src/jpeg/jddctmgr.c

/*
 * 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;
  }
}
Commit	Line	Data
	1	/*
	2	* jddctmgr.c
	3	*
	4	* Copyright (C) 1994-1996, Thomas G. Lane.
	5	* This file is part of the Independent JPEG Group's software.
	6	* For conditions of distribution and use, see the accompanying README file.
	7	*
	8	* This file contains the inverse-DCT management logic.
	9	* This code selects a particular IDCT implementation to be used,
	10	* and it performs related housekeeping chores. No code in this file
	11	* is executed per IDCT step, only during output pass setup.
	12	*
	13	* Note that the IDCT routines are responsible for performing coefficient
	14	* dequantization as well as the IDCT proper. This module sets up the
	15	* dequantization multiplier table needed by the IDCT routine.
	16	*/
	17
	18	#define JPEG_INTERNALS
	19	#include "jinclude.h"
	20	#include "jpeglib.h"
	21	#include "jdct.h" /* Private declarations for DCT subsystem */
	22
	23
	24	/*
	25	* The decompressor input side (jdinput.c) saves away the appropriate
	26	* quantization table for each component at the start of the first scan
	27	* involving that component. (This is necessary in order to correctly
	28	* decode files that reuse Q-table slots.)
	29	* When we are ready to make an output pass, the saved Q-table is converted
	30	* to a multiplier table that will actually be used by the IDCT routine.
	31	* The multiplier table contents are IDCT-method-dependent. To support
	32	* application changes in IDCT method between scans, we can remake the
	33	* multiplier tables if necessary.
	34	* In buffered-image mode, the first output pass may occur before any data
	35	* has been seen for some components, and thus before their Q-tables have
	36	* been saved away. To handle this case, multiplier tables are preset
	37	* to zeroes; the result of the IDCT will be a neutral gray level.
	38	*/
	39
	40
	41	/* Private subobject for this module */
	42
	43	typedef struct {
	44	struct jpeg_inverse_dct pub; /* public fields */
	45
	46	/* This array contains the IDCT method code that each multiplier table
	47	* is currently set up for, or -1 if it's not yet set up.
	48	* The actual multiplier tables are pointed to by dct_table in the
	49	* per-component comp_info structures.
	50	*/
	51	int cur_method[MAX_COMPONENTS];
	52	} my_idct_controller;
	53
	54	typedef my_idct_controller * my_idct_ptr;
	55
	56
	57	/* Allocated multiplier tables: big enough for any supported variant */
	58
	59	typedef union {
	60	ISLOW_MULT_TYPE islow_array[DCTSIZE2];
	61	#ifdef DCT_IFAST_SUPPORTED
	62	IFAST_MULT_TYPE ifast_array[DCTSIZE2];
	63	#endif
	64	#ifdef DCT_FLOAT_SUPPORTED
	65	FLOAT_MULT_TYPE float_array[DCTSIZE2];
	66	#endif
	67	} multiplier_table;
	68
	69
	70	/* The current scaled-IDCT routines require ISLOW-style multiplier tables,
	71	* so be sure to compile that code if either ISLOW or SCALING is requested.
	72	*/
	73	#ifdef DCT_ISLOW_SUPPORTED
	74	#define PROVIDE_ISLOW_TABLES
	75	#else
	76	#ifdef IDCT_SCALING_SUPPORTED
	77	#define PROVIDE_ISLOW_TABLES
	78	#endif
	79	#endif
	80
	81
	82	/*
	83	* Prepare for an output pass.
	84	* Here we select the proper IDCT routine for each component and build
	85	* a matching multiplier table.
	86	*/
	87
	88	METHODDEF(void)
	89	start_pass (j_decompress_ptr cinfo)
	90	{
	91	my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
	92	int ci, i;
	93	jpeg_component_info *compptr;
	94	int method = 0;
	95	inverse_DCT_method_ptr method_ptr = NULL;
	96	JQUANT_TBL * qtbl;
	97
	98	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	99	ci++, compptr++) {
	100	/* Select the proper IDCT routine for this component's scaling */
	101	switch (compptr->DCT_scaled_size) {
	102	#ifdef IDCT_SCALING_SUPPORTED
	103	case 1:
	104	method_ptr = jpeg_idct_1x1;
	105	method = JDCT_ISLOW; /* jidctred uses islow-style table */
	106	break;
	107	case 2:
	108	method_ptr = jpeg_idct_2x2;
	109	method = JDCT_ISLOW; /* jidctred uses islow-style table */
	110	break;
	111	case 4:
	112	method_ptr = jpeg_idct_4x4;
	113	method = JDCT_ISLOW; /* jidctred uses islow-style table */
	114	break;
	115	#endif
	116	case DCTSIZE:
	117	switch (cinfo->dct_method) {
	118	#ifdef DCT_ISLOW_SUPPORTED
	119	case JDCT_ISLOW:
	120	method_ptr = jpeg_idct_islow;
	121	method = JDCT_ISLOW;
	122	break;
	123	#endif
	124	#ifdef DCT_IFAST_SUPPORTED
	125	case JDCT_IFAST:
	126	method_ptr = jpeg_idct_ifast;
	127	method = JDCT_IFAST;
	128	break;
	129	#endif
	130	#ifdef DCT_FLOAT_SUPPORTED
	131	case JDCT_FLOAT:
	132	method_ptr = jpeg_idct_float;
	133	method = JDCT_FLOAT;
	134	break;
	135	#endif
	136	default:
	137	ERREXIT(cinfo, JERR_NOT_COMPILED);
	138	break;
	139	}
	140	break;
	141	default:
	142	ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
	143	break;
	144	}
	145	idct->pub.inverse_DCT[ci] = method_ptr;
	146	/* Create multiplier table from quant table.
	147	* However, we can skip this if the component is uninteresting
	148	* or if we already built the table. Also, if no quant table
	149	* has yet been saved for the component, we leave the
	150	* multiplier table all-zero; we'll be reading zeroes from the
	151	* coefficient controller's buffer anyway.
	152	*/
	153	if (! compptr->component_needed \|\| idct->cur_method[ci] == method)
	154	continue;
	155	qtbl = compptr->quant_table;
	156	if (qtbl == NULL) /* happens if no data yet for component */
	157	continue;
	158	idct->cur_method[ci] = method;
	159	switch (method) {
	160	#ifdef PROVIDE_ISLOW_TABLES
	161	case JDCT_ISLOW:
	162	{
	163	/* For LL&M IDCT method, multipliers are equal to raw quantization
	164	* coefficients, but are stored as ints to ensure access efficiency.
	165	*/
	166	ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
	167	for (i = 0; i < DCTSIZE2; i++) {
	168	ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
	169	}
	170	}
	171	break;
	172	#endif
	173	#ifdef DCT_IFAST_SUPPORTED
	174	case JDCT_IFAST:
	175	{
	176	/* For AA&N IDCT method, multipliers are equal to quantization
	177	* coefficients scaled by scalefactor[row]*scalefactor[col], where
	178	* scalefactor[0] = 1
	179	* scalefactor[k] = cos(kPI/16) sqrt(2) for k=1..7
	180	* For integer operation, the multiplier table is to be scaled by
	181	* IFAST_SCALE_BITS.
	182	*/
	183	IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
	184	#define CONST_BITS 14
	185	static const INT16 aanscales[DCTSIZE2] = {
	186	/* precomputed values scaled up by 14 bits */
	187	16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
	188	22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
	189	21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
	190	19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
	191	16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
	192	12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
	193	8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
	194	4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
	195	};
	196	SHIFT_TEMPS
	197
	198	for (i = 0; i < DCTSIZE2; i++) {
	199	ifmtbl[i] = (IFAST_MULT_TYPE)
	200	DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
	201	(INT32) aanscales[i]),
	202	CONST_BITS-IFAST_SCALE_BITS);
	203	}
	204	}
	205	break;
	206	#endif
	207	#ifdef DCT_FLOAT_SUPPORTED
	208	case JDCT_FLOAT:
	209	{
	210	/* For float AA&N IDCT method, multipliers are equal to quantization
	211	* coefficients scaled by scalefactor[row]*scalefactor[col], where
	212	* scalefactor[0] = 1
	213	* scalefactor[k] = cos(kPI/16) sqrt(2) for k=1..7
	214	*/
	215	FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
	216	int row, col;
	217	static const double aanscalefactor[DCTSIZE] = {
	218	1.0, 1.387039845, 1.306562965, 1.175875602,
	219	1.0, 0.785694958, 0.541196100, 0.275899379
	220	};
	221
	222	i = 0;
	223	for (row = 0; row < DCTSIZE; row++) {
	224	for (col = 0; col < DCTSIZE; col++) {
	225	fmtbl[i] = (FLOAT_MULT_TYPE)
	226	((double) qtbl->quantval[i] *
	227	aanscalefactor[row] * aanscalefactor[col]);
	228	i++;
	229	}
	230	}
	231	}
	232	break;
	233	#endif
	234	default:
	235	ERREXIT(cinfo, JERR_NOT_COMPILED);
	236	break;
	237	}
	238	}
	239	}
	240
	241
	242	/*
	243	* Initialize IDCT manager.
	244	*/
	245
	246	GLOBAL(void)
	247	jinit_inverse_dct (j_decompress_ptr cinfo)
	248	{
	249	my_idct_ptr idct;
	250	int ci;
	251	jpeg_component_info *compptr;
	252
	253	idct = (my_idct_ptr)
	254	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	255	SIZEOF(my_idct_controller));
	256	cinfo->idct = (struct jpeg_inverse_dct *) idct;
	257	idct->pub.start_pass = start_pass;
	258
	259	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	260	ci++, compptr++) {
	261	/* Allocate and pre-zero a multiplier table for each component */
	262	compptr->dct_table =
	263	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	264	SIZEOF(multiplier_table));
	265	MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
	266	/* Mark multiplier table not yet set up for any method */
	267	idct->cur_method[ci] = -1;
	268	}
	269	}