jcdctmgr.c | searchcode

/JuceLibraryCode/modules/juce_graphics/image_formats/jpglib/jcdctmgr.c

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/*

 * 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((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;

    }

  }

}





/*

 * 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

  }

}