jddctmgr.cpp

Go to the documentation of this file.

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "mrpt_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 = nullptr;
        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 == nullptr) /* 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;
        }
}