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/*
* jddctmgr.c
*
* Copyright (C) 1994, 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 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 */
/* Private subobject for this module */
typedef struct {
struct jpeg_inverse_dct pub; /* public fields */
/* Record the IDCT method type actually selected for each component */
J_DCT_METHOD real_method[MAX_COMPONENTS];
} my_idct_controller;
typedef my_idct_controller * my_idct_ptr;
/* ZIG[i] is the zigzag-order position of the i'th element of a DCT block */
/* read in natural order (left to right, top to bottom). */
static const int ZIG[DCTSIZE2] = {
0, 1, 5, 6, 14, 15, 27, 28,
2, 4, 7, 13, 16, 26, 29, 42,
3, 8, 12, 17, 25, 30, 41, 43,
9, 11, 18, 24, 31, 40, 44, 53,
10, 19, 23, 32, 39, 45, 52, 54,
20, 22, 33, 38, 46, 51, 55, 60,
21, 34, 37, 47, 50, 56, 59, 61,
35, 36, 48, 49, 57, 58, 62, 63
};
/* 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
/*
* Initialize for an input scan.
*
* Verify that all referenced Q-tables are present, and set up
* the multiplier table for each one.
* With a multiple-scan JPEG file, this is called during each input scan,
* NOT during the final output pass where the IDCT is actually done.
* The purpose is to save away the current Q-table contents just in case
* the encoder changes tables between scans. This decoder will dequantize
* any component using the Q-table which was current at the start of the
* first scan using that component.
*/
METHODDEF void
start_input_pass (j_decompress_ptr cinfo)
{
my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
int ci, qtblno, i;
jpeg_component_info *compptr;
JQUANT_TBL * qtbl;
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
qtblno = compptr->quant_tbl_no;
/* Make sure specified quantization table is present */
if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
cinfo->quant_tbl_ptrs[qtblno] == NULL)
ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
qtbl = cinfo->quant_tbl_ptrs[qtblno];
/* Create multiplier table from quant table, unless we already did so. */
if (compptr->dct_table != NULL)
continue;
switch (idct->real_method[compptr->component_index]) {
#ifdef PROVIDE_ISLOW_TABLES
case JDCT_ISLOW:
{
/* For LL&M IDCT method, multipliers are equal to raw quantization
* coefficients, but are stored in natural order as ints.
*/
ISLOW_MULT_TYPE * ismtbl;
compptr->dct_table =
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
DCTSIZE2 * SIZEOF(ISLOW_MULT_TYPE));
ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
for (i = 0; i < DCTSIZE2; i++) {
ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[ZIG[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. The multipliers are stored in natural order.
*/
IFAST_MULT_TYPE * ifmtbl;
#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
compptr->dct_table =
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
DCTSIZE2 * SIZEOF(IFAST_MULT_TYPE));
ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table;
for (i = 0; i < DCTSIZE2; i++) {
ifmtbl[i] = (IFAST_MULT_TYPE)
DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[ZIG[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
* The multipliers are stored in natural order.
*/
FLOAT_MULT_TYPE * fmtbl;
int row, col;
static const double aanscalefactor[DCTSIZE] = {
1.0, 1.387039845, 1.306562965, 1.175875602,
1.0, 0.785694958, 0.541196100, 0.275899379
};
compptr->dct_table =
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
DCTSIZE2 * SIZEOF(FLOAT_MULT_TYPE));
fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table;
i = 0;
for (row = 0; row < DCTSIZE; row++) {
for (col = 0; col < DCTSIZE; col++) {
fmtbl[i] = (FLOAT_MULT_TYPE)
((double) qtbl->quantval[ZIG[i]] *
aanscalefactor[row] * aanscalefactor[col]);
i++;
}
}
}
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
}
}
/*
* Prepare for an output pass that will actually perform IDCTs.
*
* start_input_pass should already have been done for all components
* of interest; we need only verify that this is true.
* Note that uninteresting components are not required to have loaded tables.
* This allows the master controller to stop before reading the whole file
* if it has obtained the data for the interesting component(s).
*/
METHODDEF void
start_output_pass (j_decompress_ptr cinfo)
{
jpeg_component_info *compptr;
int ci;
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
if (! compptr->component_needed)
continue;
if (compptr->dct_table == NULL)
ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, compptr->quant_tbl_no);
}
}
/*
* 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_input_pass = start_input_pass;
idct->pub.start_output_pass = start_output_pass;
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
compptr->dct_table = NULL; /* initialize tables to "not prepared" */
switch (compptr->DCT_scaled_size) {
#ifdef IDCT_SCALING_SUPPORTED
case 1:
idct->pub.inverse_DCT[ci] = jpeg_idct_1x1;
idct->real_method[ci] = JDCT_ISLOW; /* jidctred uses islow-style table */
break;
case 2:
idct->pub.inverse_DCT[ci] = jpeg_idct_2x2;
idct->real_method[ci] = JDCT_ISLOW; /* jidctred uses islow-style table */
break;
case 4:
idct->pub.inverse_DCT[ci] = jpeg_idct_4x4;
idct->real_method[ci] = JDCT_ISLOW; /* jidctred uses islow-style table */
break;
#endif
case DCTSIZE:
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
idct->pub.inverse_DCT[ci] = jpeg_idct_islow;
idct->real_method[ci] = JDCT_ISLOW;
break;
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
idct->pub.inverse_DCT[ci] = jpeg_idct_ifast;
idct->real_method[ci] = JDCT_IFAST;
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
idct->pub.inverse_DCT[ci] = jpeg_idct_float;
idct->real_method[ci] = JDCT_FLOAT;
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
break;
default:
ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size);
break;
}
}
}
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