src/3rdparty/libjpeg/jcdctmgr.c
changeset 30 5dc02b23752f
parent 0 1918ee327afb
--- a/src/3rdparty/libjpeg/jcdctmgr.c	Wed Jun 23 19:07:03 2010 +0300
+++ b/src/3rdparty/libjpeg/jcdctmgr.c	Tue Jul 06 15:10:48 2010 +0300
@@ -23,7 +23,7 @@
   struct jpeg_forward_dct pub;	/* public fields */
 
   /* Pointer to the DCT routine actually in use */
-  forward_DCT_method_ptr do_dct;
+  forward_DCT_method_ptr do_dct[MAX_COMPONENTS];
 
   /* The actual post-DCT divisors --- not identical to the quant table
    * entries, because of scaling (especially for an unnormalized DCT).
@@ -33,7 +33,7 @@
 
 #ifdef DCT_FLOAT_SUPPORTED
   /* Same as above for the floating-point case. */
-  float_DCT_method_ptr do_float_dct;
+  float_DCT_method_ptr do_float_dct[MAX_COMPONENTS];
   FAST_FLOAT * float_divisors[NUM_QUANT_TBLS];
 #endif
 } my_fdct_controller;
@@ -41,131 +41,16 @@
 typedef my_fdct_controller * my_fdct_ptr;
 
 
-/*
- * Initialize for a processing pass.
- * Verify that all referenced Q-tables are present, and set up
- * the divisor table for each one.
- * In the current implementation, DCT of all components is done during
- * the first pass, even if only some components will be output in the
- * first scan.  Hence all components should be examined here.
+/* The current scaled-DCT routines require ISLOW-style divisor tables,
+ * so be sure to compile that code if either ISLOW or SCALING is requested.
  */
-
-METHODDEF(void)
-start_pass_fdctmgr (j_compress_ptr cinfo)
-{
-  my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
-  int ci, qtblno, i;
-  jpeg_component_info *compptr;
-  JQUANT_TBL * qtbl;
-  DCTELEM * dtbl;
-
-  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
-       ci++, compptr++) {
-    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];
-    /* Compute divisors for this quant table */
-    /* We may do this more than once for same table, but it's not a big deal */
-    switch (cinfo->dct_method) {
 #ifdef DCT_ISLOW_SUPPORTED
-    case JDCT_ISLOW:
-      /* For LL&M IDCT method, divisors are equal to raw quantization
-       * coefficients multiplied by 8 (to counteract scaling).
-       */
-      if (fdct->divisors[qtblno] == NULL) {
-	fdct->divisors[qtblno] = (DCTELEM *)
-	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
-				      DCTSIZE2 * SIZEOF(DCTELEM));
-      }
-      dtbl = fdct->divisors[qtblno];
-      for (i = 0; i < DCTSIZE2; i++) {
-	dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3;
-      }
-      break;
+#define PROVIDE_ISLOW_TABLES
+#else
+#ifdef DCT_SCALING_SUPPORTED
+#define PROVIDE_ISLOW_TABLES
 #endif
-#ifdef DCT_IFAST_SUPPORTED
-    case JDCT_IFAST:
-      {
-	/* For AA&N IDCT method, divisors 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
-	 * We apply a further scale factor of 8.
-	 */
-#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
-
-	if (fdct->divisors[qtblno] == NULL) {
-	  fdct->divisors[qtblno] = (DCTELEM *)
-	    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
-					DCTSIZE2 * SIZEOF(DCTELEM));
-	}
-	dtbl = fdct->divisors[qtblno];
-	for (i = 0; i < DCTSIZE2; i++) {
-	  dtbl[i] = (DCTELEM)
-	    DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
-				  (INT32) aanscales[i]),
-		    CONST_BITS-3);
-	}
-      }
-      break;
 #endif
-#ifdef DCT_FLOAT_SUPPORTED
-    case JDCT_FLOAT:
-      {
-	/* For float AA&N IDCT method, divisors 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
-	 * We apply a further scale factor of 8.
-	 * What's actually stored is 1/divisor so that the inner loop can
-	 * use a multiplication rather than a division.
-	 */
-	FAST_FLOAT * fdtbl;
-	int row, col;
-	static const double aanscalefactor[DCTSIZE] = {
-	  1.0, 1.387039845, 1.306562965, 1.175875602,
-	  1.0, 0.785694958, 0.541196100, 0.275899379
-	};
-
-	if (fdct->float_divisors[qtblno] == NULL) {
-	  fdct->float_divisors[qtblno] = (FAST_FLOAT *)
-	    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
-					DCTSIZE2 * SIZEOF(FAST_FLOAT));
-	}
-	fdtbl = fdct->float_divisors[qtblno];
-	i = 0;
-	for (row = 0; row < DCTSIZE; row++) {
-	  for (col = 0; col < DCTSIZE; col++) {
-	    fdtbl[i] = (FAST_FLOAT)
-	      (1.0 / (((double) qtbl->quantval[i] *
-		       aanscalefactor[row] * aanscalefactor[col] * 8.0)));
-	    i++;
-	  }
-	}
-      }
-      break;
-#endif
-    default:
-      ERREXIT(cinfo, JERR_NOT_COMPILED);
-      break;
-    }
-  }
-}
 
 
 /*
@@ -185,43 +70,16 @@
 {
   /* This routine is heavily used, so it's worth coding it tightly. */
   my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
-  forward_DCT_method_ptr do_dct = fdct->do_dct;
+  forward_DCT_method_ptr do_dct = fdct->do_dct[compptr->component_index];
   DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
   DCTELEM workspace[DCTSIZE2];	/* work area for FDCT subroutine */
   JDIMENSION bi;
 
   sample_data += start_row;	/* fold in the vertical offset once */
 
-  for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
-    /* Load data into workspace, applying unsigned->signed conversion */
-    { register DCTELEM *workspaceptr;
-      register JSAMPROW elemptr;
-      register int elemr;
-
-      workspaceptr = workspace;
-      for (elemr = 0; elemr < DCTSIZE; elemr++) {
-	elemptr = sample_data[elemr] + start_col;
-#if DCTSIZE == 8		/* unroll the inner loop */
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-#else
-	{ register int elemc;
-	  for (elemc = DCTSIZE; elemc > 0; elemc--) {
-	    *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
-	  }
-	}
-#endif
-      }
-    }
-
+  for (bi = 0; bi < num_blocks; bi++, start_col += compptr->DCT_h_scaled_size) {
     /* Perform the DCT */
-    (*do_dct) (workspace);
+    (*do_dct) (workspace, sample_data, start_col);
 
     /* Quantize/descale the coefficients, and store into coef_blocks[] */
     { register DCTELEM temp, qval;
@@ -275,44 +133,16 @@
 {
   /* This routine is heavily used, so it's worth coding it tightly. */
   my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
-  float_DCT_method_ptr do_dct = fdct->do_float_dct;
+  float_DCT_method_ptr do_dct = fdct->do_float_dct[compptr->component_index];
   FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
   FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */
   JDIMENSION bi;
 
   sample_data += start_row;	/* fold in the vertical offset once */
 
-  for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
-    /* Load data into workspace, applying unsigned->signed conversion */
-    { register FAST_FLOAT *workspaceptr;
-      register JSAMPROW elemptr;
-      register int elemr;
-
-      workspaceptr = workspace;
-      for (elemr = 0; elemr < DCTSIZE; elemr++) {
-	elemptr = sample_data[elemr] + start_col;
-#if DCTSIZE == 8		/* unroll the inner loop */
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-#else
-	{ register int elemc;
-	  for (elemc = DCTSIZE; elemc > 0; elemc--) {
-	    *workspaceptr++ = (FAST_FLOAT)
-	      (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
-	  }
-	}
-#endif
-      }
-    }
-
+  for (bi = 0; bi < num_blocks; bi++, start_col += compptr->DCT_h_scaled_size) {
     /* Perform the DCT */
-    (*do_dct) (workspace);
+    (*do_dct) (workspace, sample_data, start_col);
 
     /* Quantize/descale the coefficients, and store into coef_blocks[] */
     { register FAST_FLOAT temp;
@@ -338,6 +168,295 @@
 
 
 /*
+ * Initialize for a processing pass.
+ * Verify that all referenced Q-tables are present, and set up
+ * the divisor table for each one.
+ * In the current implementation, DCT of all components is done during
+ * the first pass, even if only some components will be output in the
+ * first scan.  Hence all components should be examined here.
+ */
+
+METHODDEF(void)
+start_pass_fdctmgr (j_compress_ptr cinfo)
+{
+  my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
+  int ci, qtblno, i;
+  jpeg_component_info *compptr;
+  int method = 0;
+  JQUANT_TBL * qtbl;
+  DCTELEM * dtbl;
+
+  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+       ci++, compptr++) {
+    /* Select the proper DCT routine for this component's scaling */
+    switch ((compptr->DCT_h_scaled_size << 8) + compptr->DCT_v_scaled_size) {
+#ifdef DCT_SCALING_SUPPORTED
+    case ((1 << 8) + 1):
+      fdct->do_dct[ci] = jpeg_fdct_1x1;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((2 << 8) + 2):
+      fdct->do_dct[ci] = jpeg_fdct_2x2;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((3 << 8) + 3):
+      fdct->do_dct[ci] = jpeg_fdct_3x3;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((4 << 8) + 4):
+      fdct->do_dct[ci] = jpeg_fdct_4x4;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((5 << 8) + 5):
+      fdct->do_dct[ci] = jpeg_fdct_5x5;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((6 << 8) + 6):
+      fdct->do_dct[ci] = jpeg_fdct_6x6;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((7 << 8) + 7):
+      fdct->do_dct[ci] = jpeg_fdct_7x7;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((9 << 8) + 9):
+      fdct->do_dct[ci] = jpeg_fdct_9x9;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((10 << 8) + 10):
+      fdct->do_dct[ci] = jpeg_fdct_10x10;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((11 << 8) + 11):
+      fdct->do_dct[ci] = jpeg_fdct_11x11;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((12 << 8) + 12):
+      fdct->do_dct[ci] = jpeg_fdct_12x12;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((13 << 8) + 13):
+      fdct->do_dct[ci] = jpeg_fdct_13x13;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((14 << 8) + 14):
+      fdct->do_dct[ci] = jpeg_fdct_14x14;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((15 << 8) + 15):
+      fdct->do_dct[ci] = jpeg_fdct_15x15;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((16 << 8) + 16):
+      fdct->do_dct[ci] = jpeg_fdct_16x16;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((16 << 8) + 8):
+      fdct->do_dct[ci] = jpeg_fdct_16x8;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((14 << 8) + 7):
+      fdct->do_dct[ci] = jpeg_fdct_14x7;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((12 << 8) + 6):
+      fdct->do_dct[ci] = jpeg_fdct_12x6;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((10 << 8) + 5):
+      fdct->do_dct[ci] = jpeg_fdct_10x5;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((8 << 8) + 4):
+      fdct->do_dct[ci] = jpeg_fdct_8x4;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((6 << 8) + 3):
+      fdct->do_dct[ci] = jpeg_fdct_6x3;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((4 << 8) + 2):
+      fdct->do_dct[ci] = jpeg_fdct_4x2;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((2 << 8) + 1):
+      fdct->do_dct[ci] = jpeg_fdct_2x1;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((8 << 8) + 16):
+      fdct->do_dct[ci] = jpeg_fdct_8x16;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((7 << 8) + 14):
+      fdct->do_dct[ci] = jpeg_fdct_7x14;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((6 << 8) + 12):
+      fdct->do_dct[ci] = jpeg_fdct_6x12;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((5 << 8) + 10):
+      fdct->do_dct[ci] = jpeg_fdct_5x10;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((4 << 8) + 8):
+      fdct->do_dct[ci] = jpeg_fdct_4x8;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((3 << 8) + 6):
+      fdct->do_dct[ci] = jpeg_fdct_3x6;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((2 << 8) + 4):
+      fdct->do_dct[ci] = jpeg_fdct_2x4;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+    case ((1 << 8) + 2):
+      fdct->do_dct[ci] = jpeg_fdct_1x2;
+      method = JDCT_ISLOW;	/* jfdctint uses islow-style table */
+      break;
+#endif
+    case ((DCTSIZE << 8) + DCTSIZE):
+      switch (cinfo->dct_method) {
+#ifdef DCT_ISLOW_SUPPORTED
+      case JDCT_ISLOW:
+	fdct->do_dct[ci] = jpeg_fdct_islow;
+	method = JDCT_ISLOW;
+	break;
+#endif
+#ifdef DCT_IFAST_SUPPORTED
+      case JDCT_IFAST:
+	fdct->do_dct[ci] = jpeg_fdct_ifast;
+	method = JDCT_IFAST;
+	break;
+#endif
+#ifdef DCT_FLOAT_SUPPORTED
+      case JDCT_FLOAT:
+	fdct->do_float_dct[ci] = jpeg_fdct_float;
+	method = JDCT_FLOAT;
+	break;
+#endif
+      default:
+	ERREXIT(cinfo, JERR_NOT_COMPILED);
+	break;
+      }
+      break;
+    default:
+      ERREXIT2(cinfo, JERR_BAD_DCTSIZE,
+	       compptr->DCT_h_scaled_size, compptr->DCT_v_scaled_size);
+      break;
+    }
+    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];
+    /* Compute divisors for this quant table */
+    /* We may do this more than once for same table, but it's not a big deal */
+    switch (method) {
+#ifdef PROVIDE_ISLOW_TABLES
+    case JDCT_ISLOW:
+      /* For LL&M IDCT method, divisors are equal to raw quantization
+       * coefficients multiplied by 8 (to counteract scaling).
+       */
+      if (fdct->divisors[qtblno] == NULL) {
+	fdct->divisors[qtblno] = (DCTELEM *)
+	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+				      DCTSIZE2 * SIZEOF(DCTELEM));
+      }
+      dtbl = fdct->divisors[qtblno];
+      for (i = 0; i < DCTSIZE2; i++) {
+	dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3;
+      }
+      fdct->pub.forward_DCT[ci] = forward_DCT;
+      break;
+#endif
+#ifdef DCT_IFAST_SUPPORTED
+    case JDCT_IFAST:
+      {
+	/* For AA&N IDCT method, divisors 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
+	 * We apply a further scale factor of 8.
+	 */
+#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
+
+	if (fdct->divisors[qtblno] == NULL) {
+	  fdct->divisors[qtblno] = (DCTELEM *)
+	    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+					DCTSIZE2 * SIZEOF(DCTELEM));
+	}
+	dtbl = fdct->divisors[qtblno];
+	for (i = 0; i < DCTSIZE2; i++) {
+	  dtbl[i] = (DCTELEM)
+	    DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
+				  (INT32) aanscales[i]),
+		    CONST_BITS-3);
+	}
+      }
+      fdct->pub.forward_DCT[ci] = forward_DCT;
+      break;
+#endif
+#ifdef DCT_FLOAT_SUPPORTED
+    case JDCT_FLOAT:
+      {
+	/* For float AA&N IDCT method, divisors 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
+	 * We apply a further scale factor of 8.
+	 * What's actually stored is 1/divisor so that the inner loop can
+	 * use a multiplication rather than a division.
+	 */
+	FAST_FLOAT * fdtbl;
+	int row, col;
+	static const double aanscalefactor[DCTSIZE] = {
+	  1.0, 1.387039845, 1.306562965, 1.175875602,
+	  1.0, 0.785694958, 0.541196100, 0.275899379
+	};
+
+	if (fdct->float_divisors[qtblno] == NULL) {
+	  fdct->float_divisors[qtblno] = (FAST_FLOAT *)
+	    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+					DCTSIZE2 * SIZEOF(FAST_FLOAT));
+	}
+	fdtbl = fdct->float_divisors[qtblno];
+	i = 0;
+	for (row = 0; row < DCTSIZE; row++) {
+	  for (col = 0; col < DCTSIZE; col++) {
+	    fdtbl[i] = (FAST_FLOAT)
+	      (1.0 / (((double) qtbl->quantval[i] *
+		       aanscalefactor[row] * aanscalefactor[col] * 8.0)));
+	    i++;
+	  }
+	}
+      }
+      fdct->pub.forward_DCT[ci] = forward_DCT_float;
+      break;
+#endif
+    default:
+      ERREXIT(cinfo, JERR_NOT_COMPILED);
+      break;
+    }
+  }
+}
+
+
+/*
  * Initialize FDCT manager.
  */
 
@@ -353,30 +472,6 @@
   cinfo->fdct = (struct jpeg_forward_dct *) fdct;
   fdct->pub.start_pass = start_pass_fdctmgr;
 
-  switch (cinfo->dct_method) {
-#ifdef DCT_ISLOW_SUPPORTED
-  case JDCT_ISLOW:
-    fdct->pub.forward_DCT = forward_DCT;
-    fdct->do_dct = jpeg_fdct_islow;
-    break;
-#endif
-#ifdef DCT_IFAST_SUPPORTED
-  case JDCT_IFAST:
-    fdct->pub.forward_DCT = forward_DCT;
-    fdct->do_dct = jpeg_fdct_ifast;
-    break;
-#endif
-#ifdef DCT_FLOAT_SUPPORTED
-  case JDCT_FLOAT:
-    fdct->pub.forward_DCT = forward_DCT_float;
-    fdct->do_float_dct = jpeg_fdct_float;
-    break;
-#endif
-  default:
-    ERREXIT(cinfo, JERR_NOT_COMPILED);
-    break;
-  }
-
   /* Mark divisor tables unallocated */
   for (i = 0; i < NUM_QUANT_TBLS; i++) {
     fdct->divisors[i] = NULL;