www.pudn.com > imgport.rar > jcdctmgr.c, change:2008-11-05,size:12866b


/* 
 * jcdctmgr.c 
 * 
 * Copyright (C) 1994-1996, 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 forward-DCT management logic. 
 * This code selects a particular DCT implementation to be used, 
 * and it performs related housekeeping chores including coefficient 
 * quantization. 
 */ 
 
#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_forward_dct pub;	/* public fields */ 
 
  /* Pointer to the DCT routine actually in use */ 
  forward_DCT_method_ptr do_dct; 
 
  /* The actual post-DCT divisors --- not identical to the quant table 
   * entries, because of scaling (especially for an unnormalized DCT). 
   * Each table is given in normal array order. 
   */ 
  DCTELEM * divisors[NUM_QUANT_TBLS]; 
 
#ifdef DCT_FLOAT_SUPPORTED 
  /* Same as above for the floating-point case. */ 
  float_DCT_method_ptr do_float_dct; 
  FAST_FLOAT * float_divisors[NUM_QUANT_TBLS]; 
#endif 
} my_fdct_controller; 
 
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. 
 */ 
 
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; 
#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((JPEG_INT32) qtbl->quantval[i], 
				  (JPEG_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; 
    } 
  } 
} 
 
 
/* 
 * Perform forward DCT on one or more blocks of a component. 
 * 
 * The input samples are taken from the sample_data[] array starting at 
 * position start_row/start_col, and moving to the right for any additional 
 * blocks. The quantized coefficients are returned in coef_blocks[]. 
 */ 
 
METHODDEF(void) 
forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr, 
	     JSAMPARRAY sample_data, JBLOCKROW coef_blocks, 
	     JDIMENSION start_row, JDIMENSION start_col, 
	     JDIMENSION num_blocks) 
/* This version is used for integer DCT implementations. */ 
{ 
  /* 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; 
  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 
      } 
    } 
 
    /* Perform the DCT */ 
    (*do_dct) (workspace); 
 
    /* Quantize/descale the coefficients, and store into coef_blocks[] */ 
    { register DCTELEM temp, qval; 
      register int i; 
      register JCOEFPTR output_ptr = coef_blocks[bi]; 
 
      for (i = 0; i < DCTSIZE2; i++) { 
	qval = divisors[i]; 
	temp = workspace[i]; 
	/* Divide the coefficient value by qval, ensuring proper rounding. 
	 * Since C does not specify the direction of rounding for negative 
	 * quotients, we have to force the dividend positive for portability. 
	 * 
	 * In most files, at least half of the output values will be zero 
	 * (at default quantization settings, more like three-quarters...) 
	 * so we should ensure that this case is fast.  On many machines, 
	 * a comparison is enough cheaper than a divide to make a special test 
	 * a win.  Since both inputs will be nonnegative, we need only test 
	 * for a < b to discover whether a/b is 0. 
	 * If your machine's division is fast enough, define FAST_DIVIDE. 
	 */ 
#ifdef FAST_DIVIDE 
#define DIVIDE_BY(a,b)	a /= b 
#else 
#define DIVIDE_BY(a,b)	if (a >= b) a /= b; else a = 0 
#endif 
	if (temp < 0) { 
	  temp = -temp; 
	  temp += qval>>1;	/* for rounding */ 
	  DIVIDE_BY(temp, qval); 
	  temp = -temp; 
	} else { 
	  temp += qval>>1;	/* for rounding */ 
	  DIVIDE_BY(temp, qval); 
	} 
	output_ptr[i] = (JCOEF) temp; 
      } 
    } 
  } 
} 
 
 
#ifdef DCT_FLOAT_SUPPORTED 
 
METHODDEF(void) 
forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr, 
		   JSAMPARRAY sample_data, JBLOCKROW coef_blocks, 
		   JDIMENSION start_row, JDIMENSION start_col, 
		   JDIMENSION num_blocks) 
/* This version is used for floating-point DCT implementations. */ 
{ 
  /* 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; 
  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 
      } 
    } 
 
    /* Perform the DCT */ 
    (*do_dct) (workspace); 
 
    /* Quantize/descale the coefficients, and store into coef_blocks[] */ 
    { register FAST_FLOAT temp; 
      register int i; 
      register JCOEFPTR output_ptr = coef_blocks[bi]; 
 
      for (i = 0; i < DCTSIZE2; i++) { 
	/* Apply the quantization and scaling factor */ 
	temp = workspace[i] * divisors[i]; 
	/* Round to nearest integer. 
	 * Since C does not specify the direction of rounding for negative 
	 * quotients, we have to force the dividend positive for portability. 
	 * The maximum coefficient size is +-16K (for 12-bit data), so this 
	 * code should work for either 16-bit or 32-bit ints. 
	 */ 
	output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384); 
      } 
    } 
  } 
} 
 
#endif /* DCT_FLOAT_SUPPORTED */ 
 
 
/* 
 * Initialize FDCT manager. 
 */ 
 
GLOBAL(void) 
jinit_forward_dct (j_compress_ptr cinfo) 
{ 
  my_fdct_ptr fdct; 
  int i; 
 
  fdct = (my_fdct_ptr) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				SIZEOF(my_fdct_controller)); 
  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; 
#ifdef DCT_FLOAT_SUPPORTED 
    fdct->float_divisors[i] = NULL; 
#endif 
  } 
}