| /* |
| * 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; |
| } |
| } |
| } |