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/*
* Author: Francois Rigaut
*
* This file contains a number of utility functions, coded in C to gain
* execution time. It addresses functionalities that are missing in
* yorick, mostly concerning 2D image processing.
*
* Copyright (c) 2003-2007, Francois Rigaut
*
* 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 (to receive a copy of the GNU
* General Public License, write to the Free Software Foundation, Inc., 675
* Mass Ave, Cambridge, MA 02139, USA).
*
*/
void
_bilinear(float *image, long nx, long ny,
float *out, float *xout, float *yout, long nout, long skipoutside)
{
long i;
long i0,j0,i1,j1,i00,i01,i10,i11;
float wi,wj,w00,w01,w10,w11;
/* Loop on indices of output image */
for (i=0;i<nout;i++) {
if (((xout[i]<1)|(xout[i]>nx)|(yout[i]<1)|(yout[i]>ny))&skipoutside) continue;
i0 = (long)(xout[i])-1; /* -1 because C indices are zero-based */
j0 = (long)(yout[i])-1;
i1 = i0+1;
j1 = j0+1;
if (i0<0) i0=0;
if (i0>(nx-1)) i0=nx-1;
if (j0<0) j0=0;
if (j0>(ny-1)) j0=ny-1;
if (i1<0) i1=0;
if (i1>(nx-1)) i1=nx-1;
if (j1<0) j1=0;
if (j1>(ny-1)) j1=ny-1;
/* global index = col# + Ncolumns * row# */
i00 = i0+nx*j0;
i10 = i1+nx*j0;
i01 = i0+nx*j1;
i11 = i1+nx*j1;
/* Computes the weights for the 4 surrounding pixels */
wi = 1.0f-(xout[i]-(long)(xout[i]));
wj = 1.0f-(yout[i]-(long)(yout[i]));
w00 = wi*wj;
w10 = (1-wi)*wj;
w01 = wi*(1-wj);
w11 = (1-wi)*(1-wj);
/* Finaly, compute and integrate outphase */
out[i] = image[i00]*w00+image[i10]*w10+image[i01]*w01+image[i11]*w11;
}
}
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