jdmaster.c

MCB2300_ucgui_LCD320240.rar LPC2368的uc/gui的移植

/*
 * jdmaster.c
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains master control logic for the JPEG decompressor.
 * These routines are concerned with selecting the modules to be executed
 * and with determining the number of passes and the work to be done in each
 * pass.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Private state */

typedef struct
{
	struct jpeg_decomp_master	pub; /* public fields */

	int							pass_number;		/* # of passes completed */

	boolean						using_merged_upsample; /* TRUE if using merged upsample/cconvert */

	/* Saved references to initialized quantizer modules,
	 * in case we need to switch modes.
	 */
	struct jpeg_color_quantizer	*quantizer_1pass;
	struct jpeg_color_quantizer	*quantizer_2pass;
} my_decomp_master;

typedef my_decomp_master * my_master_ptr;


/*
 * Determine whether merged upsample/color conversion should be used.
 * CRUCIAL: this must match the actual capabilities of jdmerge.c!
 */

LOCAL(boolean)
use_merged_upsample(j_decompress_ptr cinfo)
{
#ifdef UPSAMPLE_MERGING_SUPPORTED
	/* Merging is the equivalent of plain box-filter upsampling */
	if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
	{
		return FALSE;
	}
	/* jdmerge.c only supports YCC=>RGB color conversion */
	if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 || cinfo->out_color_space != JCS_RGB || cinfo->out_color_components != RGB_PIXELSIZE)
	{
		return FALSE;
	}
	/* and it only handles 2h1v or 2h2v sampling ratios */
	if (cinfo->comp_info[0].h_samp_factor != 2 || cinfo->comp_info[1].h_samp_factor != 1 || cinfo->comp_info[2].h_samp_factor != 1 || cinfo->comp_info[0].v_samp_factor > 2 || cinfo->comp_info[1].v_samp_factor != 1 || cinfo->comp_info[2].v_samp_factor != 1)
	{
		return FALSE;
	}
	/* furthermore, it doesn't work if we've scaled the IDCTs differently */
	if (cinfo->comp_info[0].DCT_scaled_size != cinfo->min_DCT_scaled_size || cinfo->comp_info[1].DCT_scaled_size != cinfo->min_DCT_scaled_size || cinfo->comp_info[2].DCT_scaled_size != cinfo->min_DCT_scaled_size)
	{
		return FALSE;
	}
	/* ??? also need to test for upsample-time rescaling, when & if supported */
	return TRUE;			/* by golly, it'll work... */
#else
	return FALSE;
#endif
}


/*
 * Compute output image dimensions and related values.
 * NOTE: this is exported for possible use by application.
 * Hence it mustn't do anything that can't be done twice.
 * Also note that it may be called before the master module is initialized!
 */

GLOBAL(void)
jpeg_calc_output_dimensions(j_decompress_ptr cinfo)
/* Do computations that are needed before master selection phase */
{
#ifdef IDCT_SCALING_SUPPORTED
	int ci;
	jpeg_component_info *compptr;
#endif

	/* Prevent application from calling me at wrong times */
	if (cinfo->global_state != DSTATE_READY)
	{
		ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
	}

#ifdef IDCT_SCALING_SUPPORTED

	/* Compute actual output image dimensions and DCT scaling choices. */
	if (cinfo->scale_num * 8 <= cinfo->scale_denom)
	{
		/* Provide 1/8 scaling */
		cinfo->output_width = (JDIMENSION) jdiv_round_up((long) cinfo->image_width, 8L);
		cinfo->output_height = (JDIMENSION) jdiv_round_up((long) cinfo->image_height, 8L);
		cinfo->min_DCT_scaled_size = 1;
	}
	else if (cinfo->scale_num * 4 <= cinfo->scale_denom)
	{
		/* Provide 1/4 scaling */
		cinfo->output_width = (JDIMENSION) jdiv_round_up((long) cinfo->image_width, 4L);
		cinfo->output_height = (JDIMENSION) jdiv_round_up((long) cinfo->image_height, 4L);
		cinfo->min_DCT_scaled_size = 2;
	}
	else if (cinfo->scale_num * 2 <= cinfo->scale_denom)
	{
		/* Provide 1/2 scaling */
		cinfo->output_width = (JDIMENSION) jdiv_round_up((long) cinfo->image_width, 2L);
		cinfo->output_height = (JDIMENSION) jdiv_round_up((long) cinfo->image_height, 2L);
		cinfo->min_DCT_scaled_size = 4;
	}
	else
	{
		/* Provide 1/1 scaling */
		cinfo->output_width = cinfo->image_width;
		cinfo->output_height = cinfo->image_height;
		cinfo->min_DCT_scaled_size = DCTSIZE;
	}
	/* In selecting the actual DCT scaling for each component, we try to
	 * scale up the chroma components via IDCT scaling rather than upsampling.
	 * This saves time if the upsampler gets to use 1:1 scaling.
	 * Note this code assumes that the supported DCT scalings are powers of 2.
	 */
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
	{
		int ssize = cinfo->min_DCT_scaled_size;
		while (ssize < DCTSIZE && (compptr->h_samp_factor * ssize * 2 <= cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) && (compptr->v_samp_factor * ssize * 2 <= cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size))
		{
			ssize = ssize * 2;
		}
		compptr->DCT_scaled_size = ssize;
	}

	/* Recompute downsampled dimensions of components;
	 * application needs to know these if using raw downsampled data.
	 */
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
	{
		/* Size in samples, after IDCT scaling */
		compptr->downsampled_width = (JDIMENSION) jdiv_round_up((long) cinfo->image_width * (long) (compptr->h_samp_factor * compptr->DCT_scaled_size), (long) (cinfo->max_h_samp_factor * DCTSIZE));
		compptr->downsampled_height = (JDIMENSION) jdiv_round_up((long) cinfo->image_height * (long) (compptr->v_samp_factor * compptr->DCT_scaled_size), (long) (cinfo->max_v_samp_factor * DCTSIZE));
	}

#else /* !IDCT_SCALING_SUPPORTED */

	/* Hardwire it to "no scaling" */
	cinfo->output_width = cinfo->image_width;
	cinfo->output_height = cinfo->image_height;
	/* jdinput.c has already initialized DCT_scaled_size to DCTSIZE,
	 * and has computed unscaled downsampled_width and downsampled_height.
	 */

#endif /* IDCT_SCALING_SUPPORTED */

	/* Report number of components in selected colorspace. */
	/* Probably this should be in the color conversion module... */
	switch (cinfo->out_color_space)
	{
		case JCS_GRAYSCALE:
			cinfo->out_color_components = 1;
			break;
		case JCS_RGB:
#if RGB_PIXELSIZE != 3
			cinfo->out_color_components = RGB_PIXELSIZE;
			break;
#endif /* else share code with YCbCr */
		case JCS_YCbCr:
			cinfo->out_color_components = 3;
			break;
		case JCS_CMYK:
		case JCS_YCCK:
			cinfo->out_color_components = 4;
			break;
		default:
			/* else must be same colorspace as in file */
			cinfo->out_color_components = cinfo->num_components;
			break;
	}
	cinfo->output_components = (cinfo->quantize_colors ? 1 : cinfo->out_color_components);

	/* See if upsampler will want to emit more than one row at a time */
	if (use_merged_upsample(cinfo))
	{
		cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
	}
	else
	{
		cinfo->rec_outbuf_height = 1;
	}
}


/*
 * Several decompression processes need to range-limit values to the range
 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
 * due to noise introduced by quantization, roundoff error, etc.  These
 * processes are inner loops and need to be as fast as possible.  On most
 * machines, particularly CPUs with pipelines or instruction prefetch,
 * a (subscript-check-less) C table lookup
 *		x = sample_range_limit[x];
 * is faster than explicit tests
 *		if (x < 0)  x = 0;
 *		else if (x > MAXJSAMPLE)  x = MAXJSAMPLE;
 * These processes all use a common table prepared by the routine below.
 *
 * For most steps we can mathematically guarantee that the initial value
 * of x is within MAXJSAMPLE+1 of the legal range, so a table running from
 * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient.  But for the initial
 * limiting step (just after the IDCT), a wildly out-of-range value is 
 * possible if the input data is corrupt.  To avoid any chance of indexing
 * off the end of memory and getting a bad-pointer trap, we perform the
 * post-IDCT limiting thus:
 *		x = range_limit[x & MASK];
 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
 * samples.  Under normal circumstances this is more than enough range and
 * a correct output will be generated; with bogus input data the mask will
 * cause wraparound, and we will safely generate a bogus-but-in-range output.
 * For the post-IDCT step, we want to convert the data from signed to unsigned
 * representation by adding CENTERJSAMPLE at the same time that we limit it.
 * So the post-IDCT limiting table ends up looking like this:
 *   CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
 *   MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
 *   0  		(repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
 *   0,1,...,CENTERJSAMPLE-1
 * Negative inputs select values from the upper half of the table after
 * masking.
 *
 * We can save some space by overlapping the start of the post-IDCT table
 * with the simpler range limiting table.  The post-IDCT table begins at
 * sample_range_limit + CENTERJSAMPLE.
 *
 * Note that the table is allocated in near data space on PCs; it's small
 * enough and used often enough to justify this.
 */

LOCAL(void)
prepare_range_limit_table(j_decompress_ptr cinfo)
/* Allocate and fill in the sample_range_limit table */
{
	JSAMPLE * table;
	int i;

	table = (JSAMPLE *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (5 * (MAXJSAMPLE + 1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE));
	table += (MAXJSAMPLE + 1);	/* allow negative subscripts of simple table */
	cinfo->sample_range_limit = table;
	/* First segment of "simple" table: limit[x] = 0 for x < 0 */
	MEMZERO(table - (MAXJSAMPLE + 1), (MAXJSAMPLE + 1) * SIZEOF(JSAMPLE));
	/* Main part of "simple" table: limit[x] = x */
	for (i = 0; i <= MAXJSAMPLE; i++)
	{
		table[i] = (JSAMPLE) i;
	}
	table += CENTERJSAMPLE;	/* Point to where post-IDCT table starts */
	/* End of simple table, rest of first half of post-IDCT table */
	for (i = CENTERJSAMPLE; i < 2 * (MAXJSAMPLE + 1); i++)
	{
		table[i] = MAXJSAMPLE;
	}
	/* Second half of post-IDCT table */
	MEMZERO(table + (2 * (MAXJSAMPLE + 1)), (2 * (MAXJSAMPLE + 1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE));
	MEMCOPY(table + (4 * (MAXJSAMPLE + 1) - CENTERJSAMPLE), cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE));
}


/*
 * Master selection of decompression modules.
 * This is done once at jpeg_start_decompress time.  We determine
 * which modules will be used and give them appropriate initialization calls.
 * We also initialize the decompressor input side to begin consuming data.
 *
 * Since jpeg_read_header has finished, we know what is in the SOF
 * and (first) SOS markers.  We also have all the application parameter
 * settings.
 */

LOCAL(void)
master_selection(j_decompress_ptr cinfo)
{
	my_master_ptr master = (my_master_ptr) cinfo->master;
	boolean use_c_buffer;
	long samplesperrow;
	JDIMENSION jd_samplesperrow;

	/* Initialize dimensions and other stuff */
	jpeg_calc_output_dimensions(cinfo);
	prepare_range_limit_table(cinfo);

	/* Width of an output scanline must be representable as JDIMENSION. */
	samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
	jd_samplesperrow = (JDIMENSION) samplesperrow;
	if ((long) jd_samplesperrow != samplesperrow)
	{
		ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
	}