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/****************************************************************************/
/* */
/* IMG* Image Processing Tools Library */
/* Program: imgGrad.c */
/* Author: Simon A.J. Winder */
/* Date: Thu Oct 20 20:45:43 1994 */
/* Copyright (C) 1994 Simon A.J. Winder */
/* */
/****************************************************************************/
#include "tools.h"
#define PRGNAME "Grad"
#define ERROR(e) imgError(e,PRGNAME)
int main(int argc,char **argv)
{
it_image *in1,*out1;
int width,height,x,y,v_x,v_y,y_end,v_width;
double aa,bb,cc,dd;
it_float *in_ptr1,*in_ptr2;
it_complex *out_ptr;
IFHELP
{
fprintf(stderr,"img%s - Calculate image gradient vectors\n",
PRGNAME);
fprintf(stderr," stdin: Float\n");
fprintf(stderr," stdout: Complex\n");
exit(0);
}
imgStart(PRGNAME);
/* Loop for all images */
do {
in1=i_read_image_file(stdin,IT_FLOAT,IM_FRAGMENT);
if(in1==NULL)
ERROR("can't import image file");
width=in1->width;
height=in1->height;
out1=i_create_image(width,height,IT_COMPLEX,IM_FRAGMENT);
if(out1==NULL)
ERROR("out of memory");
v_x=in1->valid_x;
v_y=in1->valid_y;
v_width=in1->valid_width-1;
y_end=v_y+in1->valid_height-1;
/* Calculate gradient vectors from a 2x2 kernel */
for(y=v_y;y<y_end;y++)
{
in_ptr1=im_float_row(in1,y)+v_x;
in_ptr2=im_float_row(in1,y+1)+v_x;
out_ptr=im_complex_row(out1,y)+v_x;
for(x=0;x<v_width;x++)
{
aa= *in_ptr1++;
bb= *in_ptr1;
cc= *in_ptr2++;
dd= *in_ptr2;
out_ptr->Re=(bb+dd-aa-cc)*0.5;
out_ptr->Im=(aa+bb-cc-dd)*0.5;
out_ptr++;
}
}
out1->valid_x=v_x;
out1->valid_y=v_y;
out1->valid_width=v_width;
out1->valid_height=in1->valid_height-1;
i_destroy_image(in1);
i_write_image_file(stdout,out1,IF_BINARY);
i_destroy_image(out1);
} while(!feof(stdin));
imgFinish(PRGNAME);
return(0);
}
/* Version 1.0 (Oct 1994) */
/* Version 1.1 (Nov 1994) */
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