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gaussian_blur_image.c
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gaussian_blur_image.c
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#include "header.h"
void gaussian_blur_image(
int *I,
int xdim,
int ydim,
double sigma,
int precision,
int *I_out
)
{
int size;
double *G;
int i;
double x;
double pi=acos(-1);
double *row;
int j;
double norm;
int k;
double val;
double *col;
double *I_dbl;
double val_dbl;
int val_int;
/*
Allocate memory for output image in double form
*/
I_dbl= (double *)calloc(xdim*ydim,sizeof(double));
/*
Copy input image into output image
*/
for ( i= 0 ; i< ydim ; i++ ) {
for ( j= 0 ; j< xdim ; j++ ) {
I_dbl[i*xdim+j]= (double)I[i*xdim+j];
}
}
/*
We are gonna apply a 1d kernel
(defined by sigma and precision)
in both directions
*/
size= (int)((double)precision*sigma)+1;
G= (double *)calloc(size,sizeof(double));
for ( i= 0 ; i< size ; i++ ) {
x= (double)i;
G[i]= 1/(sqrt(2*pi)*sigma)*exp(-x*x/(2*sigma*sigma));
}
/*
We are gonna copy the image row by row,
convolute each row, and
put the results back in I
*/
row= (double *)calloc(xdim,sizeof(double));
for ( i= 0 ; i< ydim ; i++ ) {
for ( j= 0 ; j< xdim ; j++ ) {
norm= 0.0;
k= 0;
val= G[k]*I_dbl[i*xdim+j];
norm+= G[k];
for ( k= 1 ; k< size ; k++ ) {
if ( !( (j+k)<xdim ) )
continue;
val+= G[k]*I_dbl[i*xdim+(j+k)];
norm+= G[k];
}
for ( k= 1 ; k< size ; k++ ) {
if ( !( (j-k)>=0 ) )
continue;
val+= G[k]*I_dbl[i*xdim+(j-k)];
norm+= G[k];
}
row[j]= val/norm;
}
for ( j= 0 ; j< xdim ; j++ ) {
I_dbl[i*xdim+j]= row[j];
}
}
free(row);
/*
We are gonna copy the image col by col,
convolute each col, and
put the results back in I
*/
col= (double *)calloc(ydim,sizeof(double));
for ( j= 0 ; j< xdim ; j++ ) {
for ( i= 0 ; i< ydim ; i++ ) {
norm= 0.0;
k= 0;
val= G[k]*I_dbl[i*xdim+j];
norm+= G[k];
for ( k= 1 ; k< size ; k++ ) {
if ( !( (i+k)<ydim ) )
continue;
val+= G[k]*I_dbl[(i+k)*xdim+j];
norm+= G[k];
}
for ( k= 1 ; k< size ; k++ ) {
if ( !( (i-k)>=0 ) )
continue;
val+= G[k]*I_dbl[(i-k)*xdim+j];
norm+= G[k];
}
col[i]= val/norm;
}
for ( i= 0 ; i< ydim ; i++ ) {
I_dbl[i*xdim+j]= col[i];
}
}
free(col);
for ( i= 0 ; i< ydim ; i++ ) {
for ( j= 0 ; j< xdim ; j++ ) {
val_dbl= I_dbl[i*xdim+j];
val_int= (int)(val_dbl+0.5);
if ( val_int < 0 )
val_int= 0;
if ( val_int > 255 )
val_int= 255;
I_out[i*xdim+j]= val_int;
}
}
free(G);
/*
Free memory for output image in double form
*/
free(I_dbl);
}