The Independent JPEG Group's JPEG software v5
diff --git a/jddctmgr.c b/jddctmgr.c
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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;
+ }
+ }
+}