libvips/libvips/foreign/vips2jpeg.c

/* wrap jpeg libray for write
 *
 * 28/11/03 JC
 *	- better no-overshoot on tile loop
 * 12/11/04
 *	- better demand size choice for eval
 * 30/6/05 JC
 *	- update im_error()/im_warn()
 *	- now loads and saves exif data
 * 30/7/05
 * 	- now loads ICC profiles
 * 	- now saves ICC profiles from the VIPS header
 * 24/8/05
 * 	- jpeg load sets vips xres/yres from exif, if possible
 * 	- jpeg save sets exif xres/yres from vips, if possible
 * 29/8/05
 * 	- cut from old vips_jpeg.c
 * 20/4/06
 * 	- auto convert to sRGB/mono for save
 * 13/10/06
 * 	- add </libexif/ prefix if required
 * 19/1/07
 * 	- oop, libexif confusion
 * 2/11/07
 * 	- use im_wbuffer() API for BG writes
 * 15/2/08
 * 	- write CMYK if Bands == 4 and Type == CMYK
 * 12/5/09
 *	- fix signed/unsigned warning
 * 13/8/09
 * 	- allow "none" for profile, meaning don't embed one
 * 4/2/10
 * 	- gtkdoc
 * 17/7/10
 * 	- use g_assert()
 * 	- allow space for the header in init_destination(), helps writing very
 * 	  small JPEGs (thanks Tim Elliott)
 * 18/7/10
 * 	- collect im_vips2bufjpeg() output in a list of blocks ... we no
 * 	  longer overallocate or underallocate
 * 8/7/11
 * 	- oop CMYK write was not inverting, thanks Ole
 * 12/10/2011
 * 	- write XMP data
 * 18/10/2011
 * 	- update Orientation as well
 * 3/11/11
 * 	- rebuild exif tags from coded metadata values 
 * 24/11/11
 * 	- turn into a set of write fns ready to be called from a class
 * 7/8/12
 * 	- use VIPS_META_RESOLUTION_UNIT to select resolution unit
 * 16/11/12
 * 	- read ifds from exif fields 
 * 	- optionally parse rationals as a/b
 * 	- update exif image dimensions
 * 21/11/12
 * 	- attach IPTC data (app13), thanks Gary
 * 2/10/13 Lovell Fuller
 * 	- add optimize_coding parameter
 * 	- add progressive mode
 * 12/11/13
 * 	- add "strip" option to remove all metadata
 * 13/11/13
 * 	- add a "no_subsample" option to disable chroma subsample
 * 9/9/14
 * 	- support "none" as a resolution unit
 * 8/7/15
 * 	- omit oversized jpeg markers
 * 15/7/15
 * 	- exif tags use @name, not @title
 * 	- set arbitrary exif tags from metadata
 * 25/11/15	
 * 	- don't write JFIF headers if we are stripping, thanks Benjamin
 * 13/4/16
 * 	- remove deleted exif fields more carefully
 * 9/5/16 felixbuenemann
 * 	- add quant_table
 * 26/5/16
 * 	- switch to new orientation tag
 * 9/7/16
 * 	- turn off chroma subsample for Q >= 90
 * 7/11/16
 * 	- move exif handling out to exif.c
 * 27/2/17
 * 	- use dbuf for memory output
 * 19/12/17 Lovell
 * 	- fix a leak with an error during buffer output
 * 19/4/19
 * 	- fix another leak with error during buffer output
 * 19/7/19
 * 	- ignore large XMP
 * 14/10/19
 * 	- revise for target IO
 * 18/2/20 Elad-Laufer
 * 	- add subsample_mode, deprecate no_subsample
 * 13/9/20
 * 	- only write JFIF resolution if we don't have EXIF
 */

/*

    This file is part of VIPS.
    
    VIPS is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define VIPS_DEBUG
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>

#ifdef HAVE_JPEG

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

#include <vips/vips.h>
#include <vips/debug.h>
#include <vips/internal.h>

#include "pforeign.h"

#include "jpeg.h"

/* New output message method - send to VIPS.
 */
void
vips__new_output_message( j_common_ptr cinfo )
{
	char buffer[JMSG_LENGTH_MAX];

	(*cinfo->err->format_message)( cinfo, buffer );
	vips_error( "VipsJpeg", _( "%s" ), buffer );

#ifdef DEBUG
	printf( "vips__new_output_message: \"%s\"\n", buffer );
#endif /*DEBUG*/

	/* This is run for things like file truncated. Signal invalidate to
	 * force this op out of cache. 
	 */
        if( cinfo->client_data )
		vips_foreign_load_invalidate( VIPS_IMAGE( cinfo->client_data ) );
}

/* New error_exit handler.
 */
void
vips__new_error_exit( j_common_ptr cinfo )
{
	ErrorManager *eman = (ErrorManager *) cinfo->err;

#ifdef DEBUG
	printf( "vips__new_error_exit:\n" );
#endif /*DEBUG*/

	/* Close the fp if necessary.
	 */
	if( eman->fp ) {
		(void) fclose( eman->fp );
		eman->fp = NULL;
	}

	/* Send the error message to VIPS. This method is overridden above.
	 */
	(*cinfo->err->output_message)( cinfo );

	/* Jump back.
	 */
	longjmp( eman->jmp, 1 );
}

/* What we track during a JPEG write.
 */
typedef struct {
	VipsImage *in;
	struct jpeg_compress_struct cinfo;
        ErrorManager eman;
	JSAMPROW *row_pointer;
	VipsImage *inverted;
} Write;

static void
write_destroy( Write *write )
{
	jpeg_destroy_compress( &write->cinfo );
	VIPS_FREE( write->row_pointer );
	VIPS_UNREF( write->inverted );
	VIPS_UNREF( write->in );

	g_free( write );
}

static Write *
write_new( VipsImage *in )
{
	Write *write;

	if( !(write = g_new0( Write, 1 )) )
		return( NULL );

	write->in = NULL;
	write->row_pointer = NULL;
        write->cinfo.err = jpeg_std_error( &write->eman.pub );
	write->cinfo.dest = NULL;
	write->eman.pub.error_exit = vips__new_error_exit;
	write->eman.pub.output_message = vips__new_output_message;
	write->eman.fp = NULL;
	write->inverted = NULL;

	/* Make a copy of the input image since we may modify it with
	 * vips__exif_update() etc.
	 */
	if( vips_copy( in, &write->in, NULL ) ) {
		write_destroy( write );
		return( NULL );
	}

        return( write );
}

static int
write_blob( Write *write, const char *field, int app )
{
	unsigned char *data;
	size_t data_length;

	if( vips_image_get_typeof( write->in, field ) ) {
		if( vips_image_get_blob( write->in, field, 
			(void *) &data, &data_length ) )
			return( -1 );

		/* Single jpeg markers can only hold 64kb, large objects must
		 * be split into multiple markers.
		 *
		 * Unfortunately, how this splitting is done depends on the
		 * data type. For example, ICC and XMP have completely 
		 * different ways of doing this.
		 *
		 * For now, just ignore oversize objects and warn.
		 */
		if( data_length > 65530 ) 
			g_warning( _( "field \"%s\" is too large "
				"for a single JPEG marker, ignoring" ), 
				field );
		else {
#ifdef DEBUG
			printf( "write_blob: attaching %zd bytes of %s\n", 
				data_length, field );
#endif /*DEBUG*/

			jpeg_write_marker( &write->cinfo, app, 
				data, data_length ); 
		} 
	}

	return( 0 );
}

#define XML_URL "http://ns.adobe.com/xap/1.0/"

static int
write_xmp( Write *write )
{
	unsigned char *data;
	size_t data_length;
	char *p;

	if( !vips_image_get_typeof( write->in, VIPS_META_XMP_NAME ) ) 
		return( 0 );
	if( vips_image_get_blob( write->in, VIPS_META_XMP_NAME, 
		(void *) &data, &data_length ) )
		return( -1 );

	/* To write >64kb XMP it you need to parse the whole XMP object, 
	 * pull out the most important fields, code just them into the main 
	 * XMP block, then write any remaining XMP objects into a set of 
	 * extended XMP markers. 
	 *
	 * http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/ \
	 * 	XMPSpecificationPart3.pdf
	 *
	 * jpeg_write_marker() with some libjpeg versions will throw a fatal 
	 * error with large chunks.
	 */
	if( data_length > 60000 ) {
		g_warning( "%s", _( "VipsJpeg: large XMP not saved" ) );
		return( 0 );
	}

	/* We need to add the magic XML URL to the start, then a null
	 * character, then the data.
	 */
	p = g_malloc( data_length + strlen( XML_URL ) + 1 );
	strcpy( p, XML_URL );
	memcpy( p + strlen( XML_URL ) + 1, data, data_length );
	
	jpeg_write_marker( &write->cinfo, JPEG_APP0 + 1, 
		(unsigned char *) p, data_length + strlen( XML_URL ) + 1 ); 

	g_free( p );

	return( 0 );
}

static int
write_exif( Write *write )
{
	if( write_blob( write, VIPS_META_EXIF_NAME, JPEG_APP0 + 1 ) )
		return( -1 );

	return( 0 );
}

/* ICC writer from lcms, slight tweaks.
 */

#define ICC_MARKER  (JPEG_APP0 + 2)     /* JPEG marker code for ICC */
#define ICC_OVERHEAD_LEN  14            /* size of non-profile data in APP2 */
#define MAX_BYTES_IN_MARKER  65533      /* maximum data len of a JPEG marker */
#define MAX_DATA_BYTES_IN_MARKER  (MAX_BYTES_IN_MARKER - ICC_OVERHEAD_LEN)

/*
 * This routine writes the given ICC profile data into a JPEG file.
 * It *must* be called AFTER calling jpeg_start_compress() and BEFORE
 * the first call to jpeg_write_scanlines().
 * (This ordering ensures that the APP2 marker(s) will appear after the
 * SOI and JFIF or Adobe markers, but before all else.)
 */

static void
write_profile_data (j_compress_ptr cinfo,
                   const JOCTET *icc_data_ptr,
                   unsigned int icc_data_len)
{
  unsigned int num_markers;     /* total number of markers we'll write */
  int cur_marker = 1;           /* per spec, counting starts at 1 */
  unsigned int length;          /* number of bytes to write in this marker */

  /* rounding up will fail for length == 0 */
  g_assert( icc_data_len > 0 );

  /* Calculate the number of markers we'll need, rounding up of course */
  num_markers = (icc_data_len + MAX_DATA_BYTES_IN_MARKER - 1) / 
	  MAX_DATA_BYTES_IN_MARKER;

  while (icc_data_len > 0) {
    /* length of profile to put in this marker */
    length = icc_data_len;
    if (length > MAX_DATA_BYTES_IN_MARKER)
      length = MAX_DATA_BYTES_IN_MARKER;
    icc_data_len -= length;

    /* Write the JPEG marker header (APP2 code and marker length) */
    jpeg_write_m_header(cinfo, ICC_MARKER,
                        (unsigned int) (length + ICC_OVERHEAD_LEN));

    /* Write the marker identifying string "ICC_PROFILE" (null-terminated).
     * We code it in this less-than-transparent way so that the code works
     * even if the local character set is not ASCII.
     */
    jpeg_write_m_byte(cinfo, 0x49);
    jpeg_write_m_byte(cinfo, 0x43);
    jpeg_write_m_byte(cinfo, 0x43);
    jpeg_write_m_byte(cinfo, 0x5F);
    jpeg_write_m_byte(cinfo, 0x50);
    jpeg_write_m_byte(cinfo, 0x52);
    jpeg_write_m_byte(cinfo, 0x4F);
    jpeg_write_m_byte(cinfo, 0x46);
    jpeg_write_m_byte(cinfo, 0x49);
    jpeg_write_m_byte(cinfo, 0x4C);
    jpeg_write_m_byte(cinfo, 0x45);
    jpeg_write_m_byte(cinfo, 0x0);

    /* Add the sequencing info */
    jpeg_write_m_byte(cinfo, cur_marker);
    jpeg_write_m_byte(cinfo, (int) num_markers);

    /* Add the profile data */
    while (length--) {
      jpeg_write_m_byte(cinfo, *icc_data_ptr);
      icc_data_ptr++;
    }
    cur_marker++;
  }
}

#ifndef HAVE_EXIF
/* Set the JFIF resolution from the vips xres/yres tags.
 */
static void
vips_jfif_resolution_from_image( struct jpeg_compress_struct *cinfo, 
	VipsImage *image )
{
	int xres, yres;
	const char *p;
	int unit;

	/* Default to inches, more progs support it.
	 */
	unit = 1;
	if( vips_image_get_typeof( image, VIPS_META_RESOLUTION_UNIT ) &&
		!vips_image_get_string( image, 
			VIPS_META_RESOLUTION_UNIT, &p ) ) {
		if( vips_isprefix( "cm", p ) ) 
			unit = 2;
		else if( vips_isprefix( "none", p ) ) 
			unit = 0;
	}

	switch( unit ) {
	case 0:
		xres = VIPS_RINT( image->Xres );
		yres = VIPS_RINT( image->Yres );
		break;

	case 1:
		xres = VIPS_RINT( image->Xres * 25.4 );
		yres = VIPS_RINT( image->Yres * 25.4 );
		break;

	case 2:
		xres = VIPS_RINT( image->Xres * 10.0 );
		yres = VIPS_RINT( image->Yres * 10.0 );
		break;

	default:
		g_assert_not_reached();
		break;
	}

	VIPS_DEBUG_MSG( "vips_jfif_resolution_from_image: "
		"setting xres = %d, yres = %d, unit = %d\n", xres, yres, unit );

	cinfo->density_unit = unit;
	cinfo->X_density = xres;
	cinfo->Y_density = yres;
}
#endif /*HAVE_EXIF*/

/* Write an ICC Profile from a file into the JPEG stream.
 */
static int
write_profile_file( Write *write, const char *profile )
{
	VipsBlob *blob;

	if( vips_profile_load( profile, &blob, NULL ) )
		return( -1 );

	if( blob ) {
		size_t length;
		const void *data = vips_blob_get( blob, &length );

		write_profile_data( &write->cinfo, (JOCTET *) data, length );

#ifdef DEBUG
		printf( "write_profile_file: "
			"attached profile \"%s\"\n", profile );
#endif /*DEBUG*/

		vips_area_unref( (VipsArea *) blob );
	}

	return( 0 );
}

static int
write_profile_meta( Write *write )
{
	const void *data;
	size_t length;

	if( vips_image_get_blob( write->in, 
		VIPS_META_ICC_NAME, &data, &length ) )
		return( -1 );
	write_profile_data( &write->cinfo, data, length );

#ifdef DEBUG
	printf( "write_profile_meta: attached %zd byte profile from header\n",
		length );
#endif /*DEBUG*/

	return( 0 );
}

static int
write_jpeg_block( VipsRegion *region, VipsRect *area, void *a )
{
	Write *write = (Write *) a;
	int i;

	for( i = 0; i < area->height; i++ )
		write->row_pointer[i] = (JSAMPROW) 
			VIPS_REGION_ADDR( region, 0, area->top + i );

	/* Catch any longjmp()s from jpeg_write_scanlines() here.
	 */
	if( setjmp( write->eman.jmp ) ) 
		return( -1 );

	jpeg_write_scanlines( &write->cinfo, write->row_pointer, area->height );

	return( 0 );
}

/* Write a VIPS image to a JPEG compress struct.
 */
static int
write_vips( Write *write, int qfac, const char *profile, 
	gboolean optimize_coding, gboolean progressive, gboolean strip, 
	gboolean trellis_quant, gboolean overshoot_deringing,
	gboolean optimize_scans, int quant_table,
	VipsForeignJpegSubsample subsample_mode )
{
	VipsImage *in;
	J_COLOR_SPACE space;

	/* The image we'll be writing ... can change, see CMYK.
	 */
	in = write->in;

	/* Should have been converted for save.
	 */
        g_assert( in->BandFmt == VIPS_FORMAT_UCHAR );
	g_assert( in->Coding == VIPS_CODING_NONE );
        g_assert( in->Bands == 1 || 
		in->Bands == 3 || 
		in->Bands == 4 );

        /* Check input image.
         */
	if( vips_image_pio_input( in ) )
		return( -1 );

	/* Set compression parameters.
	 */
        write->cinfo.image_width = in->Xsize;
        write->cinfo.image_height = in->Ysize;
	write->cinfo.input_components = in->Bands;
	if( in->Bands == 4 && 
		in->Type == VIPS_INTERPRETATION_CMYK ) {
		space = JCS_CMYK;
		/* IJG always sets an Adobe marker, so we should invert CMYK.
		 */
		if( vips_invert( in, &write->inverted, NULL ) ) 
			return( -1 );
		in = write->inverted;
	}
	else if( in->Bands == 3 )
		space = JCS_RGB;
	else if( in->Bands == 1 )
		space = JCS_GRAYSCALE;
	else 
		/* Use luminance compression for all channels.
		 */
		space = JCS_UNKNOWN;
	write->cinfo.in_color_space = space; 

	/* Build VIPS output stuff now we know the image we'll be writing.
	 */
	if( !(write->row_pointer = VIPS_ARRAY( NULL, in->Ysize, JSAMPROW )) )
		return( -1 );

#ifdef HAVE_JPEG_EXT_PARAMS
	/* Reset compression profile to libjpeg defaults
	 */
	if( jpeg_c_int_param_supported( &write->cinfo, JINT_COMPRESS_PROFILE ) )
		jpeg_c_set_int_param( &write->cinfo, 
			JINT_COMPRESS_PROFILE, JCP_FASTEST );
#endif

	/* Reset to default.
	 */
        jpeg_set_defaults( &write->cinfo );

 	/* Compute optimal Huffman coding tables.
	 */
	write->cinfo.optimize_coding = optimize_coding;

#ifdef HAVE_JPEG_EXT_PARAMS
	/* Apply trellis quantisation to each 8x8 block. Implies 
	 * "optimize_coding".
	 */
	if( trellis_quant ) {
		if( jpeg_c_bool_param_supported( &write->cinfo, 
			JBOOLEAN_TRELLIS_QUANT ) ) {
			jpeg_c_set_bool_param( &write->cinfo,
				JBOOLEAN_TRELLIS_QUANT, TRUE );
			write->cinfo.optimize_coding = TRUE;
		}
		else 
			g_warning( "%s", _( "trellis_quant unsupported" ) );
	}

	/* Apply overshooting to samples with extreme values e.g. 0 & 255 
	 * for 8-bit.
	 */
	if( overshoot_deringing ) {
		if( jpeg_c_bool_param_supported( &write->cinfo, 
			JBOOLEAN_OVERSHOOT_DERINGING ) ) 
			jpeg_c_set_bool_param( &write->cinfo,
				JBOOLEAN_OVERSHOOT_DERINGING, TRUE );
		else 
			g_warning( "%s", 
				_( "overshoot_deringing unsupported" ) );
	}
	/* Split the spectrum of DCT coefficients into separate scans.
	 * Requires progressive output. Must be set before 
	 * jpeg_simple_progression.
	 */
	if( optimize_scans ) {
		if( progressive ) {
			if( jpeg_c_bool_param_supported( &write->cinfo, 
				JBOOLEAN_OPTIMIZE_SCANS ) ) 
				jpeg_c_set_bool_param( &write->cinfo, 
					JBOOLEAN_OPTIMIZE_SCANS, TRUE );
			else 
				g_warning( "%s", 
					_( "ignoring optimize_scans" ) );
		}
		else 
			g_warning( "%s", 
				_( "ignoring optimize_scans for baseline" ) );
	}

	/* Use predefined quantization table.
	 */
	if( quant_table > 0 ) {
		if( jpeg_c_int_param_supported( &write->cinfo,
			JINT_BASE_QUANT_TBL_IDX ) )
			jpeg_c_set_int_param( &write->cinfo,
				JINT_BASE_QUANT_TBL_IDX, quant_table );
		else
			g_warning( "%s", 
				_( "setting quant_table unsupported" ) );
	}
#else
	/* Using jpeglib.h without extension parameters, warn of ignored 
	 * options.
	 */
	if( trellis_quant ) 
		g_warning( "%s", _( "ignoring trellis_quant" ) );
	if( overshoot_deringing ) 
		g_warning( "%s", _( "ignoring overshoot_deringing" ) );
	if( optimize_scans ) 
		g_warning( "%s", _( "ignoring optimize_scans" ) );
	if( quant_table > 0 )
		g_warning( "%s", _( "ignoring quant_table" ) );
#endif

	/* Set compression quality. Must be called after setting params above.
	 */
        jpeg_set_quality( &write->cinfo, qfac, TRUE );

	/* Enable progressive write.
	 */
	if( progressive ) 
		jpeg_simple_progression( &write->cinfo ); 

	if( subsample_mode == VIPS_FOREIGN_JPEG_SUBSAMPLE_OFF ||
		(subsample_mode == VIPS_FOREIGN_JPEG_SUBSAMPLE_AUTO && 
			qfac >= 90) ) {
		int i;

		for( i = 0; i < in->Bands; i++ ) {
			write->cinfo.comp_info[i].h_samp_factor = 1;
			write->cinfo.comp_info[i].v_samp_factor = 1;
		}
	}

	/* Only write the JFIF headers if we are not stripping and we have no
	 * EXIF. Some readers get confused if you set both.
	 */
	write->cinfo.write_JFIF_header = FALSE;
#ifndef HAVE_EXIF
	if( !strip ) {
		vips_jfif_resolution_from_image( &write->cinfo,  write->in );
		write->cinfo.write_JFIF_header = TRUE;
	}
#endif /*HAVE_EXIF*/

	/* Write app0 and build compress tables.
	 */
	jpeg_start_compress( &write->cinfo, TRUE );

	/* All the other APP chunks come next.
	 */
	if( !strip ) {
		/* We need to rebuild the exif data block from any exif tags
		 * on the image.
		 */
		if( vips__exif_update( write->in ) ||  
			write_exif( write ) ||
			write_xmp( write ) ||
			write_blob( write, 
				VIPS_META_IPTC_NAME, JPEG_APP0 + 13 ) )
			return( -1 );

		/* A profile supplied as an argument overrides an embedded 
		 * profile. 
		 */
		if( profile ) {
			if( write_profile_file( write, profile ) )
				return( -1 );
		}
		else {
			if( vips_image_get_typeof( in, VIPS_META_ICC_NAME ) && 
				write_profile_meta( write ) )
				return( -1 );
		}
	}

	/* Write data. Note that the write function grabs the longjmp()!
	 */
	if( vips_sink_disc( in, write_jpeg_block, write ) )
		return( -1 );

	/* We have to reinstate the setjmp() before we jpeg_finish_compress().
	 */
	if( setjmp( write->eman.jmp ) ) 
		return( -1 );

	/* This should only be called on a successful write.
	 */
	jpeg_finish_compress( &write->cinfo );

	return( 0 );
}

#define TARGET_BUFFER_SIZE (4096)

typedef struct {
	/* Public jpeg fields.
	 */
	struct jpeg_destination_mgr pub;

	/* Private stuff during write.
	 */

	/* Build the output area here.
	 */
	VipsTarget *target;

	/* Our output buffer.
	 */
	unsigned char buf[TARGET_BUFFER_SIZE];
} Dest;

/* Buffer full method. This is only called when the output area is exactly 
 * full.
 */
static jboolean
empty_output_buffer( j_compress_ptr cinfo )
{
	Dest *dest = (Dest *) cinfo->dest;

	if( vips_target_write( dest->target, 
		dest->buf, TARGET_BUFFER_SIZE ) )
		ERREXIT( cinfo, JERR_FILE_WRITE );

	dest->pub.next_output_byte = dest->buf;
	dest->pub.free_in_buffer = TARGET_BUFFER_SIZE;

	return( TRUE );
}

/* Init dest method.
 */
static void
init_destination( j_compress_ptr cinfo )
{
	Dest *dest = (Dest *) cinfo->dest;

	dest->pub.next_output_byte = dest->buf;
	dest->pub.free_in_buffer = TARGET_BUFFER_SIZE;
}

/* Flush any remaining bytes to the output.
 */
static void
term_destination( j_compress_ptr cinfo )
{
        Dest *dest = (Dest *) cinfo->dest;

	if( vips_target_write( dest->target, 
		dest->buf, TARGET_BUFFER_SIZE - dest->pub.free_in_buffer ) )
		ERREXIT( cinfo, JERR_FILE_WRITE );

	vips_target_finish( dest->target );
}

/* Set dest to one of our objects.
 */
static void
target_dest( j_compress_ptr cinfo, VipsTarget *target )
{
	Dest *dest;

	if( !cinfo->dest ) {    /* first time for this JPEG object? */
		cinfo->dest = (struct jpeg_destination_mgr *)
			(*cinfo->mem->alloc_small) 
				( (j_common_ptr) cinfo, JPOOL_PERMANENT,
				  sizeof( Dest ) );
	}

	dest = (Dest *) cinfo->dest;
	dest->pub.init_destination = init_destination;
	dest->pub.empty_output_buffer = empty_output_buffer;
	dest->pub.term_destination = term_destination;
	dest->target = target;
}

int
vips__jpeg_write_target( VipsImage *in, VipsTarget *target,
	int Q, const char *profile, 
	gboolean optimize_coding, gboolean progressive,
	gboolean strip, gboolean trellis_quant,
	gboolean overshoot_deringing, gboolean optimize_scans,
	int quant_table, VipsForeignJpegSubsample subsample_mode)
{
	Write *write;

	if( !(write = write_new( in )) )
		return( -1 );

	/* Make jpeg compression object.
 	 */
	if( setjmp( write->eman.jmp ) ) {
		/* Here for longjmp() during write_vips().
		 */
		write_destroy( write );

		return( -1 );
	}
        jpeg_create_compress( &write->cinfo );

	/* Attach output.
	 */
        target_dest( &write->cinfo, target );

	/* Convert! Write errors come back here as an error return.
	 */
	if( write_vips( write, 
		Q, profile, optimize_coding, progressive, strip,
		trellis_quant, overshoot_deringing, optimize_scans, 
		quant_table, subsample_mode ) ) {
		write_destroy( write );
		return( -1 );
	}
	write_destroy( write );

	return( 0 );
}

const char *vips__jpeg_suffs[] = { ".jpg", ".jpeg", ".jpe", NULL };

#endif /*HAVE_JPEG*/