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plt-scheme  4.2.1
Defines | Functions
jfdctfst.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   8
#define FIX_0_382683433   ((INT32) 98) /* FIX(0.382683433) */
#define FIX_0_541196100   ((INT32) 139) /* FIX(0.541196100) */
#define FIX_0_707106781   ((INT32) 181) /* FIX(0.707106781) */
#define FIX_1_306562965   ((INT32) 334) /* FIX(1.306562965) */
#define DESCALE(x, n)   RIGHT_SHIFT(x, n)
#define MULTIPLY(var, const)   ((DCTELEM) DESCALE((var) * (const), CONST_BITS))

Functions

 jpeg_fdct_ifast (DCTELEM *data)

Define Documentation

#define CONST_BITS   8

Definition at line 68 of file jfdctfst.c.

#define DESCALE (   x,
 
)    RIGHT_SHIFT(x, n)

Definition at line 98 of file jfdctfst.c.

#define FIX_0_382683433   ((INT32) 98) /* FIX(0.382683433) */

Definition at line 79 of file jfdctfst.c.

#define FIX_0_541196100   ((INT32) 139) /* FIX(0.541196100) */

Definition at line 80 of file jfdctfst.c.

#define FIX_0_707106781   ((INT32) 181) /* FIX(0.707106781) */

Definition at line 81 of file jfdctfst.c.

#define FIX_1_306562965   ((INT32) 334) /* FIX(1.306562965) */

Definition at line 82 of file jfdctfst.c.

#define JPEG_INTERNALS

Definition at line 33 of file jfdctfst.c.

#define MULTIPLY (   var,
  const 
)    ((DCTELEM) DESCALE((var) * (const), CONST_BITS))

Definition at line 106 of file jfdctfst.c.


Function Documentation

jpeg_fdct_ifast ( DCTELEM data)

Definition at line 114 of file jfdctfst.c.

{
  DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
  DCTELEM tmp10, tmp11, tmp12, tmp13;
  DCTELEM z1, z2, z3, z4, z5, z11, z13;
  DCTELEM *dataptr;
  int ctr;
  SHIFT_TEMPS

  /* Pass 1: process rows. */

  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 */
    
    tmp10 = tmp0 + tmp3;    /* phase 2 */
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;
    
    dataptr[0] = tmp10 + tmp11; /* phase 3 */
    dataptr[4] = tmp10 - tmp11;
    
    z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
    dataptr[2] = tmp13 + z1;       /* phase 5 */
    dataptr[6] = tmp13 - z1;
    
    /* Odd part */

    tmp10 = tmp4 + tmp5;    /* phase 2 */
    tmp11 = tmp5 + tmp6;
    tmp12 = tmp6 + tmp7;

    /* The rotator is modified from fig 4-8 to avoid extra negations. */
    z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
    z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
    z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
    z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */

    z11 = tmp7 + z3;        /* phase 5 */
    z13 = tmp7 - z3;

    dataptr[5] = z13 + z2;  /* phase 6 */
    dataptr[3] = z13 - z2;
    dataptr[1] = z11 + z4;
    dataptr[7] = z11 - z4;

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

  /* Pass 2: process columns. */

  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 */
    
    tmp10 = tmp0 + tmp3;    /* phase 2 */
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;
    
    dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */
    dataptr[DCTSIZE*4] = tmp10 - tmp11;
    
    z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
    dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */
    dataptr[DCTSIZE*6] = tmp13 - z1;
    
    /* Odd part */

    tmp10 = tmp4 + tmp5;    /* phase 2 */
    tmp11 = tmp5 + tmp6;
    tmp12 = tmp6 + tmp7;

    /* The rotator is modified from fig 4-8 to avoid extra negations. */
    z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
    z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
    z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
    z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */

    z11 = tmp7 + z3;        /* phase 5 */
    z13 = tmp7 - z3;

    dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */
    dataptr[DCTSIZE*3] = z13 - z2;
    dataptr[DCTSIZE*1] = z11 + z4;
    dataptr[DCTSIZE*7] = z11 - z4;

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

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