libplplot-dev 5.9.9-2ubuntu2 / usr / share / doc / libplplot11 / examples / c / x19c.c

// $Id: x19c.c 11289 2010-10-29 20:44:17Z airwin $
//
//      Illustrates backdrop plotting of world, US maps.
//      Contributed by Wesley Ebisuzaki.
//

#include "plcdemos.h"

void
map_transform( PLFLT x, PLFLT y, PLFLT *xt, PLFLT *yt, PLPointer data )
{
    double radius;

    radius = 90.0 - y;
    *xt    = radius * cos( x * M_PI / 180.0 );
    *yt    = radius * sin( x * M_PI / 180.0 );
}

//--------------------------------------------------------------------------
// mapform19
//
// Defines specific coordinate transformation for example 19.
// Not to be confused with mapform in src/plmap.c.
// x[], y[] are the coordinates to be plotted.
//--------------------------------------------------------------------------

void
mapform19( PLINT n, PLFLT *x, PLFLT *y )
{
    int    i;
    double xp, yp;
    for ( i = 0; i < n; i++ )
    {
        map_transform( x[i], y[i], &xp, &yp, NULL );
        x[i] = xp;
        y[i] = yp;
    }
}

// "Normalize" longitude values so that they always fall between -180.0 and
// 180.0
PLFLT normalize_longitude( PLFLT lon )
{
    PLFLT times;
    if ( lon >= -180.0 && lon <= 180.0 )
    {
        return ( lon );
    }
    else
    {
        times = floor( ( fabs( lon ) + 180.0 ) / 360.0 );
        if ( lon < 0.0 )
        {
            return ( lon + 360.0 * times );
        }
        else
        {
            return ( lon - 360.0 * times );
        }
    }
}

// A custom axis labeling function for longitudes and latitudes.
void
geolocation_labeler( PLINT axis, PLFLT value, char *label, PLINT length, PLPointer data )
{
    const char *direction_label;
    PLFLT      label_val;

    if ( axis == PL_Y_AXIS )
    {
        label_val = value;
        if ( label_val > 0.0 )
        {
            direction_label = " N";
        }
        else if ( label_val < 0.0 )
        {
            direction_label = " S";
        }
        else
        {
            direction_label = "Eq";
        }
    }
    else if ( axis == PL_X_AXIS )
    {
        label_val = normalize_longitude( value );
        if ( label_val > 0.0 )
        {
            direction_label = " E";
        }
        else if ( label_val < 0.0 )
        {
            direction_label = " W";
        }
        else
        {
            direction_label = "";
        }
    }
    if ( axis == PL_Y_AXIS && value == 0.0 )
    {
        // A special case for the equator
        snprintf( label, length, "%s", direction_label );
    }
    else
    {
        snprintf( label, length, "%.0f%s", fabs( label_val ), direction_label );
    }
}

//--------------------------------------------------------------------------
// main
//
// Shows two views of the world map.
//--------------------------------------------------------------------------

int
main( int argc, const char **argv )
{
    PLFLT minx, maxx, miny, maxy;
    PLFLT x, y;

// Parse and process command line arguments

    (void) plparseopts( &argc, argv, PL_PARSE_FULL );

// Longitude (x) and latitude (y)

    miny = -70;
    maxy = 80;

    plinit();

// Cartesian plots
// Most of world

    minx = 190;
    maxx = 190 + 360;

    // Setup a custom latitude and longitude-based scaling function.
    plslabelfunc( geolocation_labeler, NULL );

    plcol0( 1 );
    plenv( minx, maxx, miny, maxy, 1, 70 );
    plmap( NULL, "usaglobe", minx, maxx, miny, maxy );

// The Americas

    minx = 190;
    maxx = 340;

    plcol0( 1 );
    plenv( minx, maxx, miny, maxy, 1, 70 );
    plmap( NULL, "usaglobe", minx, maxx, miny, maxy );

    // Clear the labeling function
    plslabelfunc( NULL, NULL );

// Polar, Northern hemisphere

    minx = 0;
    maxx = 360;

    plenv( -75., 75., -75., 75., 1, -1 );
    plmap( mapform19, "globe", minx, maxx, miny, maxy );

    pllsty( 2 );
    plmeridians( mapform19, 10.0, 10.0, 0.0, 360.0, -10.0, 80.0 );

// Polar, Northern hemisphere, this time with a PLplot-wide transform

    minx = 0;
    maxx = 360;

    plstransform( map_transform, NULL );

    pllsty( 1 );
    plenv( -75., 75., -75., 75., 1, -1 );
    // No need to set the map transform here as the global transform will be
    // used.
    plmap( NULL, "globe", minx, maxx, miny, maxy );

    pllsty( 2 );
    plmeridians( NULL, 10.0, 10.0, 0.0, 360.0, -10.0, 80.0 );

    // Show Baltimore, MD on the map
    plcol0( 2 );
    plssym( 0.0, 2.0 );
    x = -76.6125;
    y = 39.2902778;
    plpoin( 1, &x, &y, 18 );
    plssym( 0.0, 1.0 );
    plptex( -76.6125, 43.0, 0.0, 0.0, 0.0, "Baltimore, MD" );

    // For C, this is how the global transform is cleared
    plstransform( NULL, NULL );

    plend();
    exit( 0 );
}