tif_jpeg.c

一个国人自己实现图像库的程序（有参考价值）

	/* 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;

	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)) {
		if (segment_height > td->td_tilelength)
			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) {
		TIFFError(module, "Improper JPEG strip/tile size");
		return (0);
	}
	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) {
			TIFFError(module, "Improper JPEG sampling factors");
			return (0);
		}
		/* 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;

	/* data is expected to be read in multiples of a scanline */
	if (nrows = sp->cinfo.d.image_height)
		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);

	/* 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";

	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.
		 */
#ifdef COLORIMETRY_SUPPORT
		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);
		}
#endif
		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);