frot.c

image processing including fourier,wavelet,segmentation etc.

/*--------------------------- Commande MegaWave -----------------------------*/
/* mwcommand
   name = {frot};
   version = {"1.0"};
   author = {"Lionel Moisan"};
   function = {"Rotate a Fimage using bilinear interpolation"};
   usage = {            
 'a':[a=0.0]->a  "rotation angle (in degrees, counterclockwise, default 0.0)",
 'b':[b=0.0]->b  "background grey value (default: 0.0)",
 'k'->k_flag     "to keep original input image size (keep center position)",
 in->in          "input Fimage",
 out<-out        "output Fimage"
   };
*/

#include <stdio.h>
#include <math.h>
#include "mw.h"


void bound(x,y,ca,sa,xmin,xmax,ymin,ymax)
int x,y;
float ca,sa;
int *xmin,*xmax,*ymin,*ymax;
{   
    int rx,ry;

    rx = (int)floor(ca*(float)x+sa*(float)y);
    ry = (int)floor(-sa*(float)x+ca*(float)y);
    if (rx<*xmin) *xmin=rx; if (rx>*xmax) *xmax=rx;
    if (ry<*ymin) *ymin=ry; if (ry>*ymax) *ymax=ry;
}


/* NB : calling this module with out=in is nonsense */

void frot(in,out,a,b,k_flag)
Fimage in,out;
float  *a,*b;
char *k_flag;
{
    int    nx,ny,x,y,x1,y1,adr;
    float  ca,sa,xp,yp,a11,a12,a21,a22,ux,uy,xtrans,ytrans;
    int    tx1,ty1,tx2,ty2,xmin,xmax,ymin,ymax,sx,sy;

    nx = in->ncol;
    ny = in->nrow;
    ca = (float)cos((double)(*a)*M_PI/180.0);
    sa = (float)sin((double)(*a)*M_PI/180.0);

    /********** Compute new image location **********/
    if (k_flag) {
      /* crop image and fix center */
      xmin = ymin = 0;
      xmax = nx-1;
      ymax = ny-1;
      xtrans = 0.5*( (float)(nx-1)*(1.0-ca)+(float)(ny-1)*sa );
      ytrans = 0.5*( (float)(ny-1)*(1.0-ca)-(float)(nx-1)*sa );
    } else {
      /* extend image size to include the whole input image */
      xmin = xmax = ymin = ymax = 0;
      bound(nx-1,0,ca,sa,&xmin,&xmax,&ymin,&ymax);
      bound(0,ny-1,ca,sa,&xmin,&xmax,&ymin,&ymax);
      bound(nx-1,ny-1,ca,sa,&xmin,&xmax,&ymin,&ymax);
      xtrans = ytrans = 0.0;
    }
    sx = xmax-xmin+1;
    sy = ymax-ymin+1;
    out = mw_change_fimage(out,sy,sx);
    if (!out) mwerror(FATAL,1,"not enough memory\n");
    
    /********** Rotate image **********/
    for (x=xmin;x<=xmax;x++) 
      for (y=ymin;y<=ymax;y++) {
	  xp = ca*(float)x-sa*(float)y + xtrans;
	  yp = sa*(float)x+ca*(float)y + ytrans;
	  x1 = (int)floor(xp); 
	  y1 = (int)floor(yp); 
	  ux = xp-(float)x1;
	  uy = yp-(float)y1;
	  adr = y1*nx+x1;
	  tx1 = (x1>=0 && x1<nx);
	  tx2 = (x1+1>=0 && x1+1<nx);
	  ty1 = (y1>=0 && y1<ny);
	  ty2 = (y1+1>=0 && y1+1<ny);
	  a11 = (tx1 && ty1? in->gray[adr]:*b);
	  a12 = (tx1 && ty2? in->gray[adr+nx]:*b);
	  a21 = (tx2 && ty1? in->gray[adr+1]:*b);
	  a22 = (tx2 && ty2? in->gray[adr+nx+1]:*b);
	  out->gray[(y-ymin)*sx+x-xmin] = 
	    (1.0-uy)*((1.0-ux)*a11+ux*a21)+uy*((1.0-ux)*a12+ux*a22);
      }
}