jddctmgr.c

MCB2300_ucgui_LCD320240.rar LPC2368的uc/gui的移植

/*
 * jddctmgr.c
 *
 * Copyright (C) 1994-1996, 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 the inverse-DCT management logic.
 * This code selects a particular IDCT implementation to be used,
 * and it performs related housekeeping chores.  No code in this file
 * is executed per IDCT step, only during output pass setup.
 *
 * Note that the IDCT routines are responsible for performing coefficient
 * dequantization as well as the IDCT proper.  This module sets up the
 * dequantization multiplier table needed by the IDCT routine.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"		/* Private declarations for DCT subsystem */


/*
 * The decompressor input side (jdinput.c) saves away the appropriate
 * quantization table for each component at the start of the first scan
 * involving that component.  (This is necessary in order to correctly
 * decode files that reuse Q-table slots.)
 * When we are ready to make an output pass, the saved Q-table is converted
 * to a multiplier table that will actually be used by the IDCT routine.
 * The multiplier table contents are IDCT-method-dependent.  To support
 * application changes in IDCT method between scans, we can remake the
 * multiplier tables if necessary.
 * In buffered-image mode, the first output pass may occur before any data
 * has been seen for some components, and thus before their Q-tables have
 * been saved away.  To handle this case, multiplier tables are preset
 * to zeroes; the result of the IDCT will be a neutral gray level.
 */


/* Private subobject for this module */

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

	/* This array contains the IDCT method code that each multiplier table
	 * is currently set up for, or -1 if it's not yet set up.
	 * The actual multiplier tables are pointed to by dct_table in the
	 * per-component comp_info structures.
	 */
	int						cur_method[MAX_COMPONENTS];
} my_idct_controller;

typedef my_idct_controller * my_idct_ptr;


/* Allocated multiplier tables: big enough for any supported variant */

typedef union
{
	ISLOW_MULT_TYPE	islow_array[DCTSIZE2];
#ifdef DCT_IFAST_SUPPORTED
	IFAST_MULT_TYPE	ifast_array[DCTSIZE2];
#endif
#ifdef DCT_FLOAT_SUPPORTED
	FLOAT_MULT_TYPE	float_array[DCTSIZE2];
#endif
} multiplier_table;


/* The current scaled-IDCT routines require ISLOW-style multiplier tables,
 * so be sure to compile that code if either ISLOW or SCALING is requested.
 */
#ifdef DCT_ISLOW_SUPPORTED
#define PROVIDE_ISLOW_TABLES
#else
#ifdef IDCT_SCALING_SUPPORTED
#define PROVIDE_ISLOW_TABLES
#endif
#endif


/*
 * Prepare for an output pass.
 * Here we select the proper IDCT routine for each component and build
 * a matching multiplier table.
 */

METHODDEF(void) start_pass(j_decompress_ptr cinfo)
{
					my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
					int ci, i;
					jpeg_component_info *compptr;
					int method = 0;
					inverse_DCT_method_ptr method_ptr = NULL;
					JQUANT_TBL * qtbl;

					for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
					{
						/* Select the proper IDCT routine for this component's scaling */
						switch (compptr->DCT_scaled_size)
						{
#ifdef IDCT_SCALING_SUPPORTED
							case 1:
								method_ptr = jpeg_idct_1x1;
								method = JDCT_ISLOW;	/* jidctred uses islow-style table */
								break;
							case 2:
								method_ptr = jpeg_idct_2x2;
								method = JDCT_ISLOW;	/* jidctred uses islow-style table */
								break;
							case 4:
								method_ptr = jpeg_idct_4x4;
								method = JDCT_ISLOW;	/* jidctred uses islow-style table */
								break;
#endif
							case DCTSIZE:
								switch (cinfo->dct_method)
								{
#ifdef DCT_ISLOW_SUPPORTED
									case JDCT_ISLOW:
										method_ptr = jpeg_idct_islow;
										method = JDCT_ISLOW;
										break;
#endif
#ifdef DCT_IFAST_SUPPORTED
									case JDCT_IFAST:
										method_ptr = jpeg_idct_ifast;
										method = JDCT_IFAST;
										break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
									case JDCT_FLOAT:
										method_ptr = jpeg_idct_float;
										method = JDCT_FLOAT;
										break;
#endif
									default:
										ERREXIT(cinfo, JERR_NOT_COMPILED);
										break;
								}
								break;
							default:
								ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
								break;
						}
						idct->pub.inverse_DCT[ci] = method_ptr;
						/* Create multiplier table from quant table.
						 * However, we can skip this if the component is uninteresting
						 * or if we already built the table.  Also, if no quant table
						 * has yet been saved for the component, we leave the
						 * multiplier table all-zero; we'll be reading zeroes from the
						 * coefficient controller's buffer anyway.
						 */
						if (!compptr->component_needed || idct->cur_method[ci] == method)
						{
							continue;
						}
						qtbl = compptr->quant_table;
						if (qtbl == NULL)		/* happens if no data yet for component */
						{
							continue;
						}
						idct->cur_method[ci] = method;
						switch (method)
						{
#ifdef PROVIDE_ISLOW_TABLES
							case JDCT_ISLOW:
								{
									/* For LL&M IDCT method, multipliers are equal to raw quantization
									 * coefficients, but are stored as ints to ensure access efficiency.
									 */
									ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
									for (i = 0; i < DCTSIZE2; i++)
									{
										ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
									}
								}
								break;
#endif
#ifdef DCT_IFAST_SUPPORTED
							case JDCT_IFAST:
								{
									/* For AA&N IDCT method, multipliers are equal to quantization
									 * coefficients scaled by scalefactor[row]*scalefactor[col], where
									 *   scalefactor[0] = 1
									 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)	for k=1..7
									 * For integer operation, the multiplier table is to be scaled by
									 * IFAST_SCALE_BITS.
									 */
									IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
#define CONST_BITS 14
									static const INT16 aanscales[DCTSIZE2] = {
									/* precomputed values scaled up by 14 bits */
									16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
									22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
									21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
									19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
									16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
									12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
									8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
									4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
									};
									SHIFT_TEMPS

									for (i = 0; i < DCTSIZE2; i++)
									{
										ifmtbl[i] = (IFAST_MULT_TYPE) DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i], (INT32) aanscales[i]), CONST_BITS - IFAST_SCALE_BITS);
									}
								}
								break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
							case JDCT_FLOAT:
								{
									/* For float AA&N IDCT method, multipliers are equal to quantization
									 * coefficients scaled by scalefactor[row]*scalefactor[col], where
									 *   scalefactor[0] = 1
									 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)	for k=1..7
									 */
									FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
									int row, col;
									static const double aanscalefactor[DCTSIZE] = {
									1.0, 1.387039845, 1.306562965, 1.175875602,
									1.0, 0.785694958, 0.541196100, 0.275899379
									};

									i = 0;
									for (row = 0; row < DCTSIZE; row++)
									{
										for (col = 0; col < DCTSIZE; col++)
										{
											fmtbl[i] = (FLOAT_MULT_TYPE) ((double) qtbl->quantval[i] * aanscalefactor[row] * aanscalefactor[col]);
											i++;
										}
									}
								}
								break;
#endif
							default:
								ERREXIT(cinfo, JERR_NOT_COMPILED);
								break;
						}
					}
}


/*
 * Initialize IDCT manager.
 */

GLOBAL(void)
jinit_inverse_dct(j_decompress_ptr cinfo)
{
	my_idct_ptr idct;
	int ci;
	jpeg_component_info *compptr;

	idct = (my_idct_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_idct_controller));
	cinfo->idct = (struct jpeg_inverse_dct *) idct;
	idct->pub.start_pass = start_pass;

	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
	{
		/* Allocate and pre-zero a multiplier table for each component */
		compptr->dct_table = (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(multiplier_table));
		MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
		/* Mark multiplier table not yet set up for any method */
		idct->cur_method[ci] = -1;
	}
}