PHPMapScript : pixels to geo problem using dynamic symbols

Mon Mar 7 07:39:02 PST 2005

I am testing out creating dynamic symbols on a map using examples on the
wiki.  If I click on the center of the map, it works fine.  However as I
get to the outer regions of the map, the Y position is correct, but the
X position is off.  Any idea what is causing this? I'm sure it's obvious
I am overlooking.

the example I am testing out can be viewed here
http://www.ranetproject.net/apps/maps/ms/africa_view2.php

here is my map file
NAME "Africa"
        SIZE 800 600
        STATUS ON

        EXTENT -17.533 -46.970 55.541 37.340
        UNITS METERS
        SHAPEPATH "data"

        WEB
            IMAGEPATH "f:\inetpub\ranet\apps\maps\ms\tmp\"
            IMAGEURL "tmp/"
        END

        SYMBOL
                NAME 'star'
                TYPE VECTOR
                FILLED TRUE
                POINTS
                      0 .375
                      .35 .375
                      .5 0
                      .65 .375
                      1 .375
                      .75 .625
                      .875 1
                      .5 .75
                      .125 1
                      .25 .625
                END
          END

        LAYER
                NAME "INLINE"
                TYPE POINT
                STATUS ON
               CLASS
                       NAME "0"
                       STYLE
                         COLOR 255 0 0 # red

                         SYMBOL 'star'
                         SIZE 16
                       END #style
               END #class
         END #layer

        LAYER
            NAME "Africa"
            TYPE POLYGON
            STATUS ON
            DATA "africa"
            CLASS
                STYLE
                    COLOR 255 243 227
                    OUTLINECOLOR 200 200 200
                    SYMBOL 0
                END
            END
        END

        END

and here is my php code (just using example code)

<?
//Convert pixels to map units (got from PHPMapscriptSnippet1)
function click2map ($click_x, $click_y) {

    global $map;
    $e= &$map->extent; //for saving writing
    $x_pct = ($click_x / $map->width);
    $y_pct = 1 - ($click_y / $map->height);
    $x_map = $e->minx + ( ($e->maxx - $e->minx) * $x_pct);
    $y_map = $e->miny + ( ($e->maxy - $e->miny) * $y_pct);

    return array($x_map, $y_map);
}

$map= ms_newMapObj('africa.map');
//Convert pixels to map units
$map_pt = click2map($_GET['image_x'],$_GET['image_y'],$map->extent);
//Create the point
$pt = ms_newPointObj();
$pt-> setXY($map_pt[0],$map_pt[1]);

//Draw the map and add the point
$img = $map->draw();
$layer = $map->getLayerByName('INLINE');
$pt->draw($map, $layer, $img, 0 ,'yuhuu');
$url = $img->saveWebImage();
?>

<html><head></head><body>

<form method="get" action="africa_view2.php" >
   <input style="border:thin solid black;" type="image"
          name="image" src="<?php echo $url?>" />
</form>

<pre>
<!-- Debug Lines -->
<?php
echo "GET\n";
print_r($_GET);
echo "Point:\n";
print_r($pt); ?>
?>
</pre>
</body>
</html>

--
Geoffrey Rowland
Technical Officer
Climate Information Project
NOAA Research
Office of  Global Programs
http://www.cip.noaa.gov
http://www.ranetproject.net
Contractor,
RGII Technologies, Inc., a Computer Horizons Company
http://www.rg2.com
Phone: 301-427-2089x186
Fax : 301-427-2082
geoffrey.rowland at noaa.gov