[OpenLayers-Users] Zoom-based feature styling

[Arnd Wippermann]

Hi,

Have a look at this example

http://openlayers.org/dev/examples/styles-context.html
 
The context option of an OpenLayers.Style object offers the possibility to
style features by own declared functions.

Arnd

-----Ursprüngliche Nachricht-----
Von: users-bounces at openlayers.org [mailto:users-bounces at openlayers.org] Im
Auftrag von Mak Kolybabi
Gesendet: Dienstag, 29. Dezember 2009 17:19
An: users at openlayers.org
Betreff: [OpenLayers-Users] Zoom-based feature styling

I expect that there's an easy way to do this, but it so far eludes me. I
have an OpenLayers.Layer.Vector object called "icons". Each feature in this
layer has two attributes that I need to worry about: type and zoom. There
are fifty different types, and five different zooms, so far. I already have
type-based styling using:

new OpenLayers.Rule({
    filter: new OpenLayers.Filter.Comparison({
        type: OpenLayers.Filter.Comparison.EQUAL_TO,
        property: "type",
        value: "type_1"
    }),
    symbolizer: {
        externalGraphic: "/path/to/images/1.png",
        graphicHeight: 25,
        graphicWidth: 25,
        graphicOpacity: 1.0
    }
}));

I realize I could use max/minScaleDenominator to restrict zooms, but 5x50
rules is excessive. What I'm looking for is something like:

new OpenLayers.Rule({
    filter: new OpenLayers.Filter.Logical({
        filters: [
            new OpenLayers.Filter.Comparison({
                type: OpenLayers.Filter.Comparison.EQUAL_TO,
                property: "type",
                value: "type_1"
            }),
            new OpenLayers.Filter.Comparison({
                type: OpenLayers.Filter.Comparison.LESS_THAN_OR_EQUAL_TO,
                property: "zoom",
                value: map.zoom
            })
        ],
        type: OpenLayers.Filter.Logical.AND
    }),
    symbolizer: {
        externalGraphic: "/path/to/images/1.png",
        graphicHeight: 25,
        graphicWidth: 25,
        graphicOpacity: 1.0
    }
}));

Except where map.zoom is dynamically evaluated, instead of it being
evaluated only when the style is created.

Any ideas or suggestions are appreciated.

--
Mak Kolybabi
Programmer
Telenium Inc.
204-957-2821