src/jpeg/jidctred.c

/*
 * jidctred.c
 *
 * Copyright (C) 1994-1998, 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 inverse-DCT routines that produce reduced-size output:
 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
 *
 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
 * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
 * with an 8-to-4 step that produces the four averages of two adjacent outputs
 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
 * These steps were derived by computing the corresponding values at the end
 * of the normal LL&M code, then simplifying as much as possible.
 *
 * 1x1 is trivial: just take the DC coefficient divided by 8.
 *
 * See jidctint.c for additional comments.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"		/* Private declarations for DCT subsystem */

#ifdef IDCT_SCALING_SUPPORTED


/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#if DCTSIZE != 8
  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
#endif


/* Scaling is the same as in jidctint.c. */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  13
#define PASS1_BITS  2
#else
#define CONST_BITS  13
#define PASS1_BITS  1		/* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 13
#define FIX_0_211164243  ((JPEG_INT32)  1730)	/* FIX(0.211164243) */
#define FIX_0_509795579  ((JPEG_INT32)  4176)	/* FIX(0.509795579) */
#define FIX_0_601344887  ((JPEG_INT32)  4926)	/* FIX(0.601344887) */
#define FIX_0_720959822  ((JPEG_INT32)  5906)	/* FIX(0.720959822) */
#define FIX_0_765366865  ((JPEG_INT32)  6270)	/* FIX(0.765366865) */
#define FIX_0_850430095  ((JPEG_INT32)  6967)	/* FIX(0.850430095) */
#define FIX_0_899976223  ((JPEG_INT32)  7373)	/* FIX(0.899976223) */
#define FIX_1_061594337  ((JPEG_INT32)  8697)	/* FIX(1.061594337) */
#define FIX_1_272758580  ((JPEG_INT32)  10426)	/* FIX(1.272758580) */
#define FIX_1_451774981  ((JPEG_INT32)  11893)	/* FIX(1.451774981) */
#define FIX_1_847759065  ((JPEG_INT32)  15137)	/* FIX(1.847759065) */
#define FIX_2_172734803  ((JPEG_INT32)  17799)	/* FIX(2.172734803) */
#define FIX_2_562915447  ((JPEG_INT32)  20995)	/* FIX(2.562915447) */
#define FIX_3_624509785  ((JPEG_INT32)  29692)	/* FIX(3.624509785) */
#else
#define FIX_0_211164243  FIX(0.211164243)
#define FIX_0_509795579  FIX(0.509795579)
#define FIX_0_601344887  FIX(0.601344887)
#define FIX_0_720959822  FIX(0.720959822)
#define FIX_0_765366865  FIX(0.765366865)
#define FIX_0_850430095  FIX(0.850430095)
#define FIX_0_899976223  FIX(0.899976223)
#define FIX_1_061594337  FIX(1.061594337)
#define FIX_1_272758580  FIX(1.272758580)
#define FIX_1_451774981  FIX(1.451774981)
#define FIX_1_847759065  FIX(1.847759065)
#define FIX_2_172734803  FIX(2.172734803)
#define FIX_2_562915447  FIX(2.562915447)
#define FIX_3_624509785  FIX(3.624509785)
#endif


/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */

#if BITS_IN_JSAMPLE == 8
#define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
#else
#define MULTIPLY(var,const)  ((var) * (const))
#endif


/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */

#define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 4x4 output block.
 */

GLOBAL(void)
jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	       JCOEFPTR coef_block,
	       JSAMPARRAY output_buf, JDIMENSION output_col)
{
  JPEG_INT32 tmp0, tmp2, tmp10, tmp12;
  JPEG_INT32 z1, z2, z3, z4;
  JCOEFPTR inptr;
  ISLOW_MULT_TYPE * quantptr;
  int * wsptr;
  JSAMPROW outptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  int ctr;
  int workspace[DCTSIZE*4];	/* buffers data between passes */
  SHIFT_TEMPS

  /* Pass 1: process columns from input, store into work array. */

  inptr = coef_block;
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  wsptr = workspace;
  for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
    /* Don't bother to process column 4, because second pass won't use it */
    if (ctr == DCTSIZE-4)
      continue;
    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
	inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
      /* AC terms all zero; we need not examine term 4 for 4x4 output */
      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;

      wsptr[DCTSIZE*0] = dcval;
      wsptr[DCTSIZE*1] = dcval;
      wsptr[DCTSIZE*2] = dcval;
      wsptr[DCTSIZE*3] = dcval;

      continue;
    }

    /* Even part */

    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
    tmp0 <<= (CONST_BITS+1);

    z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
    z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);

    tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);

    tmp10 = tmp0 + tmp2;
    tmp12 = tmp0 - tmp2;

    /* Odd part */

    z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
    z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
    z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
    z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);

    tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
	 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
	 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
	 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

    tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
	 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
	 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
	 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

    /* Final output stage */

    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
    wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
    wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
    wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
  }

  /* Pass 2: process 4 rows from work array, store into output array. */

  wsptr = workspace;
  for (ctr = 0; ctr < 4; ctr++) {
    outptr = output_buf[ctr] + output_col;
    /* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
      /* AC terms all zero */
      JSAMPLE dcval = range_limit[(int) DESCALE((JPEG_INT32) wsptr[0], PASS1_BITS+3)
				  & RANGE_MASK];

      outptr[0] = dcval;
      outptr[1] = dcval;
      outptr[2] = dcval;
      outptr[3] = dcval;

      wsptr += DCTSIZE;		/* advance pointer to next row */
      continue;
    }
#endif

    /* Even part */

    tmp0 = ((JPEG_INT32) wsptr[0]) << (CONST_BITS+1);

    tmp2 = MULTIPLY((JPEG_INT32) wsptr[2], FIX_1_847759065)
	 + MULTIPLY((JPEG_INT32) wsptr[6], - FIX_0_765366865);

    tmp10 = tmp0 + tmp2;
    tmp12 = tmp0 - tmp2;

    /* Odd part */

    z1 = (JPEG_INT32) wsptr[7];
    z2 = (JPEG_INT32) wsptr[5];
    z3 = (JPEG_INT32) wsptr[3];
    z4 = (JPEG_INT32) wsptr[1];

    tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
	 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
	 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
	 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

    tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
	 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
	 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
	 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

    /* Final output stage */

    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
					  CONST_BITS+PASS1_BITS+3+1)
			    & RANGE_MASK];
    outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
					  CONST_BITS+PASS1_BITS+3+1)
			    & RANGE_MASK];
    outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
					  CONST_BITS+PASS1_BITS+3+1)
			    & RANGE_MASK];
    outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
					  CONST_BITS+PASS1_BITS+3+1)
			    & RANGE_MASK];

    wsptr += DCTSIZE;		/* advance pointer to next row */
  }
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 2x2 output block.
 */

GLOBAL(void)
jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	       JCOEFPTR coef_block,
	       JSAMPARRAY output_buf, JDIMENSION output_col)
{
  JPEG_INT32 tmp0, tmp10, z1;
  JCOEFPTR inptr;
  ISLOW_MULT_TYPE * quantptr;
  int * wsptr;
  JSAMPROW outptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  int ctr;
  int workspace[DCTSIZE*2];	/* buffers data between passes */
  SHIFT_TEMPS

  /* Pass 1: process columns from input, store into work array. */

  inptr = coef_block;
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  wsptr = workspace;
  for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
    /* Don't bother to process columns 2,4,6 */
    if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
      continue;
    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
      /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;

      wsptr[DCTSIZE*0] = dcval;
      wsptr[DCTSIZE*1] = dcval;

      continue;
    }

    /* Even part */

    z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
    tmp10 = z1 << (CONST_BITS+2);

    /* Odd part */

    z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
    tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
    z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
    tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
    z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
    tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
    z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
    tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

    /* Final output stage */

    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
    wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
  }

  /* Pass 2: process 2 rows from work array, store into output array. */

  wsptr = workspace;
  for (ctr = 0; ctr < 2; ctr++) {
    outptr = output_buf[ctr] + output_col;
    /* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
    if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
      /* AC terms all zero */
      JSAMPLE dcval = range_limit[(int) DESCALE((JPEG_INT32) wsptr[0], PASS1_BITS+3)
				  & RANGE_MASK];

      outptr[0] = dcval;
      outptr[1] = dcval;

      wsptr += DCTSIZE;		/* advance pointer to next row */
      continue;
    }
#endif

    /* Even part */

    tmp10 = ((JPEG_INT32) wsptr[0]) << (CONST_BITS+2);

    /* Odd part */

    tmp0 = MULTIPLY((JPEG_INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
	 + MULTIPLY((JPEG_INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
	 + MULTIPLY((JPEG_INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
	 + MULTIPLY((JPEG_INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

    /* Final output stage */

    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
					  CONST_BITS+PASS1_BITS+3+2)
			    & RANGE_MASK];
    outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
					  CONST_BITS+PASS1_BITS+3+2)
			    & RANGE_MASK];

    wsptr += DCTSIZE;		/* advance pointer to next row */
  }
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 1x1 output block.
 */

GLOBAL(void)
jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	       JCOEFPTR coef_block,
	       JSAMPARRAY output_buf, JDIMENSION output_col)
{
  int dcval;
  ISLOW_MULT_TYPE * quantptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  SHIFT_TEMPS

  /* We hardly need an inverse DCT routine for this: just take the
   * average pixel value, which is one-eighth of the DC coefficient.
   */
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
  dcval = (int) DESCALE((JPEG_INT32) dcval, 3);

  output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}

#endif /* IDCT_SCALING_SUPPORTED */
Commit	Line	Data
	1	/*
	2	* jidctred.c
	3	*
	4	* Copyright (C) 1994-1998, Thomas G. Lane.
	5	* This file is part of the Independent JPEG Group's software.
	6	* For conditions of distribution and use, see the accompanying README file.
	7	*
	8	* This file contains inverse-DCT routines that produce reduced-size output:
	9	* either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
	10	*
	11	* The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
	12	* algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step
	13	* with an 8-to-4 step that produces the four averages of two adjacent outputs
	14	* (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
	15	* These steps were derived by computing the corresponding values at the end
	16	* of the normal LL&M code, then simplifying as much as possible.
	17	*
	18	* 1x1 is trivial: just take the DC coefficient divided by 8.
	19	*
	20	* See jidctint.c for additional comments.
	21	*/
	22
	23	#define JPEG_INTERNALS
	24	#include "jinclude.h"
	25	#include "jpeglib.h"
	26	#include "jdct.h" /* Private declarations for DCT subsystem */
	27
	28	#ifdef IDCT_SCALING_SUPPORTED
	29
	30
	31	/*
	32	* This module is specialized to the case DCTSIZE = 8.
	33	*/
	34
	35	#if DCTSIZE != 8
	36	Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
	37	#endif
	38
	39
	40	/* Scaling is the same as in jidctint.c. */
	41
	42	#if BITS_IN_JSAMPLE == 8
	43	#define CONST_BITS 13
	44	#define PASS1_BITS 2
	45	#else
	46	#define CONST_BITS 13
	47	#define PASS1_BITS 1 /* lose a little precision to avoid overflow */
	48	#endif
	49
	50	/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
	51	* causing a lot of useless floating-point operations at run time.
	52	* To get around this we use the following pre-calculated constants.
	53	* If you change CONST_BITS you may want to add appropriate values.
	54	* (With a reasonable C compiler, you can just rely on the FIX() macro...)
	55	*/
	56
	57	#if CONST_BITS == 13
	58	#define FIX_0_211164243 ((JPEG_INT32) 1730) /* FIX(0.211164243) */
	59	#define FIX_0_509795579 ((JPEG_INT32) 4176) /* FIX(0.509795579) */
	60	#define FIX_0_601344887 ((JPEG_INT32) 4926) /* FIX(0.601344887) */
	61	#define FIX_0_720959822 ((JPEG_INT32) 5906) /* FIX(0.720959822) */
	62	#define FIX_0_765366865 ((JPEG_INT32) 6270) /* FIX(0.765366865) */
	63	#define FIX_0_850430095 ((JPEG_INT32) 6967) /* FIX(0.850430095) */
	64	#define FIX_0_899976223 ((JPEG_INT32) 7373) /* FIX(0.899976223) */
	65	#define FIX_1_061594337 ((JPEG_INT32) 8697) /* FIX(1.061594337) */
	66	#define FIX_1_272758580 ((JPEG_INT32) 10426) /* FIX(1.272758580) */
	67	#define FIX_1_451774981 ((JPEG_INT32) 11893) /* FIX(1.451774981) */
	68	#define FIX_1_847759065 ((JPEG_INT32) 15137) /* FIX(1.847759065) */
	69	#define FIX_2_172734803 ((JPEG_INT32) 17799) /* FIX(2.172734803) */
	70	#define FIX_2_562915447 ((JPEG_INT32) 20995) /* FIX(2.562915447) */
	71	#define FIX_3_624509785 ((JPEG_INT32) 29692) /* FIX(3.624509785) */
	72	#else
	73	#define FIX_0_211164243 FIX(0.211164243)
	74	#define FIX_0_509795579 FIX(0.509795579)
	75	#define FIX_0_601344887 FIX(0.601344887)
	76	#define FIX_0_720959822 FIX(0.720959822)
	77	#define FIX_0_765366865 FIX(0.765366865)
	78	#define FIX_0_850430095 FIX(0.850430095)
	79	#define FIX_0_899976223 FIX(0.899976223)
	80	#define FIX_1_061594337 FIX(1.061594337)
	81	#define FIX_1_272758580 FIX(1.272758580)
	82	#define FIX_1_451774981 FIX(1.451774981)
	83	#define FIX_1_847759065 FIX(1.847759065)
	84	#define FIX_2_172734803 FIX(2.172734803)
	85	#define FIX_2_562915447 FIX(2.562915447)
	86	#define FIX_3_624509785 FIX(3.624509785)
	87	#endif
	88
	89
	90	/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
	91	* For 8-bit samples with the recommended scaling, all the variable
	92	* and constant values involved are no more than 16 bits wide, so a
	93	* 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
	94	* For 12-bit samples, a full 32-bit multiplication will be needed.
	95	*/
	96
	97	#if BITS_IN_JSAMPLE == 8
	98	#define MULTIPLY(var,const) MULTIPLY16C16(var,const)
	99	#else
	100	#define MULTIPLY(var,const) ((var) * (const))
	101	#endif
	102
	103
	104	/* Dequantize a coefficient by multiplying it by the multiplier-table
	105	* entry; produce an int result. In this module, both inputs and result
	106	* are 16 bits or less, so either int or short multiply will work.
	107	*/
	108
	109	#define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))
	110
	111
	112	/*
	113	* Perform dequantization and inverse DCT on one block of coefficients,
	114	* producing a reduced-size 4x4 output block.
	115	*/
	116
	117	GLOBAL(void)
	118	jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	119	JCOEFPTR coef_block,
	120	JSAMPARRAY output_buf, JDIMENSION output_col)
	121	{
	122	JPEG_INT32 tmp0, tmp2, tmp10, tmp12;
	123	JPEG_INT32 z1, z2, z3, z4;
	124	JCOEFPTR inptr;
	125	ISLOW_MULT_TYPE * quantptr;
	126	int * wsptr;
	127	JSAMPROW outptr;
	128	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	129	int ctr;
	130	int workspace[DCTSIZE4]; / buffers data between passes */
	131	SHIFT_TEMPS
	132
	133	/* Pass 1: process columns from input, store into work array. */
	134
	135	inptr = coef_block;
	136	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	137	wsptr = workspace;
	138	for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
	139	/* Don't bother to process column 4, because second pass won't use it */
	140	if (ctr == DCTSIZE-4)
	141	continue;
	142	if (inptr[DCTSIZE1] == 0 && inptr[DCTSIZE2] == 0 &&
	143	inptr[DCTSIZE3] == 0 && inptr[DCTSIZE5] == 0 &&
	144	inptr[DCTSIZE6] == 0 && inptr[DCTSIZE7] == 0) {
	145	/* AC terms all zero; we need not examine term 4 for 4x4 output */
	146	int dcval = DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]) << PASS1_BITS;
	147
	148	wsptr[DCTSIZE*0] = dcval;
	149	wsptr[DCTSIZE*1] = dcval;
	150	wsptr[DCTSIZE*2] = dcval;
	151	wsptr[DCTSIZE*3] = dcval;
	152
	153	continue;
	154	}
	155
	156	/* Even part */
	157
	158	tmp0 = DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]);
	159	tmp0 <<= (CONST_BITS+1);
	160
	161	z2 = DEQUANTIZE(inptr[DCTSIZE2], quantptr[DCTSIZE2]);
	162	z3 = DEQUANTIZE(inptr[DCTSIZE6], quantptr[DCTSIZE6]);
	163
	164	tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
	165
	166	tmp10 = tmp0 + tmp2;
	167	tmp12 = tmp0 - tmp2;
	168
	169	/* Odd part */
	170
	171	z1 = DEQUANTIZE(inptr[DCTSIZE7], quantptr[DCTSIZE7]);
	172	z2 = DEQUANTIZE(inptr[DCTSIZE5], quantptr[DCTSIZE5]);
	173	z3 = DEQUANTIZE(inptr[DCTSIZE3], quantptr[DCTSIZE3]);
	174	z4 = DEQUANTIZE(inptr[DCTSIZE1], quantptr[DCTSIZE1]);
	175
	176	tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
	177	+ MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
	178	+ MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
	179	+ MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
	180
	181	tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
	182	+ MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
	183	+ MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
	184	+ MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
	185
	186	/* Final output stage */
	187
	188	wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
	189	wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
	190	wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
	191	wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
	192	}
	193
	194	/* Pass 2: process 4 rows from work array, store into output array. */
	195
	196	wsptr = workspace;
	197	for (ctr = 0; ctr < 4; ctr++) {
	198	outptr = output_buf[ctr] + output_col;
	199	/* It's not clear whether a zero row test is worthwhile here ... */
	200
	201	#ifndef NO_ZERO_ROW_TEST
	202	if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
	203	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
	204	/* AC terms all zero */
	205	JSAMPLE dcval = range_limit[(int) DESCALE((JPEG_INT32) wsptr[0], PASS1_BITS+3)
	206	& RANGE_MASK];
	207
	208	outptr[0] = dcval;
	209	outptr[1] = dcval;
	210	outptr[2] = dcval;
	211	outptr[3] = dcval;
	212
	213	wsptr += DCTSIZE; /* advance pointer to next row */
	214	continue;
	215	}
	216	#endif
	217
	218	/* Even part */
	219
	220	tmp0 = ((JPEG_INT32) wsptr[0]) << (CONST_BITS+1);
	221
	222	tmp2 = MULTIPLY((JPEG_INT32) wsptr[2], FIX_1_847759065)
	223	+ MULTIPLY((JPEG_INT32) wsptr[6], - FIX_0_765366865);
	224
	225	tmp10 = tmp0 + tmp2;
	226	tmp12 = tmp0 - tmp2;
	227
	228	/* Odd part */
	229
	230	z1 = (JPEG_INT32) wsptr[7];
	231	z2 = (JPEG_INT32) wsptr[5];
	232	z3 = (JPEG_INT32) wsptr[3];
	233	z4 = (JPEG_INT32) wsptr[1];
	234
	235	tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
	236	+ MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
	237	+ MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
	238	+ MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
	239
	240	tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
	241	+ MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
	242	+ MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
	243	+ MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
	244
	245	/* Final output stage */
	246
	247	outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
	248	CONST_BITS+PASS1_BITS+3+1)
	249	& RANGE_MASK];
	250	outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
	251	CONST_BITS+PASS1_BITS+3+1)
	252	& RANGE_MASK];
	253	outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
	254	CONST_BITS+PASS1_BITS+3+1)
	255	& RANGE_MASK];
	256	outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
	257	CONST_BITS+PASS1_BITS+3+1)
	258	& RANGE_MASK];
	259
	260	wsptr += DCTSIZE; /* advance pointer to next row */
	261	}
	262	}
	263
	264
	265	/*
	266	* Perform dequantization and inverse DCT on one block of coefficients,
	267	* producing a reduced-size 2x2 output block.
	268	*/
	269
	270	GLOBAL(void)
	271	jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	272	JCOEFPTR coef_block,
	273	JSAMPARRAY output_buf, JDIMENSION output_col)
	274	{
	275	JPEG_INT32 tmp0, tmp10, z1;
	276	JCOEFPTR inptr;
	277	ISLOW_MULT_TYPE * quantptr;
	278	int * wsptr;
	279	JSAMPROW outptr;
	280	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	281	int ctr;
	282	int workspace[DCTSIZE2]; / buffers data between passes */
	283	SHIFT_TEMPS
	284
	285	/* Pass 1: process columns from input, store into work array. */
	286
	287	inptr = coef_block;
	288	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	289	wsptr = workspace;
	290	for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
	291	/* Don't bother to process columns 2,4,6 */
	292	if (ctr == DCTSIZE-2 \|\| ctr == DCTSIZE-4 \|\| ctr == DCTSIZE-6)
	293	continue;
	294	if (inptr[DCTSIZE1] == 0 && inptr[DCTSIZE3] == 0 &&
	295	inptr[DCTSIZE5] == 0 && inptr[DCTSIZE7] == 0) {
	296	/* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
	297	int dcval = DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]) << PASS1_BITS;
	298
	299	wsptr[DCTSIZE*0] = dcval;
	300	wsptr[DCTSIZE*1] = dcval;
	301
	302	continue;
	303	}
	304
	305	/* Even part */
	306
	307	z1 = DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]);
	308	tmp10 = z1 << (CONST_BITS+2);
	309
	310	/* Odd part */
	311
	312	z1 = DEQUANTIZE(inptr[DCTSIZE7], quantptr[DCTSIZE7]);
	313	tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
	314	z1 = DEQUANTIZE(inptr[DCTSIZE5], quantptr[DCTSIZE5]);
	315	tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
	316	z1 = DEQUANTIZE(inptr[DCTSIZE3], quantptr[DCTSIZE3]);
	317	tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
	318	z1 = DEQUANTIZE(inptr[DCTSIZE1], quantptr[DCTSIZE1]);
	319	tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
	320
	321	/* Final output stage */
	322
	323	wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
	324	wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
	325	}
	326
	327	/* Pass 2: process 2 rows from work array, store into output array. */
	328
	329	wsptr = workspace;
	330	for (ctr = 0; ctr < 2; ctr++) {
	331	outptr = output_buf[ctr] + output_col;
	332	/* It's not clear whether a zero row test is worthwhile here ... */
	333
	334	#ifndef NO_ZERO_ROW_TEST
	335	if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
	336	/* AC terms all zero */
	337	JSAMPLE dcval = range_limit[(int) DESCALE((JPEG_INT32) wsptr[0], PASS1_BITS+3)
	338	& RANGE_MASK];
	339
	340	outptr[0] = dcval;
	341	outptr[1] = dcval;
	342
	343	wsptr += DCTSIZE; /* advance pointer to next row */
	344	continue;
	345	}
	346	#endif
	347
	348	/* Even part */
	349
	350	tmp10 = ((JPEG_INT32) wsptr[0]) << (CONST_BITS+2);
	351
	352	/* Odd part */
	353
	354	tmp0 = MULTIPLY((JPEG_INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
	355	+ MULTIPLY((JPEG_INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
	356	+ MULTIPLY((JPEG_INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
	357	+ MULTIPLY((JPEG_INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
	358
	359	/* Final output stage */
	360
	361	outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
	362	CONST_BITS+PASS1_BITS+3+2)
	363	& RANGE_MASK];
	364	outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
	365	CONST_BITS+PASS1_BITS+3+2)
	366	& RANGE_MASK];
	367
	368	wsptr += DCTSIZE; /* advance pointer to next row */
	369	}
	370	}
	371
	372
	373	/*
	374	* Perform dequantization and inverse DCT on one block of coefficients,
	375	* producing a reduced-size 1x1 output block.
	376	*/
	377
	378	GLOBAL(void)
	379	jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	380	JCOEFPTR coef_block,
	381	JSAMPARRAY output_buf, JDIMENSION output_col)
	382	{
	383	int dcval;
	384	ISLOW_MULT_TYPE * quantptr;
	385	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	386	SHIFT_TEMPS
	387
	388	/* We hardly need an inverse DCT routine for this: just take the
	389	* average pixel value, which is one-eighth of the DC coefficient.
	390	*/
	391	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	392	dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
	393	dcval = (int) DESCALE((JPEG_INT32) dcval, 3);
	394
	395	output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
	396	}
	397
	398	#endif /* IDCT_SCALING_SUPPORTED */