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plt-scheme  4.2.1
Defines | Functions
jfdctint.c File Reference
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"

Go to the source code of this file.

Defines

#define JPEG_INTERNALS
#define CONST_BITS   13
#define PASS1_BITS   2
#define FIX_0_298631336   ((INT32) 2446) /* FIX(0.298631336) */
#define FIX_0_390180644   ((INT32) 3196) /* FIX(0.390180644) */
#define FIX_0_541196100   ((INT32) 4433) /* FIX(0.541196100) */
#define FIX_0_765366865   ((INT32) 6270) /* FIX(0.765366865) */
#define FIX_0_899976223   ((INT32) 7373) /* FIX(0.899976223) */
#define FIX_1_175875602   ((INT32) 9633) /* FIX(1.175875602) */
#define FIX_1_501321110   ((INT32) 12299) /* FIX(1.501321110) */
#define FIX_1_847759065   ((INT32) 15137) /* FIX(1.847759065) */
#define FIX_1_961570560   ((INT32) 16069) /* FIX(1.961570560) */
#define FIX_2_053119869   ((INT32) 16819) /* FIX(2.053119869) */
#define FIX_2_562915447   ((INT32) 20995) /* FIX(2.562915447) */
#define FIX_3_072711026   ((INT32) 25172) /* FIX(3.072711026) */
#define MULTIPLY(var, const)   MULTIPLY16C16(var,const)

Functions

 jpeg_fdct_islow (DCTELEM *data)

Define Documentation

#define CONST_BITS   13

Definition at line 78 of file jfdctint.c.

#define FIX_0_298631336   ((INT32) 2446) /* FIX(0.298631336) */

Definition at line 93 of file jfdctint.c.

#define FIX_0_390180644   ((INT32) 3196) /* FIX(0.390180644) */

Definition at line 94 of file jfdctint.c.

#define FIX_0_541196100   ((INT32) 4433) /* FIX(0.541196100) */

Definition at line 95 of file jfdctint.c.

#define FIX_0_765366865   ((INT32) 6270) /* FIX(0.765366865) */

Definition at line 96 of file jfdctint.c.

#define FIX_0_899976223   ((INT32) 7373) /* FIX(0.899976223) */

Definition at line 97 of file jfdctint.c.

#define FIX_1_175875602   ((INT32) 9633) /* FIX(1.175875602) */

Definition at line 98 of file jfdctint.c.

#define FIX_1_501321110   ((INT32) 12299) /* FIX(1.501321110) */

Definition at line 99 of file jfdctint.c.

#define FIX_1_847759065   ((INT32) 15137) /* FIX(1.847759065) */

Definition at line 100 of file jfdctint.c.

#define FIX_1_961570560   ((INT32) 16069) /* FIX(1.961570560) */

Definition at line 101 of file jfdctint.c.

#define FIX_2_053119869   ((INT32) 16819) /* FIX(2.053119869) */

Definition at line 102 of file jfdctint.c.

#define FIX_2_562915447   ((INT32) 20995) /* FIX(2.562915447) */

Definition at line 103 of file jfdctint.c.

#define FIX_3_072711026   ((INT32) 25172) /* FIX(3.072711026) */

Definition at line 104 of file jfdctint.c.

#define JPEG_INTERNALS

Definition at line 26 of file jfdctint.c.

#define MULTIPLY (   var,
  const 
)    MULTIPLY16C16(var,const)

Definition at line 129 of file jfdctint.c.

#define PASS1_BITS   2

Definition at line 79 of file jfdctint.c.


Function Documentation

jpeg_fdct_islow ( DCTELEM data)

Definition at line 140 of file jfdctint.c.

{
  INT32 tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
  INT32 tmp10, tmp11, tmp12, tmp13;
  INT32 z1, z2, z3, z4, z5;
  DCTELEM *dataptr;
  int ctr;
  SHIFT_TEMPS

  /* 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. */

  dataptr = data;
  for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
    tmp0 = dataptr[0] + dataptr[7];
    tmp7 = dataptr[0] - dataptr[7];
    tmp1 = dataptr[1] + dataptr[6];
    tmp6 = dataptr[1] - dataptr[6];
    tmp2 = dataptr[2] + dataptr[5];
    tmp5 = dataptr[2] - dataptr[5];
    tmp3 = dataptr[3] + dataptr[4];
    tmp4 = dataptr[3] - dataptr[4];
    
    /* Even part per LL&M figure 1 --- note that published figure is faulty;
     * rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
     */
    
    tmp10 = tmp0 + tmp3;
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;
    
    dataptr[0] = (DCTELEM) ((tmp10 + tmp11) << PASS1_BITS);
    dataptr[4] = (DCTELEM) ((tmp10 - tmp11) << PASS1_BITS);
    
    z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
    dataptr[2] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
                               CONST_BITS-PASS1_BITS);
    dataptr[6] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
                               CONST_BITS-PASS1_BITS);
    
    /* Odd part per figure 8 --- note paper omits factor of sqrt(2).
     * cK represents cos(K*pi/16).
     * i0..i3 in the paper are tmp4..tmp7 here.
     */
    
    z1 = tmp4 + tmp7;
    z2 = tmp5 + tmp6;
    z3 = tmp4 + tmp6;
    z4 = tmp5 + tmp7;
    z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
    
    tmp4 = MULTIPLY(tmp4, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
    tmp5 = MULTIPLY(tmp5, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
    tmp6 = MULTIPLY(tmp6, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
    tmp7 = MULTIPLY(tmp7, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
    z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
    z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
    z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
    z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
    
    z3 += z5;
    z4 += z5;
    
    dataptr[7] = (DCTELEM) DESCALE(tmp4 + z1 + z3, CONST_BITS-PASS1_BITS);
    dataptr[5] = (DCTELEM) DESCALE(tmp5 + z2 + z4, CONST_BITS-PASS1_BITS);
    dataptr[3] = (DCTELEM) DESCALE(tmp6 + z2 + z3, CONST_BITS-PASS1_BITS);
    dataptr[1] = (DCTELEM) DESCALE(tmp7 + z1 + z4, CONST_BITS-PASS1_BITS);
    
    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 = DCTSIZE-1; ctr >= 0; ctr--) {
    tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
    tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
    tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
    tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
    tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
    tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
    tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
    tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
    
    /* Even part per LL&M figure 1 --- note that published figure is faulty;
     * rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
     */
    
    tmp10 = tmp0 + tmp3;
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;
    
    dataptr[DCTSIZE*0] = (DCTELEM) DESCALE(tmp10 + tmp11, PASS1_BITS);
    dataptr[DCTSIZE*4] = (DCTELEM) DESCALE(tmp10 - tmp11, PASS1_BITS);
    
    z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
    dataptr[DCTSIZE*2] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
                                      CONST_BITS+PASS1_BITS);
    dataptr[DCTSIZE*6] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
                                      CONST_BITS+PASS1_BITS);
    
    /* Odd part per figure 8 --- note paper omits factor of sqrt(2).
     * cK represents cos(K*pi/16).
     * i0..i3 in the paper are tmp4..tmp7 here.
     */
    
    z1 = tmp4 + tmp7;
    z2 = tmp5 + tmp6;
    z3 = tmp4 + tmp6;
    z4 = tmp5 + tmp7;
    z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
    
    tmp4 = MULTIPLY(tmp4, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
    tmp5 = MULTIPLY(tmp5, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
    tmp6 = MULTIPLY(tmp6, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
    tmp7 = MULTIPLY(tmp7, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
    z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
    z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
    z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
    z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
    
    z3 += z5;
    z4 += z5;
    
    dataptr[DCTSIZE*7] = (DCTELEM) DESCALE(tmp4 + z1 + z3,
                                      CONST_BITS+PASS1_BITS);
    dataptr[DCTSIZE*5] = (DCTELEM) DESCALE(tmp5 + z2 + z4,
                                      CONST_BITS+PASS1_BITS);
    dataptr[DCTSIZE*3] = (DCTELEM) DESCALE(tmp6 + z2 + z3,
                                      CONST_BITS+PASS1_BITS);
    dataptr[DCTSIZE*1] = (DCTELEM) DESCALE(tmp7 + z1 + z4,
                                      CONST_BITS+PASS1_BITS);
    
    dataptr++;                     /* advance pointer to next column */
  }
}

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