nuclear@14: /*
nuclear@14:  * jddctmgr.c
nuclear@14:  *
nuclear@14:  * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@14:  * This file is part of the Independent JPEG Group's software.
nuclear@14:  * For conditions of distribution and use, see the accompanying README file.
nuclear@14:  *
nuclear@14:  * This file contains the inverse-DCT management logic.
nuclear@14:  * This code selects a particular IDCT implementation to be used,
nuclear@14:  * and it performs related housekeeping chores.  No code in this file
nuclear@14:  * is executed per IDCT step, only during output pass setup.
nuclear@14:  *
nuclear@14:  * Note that the IDCT routines are responsible for performing coefficient
nuclear@14:  * dequantization as well as the IDCT proper.  This module sets up the
nuclear@14:  * dequantization multiplier table needed by the IDCT routine.
nuclear@14:  */
nuclear@14: 
nuclear@14: #define JPEG_INTERNALS
nuclear@14: #include "jinclude.h"
nuclear@14: #include "jpeglib.h"
nuclear@14: #include "jdct.h"		/* Private declarations for DCT subsystem */
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * The decompressor input side (jdinput.c) saves away the appropriate
nuclear@14:  * quantization table for each component at the start of the first scan
nuclear@14:  * involving that component.  (This is necessary in order to correctly
nuclear@14:  * decode files that reuse Q-table slots.)
nuclear@14:  * When we are ready to make an output pass, the saved Q-table is converted
nuclear@14:  * to a multiplier table that will actually be used by the IDCT routine.
nuclear@14:  * The multiplier table contents are IDCT-method-dependent.  To support
nuclear@14:  * application changes in IDCT method between scans, we can remake the
nuclear@14:  * multiplier tables if necessary.
nuclear@14:  * In buffered-image mode, the first output pass may occur before any data
nuclear@14:  * has been seen for some components, and thus before their Q-tables have
nuclear@14:  * been saved away.  To handle this case, multiplier tables are preset
nuclear@14:  * to zeroes; the result of the IDCT will be a neutral gray level.
nuclear@14:  */
nuclear@14: 
nuclear@14: 
nuclear@14: /* Private subobject for this module */
nuclear@14: 
nuclear@14: typedef struct {
nuclear@14:   struct jpeg_inverse_dct pub;	/* public fields */
nuclear@14: 
nuclear@14:   /* This array contains the IDCT method code that each multiplier table
nuclear@14:    * is currently set up for, or -1 if it's not yet set up.
nuclear@14:    * The actual multiplier tables are pointed to by dct_table in the
nuclear@14:    * per-component comp_info structures.
nuclear@14:    */
nuclear@14:   int cur_method[MAX_COMPONENTS];
nuclear@14: } my_idct_controller;
nuclear@14: 
nuclear@14: typedef my_idct_controller * my_idct_ptr;
nuclear@14: 
nuclear@14: 
nuclear@14: /* Allocated multiplier tables: big enough for any supported variant */
nuclear@14: 
nuclear@14: typedef union {
nuclear@14:   ISLOW_MULT_TYPE islow_array[DCTSIZE2];
nuclear@14: #ifdef DCT_IFAST_SUPPORTED
nuclear@14:   IFAST_MULT_TYPE ifast_array[DCTSIZE2];
nuclear@14: #endif
nuclear@14: #ifdef DCT_FLOAT_SUPPORTED
nuclear@14:   FLOAT_MULT_TYPE float_array[DCTSIZE2];
nuclear@14: #endif
nuclear@14: } multiplier_table;
nuclear@14: 
nuclear@14: 
nuclear@14: /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
nuclear@14:  * so be sure to compile that code if either ISLOW or SCALING is requested.
nuclear@14:  */
nuclear@14: #ifdef DCT_ISLOW_SUPPORTED
nuclear@14: #define PROVIDE_ISLOW_TABLES
nuclear@14: #else
nuclear@14: #ifdef IDCT_SCALING_SUPPORTED
nuclear@14: #define PROVIDE_ISLOW_TABLES
nuclear@14: #endif
nuclear@14: #endif
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Prepare for an output pass.
nuclear@14:  * Here we select the proper IDCT routine for each component and build
nuclear@14:  * a matching multiplier table.
nuclear@14:  */
nuclear@14: 
nuclear@14: METHODDEF(void)
nuclear@14: start_pass (j_decompress_ptr cinfo)
nuclear@14: {
nuclear@14:   my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
nuclear@14:   int ci, i;
nuclear@14:   jpeg_component_info *compptr;
nuclear@14:   int method = 0;
nuclear@14:   inverse_DCT_method_ptr method_ptr = NULL;
nuclear@14:   JQUANT_TBL * qtbl;
nuclear@14: 
nuclear@14:   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@14:        ci++, compptr++) {
nuclear@14:     /* Select the proper IDCT routine for this component's scaling */
nuclear@14:     switch (compptr->DCT_scaled_size) {
nuclear@14: #ifdef IDCT_SCALING_SUPPORTED
nuclear@14:     case 1:
nuclear@14:       method_ptr = jpeg_idct_1x1;
nuclear@14:       method = JDCT_ISLOW;	/* jidctred uses islow-style table */
nuclear@14:       break;
nuclear@14:     case 2:
nuclear@14:       method_ptr = jpeg_idct_2x2;
nuclear@14:       method = JDCT_ISLOW;	/* jidctred uses islow-style table */
nuclear@14:       break;
nuclear@14:     case 4:
nuclear@14:       method_ptr = jpeg_idct_4x4;
nuclear@14:       method = JDCT_ISLOW;	/* jidctred uses islow-style table */
nuclear@14:       break;
nuclear@14: #endif
nuclear@14:     case DCTSIZE:
nuclear@14:       switch (cinfo->dct_method) {
nuclear@14: #ifdef DCT_ISLOW_SUPPORTED
nuclear@14:       case JDCT_ISLOW:
nuclear@14: 	method_ptr = jpeg_idct_islow;
nuclear@14: 	method = JDCT_ISLOW;
nuclear@14: 	break;
nuclear@14: #endif
nuclear@14: #ifdef DCT_IFAST_SUPPORTED
nuclear@14:       case JDCT_IFAST:
nuclear@14: 	method_ptr = jpeg_idct_ifast;
nuclear@14: 	method = JDCT_IFAST;
nuclear@14: 	break;
nuclear@14: #endif
nuclear@14: #ifdef DCT_FLOAT_SUPPORTED
nuclear@14:       case JDCT_FLOAT:
nuclear@14: 	method_ptr = jpeg_idct_float;
nuclear@14: 	method = JDCT_FLOAT;
nuclear@14: 	break;
nuclear@14: #endif
nuclear@14:       default:
nuclear@14: 	ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@14: 	break;
nuclear@14:       }
nuclear@14:       break;
nuclear@14:     default:
nuclear@14:       ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
nuclear@14:       break;
nuclear@14:     }
nuclear@14:     idct->pub.inverse_DCT[ci] = method_ptr;
nuclear@14:     /* Create multiplier table from quant table.
nuclear@14:      * However, we can skip this if the component is uninteresting
nuclear@14:      * or if we already built the table.  Also, if no quant table
nuclear@14:      * has yet been saved for the component, we leave the
nuclear@14:      * multiplier table all-zero; we'll be reading zeroes from the
nuclear@14:      * coefficient controller's buffer anyway.
nuclear@14:      */
nuclear@14:     if (! compptr->component_needed || idct->cur_method[ci] == method)
nuclear@14:       continue;
nuclear@14:     qtbl = compptr->quant_table;
nuclear@14:     if (qtbl == NULL)		/* happens if no data yet for component */
nuclear@14:       continue;
nuclear@14:     idct->cur_method[ci] = method;
nuclear@14:     switch (method) {
nuclear@14: #ifdef PROVIDE_ISLOW_TABLES
nuclear@14:     case JDCT_ISLOW:
nuclear@14:       {
nuclear@14: 	/* For LL&M IDCT method, multipliers are equal to raw quantization
nuclear@14: 	 * coefficients, but are stored as ints to ensure access efficiency.
nuclear@14: 	 */
nuclear@14: 	ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
nuclear@14: 	for (i = 0; i < DCTSIZE2; i++) {
nuclear@14: 	  ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
nuclear@14: 	}
nuclear@14:       }
nuclear@14:       break;
nuclear@14: #endif
nuclear@14: #ifdef DCT_IFAST_SUPPORTED
nuclear@14:     case JDCT_IFAST:
nuclear@14:       {
nuclear@14: 	/* For AA&N IDCT method, multipliers are equal to quantization
nuclear@14: 	 * coefficients scaled by scalefactor[row]*scalefactor[col], where
nuclear@14: 	 *   scalefactor[0] = 1
nuclear@14: 	 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
nuclear@14: 	 * For integer operation, the multiplier table is to be scaled by
nuclear@14: 	 * IFAST_SCALE_BITS.
nuclear@14: 	 */
nuclear@14: 	IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
nuclear@14: #define CONST_BITS 14
nuclear@14: 	static const INT16 aanscales[DCTSIZE2] = {
nuclear@14: 	  /* precomputed values scaled up by 14 bits */
nuclear@14: 	  16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
nuclear@14: 	  22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
nuclear@14: 	  21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
nuclear@14: 	  19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
nuclear@14: 	  16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
nuclear@14: 	  12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
nuclear@14: 	   8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
nuclear@14: 	   4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
nuclear@14: 	};
nuclear@14: 	SHIFT_TEMPS
nuclear@14: 
nuclear@14: 	for (i = 0; i < DCTSIZE2; i++) {
nuclear@14: 	  ifmtbl[i] = (IFAST_MULT_TYPE)
nuclear@14: 	    DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
nuclear@14: 				  (INT32) aanscales[i]),
nuclear@14: 		    CONST_BITS-IFAST_SCALE_BITS);
nuclear@14: 	}
nuclear@14:       }
nuclear@14:       break;
nuclear@14: #endif
nuclear@14: #ifdef DCT_FLOAT_SUPPORTED
nuclear@14:     case JDCT_FLOAT:
nuclear@14:       {
nuclear@14: 	/* For float AA&N IDCT method, multipliers are equal to quantization
nuclear@14: 	 * coefficients scaled by scalefactor[row]*scalefactor[col], where
nuclear@14: 	 *   scalefactor[0] = 1
nuclear@14: 	 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
nuclear@14: 	 */
nuclear@14: 	FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
nuclear@14: 	int row, col;
nuclear@14: 	static const double aanscalefactor[DCTSIZE] = {
nuclear@14: 	  1.0, 1.387039845, 1.306562965, 1.175875602,
nuclear@14: 	  1.0, 0.785694958, 0.541196100, 0.275899379
nuclear@14: 	};
nuclear@14: 
nuclear@14: 	i = 0;
nuclear@14: 	for (row = 0; row < DCTSIZE; row++) {
nuclear@14: 	  for (col = 0; col < DCTSIZE; col++) {
nuclear@14: 	    fmtbl[i] = (FLOAT_MULT_TYPE)
nuclear@14: 	      ((double) qtbl->quantval[i] *
nuclear@14: 	       aanscalefactor[row] * aanscalefactor[col]);
nuclear@14: 	    i++;
nuclear@14: 	  }
nuclear@14: 	}
nuclear@14:       }
nuclear@14:       break;
nuclear@14: #endif
nuclear@14:     default:
nuclear@14:       ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@14:       break;
nuclear@14:     }
nuclear@14:   }
nuclear@14: }
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Initialize IDCT manager.
nuclear@14:  */
nuclear@14: 
nuclear@14: GLOBAL(void)
nuclear@14: jinit_inverse_dct (j_decompress_ptr cinfo)
nuclear@14: {
nuclear@14:   my_idct_ptr idct;
nuclear@14:   int ci;
nuclear@14:   jpeg_component_info *compptr;
nuclear@14: 
nuclear@14:   idct = (my_idct_ptr)
nuclear@14:     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@14: 				SIZEOF(my_idct_controller));
nuclear@14:   cinfo->idct = (struct jpeg_inverse_dct *) idct;
nuclear@14:   idct->pub.start_pass = start_pass;
nuclear@14: 
nuclear@14:   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@14:        ci++, compptr++) {
nuclear@14:     /* Allocate and pre-zero a multiplier table for each component */
nuclear@14:     compptr->dct_table =
nuclear@14:       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@14: 				  SIZEOF(multiplier_table));
nuclear@14:     MEMZERO(compptr->dct_table, SIZEOF(multiplier_table));
nuclear@14:     /* Mark multiplier table not yet set up for any method */
nuclear@14:     idct->cur_method[ci] = -1;
nuclear@14:   }
nuclear@14: }