jfdctint.c

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    /* Even part */

    tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[3]);
    tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[2]);

    tmp10 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[3]);
    tmp11 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[2]);

    /* Apply unsigned->signed conversion */
    dataptr[0] = (DCTELEM)
      ((tmp0 + tmp1 - 4 * CENTERJSAMPLE) << (PASS1_BITS+2));
    dataptr[2] = (DCTELEM) ((tmp0 - tmp1) << (PASS1_BITS+2));

    /* Odd part */

    tmp0 = MULTIPLY(tmp10 + tmp11, FIX_0_541196100);       /* c6 */
    /* Add fudge factor here for final descale. */
    tmp0 += ONE << (CONST_BITS-PASS1_BITS-3);

    dataptr[1] = (DCTELEM)
      RIGHT_SHIFT(tmp0 + MULTIPLY(tmp10, FIX_0_765366865), /* c2-c6 */
		  CONST_BITS-PASS1_BITS-2);
    dataptr[3] = (DCTELEM)
      RIGHT_SHIFT(tmp0 - MULTIPLY(tmp11, FIX_1_847759065), /* c2+c6 */
		  CONST_BITS-PASS1_BITS-2);

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

  /* Pass 2: process columns.
   * We remove the PASS1_BITS scaling, but leave the results scaled up
   * by an overall factor of 8.
   */

  dataptr = data;
  for (ctr = 0; ctr < 4; ctr++) {
    /* Even part */

    /* Add fudge factor here for final descale. */
    tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*3] + (ONE << (PASS1_BITS-1));
    tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*2];

    tmp10 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*3];
    tmp11 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*2];

    dataptr[DCTSIZE*0] = (DCTELEM) RIGHT_SHIFT(tmp0 + tmp1, PASS1_BITS);
    dataptr[DCTSIZE*2] = (DCTELEM) RIGHT_SHIFT(tmp0 - tmp1, PASS1_BITS);

    /* Odd part */

    tmp0 = MULTIPLY(tmp10 + tmp11, FIX_0_541196100);       /* c6 */
    /* Add fudge factor here for final descale. */
    tmp0 += ONE << (CONST_BITS+PASS1_BITS-1);

    dataptr[DCTSIZE*1] = (DCTELEM)
      RIGHT_SHIFT(tmp0 + MULTIPLY(tmp10, FIX_0_765366865), /* c2-c6 */
		  CONST_BITS+PASS1_BITS);
    dataptr[DCTSIZE*3] = (DCTELEM)
      RIGHT_SHIFT(tmp0 - MULTIPLY(tmp11, FIX_1_847759065), /* c2+c6 */
		  CONST_BITS+PASS1_BITS);

    dataptr++;			/* advance pointer to next column */
  }
}


/*
 * Perform the forward DCT on a 3x3 sample block.
 */

GLOBAL(void)
jpeg_fdct_3x3 (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
{
  INT32 tmp0, tmp1, tmp2;
  DCTELEM *dataptr;
  JSAMPROW elemptr;
  int ctr;
  SHIFT_TEMPS

  /* Pre-zero output coefficient block. */
  MEMZERO(data, SIZEOF(DCTELEM) * DCTSIZE2);

  /* Pass 1: process rows. */
  /* Note results are scaled up by sqrt(8) compared to a true DCT; */
  /* furthermore, we scale the results by 2**PASS1_BITS. */
  /* We scale the results further by 2**2 as part of output adaption */
  /* scaling for different DCT size. */
  /* cK represents sqrt(2) * cos(K*pi/6). */

  dataptr = data;
  for (ctr = 0; ctr < 3; ctr++) {
    elemptr = sample_data[ctr] + start_col;

    /* Even part */

    tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[2]);
    tmp1 = GETJSAMPLE(elemptr[1]);

    tmp2 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[2]);

    /* Apply unsigned->signed conversion */
    dataptr[0] = (DCTELEM)
      ((tmp0 + tmp1 - 3 * CENTERJSAMPLE) << (PASS1_BITS+2));
    dataptr[2] = (DCTELEM)
      DESCALE(MULTIPLY(tmp0 - tmp1 - tmp1, FIX(0.707106781)), /* c2 */
	      CONST_BITS-PASS1_BITS-2);

    /* Odd part */

    dataptr[1] = (DCTELEM)
      DESCALE(MULTIPLY(tmp2, FIX(1.224744871)),               /* c1 */
	      CONST_BITS-PASS1_BITS-2);

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

  /* Pass 2: process columns.
   * We remove the PASS1_BITS scaling, but leave the results scaled up
   * by an overall factor of 8.
   * We must also scale the output by (8/3)**2 = 64/9, which we partially
   * fold into the constant multipliers (other part was done in pass 1):
   * cK now represents sqrt(2) * cos(K*pi/6) * 16/9.
   */

  dataptr = data;
  for (ctr = 0; ctr < 3; ctr++) {
    /* Even part */

    tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*2];
    tmp1 = dataptr[DCTSIZE*1];

    tmp2 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*2];

    dataptr[DCTSIZE*0] = (DCTELEM)
      DESCALE(MULTIPLY(tmp0 + tmp1, FIX(1.777777778)),        /* 16/9 */
	      CONST_BITS+PASS1_BITS);
    dataptr[DCTSIZE*2] = (DCTELEM)
      DESCALE(MULTIPLY(tmp0 - tmp1 - tmp1, FIX(1.257078722)), /* c2 */
	      CONST_BITS+PASS1_BITS);

    /* Odd part */

    dataptr[DCTSIZE*1] = (DCTELEM)
      DESCALE(MULTIPLY(tmp2, FIX(2.177324216)),               /* c1 */
	      CONST_BITS+PASS1_BITS);

    dataptr++;			/* advance pointer to next column */
  }
}


/*
 * Perform the forward DCT on a 2x2 sample block.
 */

GLOBAL(void)
jpeg_fdct_2x2 (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
{
  INT32 tmp0, tmp1, tmp2, tmp3;
  JSAMPROW elemptr;

  /* Pre-zero output coefficient block. */
  MEMZERO(data, SIZEOF(DCTELEM) * DCTSIZE2);

  /* Pass 1: process rows. */
  /* Note results are scaled up by sqrt(8) compared to a true DCT. */

  /* Row 0 */
  elemptr = sample_data[0] + start_col;

  tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[1]);
  tmp1 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[1]);

  /* Row 1 */
  elemptr = sample_data[1] + start_col;

  tmp2 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[1]);
  tmp3 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[1]);

  /* Pass 2: process columns.
   * We leave the results scaled up by an overall factor of 8.
   * We must also scale the output by (8/2)**2 = 2**4.
   */

  /* Column 0 */
  /* Apply unsigned->signed conversion */
  data[DCTSIZE*0] = (DCTELEM) ((tmp0 + tmp2 - 4 * CENTERJSAMPLE) << 4);
  data[DCTSIZE*1] = (DCTELEM) ((tmp0 - tmp2) << 4);

  /* Column 1 */
  data[DCTSIZE*0+1] = (DCTELEM) ((tmp1 + tmp3) << 4);
  data[DCTSIZE*1+1] = (DCTELEM) ((tmp1 - tmp3) << 4);
}


/*
 * Perform the forward DCT on a 1x1 sample block.
 */

GLOBAL(void)
jpeg_fdct_1x1 (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
{
  /* Pre-zero output coefficient block. */
  MEMZERO(data, SIZEOF(DCTELEM) * DCTSIZE2);

  /* We leave the result scaled up by an overall factor of 8. */
  /* We must also scale the output by (8/1)**2 = 2**6. */
  /* Apply unsigned->signed conversion */
  data[0] = (DCTELEM)
    ((GETJSAMPLE(sample_data[0][start_col]) - CENTERJSAMPLE) << 6);
}


/*
 * Perform the forward DCT on a 9x9 sample block.
 */

GLOBAL(void)
jpeg_fdct_9x9 (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
{
  INT32 tmp0, tmp1, tmp2, tmp3, tmp4;
  INT32 tmp10, tmp11, tmp12, tmp13;
  INT32 z1, z2;
  DCTELEM workspace[8];
  DCTELEM *dataptr;
  DCTELEM *wsptr;
  JSAMPROW elemptr;
  int ctr;
  SHIFT_TEMPS

  /* Pass 1: process rows. */
  /* Note results are scaled up by sqrt(8) compared to a true DCT; */
  /* we scale the results further by 2 as part of output adaption */
  /* scaling for different DCT size. */
  /* cK represents sqrt(2) * cos(K*pi/18). */

  dataptr = data;
  ctr = 0;
  for (;;) {
    elemptr = sample_data[ctr] + start_col;

    /* Even part */

    tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[8]);
    tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[7]);
    tmp2 = GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[6]);
    tmp3 = GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[5]);
    tmp4 = GETJSAMPLE(elemptr[4]);

    tmp10 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[8]);
    tmp11 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[7]);
    tmp12 = GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[6]);
    tmp13 = GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[5]);

    z1 = tmp0 + tmp2 + tmp3;
    z2 = tmp1 + tmp4;
    /* Apply unsigned->signed conversion */
    dataptr[0] = (DCTELEM) ((z1 + z2 - 9 * CENTERJSAMPLE) << 1);
    dataptr[6] = (DCTELEM)
      DESCALE(MULTIPLY(z1 - z2 - z2, FIX(0.707106781)),  /* c6 */
	      CONST_BITS-1);
    z1 = MULTIPLY(tmp0 - tmp2, FIX(1.328926049));        /* c2 */
    z2 = MULTIPLY(tmp1 - tmp4 - tmp4, FIX(0.707106781)); /* c6 */
    dataptr[2] = (DCTELEM)
      DESCALE(MULTIPLY(tmp2 - tmp3, FIX(1.083350441))    /* c4 */
	      + z1 + z2, CONST_BITS-1);
    dataptr[4] = (DCTELEM)
      DESCALE(MULTIPLY(tmp3 - tmp0, FIX(0.245575608))    /* c8 */
	      + z1 - z2, CONST_BITS-1);

    /* Odd part */

    dataptr[3] = (DCTELEM)
      DESCALE(MULTIPLY(tmp10 - tmp12 - tmp13, FIX(1.224744871)), /* c3 */
	      CONST_BITS-1);

    tmp11 = MULTIPLY(tmp11, FIX(1.224744871));        /* c3 */
    tmp0 = MULTIPLY(tmp10 + tmp12, FIX(0.909038955)); /* c5 */
    tmp1 = MULTIPLY(tmp10 + tmp13, FIX(0.483689525)); /* c7 */

    dataptr[1] = (DCTELEM) DESCALE(tmp11 + tmp0 + tmp1, CONST_BITS-1);

    tmp2 = MULTIPLY(tmp12 - tmp13, FIX(1.392728481)); /* c1 */

    dataptr[5] = (DCTELEM) DESCALE(tmp0 - tmp11 - tmp2, CONST_BITS-1);
    dataptr[7] = (DCTELEM) DESCALE(tmp1 - tmp11 + tmp2, CONST_BITS-1);

    ctr++;

    if (ctr != DCTSIZE) {
      if (ctr == 9)
	break;			/* Done. */
      dataptr += DCTSIZE;	/* advance pointer to next row */
    } else
      dataptr = workspace;	/* switch pointer to extended workspace */
  }

  /* Pass 2: process columns.
   * We leave the results scaled up by an overall factor of 8.
   * We must also scale the output by (8/9)**2 = 64/81, which we partially
   * fold into the constant multipliers and final/initial shifting:
   * cK now represents sqrt(2) * cos(K*pi/18) * 128/81.
   */

  dataptr = data;
  wsptr = workspace;
  for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
    /* Even part */

    tmp0 = dataptr[DCTSIZE*0] + wsptr[DCTSIZE*0];
    tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*7];
    tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*6];
    tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*5];
    tmp4 = dataptr[DCTSIZE*4];

    tmp10 = dataptr[DCTSIZE*0] - wsptr[DCTSIZE*0];
    tmp11 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*7];
    tmp12 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*6];
    tmp13 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*5];

    z1 = tmp0 + tmp2 + tmp3;
    z2 = tmp1 + tmp4;
    dataptr[DCTSIZE*0] = (DCTELEM)
      DESCALE(MULTIPLY(z1 + z2, FIX(1.580246914)),       /* 128/81 */
	      CONST_BITS+2);
    dataptr[DCTSIZE*6] = (DCTELEM)
      DESCALE(MULTIPLY(z1 - z2 - z2, FIX(1.117403309)),  /* c6 */
	      CONST_BITS+2);
    z1 = MULTIPLY(tmp0 - tmp2, FIX(2.100031287));        /* c2 */
    z2 = MULTIPLY(tmp1 - tmp4 - tmp4, FIX(1.117403309)); /* c6 */
    dataptr[DCTSIZE*2] = (DCTELEM)
      DESCALE(MULTIPLY(tmp2 - tmp3, FIX(1.711961190))    /* c4 */
	      + z1 + z2, CONST_BITS+2);
    dataptr[DCTSIZE*4] = (DCTELEM)
      DESCALE(MULTIPLY(tmp3 - tmp0, FIX(0.388070096))    /* c8 */
	      + z1 - z2, CONST_BITS+2);

    /* Odd part */

    dataptr[DCTSIZE*3] = (DCTELEM)
      DESCALE(MULTIPLY(tmp10 - tmp12 - tmp13, FIX(1.935399303)), /* c3 */
	      CONST_BITS+2);

    tmp11 = MULTIPLY(tmp11, FIX(1.935399303));        /* c3 */
    tmp0 = MULTIPLY(tmp10 + tmp12, FIX(1.436506004)); /* c5 */
    tmp1 = MULTIPLY(tmp10 + tmp13, FIX(0.764348879)); /* c7 */

    dataptr[DCTSIZE*1] = (DCTELEM)
      DESCALE(tmp11 + tmp0 + tmp1, CONST_BITS+2);

    tmp2 = MULTIPLY(tmp12 - tmp13, FIX(2.200854883)); /* c1 */