[mapguide-users] Watermarking a Map

[gingerbbm]

Dear all

Here's a revised JavaScript method for watermarking. This will only overlay
the map. I've added a new parameter elName which is the DIV which contains
the map image. In the Ajax viewer the required value is "mapSpace", so it
could be hard-coded if desired.

	/**
	 * Place a tiled image between the map and the scale slider
	 * to represent a watermark on the map. The image is expected to have a 
	 * transparent background.
	 *
	 * @doc       The document object.
	 * @elName    The name of the element before which the watermark will be
put.
	 * @imageUrl  The URL of the map image used for the watermark.
	 *
	 */
	ShowWatermark: function(doc, elName, imageUrl) {

		if (!doc) return;
		if ((!elName) || (!doc.getElementById(elName))) return;
		if (!imageUrl) return;

		//
		// Create a DIV to hold the watermark.
		//
		var watermark = doc.createElement('div');

		//
		// Assign the passed-in background image URL.
		//
		watermark.style.backgroundImage = 'url(' + imageUrl + ')';

		//
		// This value is very important. It must be less than the lowest z-index
		// value used by the scale slider (which happens to be 4 at the time of 
		// writing.
		//
		watermark.style.zIndex = '3';

		//
		// The rest of the styles.
		// TODO: Make this more sustainable. External CSS?
		//
		watermark.style.position = 'absolute';
		watermark.style.width = '100%';
		watermark.style.height = '100%';
		watermark.style.opacity = 0.5;
		watermark.style.filter = 'alpha(opacity=50)';

		watermark.setAttribute('id', this.WATERMARK_ID);

		//
		// Insert it into the DOM. 
		//
		var el = doc.getElementById(elName);
		el.parentNode.insertBefore(watermark, el);
	}

Cheers
Stuart
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