align_window.c

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#include <stdio.h>
#include <math.h>
#include <grass/gis.h>


char *G_align_window(struct Cell_head *window, const struct Cell_head *ref)
{
    int preserve;

    window->ns_res = ref->ns_res;
    window->ew_res = ref->ew_res;
    window->zone = ref->zone;
    window->proj = ref->proj;

    preserve = window->proj == PROJECTION_LL &&
        window->east == (window->west + 360);
    window->south =
        G_row_to_northing(ceil(G_northing_to_row(window->south, ref)), ref);
    window->north =
        G_row_to_northing(floor(G_northing_to_row(window->north, ref)), ref);
    window->east =
        G_col_to_easting(ceil(G_easting_to_col(window->east, ref)), ref);
    window->west =
        G_col_to_easting(floor(G_easting_to_col(window->west, ref)), ref);

    if (window->proj == PROJECTION_LL) {
        while (window->north > 90.0)
            window->north -= window->ns_res;
        while (window->south < -90.0)
            window->south += window->ns_res;

        if (preserve)
            window->east = window->west + 360;
        else
            while (window->east - window->west > 360.0)
                window->east -= window->ew_res;
    }

    return G_adjust_Cell_head(window, 0, 0);
}