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DEFINITIONS
This source file includes following definitions.
- dct
- idct
- preparequant
- innerdct
- dct2
- zigzag
/* dct.c
DCT implementations and test routines.
Copyright (c) 2003 Matthias Kramm <kramm@quiss.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include <memory.h>
int zigzagtable[64] = {
0, 1, 5, 6, 14, 15, 27, 28,
2, 4, 7, 13, 16, 26, 29, 42,
3, 8, 12, 17, 25, 30, 41, 43,
9, 11, 18, 24, 31, 40, 44, 53,
10, 19, 23, 32, 39, 45, 52, 54,
20, 22, 33, 38, 46, 51, 55, 60,
21, 34, 37, 47, 50, 56, 59, 61,
35, 36, 48, 49, 57, 58, 62, 63};
static double table[8][8] =
{
{0.707106781186548,0.707106781186548,0.707106781186548,0.707106781186548,0.707106781186548,0.707106781186548,0.707106781186548,0.707106781186548},
{0.980785280403230,0.831469612302545,0.555570233019602,0.195090322016128,-0.195090322016128,-0.555570233019602,-0.831469612302545,-0.980785280403230},
{0.923879532511287,0.382683432365090,-0.382683432365090,-0.923879532511287,-0.923879532511287,-0.382683432365090,0.382683432365090,0.923879532511287},
{0.831469612302545,-0.195090322016128,-0.980785280403230,-0.555570233019602,0.555570233019602,0.980785280403230,0.195090322016129,-0.831469612302545},
{0.707106781186548,-0.707106781186547,-0.707106781186548,0.707106781186547,0.707106781186548,-0.707106781186547,-0.707106781186547,0.707106781186547},
{0.555570233019602,-0.980785280403230,0.195090322016128,0.831469612302545,-0.831469612302545,-0.195090322016128,0.980785280403231,-0.555570233019602},
{0.382683432365090,-0.923879532511287,0.923879532511287,-0.382683432365090,-0.382683432365091,0.923879532511287,-0.923879532511286,0.382683432365090},
{0.195090322016128,-0.555570233019602,0.831469612302545,-0.980785280403231,0.980785280403230,-0.831469612302545,0.555570233019602,-0.195090322016129}
};
void dct(int*src)
{
double tmp[64];
int x,y,u,v,t;
for(v=0;v<8;v++)
for(u=0;u<8;u++)
{
double c = 0;
for(x=0;x<8;x++)
{
c+=table[u][x]*src[v*8+x];
}
tmp[v*8+u] = c;
}
for(u=0;u<8;u++)
for(v=0;v<8;v++)
{
double c = 0;
for(y=0;y<8;y++)
{
c+=table[v][y]*tmp[y*8+u];
}
src[v*8+u] = (int)(c*0.25+0.5);
}
}
void idct(int*src)
{
double tmp[64];
int x,y,u,v;
for(y=0;y<8;y++)
for(x=0;x<8;x++)
{
double c = 0;
for(u=0;u<8;u++)
{
c+=table[u][x]*src[y*8+u];
}
tmp[y*8+x] = c;
}
for(y=0;y<8;y++)
for(x=0;x<8;x++)
{
double c = 0;
for(v=0;v<8;v++)
{
c+=table[v][y]*tmp[v*8+x];
}
src[y*8+x] = (int)(c*0.25+0.5);
}
}
static double c[8] = {1.0,
0.980785280403230, // cos(Pi*1/16), sin(Pi*7/16)
0.923879532511287, // cos(Pi*2/16), sin(Pi*6/16)
0.831469612302545, // cos(Pi*3/16), sin(Pi*5/16)
0.707106781186548, // cos(Pi*4/16), sin(Pi*4/16), 1/sqrt(2)
0.555570233019602, // cos(Pi*5/16), sin(Pi*3/16)
0.382683432365090, // cos(Pi*6/16), sin(Pi*2/16)
0.195090322016128 // cos(Pi*7/16), sin(Pi*1/16)
};
static double cc[8];
static int ccquant = -1;
void preparequant(int quant)
{
if(ccquant == quant)
return;
cc[0] = c[0]/(quant*2*4);
cc[1] = c[1]/(quant*2*4);
cc[2] = c[2]/(quant*2*4);
cc[3] = c[3]/(quant*2*4);
cc[4] = c[4]/(quant*2*4);
cc[5] = c[5]/(quant*2*4);
cc[6] = c[6]/(quant*2*4);
cc[7] = c[7]/(quant*2*4);
ccquant = quant;
}
inline static void innerdct(const double*a,double*b, const double*c)
{
// c1*c7*2 = c6
// c2*c6*2 = c4
// c3*c5*2 = c2
// c4*c4*2 = 1
//{ 1, 3, 5, 7, -7, -5, -3, -1},
//{ 3, -7, -1, -5, 5, 1, 7, -3},
//{ 5, -1, 7, 3, -3, -7, 1, -5},
//{ 7, -5, 3, -1, 1, -3, 5, -7}
double b0,b1,b2,b3,b4,b5;
b2 = (a[0]+a[7]);
b3 = (a[1]+a[6]);
b4 = (a[2]+a[5]);
b5 = (a[3]+a[4]);
b0 = (b2+b5)*c[4];
b1 = (b3+b4)*c[4];
b[0*8] = b0 + b1;
b[4*8] = b0 - b1;
b[2*8] = (b2-b5)*c[2] + (b3-b4)*c[6];
b[6*8] = (b2-b5)*c[6] + (b4-b3)*c[2];
b0 = (a[0]-a[7]);
b1 = (a[1]-a[6]);
b2 = (a[2]-a[5]);
b3 = (a[3]-a[4]);
b[1*8] = b0*c[1] + b1*c[3] + b2*c[5] + b3*c[7];
b[3*8] = b0*c[3] - b1*c[7] - b2*c[1] - b3*c[5];
b[5*8] = b0*c[5] - b1*c[1] + b2*c[7] + b3*c[3];
b[7*8] = b0*c[7] - b1*c[5] + b2*c[3] - b3*c[1];
}
void dct2(int*src, int*dest)
{
double tmp[64], tmp2[64];
double*p;
int u,x,v,t;
for(t=0;t<64;t++)
tmp2[t] = src[t];
for(v=0;v<8;v++)
{
double* a=&tmp2[v*8];
double* b=&tmp[v];
innerdct(a,b,c);
}
for(v=0;v<8;v++)
{
double* a=&tmp[v*8];
double* b=&tmp2[v];
innerdct(a,b,cc);
}
for(t=0;t<64;t++) {
int v = (int)(tmp2[t]);
dest[zigzagtable[t]] = v;
}
}
void zigzag(int*src)
{
int tmp[64];
int t;
for(t=0;t<64;t++) {
tmp[zigzagtable[t]] = src[t];
}
memcpy(src, tmp, sizeof(int)*64);
}