTSIZE,
                                (JDIMENSION) (compptr->v_samp_factor*DCTSIZE));
                if (buf == NULL)
                        return (0);
                sp->ds_buffer[ci] = buf;
        }
        sp->samplesperclump = samples_per_clump;
        return (1);
}


/*
 * JPEG Decoding.
 */

static int
JPEGSetupDecode(TIFF* tif)
{
        JPEGState* sp = JState(tif);
        TIFFDirectory *td = &tif->tif_dir;

        JPEGInitializeLibJPEG( tif );

        assert(sp != NULL);
        assert(sp->cinfo.comm.is_decompressor);

        /* Read JPEGTables if it is present */
        if (TIFFFieldSet(tif,FIELD_JPEGTABLES)) {
                TIFFjpeg_tables_src(sp, tif);
                if(TIFFjpeg_read_header(sp,FALSE) != JPEG_HEADER_TABLES_ONLY) {
                        TIFFError("JPEGSetupDecode", "Bogus JPEGTables field");
                        return (0);
                }
        }

        /* Grab parameters that are same for all strips/tiles */
        sp->photometric = td->td_photometric;
        switch (sp->photometric) {
        case PHOTOMETRIC_YCBCR:
                sp->h_sampling = td->td_ycbcrsubsampling[0];
                sp->v_sampling = td->td_ycbcrsubsampling[1];
                break;
        default:
                /* TIFF 6.0 forbids subsampling of all other color spaces */
                sp->h_sampling = 1;
                sp->v_sampling = 1;
                break;
        }

        /* Set up for reading normal data */
        TIFFjpeg_data_src(sp, tif);
        tif->tif_postdecode = _TIFFNoPostDecode; /* override byte swapping */
        return (1);
}

/*
 * Set up for decoding a strip or tile.
 */
static int
JPEGPreDecode(TIFF* tif, tsample_t s)
{
        JPEGState *sp = JState(tif);
        TIFFDirectory *td = &tif->tif_dir;
        static const char module[] = "JPEGPreDecode";
        uint32 segment_width, segment_height;
        int downsampled_output;
        int ci;

        assert(sp != NULL);
        assert(sp->cinfo.comm.is_decompressor);
        /*
         * Reset decoder state from any previous strip/tile,
         * in case application didn't read the whole strip.
         */
        if (!TIFFjpeg_abort(sp))
                return (0);
        /*
         * Read the header for this strip/tile.
         */
        if (TIFFjpeg_read_header(sp, TRUE) != JPEG_HEADER_OK)
                return (0);
        /*
         * Check image parameters and set decompression parameters.
         */
        segment_width = td->td_imagewidth;
        segment_height = td->td_imagelength - tif->tif_row;
        if (isTiled(tif)) {
                segment_width = td->td_tilewidth;
                segment_height = td->td_tilelength;
                sp->bytesperline = TIFFTileRowSize(tif);
        } else {
                if (segment_height > td->td_rowsperstrip)
                        segment_height = td->td_rowsperstrip;
                sp->bytesperline = TIFFScanlineSize(tif);
        }
        if (td->td_planarconfig == PLANARCONFIG_SEPARATE && s > 0) {
                /*
                 * For PC 2, scale down the expected strip/tile size
                 * to match a downsampled component
                 */
                segment_width = TIFFhowmany(segment_width, sp->h_sampling);
                segment_height = TIFFhowmany(segment_height, sp->v_sampling);
        }
        if (sp->cinfo.d.image_width != segment_width ||
            sp->cinfo.d.image_height != segment_height) {
                TIFFWarning(module, 
                 "Improper JPEG strip/tile size, expected %dx%d, got %dx%d",
                          segment_width, 
                          segment_height,
                          sp->cinfo.d.image_width, 
                          sp->cinfo.d.image_height);
        }
        if (sp->cinfo.d.num_components !=
            (td->td_planarconfig == PLANARCONFIG_CONTIG ?
             td->td_samplesperpixel : 1)) {
                TIFFError(module, "Improper JPEG component count");
                return (0);
        }
        if (sp->cinfo.d.data_precision != td->td_bitspersample) {
                TIFFError(module, "Improper JPEG data precision");
                return (0);
        }
        if (td->td_planarconfig == PLANARCONFIG_CONTIG) {
                /* Component 0 should have expected sampling factors */
                if (sp->cinfo.d.comp_info[0].h_samp_factor != sp->h_sampling ||
                    sp->cinfo.d.comp_info[0].v_samp_factor != sp->v_sampling) {
                        TIFFWarning(module, 
                                    "Improper JPEG sampling factors %d,%d\n"
                                    "Apparently should be %d,%d, "
                                    "decompressor will try reading with "
                                    "sampling %d,%d",
                                    sp->cinfo.d.comp_info[0].h_samp_factor,
                                    sp->cinfo.d.comp_info[0].v_samp_factor,
                                    sp->h_sampling, 
                                    sp->v_sampling,
                                    sp->cinfo.d.comp_info[0].h_samp_factor,
                                    sp->cinfo.d.comp_info[0].v_samp_factor );

                        sp->h_sampling = (uint16)
                            sp->cinfo.d.comp_info[0].h_samp_factor;
                        sp->v_sampling = (uint16)
                            sp->cinfo.d.comp_info[0].v_samp_factor;
                }
                /* Rest should have sampling factors 1,1 */
                for (ci = 1; ci < sp->cinfo.d.num_components; ci++) {
                        if (sp->cinfo.d.comp_info[ci].h_samp_factor != 1 ||
                            sp->cinfo.d.comp_info[ci].v_samp_factor != 1) {
                                TIFFError(module, "Improper JPEG sampling factors");
                                return (0);
                        }
                }
        } else {
                /* PC 2's single component should have sampling factors 1,1 */
                if (sp->cinfo.d.comp_info[0].h_samp_factor != 1 ||
                    sp->cinfo.d.comp_info[0].v_samp_factor != 1) {
                        TIFFError(module, "Improper JPEG sampling factors");
                        return (0);
                }
        }
        downsampled_output = FALSE;
        if (td->td_planarconfig == PLANARCONFIG_CONTIG &&
            sp->photometric == PHOTOMETRIC_YCBCR &&
            sp->jpegcolormode == JPEGCOLORMODE_RGB) {
        /* Convert YCbCr to RGB */
                sp->cinfo.d.jpeg_color_space = JCS_YCbCr;
                sp->cinfo.d.out_color_space = JCS_RGB;
        } else {
                        /* Suppress colorspace handling */
                sp->cinfo.d.jpeg_color_space = JCS_UNKNOWN;
                sp->cinfo.d.out_color_space = JCS_UNKNOWN;
                if (td->td_planarconfig == PLANARCONFIG_CONTIG &&
                    (sp->h_sampling != 1 || sp->v_sampling != 1))
                        downsampled_output = TRUE;
                /* XXX what about up-sampling? */
        }
        if (downsampled_output) {
                /* Need to use raw-data interface to libjpeg */
                sp->cinfo.d.raw_data_out = TRUE;
                tif->tif_decoderow = JPEGDecodeRaw;
                tif->tif_decodestrip = JPEGDecodeRaw;
                tif->tif_decodetile = JPEGDecodeRaw;
        } else {
                /* Use normal interface to libjpeg */
                sp->cinfo.d.raw_data_out = FALSE;
                tif->tif_decoderow = JPEGDecode;
                tif->tif_decodestrip = JPEGDecode;
                tif->tif_decodetile = JPEGDecode;
        }
        /* Start JPEG decompressor */
        if (!TIFFjpeg_start_decompress(sp))
                return (0);
        /* Allocate downsampled-data buffers if needed */
        if (downsampled_output) {
                if (!alloc_downsampled_buffers(tif, sp->cinfo.d.comp_info,
                                               sp->cinfo.d.num_components))
                        return (0);
                sp->scancount = DCTSIZE;        /* mark buffer empty */
        }
        return (1);
}

/*
 * Decode a chunk of pixels.
 * "Standard" case: returned data is not downsampled.
 */
/*ARGSUSED*/ static int
JPEGDecode(TIFF* tif, tidata_t buf, tsize_t cc, tsample_t s)
{
    JPEGState *sp = JState(tif);
    tsize_t nrows;

    nrows = cc / sp->bytesperline;
    if (cc % sp->bytesperline)
        TIFFWarning(tif->tif_name, "fractional scanline not read");

    if( nrows > (int) sp->cinfo.d.image_height )
        nrows = sp->cinfo.d.image_height;

    /* data is expected to be read in multiples of a scanline */
    if (nrows)
    {
        do {
            JSAMPROW bufptr = (JSAMPROW)buf;

            if (TIFFjpeg_read_scanlines(sp, &bufptr, 1) != 1)
                return (0);
            ++tif->tif_row;
            buf += sp->bytesperline;
            cc -= sp->bytesperline;
        } while (--nrows > 0);
    }
    /* Close down the decompressor if we've finished the strip or tile. */
    return sp->cinfo.d.output_scanline < sp->cinfo.d.output_height
        || TIFFjpeg_finish_decompress(sp);
}

/*
 * Decode a chunk of pixels.
 * Returned data is downsampled per sampling factors.
 */
/*ARGSUSED*/ static int
JPEGDecodeRaw(TIFF* tif, tidata_t buf, tsize_t cc, tsample_t s)
{
        JPEGState *sp = JState(tif);
        tsize_t nrows;

        /* data is expected to be read in multiples of a scanline */
        if ( (nrows = sp->cinfo.d.image_height) ) {
                /* Cb,Cr both have sampling factors 1, so this is correct */
                JDIMENSION clumps_per_line = sp->cinfo.d.comp_info[1].downsampled_width;
                int samples_per_clump = sp->samplesperclump;
        
                do {
                        jpeg_component_info *compptr;
                        int ci, clumpoffset;

                        /* Reload downsampled-data buffer if needed */
                        if (sp->scancount >= DCTSIZE) {
                                int n = sp->cinfo.d.max_v_samp_factor * DCTSIZE;

                                if (TIFFjpeg_read_raw_data(sp, sp->ds_buffer, n)
                                        != n)
                                        return (0);
                                sp->scancount = 0;
                        }
                        /*
                         * Fastest way to unseparate data is to make one pass
                         * over the scanline for each row of each component.
                         */
                        clumpoffset = 0;        /* first sample in clump */
                        for (ci = 0, compptr = sp->cinfo.d.comp_info;
                             ci < sp->cinfo.d.num_components;
                             ci++, compptr++) {
                            int hsamp = compptr->h_samp_factor;
                            int vsamp = compptr->v_samp_factor;
                            int ypos;

                            for (ypos = 0; ypos < vsamp; ypos++) {
                                JSAMPLE *inptr = sp->ds_buffer[ci][sp->scancount*vsamp + ypos];
                                JSAMPLE *outptr = (JSAMPLE*)buf + clumpoffset;
                                JDIMENSION nclump;

                                if (hsamp == 1) {
                                    /* fast path for at least Cb and Cr */
                                    for (nclump = clumps_per_line; nclump-- > 0; ) {
                                        outptr[0] = *inptr++;
                                        outptr += samples_per_clump;
                                    }
                                } else {
                                        int xpos;

                                    /* general case */
                                    for (nclump = clumps_per_line; nclump-- > 0; ) {
                                        for (xpos = 0; xpos < hsamp; xpos++)
                                            outptr[xpos] = *inptr++;
                                        outptr += samples_per_clump;
                                    }
                                }
                                clumpoffset += hsamp;
                            }
                        }
                        ++sp->scancount;
                        ++tif->tif_row;
                        buf += sp->bytesperline;
                        cc -= sp->bytesperline;
                } while (--nrows > 0);
        }

        /* Close down the decompressor if done. */
        return sp->cinfo.d.output_scanline < sp->cinfo.d.output_height
            || TIFFjpeg_finish_decompress(sp);
}


/*
 * JPEG Encoding.
 */

static void
unsuppress_quant_table (JPEGState* sp, int tblno)
{
        JQUANT_TBL* qtbl;

        if ((qtbl = sp->cinfo.c.quant_tbl_ptrs[tblno]) != NULL)
                qtbl->sent_table = FALSE;
}

static void
unsuppress_huff_table (JPEGState* sp, int tblno)
{
        JHUFF_TBL* htbl;

        if ((htbl = sp->cinfo.c.dc_huff_tbl_ptrs[tblno]) != NULL)
                htbl->sent_table = FALSE;
        if ((htbl = sp->cinfo.c.ac_huff_tbl_ptrs[tblno]) != NULL)
                htbl->sent_table = FALSE;
}

static int
prepare_JPEGTables(TIFF* tif)
{
        JPEGState* sp = JState(tif);

        JPEGInitializeLibJPEG( tif );

        /* Initialize quant tables for current quality setting */
        if (!TIFFjpeg_set_quality(sp, sp->jpegquality, FALSE))
                return (0);
        /* Mark only the tables we want for output */
        /* NB: chrominance tables are currently used only with YCbCr */
        if (!TIFFjpeg_suppress_tables(sp, TRUE))
                return (0);
        if (sp->jpegtablesmode & JPEGTABLESMODE_QUANT) {
                unsuppress_quant_table(sp, 0);
                if (sp->photometric == PHOTOMETRIC_YCBCR)
                        unsuppress_quant_table(sp, 1);
        }
        if (sp->jpegtablesmode & JPEGTABLESMODE_HUFF) {
                unsuppress_huff_table(sp, 0);
                if (sp->photometric == PHOTOMETRIC_YCBCR)
                        unsuppress_huff_table(sp, 1);
        }
        /* Direct libjpeg output into jpegtables */
        if (!TIFFjpeg_tables_dest(sp, tif))
                return (0);
        /* Emit tables-only datastream */
        if (!TIFFjpeg_write_tables(sp))
                return (0);

        return (1);
}

static int
JPEGSetupEncode(TIFF* tif)
{
        JPEGState* sp = JState(tif);
        TIFFDirectory *td = &tif->tif_dir;
        static const char module[] = "JPEGSetupEncode";

        JPEGInitializeLibJPEG( tif );

        assert(sp != NULL);
        assert(!sp->cinfo.comm.is_decompressor);

        /*
         * Initialize all JPEG parameters to default values.
         * Note that jpeg_set_defaults needs legal values for
         * in_color_space and input_components.
         */
        sp->cinfo.c.in_color_space = JCS_UNKNOWN;
        sp->cinfo.c.input_components = 1;
        if (!TIFFjpeg_set_defaults(sp))
                return (0);
        /* Set per-file parameters */
        sp->photometric = td->td_photometric;
        switch (sp->photometric) {
        case PHOTOMETRIC_YCBCR:
                sp->h_sampling = td->td_ycbcrsubsampling[0];
                sp->v_sampling = td->td_ycbcrsubsampling[1];
                /*
                 * A ReferenceBlackWhite field *must* be present since the
                 * default value is inappropriate for YCbCr.  Fill in the
                 * proper value if application didn't set it.
                 */
                if (!TIFFFieldSet(tif, FIELD_REFBLACKWHITE)) {
                        float refbw[6];
                        long top = 1L << td->td_bitspersample;
                        refbw[0] = 0;
                        refbw[1] = (float)(top-1L);
                        refbw[2] = (float)(top>>1);
                        refbw[3] = refbw[1];
                        refbw[4] = refbw[2];
                        refbw[5] = refbw[1];
                        TIFFSetField(tif, TIFFTAG_REFERENCEBLACKWHITE, refbw);
                }
                break;
        case PHOTOMETRIC_PALETTE:               /* disallowed by Tech Note */
        case PHOTOMETRIC_MASK:
                TIFFError(module,
                          "PhotometricInterpretation %d not allowed for JPEG",
                          (int) sp->photometric);
                return (0);
        default:
                /* TIFF 6.0 forbids subsampling of all other color spaces */
                sp->h_sampling = 1;
                sp->v_sampling = 1;
                break;
        }
        
        /* Verify miscellaneous parameters */

        /*
         * This would need work if libtiff ever supports different
         * depths for different components, or if libjpeg ever supports
         * run-time selection of depth.  Neither is imminent.
         */
        if (td->td_bitspersample != BITS_IN_JSAMPLE) {
                TIFFError(module, "BitsPerSample %d not allowed for JPEG",
                          (int) td->td_bitspersample);
                return (0);
        }
        sp->cinfo.c.data_precision = td->td_bitspersample;
        if (isTiled(tif)) {
                if ((td->td_tilelength % (sp->v_sampling * DCTSIZE)) != 0) {
                        TIFFError(module,
                                  "JPEG tile height must be multiple of %d",
                                  sp->v_sampling * DCTSIZE);
                        return (0);
                }
                if ((td->td_tilewidth % (sp->h_sampling * DCTSIZE)) != 0) {
                        TIFFError(module,
                                  "JPEG tile width must be multiple of %d",
                                  sp->h_sampling * DCTSIZE);
                        return (0);
                }
        } else {
                if (td->td_rowsperstrip < td->td_imagelength &&
                    (td->td_rowsperstrip % (sp->v_sampling * DCTSIZE)) != 0) {
                        TIFFError(module,
                                  "RowsPerStrip must be multiple of %d for JPEG",
                                  sp->v_sampling * DCTSIZE);
                        return (0);
                }
        }

        /* Create a JPEGTables field if appropriate */
        if (sp->jpegtablesmode & (JPEGTABLESMODE_QUANT|JPEGTABLESMODE_HUFF)) {
                if (!prepare_JPEGTables(tif))
                        return (0);
                /* Mark the field present */
                /* Can't use TIFFSetField since BEENWRITING is already set! */
                TIFFSetFieldBit(tif, FIELD_JPEGTABLES);
                tif->tif_flags |= TIFF_DIRTYDIRECT;
        } else {
                /* We do not support application-supplied JPEGTables, */
                /* so mark the field not present */
                TIFFClrFieldBit(tif, FIELD_JPEGTABLES);
        }

        /* Direct libjpeg output to libtiff's output buffer */
        TIFFjpeg_data_dest(sp, tif);

        return (1);
}

/*
 * Set encoding state at the start of a strip or tile.
 */
static int
JPEGPreEncode(TIFF* tif, tsample_t s)
{
        JPEGState *sp = JState(tif);
        TIFFDirectory *td = &tif->tif_dir;
        static const char module[] = "JPEGPreEncode";
        uint32 segment_width, segment_height;
        int downsampled_input;

        assert(sp != NULL);
        assert(!sp->cinfo.comm.is_decompressor);
        /*
         * Set encoding parameters for this strip/tile.
         */
        if (isTiled(tif)) {
                segment_width = td->td_tilewidth;
                segment_height = td->td_tilelength;
                sp->bytesperline = TIFFTileRowSize(tif);
        } else {
                segment_width = td->td_imagewidth;
                segment_height = td->td_imagelength - tif->tif_row;
                if (segment_height > td->td_rowsperstrip)
                        segment_height = td->td_rowsperstrip;
                sp->bytesperline = TIFFScanlineSize(tif);
        }
        if (td->td_planarconfig == PLANARCONFIG_SEPARATE && s > 0) {
                /* for PC 2, scale down the strip/tile size
                 * to match a downsampled component
                 */
                segment_width = TIFFhowmany(segment_width, sp->h_sampling);
                segment_height = TIFFhowmany(segment_height, sp->v_sampling);
        }
        if (segment_width > 65535 || segment_height > 65535) {
                TIFFError(module, "Strip/tile too large for JPEG");
                return (0);
        }
        sp->cinfo.c.image_width = segment_width;
        sp->cinfo.c.image_height = segment_height;
        downsampled_input = FALSE;
        if (td->td_planarconfig == PLANARCONFIG_CONTIG) {
                sp->cinfo.c.input_components = td->td_samplesperpixel;
                if (sp->photometric == PHOTOMETRIC_YCBCR) {
                        if (sp->jpegcolormode == JPEGCOLORMODE_RGB) {
                                sp->cinfo.c.in_color_space = JCS_RGB;
                        } else {
                                sp->cinfo.c.in_color_space = JCS_YCbCr;
                                if (sp->h_sampling != 1 || sp->v_sampling != 1)
                                        downsampled_input = TRUE;
                        }
                        if (!TIFFjpeg_set_colorspace(sp, JCS_YCbCr))
                                return (0);
                        /*
                         * Set Y sampling factors;
                         * we assume jpeg_set_colorspace() set the rest to 1
                         */
                        sp->cinfo.c.comp_info[0].h_samp_factor = sp->h_sampling;
                        sp->cinfo.c.comp_info[0].v_samp_factor = sp->v_sampling;
                } else {
                        sp->cinfo.c.in_color_space = JCS_UNKNOWN;
                        if (!TIFFjpeg_set_colorspace(sp, JCS_UNKNOWN))
                                return (0);
                        /* jpeg_set_colorspace set all sampling factors to 1 */
                }
        } else {
                sp->cinfo.c.input_components = 1;
                sp->cinfo.c.in_color_space = JCS_UNKNOWN;
                if (!TIFFjpeg_set_colorspace(sp, JCS_UNKNOWN))
                        return (0);
                sp->cinfo.c.comp_info[0].component_id = s;
                /* jpeg_set_colorspace() set sampling factors to 1 */
                if (sp->photometric == PHOTOMETRIC_YCBCR && s > 0) {
                        sp->cinfo.c.comp_info[0].quant_tbl_no = 1;
                        sp->cinfo.c.comp_info[0].dc_tbl_no = 1;
                        sp->cinfo.c.comp_info[0].ac_tbl_no = 1;
                }
        }
        /* ensure libjpeg won't write any extraneous markers */
        sp->cinfo.c.write_JFIF_header = FALSE;
        sp->cinfo.c.write_Adobe_marker = FALSE;
        /* set up table handling correctly */
        if (! (sp->jpegtablesmode & JPEGTABLESMODE_QUANT)) {
                if (!TIFFjpeg_set_quality(sp, sp->jpegquality, FALSE))
                        return (0);
                unsuppress_quant_table(sp, 0);
                unsuppress_quant_table(sp, 1);
        }
        if (sp->jpegtablesmode & JPEGTABLESMODE_HUFF)
                sp->cinfo.c.optimize_coding = FALSE;
        else
                sp->cinfo.c.optimize_coding = TRUE;
        if (downsampled_input) {
                /* Need to use raw-data interface to libjpeg */
                sp->cinfo.c.raw_data_in = TRUE;
                tif->tif_encoderow = JPEGEncodeRaw;
                tif->tif_encodestrip = JPEGEncodeRaw;
                tif->tif_encodetile = JPEGEncodeRaw;
        } else {
                /* Use normal interface to libjpeg */
                sp->cinfo.c.raw_data_in = FALSE;
                tif->tif_encoderow = JPEGEncode;
                tif->tif_encodestrip = JPEGEncode;
                tif->tif_encodetile = JPEGEncode;
        }
        /* Start JPEG compressor */
        if (!TIFFjpeg_start_compress(sp, FALSE))
                return (0);
        /* Allocate downsampled-data buffers if needed */
        if (downsampled_input) {
                if (!alloc_downsampled_buffers(tif, sp->cinfo.c.comp_info,
                                               sp->cinfo.c.num_components))
                        return (0);
        }
        sp->scancount = 0;

        return (1);
}

/*
 * Encode a chunk of pixels.
 * "Standard" case: incoming data is not downsampled.
 */
static int
JPEGEncode(TIFF* tif, tidata_t buf, tsize_t cc, tsample_t s)
{
        JPEGState *sp = JState(tif);
        tsize_t nrows;
        JSAMPROW bufptr[1];

        (void) s;
        assert(sp != NULL);
        /* data is expected to be supplied in multiples of a scanline */
        nrows = cc / sp->bytesperline;
        if (cc % sp->bytesperline)
                TIFFWarning(tif->tif_name, "fractional scanline discarded");

        while (nrows-- > 0) {
                bufptr[0] = (JSAMPROW) buf;
                if (TIFFjpeg_write_scanlines(sp, bufptr, 1) != 1)
                        return (0);
                if (nrows > 0)
                        tif->tif_row++;
                buf += sp->bytesperline;
        }
        return (1);
}

/*
 * Encode a chunk of pixels.
 * Incoming data is expected to be downsampled per sampling factors.
 */
static int
JPEGEncodeRaw(TIFF* tif, tidata_t buf, tsize_t cc, tsample_t s)
{
        JPEGState *sp = JState(tif);
        JSAMPLE* inptr;
        JSAMPLE* outptr;
        tsize_t nrows;
        JDIMENSION clumps_per_line, nclump;
        int clumpoffset, ci, xpos, ypos;
        jpeg_component_info* compptr;
        int samples_per_clump = sp->samplesperclump;

        (void) s;
        assert(sp != NULL);
        /* data is expected to be supplied in multiples of a scanline */
        nrows = cc / sp->bytesperline;
        if (cc % sp->bytesperline)
                TIFFWarning(tif->tif_name, "fractional scanline discarded");

        /* Cb,Cr both have sampling factors 1, so this is correct */
        clumps_per_line = sp->cinfo.c.comp_info[1].downsampled_width;

        while (nrows-- > 0) {
                /*
                 * Fastest way to separate the data is to make one pass
                 * over the scanline for each row of each component.
                 */
                clumpoffset = 0;                /* first sample in clump */
                for (ci = 0, compptr = sp->cinfo.c.comp_info;
                     ci < sp->cinfo.c.num_components;
                     ci++, compptr++) {
                    int hsamp = compptr->h_samp_factor;
                    int vsamp = compptr->v_samp_factor;
                    int padding = (int) (compptr->width_in_blocks * DCTSIZE -
                                         clumps_per_line * hsamp);
                    for (ypos = 0; ypos < vsamp; ypos++) {
                        inptr = ((JSAMPLE*) buf) + clumpoffset;
                        outptr = sp->ds_buffer[ci][sp->scancount*vsamp + ypos];
                        if (hsamp == 1) {
                            /* fast path for at least Cb and Cr */
                            for (nclump = clumps_per_line; nclump-- > 0; ) {
                                *outptr++ = inptr[0];
                                inptr += samples_per_clump;
                            }
                        } else {
                            /* general case */
                            for (nclump = clumps_per_line; nclump-- > 0; ) {
                                for (xpos = 0; xpos < hsamp; xpos++)
                                    *outptr++ = inptr[xpos];
                                inptr += samples_per_clump;
                            }
                        }
                        /* pad each scanline as needed */
                        for (xpos = 0; xpos < padding; xpos++) {
                            *outptr = outptr[-1];
                            outptr++;
                        }
                        clumpoffset += hsamp;
                    }
                }
                sp->scancount++;
                if (sp->scancount >= DCTSIZE) {
                        int n = sp->cinfo.c.max_v_samp_factor * DCTSIZE;
                        if (TIFFjpeg_write_raw_data(sp, sp->ds_buffer, n) != n)
                                return (0);
                        sp->scancount = 0;
                }
                if (nrows > 0)
                        tif->tif_row++;
                buf += sp->bytesperline;
        }
        return (1);
}

/*
 * Finish up at the end of a strip or tile.
 */
static int
JPEGPostEncode(TIFF* tif)
{
        JPEGState *sp = JState(tif);

        if (sp->scancount > 0) {
                /*
                 * Need to emit a partial bufferload of downsampled data.
                 * Pad the data vertically.
                 */
                int ci, ypos, n;
                jpeg_component_info* compptr;

                for (ci = 0, compptr = sp->cinfo.c.comp_info;
                     ci < sp->cinfo.c.num_components;
                     ci++, compptr++) {
                        int vsamp = compptr->v_samp_factor;
                        tsize_t row_width = compptr->width_in_blocks * DCTSIZE
                                * sizeof(JSAMPLE);
                        for (ypos = sp->scancount * vsamp;
                             ypos < DCTSIZE * vsamp; ypos++) {
                                _TIFFmemcpy((tdata_t)sp->ds_buffer[ci][ypos],
                                            (tdata_t)sp->ds_buffer[ci][ypos-1],
                                            row_width);

                        }
                }
                n = sp->cinfo.c.max_v_samp_factor * DCTSIZE;
                if (TIFFjpeg_write_raw_data(sp, sp->ds_buffer, n) != n)
                        return (0);
        }

        return (TIFFjpeg_finish_compress(JState(tif)));
}

static void
JPEGCleanup(TIFF* tif)
{
        if (tif->tif_data) {
                JPEGState *sp = JState(tif);
                if( sp->cinfo_initialized )
                    TIFFjpeg_destroy(sp);       /* release libjpeg resources */
                if (sp->jpegtables)             /* tag value */
                        _TIFFfree(sp->jpegtables);
                _TIFFfree(tif->tif_data);       /* release local state */
                tif->tif_data = NULL;
        }
}

static int
JPEGVSetField(TIFF* tif, ttag_t tag, va_list ap)
{
        JPEGState* sp = JState(tif);
        TIFFDirectory* td = &tif->tif_dir;
        uint32 v32;

        switch (tag) {
        case TIFFTAG_JPEGTABLES:
                v32 = va_arg(ap, uint32);
                if (v32 == 0) {
                        /* XXX */
                        return (0);
                }
                _TIFFsetByteArray(&sp->jpegtables, va_arg(ap, void*),
                    (long) v32);
                sp->jpegtables_length = v32;
                TIFFSetFieldBit(tif, FIELD_JPEGTABLES);
                break;
        case TIFFTAG_JPEGQUALITY:
                sp->jpegquality = va_arg(ap, int);
                return (1);                     /* pseudo tag */
        case TIFFTAG_JPEGCOLORMODE:
                sp->jpegcolormode = va_arg(ap, int);
                /*
                 * Mark whether returned data is up-sampled or not
                 * so TIFFStripSize and TIFFTileSize return values
                 * that reflect the true amount of data.
                 */
                tif->tif_flags &= ~TIFF_UPSAMPLED;
                if (td->td_planarconfig == PLANARCONFIG_CONTIG) {
                    if (td->td_photometric == PHOTOMETRIC_YCBCR &&
                      sp->jpegcolormode == JPEGCOLORMODE_RGB) {
                        tif->tif_flags |= TIFF_UPSAMPLED;
                    } else {
                        if (td->td_ycbcrsubsampling[0] != 1 ||
                            td->td_ycbcrsubsampling[1] != 1)
                            ; /* XXX what about up-sampling? */
                    }
                }
                /*
                 * Must recalculate cached tile size
                 * in case sampling state changed.
                 */
                tif->tif_tilesize = TIFFTileSize(tif);
                return (1);                     /* pseudo tag */
        case TIFFTAG_JPEGTABLESMODE:
                sp->jpegtablesmode = va_arg(ap, int);
                return (1);                     /* pseudo tag */
        case TIFFTAG_YCBCRSUBSAMPLING:
                /* mark the fact that we have a real ycbcrsubsampling! */
                sp->ycbcrsampling_fetched = 1;
                return (*sp->vsetparent)(tif, tag, ap);
        default:
                return (*sp->vsetparent)(tif, tag, ap);
        }
        tif->tif_flags |= TIFF_DIRTYDIRECT;
        return (1);
}

/*
 * Some JPEG-in-TIFF produces do not emit the YCBCRSUBSAMPLING values in
 * the TIFF tags, but still use non-default (2,2) values within the jpeg
 * data stream itself.  In order for TIFF applications to work properly
 * - for instance to get the strip buffer size right - it is imperative
 * that the subsampling be available before we start reading the image
 * data normally.  This function will attempt to load the first strip in
 * order to get the sampling values from the jpeg data stream.  Various
 * hacks are various places are done to ensure this function gets called
 * before the td_ycbcrsubsampling values are used from the directory structure,
 * including calling TIFFGetField() for the YCBCRSUBSAMPLING field from 
 * TIFFStripSize(), and the printing code in tif_print.c. 
 *
 * Note that JPEGPreDeocode() will produce a fairly loud warning when the
 * discovered sampling does not match the default sampling (2,2) or whatever
 * was actually in the tiff tags. 
 *
 * Problems:
 *  o This code will cause one whole strip/tile of compressed data to be
 *    loaded just to get the tags right, even if the imagery is never read.
 *    It would be more efficient to just load a bit of the header, and
 *    initialize things from that. 
 *
 * See the bug in bugzilla for details:
 *
 * http://bugzilla.remotesensing.org/show_bug.cgi?id=168
 *
 * Frank Warmerdam, July 2002
 */

static void 
JPEGFixupTestSubsampling( TIFF * tif )
{
#if CHECK_JPEG_YCBCR_SUBSAMPLING == 1
    JPEGState *sp = JState(tif);
    TIFFDirectory *td = &tif->tif_dir;

    JPEGInitializeLibJPEG( tif );

    /*
     * Some JPEG-in-TIFF files don't provide the ycbcrsampling tags, 
     * and use a sampling schema other than the default 2,2.  To handle
     * this we actually have to scan the header of a strip or tile of
     * jpeg data to get the sampling.  
     */
    if( !sp->cinfo.comm.is_decompressor 
        || sp->ycbcrsampling_fetched  
        || td->td_photometric != PHOTOMETRIC_YCBCR )
        return;

    sp->ycbcrsampling_fetched = 1;
    if( TIFFIsTiled( tif ) )
    {
        if( !TIFFFillTile( tif, 0 ) )
            return;
    }
    else
    {
        if( !TIFFFillStrip( tif, 0 ) )
            return;
    }

    TIFFSetField( tif, TIFFTAG_YCBCRSUBSAMPLING, 
                  (uint16) sp->h_sampling, (uint16) sp->v_sampling );
#endif /* CHECK_JPEG_YCBCR_SUBSAMPLING == 1 */
}

static int
JPEGVGetField(TIFF* tif, ttag_t tag, va_list ap)
{
        JPEGState* sp = JState(tif);

        switch (tag) {
        case TIFFTAG_JPEGTABLES:
                /* u_short is bogus --- should be uint32 ??? */
                /* TIFFWriteNormalTag needs fixed  XXX */
                *va_arg(ap, u_short*) = (u_short) sp->jpegtables_length;
                *va_arg(ap, void**) = sp->jpegtables;
                break;
        case TIFFTAG_JPEGQUALITY:
                *va_arg(ap, int*) = sp->jpegquality;
                break;
        case TIFFTAG_JPEGCOLORMODE:
                *va_arg(ap, int*) = sp->jpegcolormode;
                break;
        case TIFFTAG_JPEGTABLESMODE:
                *va_arg(ap, int*) = sp->jpegtablesmode;
                break;
        case TIFFTAG_YCBCRSUBSAMPLING:
                JPEGFixupTestSubsampling( tif );
                return (*sp->vgetparent)(tif, tag, ap);
                break;
        default:
                return (*sp->vgetparent)(tif, tag, ap);
        }
        return (1);
}

static void
JPEGPrintDir(TIFF* tif, FILE* fd, long flags)
{
        JPEGState* sp = JState(tif);

        (void) flags;
        if (TIFFFieldSet(tif,FIELD_JPEGTABLES))
                fprintf(fd, "  JPEG Tables: (%lu bytes)\n",
                        (u_long) sp->jpegtables_length);
}

static uint32
JPEGDefaultStripSize(TIFF* tif, uint32 s)
{
        JPEGState* sp = JState(tif);
        TIFFDirectory *td = &tif->tif_dir;

        s = (*sp->defsparent)(tif, s);
        if (s < td->td_imagelength)
                s = TIFFroundup(s, td->td_ycbcrsubsampling[1] * DCTSIZE);
        return (s);
}

static void
JPEGDefaultTileSize(TIFF* tif, uint32* tw, uint32* th)
{
        JPEGState* sp = JState(tif);
        TIFFDirectory *td = &tif->tif_dir;

        (*sp->deftparent)(tif, tw, th);
        *tw = TIFFroundup(*tw, td->td_ycbcrsubsampling[0] * DCTSIZE);
        *th = TIFFroundup(*th, td->td_ycbcrsubsampling[1] * DCTSIZE);
}

/*
 * The JPEG library initialized used to be done in TIFFInitJPEG(), but
 * now that we allow a TIFF file to be opened in update mode it is necessary
 * to have some way of deciding whether compression or decompression is
 * desired other than looking at tif->tif_mode.  We accomplish this by 
 * examining {TILE/STRIP}BYTECOUNTS to see if there is a non-zero entry.
 * If so, we assume decompression is desired. 
 *
 * This is tricky, because TIFFInitJPEG() is called while the directory is
 * being read, and generally speaking the BYTECOUNTS tag won't have been read
 * at that point.  So we try to defer jpeg library initialization till we
 * do have that tag ... basically any access that might require the compressor
 * or decompressor that occurs after the reading of the directory. 
 *
 * In an ideal world compressors or decompressors would be setup
 * at the point where a single tile or strip was accessed (for read or write)
 * so that stuff like update of missing tiles, or replacement of tiles could
 * be done. However, we aren't trying to crack that nut just yet ...
 *
 * NFW, Feb 3rd, 2003.
 */

static int JPEGInitializeLibJPEG( TIFF * tif )
{
    JPEGState* sp = JState(tif);
    uint32 *byte_counts = NULL;
    int     data_is_empty = TRUE;

    if( sp->cinfo_initialized )
        return 1;

    /*
     * Do we have tile data already?  Make sure we initialize the
     * the state in decompressor mode if we have tile data, even if we
     * are not in read-only file access mode. 
     */
    if( TIFFIsTiled( tif ) 
        && TIFFGetField( tif, TIFFTAG_TILEBYTECOUNTS, &byte_counts ) 
        && byte_counts != NULL )
    {
        data_is_empty = byte_counts[0] == 0;
    }
    if( !TIFFIsTiled( tif ) 
        && TIFFGetField( tif, TIFFTAG_STRIPBYTECOUNTS, &byte_counts) 
        && byte_counts != NULL )
    {
        data_is_empty = byte_counts[0] == 0;
    }

    /*
     * Initialize libjpeg.
     */
    if (tif->tif_mode == O_RDONLY || !data_is_empty ) {
        if (!TIFFjpeg_create_decompress(sp))
            return (0);

    } else {
        if (!TIFFjpeg_create_compress(sp))
            return (0);
    }

    sp->cinfo_initialized = TRUE;

    return 1;
}

int
TIFFInitJPEG(TIFF* tif, int scheme)
{
        JPEGState* sp;

        assert(scheme == COMPRESSION_JPEG);

        /*
         * Allocate state block so tag methods have storage to record values.
         */
        tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (JPEGState));

        if (tif->tif_data == NULL) {
                TIFFError("TIFFInitJPEG", "No space for JPEG state block");
                return (0);
        }
        memset( tif->tif_data, 0, sizeof(JPEGState));

        sp = JState(tif);
        sp->tif = tif;                          /* back link */

        /*
         * Merge codec-specific tag information and
         * override parent get/set field methods.
         */
        _TIFFMergeFieldInfo(tif, jpegFieldInfo, N(jpegFieldInfo));
        sp->vgetparent = tif->tif_tagmethods.vgetfield;
        tif->tif_tagmethods.vgetfield = JPEGVGetField;  /* hook for codec tags */
        sp->vsetparent = tif->tif_tagmethods.vsetfield;
        tif->tif_tagmethods.vsetfield = JPEGVSetField;  /* hook for codec tags */
        tif->tif_tagmethods.printdir = JPEGPrintDir;    /* hook for codec tags */

        /* Default values for codec-specific fields */
        sp->jpegtables = NULL;
        sp->jpegtables_length = 0;
        sp->jpegquality = 75;                   /* Default IJG quality */
        sp->jpegcolormode = JPEGCOLORMODE_RAW;
        sp->jpegtablesmode = JPEGTABLESMODE_QUANT | JPEGTABLESMODE_HUFF;

        sp->ycbcrsampling_fetched = 0;

        /*
         * Install codec methods.
         */
        tif->tif_setupdecode = JPEGSetupDecode;
        tif->tif_predecode = JPEGPreDecode;
        tif->tif_decoderow = JPEGDecode;
        tif->tif_decodestrip = JPEGDecode;
        tif->tif_decodetile = JPEGDecode;
        tif->tif_setupencode = JPEGSetupEncode;
        tif->tif_preencode = JPEGPreEncode;
        tif->tif_postencode = JPEGPostEncode;
        tif->tif_encoderow = JPEGEncode;
        tif->tif_encodestrip = JPEGEncode;
        tif->tif_encodetile = JPEGEncode;
        tif->tif_cleanup = JPEGCleanup;
        sp->defsparent = tif->tif_defstripsize;
        tif->tif_defstripsize = JPEGDefaultStripSize;
        sp->deftparent = tif->tif_deftilesize;
        tif->tif_deftilesize = JPEGDefaultTileSize;
        tif->tif_flags |= TIFF_NOBITREV;        /* no bit reversal, please */

        sp->cinfo_initialized = FALSE;

        /*
         * Mark the TIFFTAG_YCBCRSAMPLES as present even if it is not
         * see: JPEGFixupTestSubsampling().
         */
        TIFFSetFieldBit( tif, FIELD_YCBCRSUBSAMPLING );

        return (1);
}
#endif /* JPEG_SUPPORT */