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get_grid_cell_median_color.c
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get_grid_cell_median_color.c
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#include "header.h"
/*
Define the comparison function to sort the colors
*/
static int get_grid_cell_median_color_compare(
const void *p1,
const void *p2
)
{
int var1;
int var2;
var1= *(int *)p1;
var2= *(int *)p2;
/*
Sort w/r to increasing value
*/
if ( var1 < var2 )
return -1;
if ( var1 > var2 )
return +1;
/*
Sort w/r to decreasing value
*/
/*
if ( var1 > var2 )
return -1;
if ( var1 < var2 )
return +1;
*/
return 0;
}
void get_grid_cell_median_color(
int *rgb_image_arr,
int width,
int height,
int inp_i,
int inp_j,
int grid,
int rgb[3]
)
/*
inp_i,inp_j is the top left corner of the grid cell
*/
{
int *var_arr;
int cind;
int grid_i;
int grid_j;
int i;
int j;
int pixel;
int var;
int var_arr_ind;
int var_arr_ind2;
/*
Process each color channel independently
*/
for ( cind= 0 ; cind< 3 ; cind++ ) {
var_arr= (int *)calloc(grid*grid,sizeof(int));
for ( grid_i= 0 ; grid_i< grid ; grid_i++ ) {
i= inp_i+grid_i;
if ( !(i < height) )
continue;
for ( grid_j= 0 ; grid_j< grid ; grid_j++ ) {
j= inp_j+grid_j;
if ( !(j < width) )
continue;
pixel= i*width+j;
var= rgb_image_arr[3*pixel+cind];
var_arr_ind= grid_i*grid+grid_j;
var_arr[var_arr_ind]= var;
}
}
/*
Sort var_arr w/r to increasing value
*/
/*
The old fashioned way
*/
/*
for ( var_arr_ind= 0 ;
var_arr_ind< grid*grid ;
var_arr_ind++ ) {
for ( var_arr_ind2= var_arr_ind+1 ;
var_arr_ind2< grid*grid ;
var_arr_ind2++ ) {
if ( var_arr[var_arr_ind2] < var_arr[var_arr_ind] ) {
var= var_arr[var_arr_ind];
var_arr[var_arr_ind]= var_arr[var_arr_ind2];
var_arr[var_arr_ind2]= var;
}
}
}
*/
/*
Using qsort
*/
qsort(
var_arr,
grid*grid,
sizeof(int),
get_grid_cell_median_color_compare
);
/*
Check that var_arr was properly sorted
*/
for ( var_arr_ind= 0 ;
var_arr_ind< grid*grid-1 ;
var_arr_ind++ ) {
var_arr_ind2= var_arr_ind+1;
if ( var_arr[var_arr_ind2] < var_arr[var_arr_ind] ) {
error_handler((char *)"get_grid_cell_median_color");
}
}
/*
Get the median
*/
rgb[cind]= var_arr[grid*grid/2];
free(var_arr);
}
}