/******************************************************** * Some code. Copyright (C) 2003 by Pascal Massimino.   * * All Rights Reserved.      (http://skal.planet-d.net) * * For Educational/Academic use ONLY. See 'LICENSE.TXT'.* ********************************************************//* *  skl_img_flt_c.cpp * *   Image filtering * ********************************************************/#include <math.h>extern "C" {  // so we don't even have to include skl.htypedef unsigned char SKL_BYTE;typedef signed char SKL_INT8;//////////////////////////////////////////////////////////// Downsampling 4x4 filters:////        [1 3 3 1]      [-1 -3  3  1]     [-1 -3 -3 -1]// Smooth:[3 9 9 3]   Gx:[-3 -9  9  3]  Gy:[-3 -9 -9 -3]//        [3 9 9 3]      [-3 -9  9  3]     [ 3  9  9  3]//        [1 3 3 1]      [-1 -3  3  1]     [ 1  3  3  1]////  Input:18x18   Output:8x8//////////////////////////////////////////////////////////#define STORE(x)   *d = (x); d += Dst_BpSvoid Skl_Smooth_18x18_To_8x8_C(SKL_BYTE *Dst, int Dst_BpS,                              const SKL_BYTE *Src, int Src_BpS){#define LOAD(x) (x) = 3*(s[1]+s[0]) +s[2]+s[-1]; s += Src_BpS  int i;  Src -= Src_BpS;  for(i=0; i<8; ++i)  {    int mx0, mx1, tmp;    int j;    const SKL_BYTE *s = Src + 2*i;    SKL_BYTE *d = Dst + i;    LOAD(mx0);    LOAD(tmp);    mx0 += 3*tmp;    for(j=4; j>0; --j) {      LOAD(mx1); mx0 += 3*mx1;      LOAD(tmp); mx0 += tmp; mx1 += 3*tmp;      STORE( (32+mx0)>>6 );      LOAD(mx0); mx1 += 3*mx0;      LOAD(tmp); mx1 += tmp; mx0 += 3*tmp;      STORE( (32+mx1)>>6 );    }  }#undef LOAD}void Skl_Gradx_18x18_To_8x8_C(SKL_INT8 *Dst, int Dst_BpS,                              const SKL_BYTE *Src, int Src_BpS){#define LOAD(x) (x) =   3*(s[1]-s[0]) +s[2]-s[-1]; s += Src_BpS  int i;  Src -= Src_BpS;  for(i=0; i<8; ++i)  {    int mx0, mx1, tmp;    int j;    const SKL_BYTE *s = Src + 2*i;    SKL_INT8 *d = Dst + i;    LOAD(mx0);    LOAD(tmp);    mx0 += 3*tmp;    for(j=4; j>0; --j)    {      LOAD(mx1); mx0 += 3*mx1;      LOAD(tmp); mx0 += tmp;      mx1 += 3*tmp;      STORE( (64+mx0)>>7 );      LOAD(mx0); mx1 += 3*mx0;      LOAD(tmp); mx1 += tmp;      mx0 += 3*tmp;      STORE( (64+mx1)>>7 );    }  }#undef LOAD}void Skl_Grady_18x18_To_8x8_C(SKL_INT8 *Dst, int Dst_BpS,                              const SKL_BYTE *Src, int Src_BpS){#define LOAD(x) (x) = 3*(s[1]+s[0]) +s[2]+s[-1]; s += Src_BpS  int i;  Src -= Src_BpS;  for(i=0; i<8; ++i)  {    int mx0, mx1, tmp;    int j;    const SKL_BYTE *s = Src + 2*i;    SKL_INT8 *d = Dst + i;    LOAD(mx0);    LOAD(tmp);    mx0 += 3*tmp;    for(j=4; j>0; --j)    {      LOAD(mx1); mx0 -= 3*mx1;      LOAD(tmp); mx0 -= tmp;      mx1 += 3*tmp;      STORE( (64-mx0)>>7 );      LOAD(mx0); mx1 -= 3*mx0;      LOAD(tmp); mx1 -= tmp;      mx0 += 3*tmp;      STORE( (64-mx1)>>7 );    }  }#undef LOAD}void Skl_Grad2_18x18_To_8x8_C(SKL_BYTE *Dst, int Dst_BpS,                             const SKL_BYTE *Src, int Src_BpS){#define LOAD(x,y) (x) = s[-1] + 3*s[0]; (y) = 3*s[1] + s[2]; s += Src_BpS#define THRESH 24  int i;  Src -= Src_BpS;  for(i=0; i<8; ++i)  {    int mx0, mx1, my0, my1, tmpx, tmpy;    int j;    const SKL_BYTE *s = Src + 2*i;    SKL_BYTE *d = Dst + i;    LOAD(mx0,my0);     LOAD(tmpx,tmpy);    mx0 += 3*tmpx; my0 += 3*tmpy;        for(j=4; j>0; --j)    {      LOAD(mx1,my1);   mx0 -= 3*my1; my0 -= 3*mx1;      LOAD(tmpx,tmpy); mx0 -= tmpy;  my0 -= tmpx;      mx1 += 3*tmpx; my1 += 3*tmpy;        // at this point:         //   Gx  = (64+mx0-my0)>>7        //   Gy  = (64-mx0-my0)>>7        //   => Gx*Gx+Gy*Gy ~= 2*( mx0*mx0 + my0*my0 )      mx0 = (mx0+32)>>6; my0 = (my0+32)>>6;      tmpx = mx0*mx0 + my0*my0;      tmpx = (tmpx>255 ? 255 : tmpx);      // tmpx = (tmpx>THRESH ? 255 : 0);      STORE( tmpx );      LOAD(mx0,my0);   mx1 -= 3*my0; my1 -= 3*mx0;      LOAD(tmpx,tmpy); mx1 -= tmpy;  my1 -= tmpx;      mx0 += 3*tmpx; my0 += 3*tmpy;      mx1 = (mx1+32)>>6; my1 = (my1+32)>>6;      tmpx = mx1*mx1 + my1*my1;      tmpx = (tmpx>255 ? 255 : tmpx);      // tmpx = (tmpx>THRESH ? 255 : 0);      STORE( tmpx );    }  }#undef THRESH#undef LOAD}#undef STORE//////////////////////////////////////////////////////////}   // extern "C"