ui/src/main/java/ucar/nc2/ui/image/PictureCache.java
public static boolean stopBackgroundLoadingExcept( URL exemptionURL ) {
		SourcePicture sp;
		String exemptionURLString = exemptionURL.toString();
		Enumeration e = cacheLoadsInProgress.elements();
		boolean inProgress = false;
		while ( e.hasMoreElements() ) {
			sp = ((SourcePicture) e.nextElement());
			if ( ! sp.getUrlString().equals( exemptionURLString ) )
				sp.stopLoading();
			else {
				Tools.log( "PictureCache.stopBackgroundLoading: picture was already loading");
				inProgress = true;
			}
		}
		return inProgress;
	}
public static boolean stopBackgroundLoadingExcept( URL exemptionURL ) {
		SourcePicture sp;
		String exemptionURLString = exemptionURL.toString();
		Enumeration e = cacheLoadsInProgress.elements();
		boolean inProgress = false;
		while ( e.hasMoreElements() ) {
			sp = ((SourcePicture) e.nextElement());
			if ( ! sp.getUrlString().equals( exemptionURLString ) )
				sp.stopLoading();
			else {
				Tools.log( "PictureCache.stopBackgroundLoading: picture was already loading");
				inProgress = true;
			}
		}
		return inProgress;
	}
method to stop all background loading except the indicated file. Returns whether the
image is already being loaded. True = loading in progress, False = not in progress.