The Independent JPEG Group's JPEG software v5

1 files changed, 282 insertions, 0 deletions

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;
+    }
+  }
+}