5  * Copyright (C) 1994-1996, Thomas G. Lane.
6  * Modified 2002-2010 by Guido Vollbeding.
7  * libjpeg-turbo Modifications:
14  * This file contains the inverse-DCT management logic.
17  * is executed per IDCT step, only during output pass setup.
36  * decode files that reuse Q-table slots.)
37  * When we are ready to make an output pass, the saved Q-table is converted
39  * The multiplier table contents are IDCT-method-dependent.  To support
42  * In buffered-image mode, the first output pass may occur before any data
43  * has been seen for some components, and thus before their Q-tables have
55    * is currently set up for, or -1 if it's not yet set up.
57    * per-component comp_info structures.
78 /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
91  * Prepare for an output pass.
99   my_idct_ptr idct = (my_idct_ptr)cinfo->idct;  in start_pass()
100   int ci, i;  in start_pass()  local
106   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;  in start_pass()
107        ci++, compptr++) {  in start_pass()
109     switch (compptr->_DCT_scaled_size) {  in start_pass()
113       method = JDCT_ISLOW;      /* jidctred uses islow-style table */  in start_pass()
120       method = JDCT_ISLOW;      /* jidctred uses islow-style table */  in start_pass()
124       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
131       method = JDCT_ISLOW;      /* jidctred uses islow-style table */  in start_pass()
135       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
144       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
148       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
152       switch (cinfo->dct_method) {  in start_pass()
188       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
192       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
196       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
205       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
209       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
213       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
217       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
221       method = JDCT_ISLOW;      /* jidctint uses islow-style table */  in start_pass()
225       ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->_DCT_scaled_size);  in start_pass()
228     idct->pub.inverse_DCT[ci] = method_ptr;  in start_pass()
233      * multiplier table all-zero; we'll be reading zeroes from the  in start_pass()
236     if (!compptr->component_needed || idct->cur_method[ci] == method)  in start_pass()
238     qtbl = compptr->quant_table;  in start_pass()
241     idct->cur_method[ci] = method;  in start_pass()
249         ISLOW_MULT_TYPE *ismtbl = (ISLOW_MULT_TYPE *)compptr->dct_table;  in start_pass()
251           ismtbl[i] = (ISLOW_MULT_TYPE)qtbl->quantval[i];  in start_pass()
266         IFAST_MULT_TYPE *ifmtbl = (IFAST_MULT_TYPE *)compptr->dct_table;  in start_pass()
283             DESCALE(MULTIPLY16V16((JLONG)qtbl->quantval[i],  in start_pass()
285                     CONST_BITS - IFAST_SCALE_BITS);  in start_pass()
298         FLOAT_MULT_TYPE *fmtbl = (FLOAT_MULT_TYPE *)compptr->dct_table;  in start_pass()
309               ((double)qtbl->quantval[i] *  in start_pass()
333   int ci;  in jinit_inverse_dct()  local
337     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,  in jinit_inverse_dct()
339   cinfo->idct = (struct jpeg_inverse_dct *)idct;  in jinit_inverse_dct()
340   idct->pub.start_pass = start_pass;  in jinit_inverse_dct()
342   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;  in jinit_inverse_dct()
343        ci++, compptr++) {  in jinit_inverse_dct()
344     /* Allocate and pre-zero a multiplier table for each component */  in jinit_inverse_dct()
345     compptr->dct_table =  in jinit_inverse_dct()
346       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,  in jinit_inverse_dct()
348     MEMZERO(compptr->dct_table, sizeof(multiplier_table));  in jinit_inverse_dct()
350     idct->cur_method[ci] = -1;  in jinit_inverse_dct()