view release on metacpan or  search on metacpan

src/Source/LibJPEG/jddctmgr.c  view on Meta::CPAN

 * and it performs related housekeeping chores.  No code in this file
 * is executed per IDCT step, only during output 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 */


/*
 * The decompressor input side (jdinput.c) saves away the appropriate
 * quantization table for each component at the start of the first scan
 * involving that component.  (This is necessary in order to correctly
 * decode files that reuse Q-table slots.)
 * When we are ready to make an output pass, the saved Q-table is converted
 * to a multiplier table that will actually be used by the IDCT routine.
 * The multiplier table contents are IDCT-method-dependent.  To support
 * application changes in IDCT method between scans, we can remake the
 * multiplier tables if necessary.
 * In buffered-image mode, the first output pass may occur before any data
 * has been seen for some components, and thus before their Q-tables have
 * been saved away.  To handle this case, multiplier tables are preset
 * to zeroes; the result of the IDCT will be a neutral gray level.
 */


/* Private subobject for this module */

typedef struct {
  struct jpeg_inverse_dct pub;	/* public fields */

  /* This array contains the IDCT method code that each multiplier table
   * is currently set up for, or -1 if it's not yet set up.
   * The actual multiplier tables are pointed to by dct_table in the
   * per-component comp_info structures.
   */
  int cur_method[MAX_COMPONENTS];
} my_idct_controller;

typedef my_idct_controller * my_idct_ptr;


/* Allocated multiplier tables: big enough for any supported variant */

typedef union {
  ISLOW_MULT_TYPE islow_array[DCTSIZE2];
#ifdef DCT_IFAST_SUPPORTED
  IFAST_MULT_TYPE ifast_array[DCTSIZE2];
#endif
#ifdef DCT_FLOAT_SUPPORTED
  FLOAT_MULT_TYPE float_array[DCTSIZE2];
#endif
} multiplier_table;


/* 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


/*
 * Prepare for an output pass.
 * Here we select the proper IDCT routine for each component and build
 * a matching multiplier table.
 */

METHODDEF(void)
start_pass (j_decompress_ptr cinfo)
{
  my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
  int ci, i;
  jpeg_component_info *compptr;
  int method = 0;
  inverse_DCT_method_ptr method_ptr = NULL;
  JQUANT_TBL * qtbl;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Select the proper IDCT routine for this component's scaling */
    switch ((compptr->DCT_h_scaled_size << 8) + compptr->DCT_v_scaled_size) {
#ifdef IDCT_SCALING_SUPPORTED
    case ((1 << 8) + 1):
      method_ptr = jpeg_idct_1x1;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((2 << 8) + 2):
      method_ptr = jpeg_idct_2x2;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((3 << 8) + 3):
      method_ptr = jpeg_idct_3x3;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((4 << 8) + 4):
      method_ptr = jpeg_idct_4x4;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((5 << 8) + 5):
      method_ptr = jpeg_idct_5x5;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((6 << 8) + 6):
      method_ptr = jpeg_idct_6x6;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((7 << 8) + 7):
      method_ptr = jpeg_idct_7x7;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((9 << 8) + 9):
      method_ptr = jpeg_idct_9x9;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((10 << 8) + 10):
      method_ptr = jpeg_idct_10x10;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((11 << 8) + 11):
      method_ptr = jpeg_idct_11x11;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((12 << 8) + 12):
      method_ptr = jpeg_idct_12x12;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((13 << 8) + 13):
      method_ptr = jpeg_idct_13x13;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((14 << 8) + 14):
      method_ptr = jpeg_idct_14x14;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((15 << 8) + 15):
      method_ptr = jpeg_idct_15x15;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((16 << 8) + 16):
      method_ptr = jpeg_idct_16x16;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((16 << 8) + 8):
      method_ptr = jpeg_idct_16x8;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((14 << 8) + 7):
      method_ptr = jpeg_idct_14x7;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((12 << 8) + 6):
      method_ptr = jpeg_idct_12x6;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((10 << 8) + 5):
      method_ptr = jpeg_idct_10x5;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((8 << 8) + 4):
      method_ptr = jpeg_idct_8x4;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((6 << 8) + 3):
      method_ptr = jpeg_idct_6x3;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((4 << 8) + 2):
      method_ptr = jpeg_idct_4x2;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((2 << 8) + 1):
      method_ptr = jpeg_idct_2x1;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((8 << 8) + 16):
      method_ptr = jpeg_idct_8x16;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((7 << 8) + 14):
      method_ptr = jpeg_idct_7x14;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((6 << 8) + 12):
      method_ptr = jpeg_idct_6x12;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((5 << 8) + 10):
      method_ptr = jpeg_idct_5x10;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((4 << 8) + 8):
      method_ptr = jpeg_idct_4x8;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((3 << 8) + 6):
      method_ptr = jpeg_idct_3x6;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((2 << 8) + 4):
      method_ptr = jpeg_idct_2x4;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
    case ((1 << 8) + 2):
      method_ptr = jpeg_idct_1x2;
      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
      break;
#endif
    case ((DCTSIZE << 8) + DCTSIZE):
      switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
      case JDCT_ISLOW:
	method_ptr = jpeg_idct_islow;
	method = JDCT_ISLOW;
	break;
#endif
#ifdef DCT_IFAST_SUPPORTED
      case JDCT_IFAST:
	method_ptr = jpeg_idct_ifast;
	method = JDCT_IFAST;
	break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
      case JDCT_FLOAT:
	method_ptr = jpeg_idct_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;
    }
    idct->pub.inverse_DCT[ci] = method_ptr;
    /* Create multiplier table from quant table.
     * However, we can skip this if the component is uninteresting
     * or if we already built the table.  Also, if no quant table
     * has yet been saved for the component, we leave the
     * multiplier table all-zero; we'll be reading zeroes from the
     * coefficient controller's buffer anyway.
     */
    if (! compptr->component_needed || idct->cur_method[ci] == method)
      continue;
    qtbl = compptr->quant_table;
    if (qtbl == NULL)		/* happens if no data yet for component */
      continue;
    idct->cur_method[ci] = method;
    switch (method) {
#ifdef PROVIDE_ISLOW_TABLES
    case JDCT_ISLOW:
      {
	/* For LL&M IDCT method, multipliers are equal to raw quantization
	 * coefficients, but are stored as ints to ensure access efficiency.
	 */
	ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table;
	for (i = 0; i < DCTSIZE2; i++) {
	  ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
	}
      }
      break;
#endif