function ImageTrack(trackMeta, url, refSeq, browserParams) {
    Track.call(this, trackMeta.label, trackMeta.key,
               false, browserParams.changeCallback);
    this.refSeq = refSeq;
    this.tileToImage = {};
    this.zoomCache = {};
    this.baseUrl = (browserParams.baseUrl ? browserParams.baseUrl : "");
    var curTrack = this;
    dojo.xhrGet({url: this.baseUrl + url,
		 handleAs: "json",
		 load: function(o) { curTrack.loadSuccess(o); }
	});
}

ImageTrack.prototype = new Track("");

ImageTrack.prototype.loadSuccess = function(o) {
    //tileWidth: width, in pixels, of the tiles
    this.tileWidth = o.tileWidth;
    //zoomLevels: array of {basesPerTile, scale, height, urlPrefix} hashes
    this.zoomLevels = o.zoomLevels;
    this.setLoaded();
};

ImageTrack.prototype.setViewInfo = function(numBlocks, trackDiv, labelDiv,
                                            widthPct, widthPx, scale) {
    Track.prototype.setViewInfo.apply(this, [numBlocks, trackDiv, labelDiv,
                                             widthPct, widthPx, scale]);
    this.setLabel(this.key);
};

ImageTrack.prototype.getZoom = function(scale) {
    var result = this.zoomCache[scale];
    if (result) return result;

    result = this.zoomLevels[0];
    var desiredBases = this.tileWidth / scale;
    for (i = 1; i < this.zoomLevels.length; i++) {
        if (Math.abs(this.zoomLevels[i].basesPerTile - desiredBases)
            < Math.abs(result.basesPerTile - desiredBases))
            result = this.zoomLevels[i];
    }

    this.zoomCache[scale] = result;
    return result;
};

ImageTrack.prototype.getImages = function(zoom, startBase, endBase) {
    //var startTile = ((startBase - this.refSeq.start) / zoom.basesPerTile) | 0;
    //var endTile = ((endBase - this.refSeq.start) / zoom.basesPerTile) | 0;
    var startTile = (startBase / zoom.basesPerTile) | 0;
    var endTile = (endBase / zoom.basesPerTile) | 0;
    startTile = Math.max(startTile, 0);
    var result = [];
    var im;
    for (var i = startTile; i <= endTile; i++) {
	im = this.tileToImage[i];
	if (!im) {
	    im = document.createElement("img");
            //prepend this.baseUrl if zoom.urlPrefix is relative
            im.src = (zoom.urlPrefix.match(/^(([^/]+:)|\/)/) ? "" : this.baseUrl)
                     + zoom.urlPrefix + i + ".png";
            //TODO: need image coord systems that don't start at 0?
	    im.startBase = (i * zoom.basesPerTile); // + this.refSeq.start;
	    im.baseWidth = zoom.basesPerTile;
	    im.tileNum = i;
	    this.tileToImage[i] = im;
	}
	result.push(im);
    }
    return result;
};

ImageTrack.prototype.fillBlock = function(block, leftBlock, rightBlock, leftBase, rightBase, scale, stripeWidth) {
    var zoom = this.getZoom(scale);
    var blockWidth = rightBase - leftBase;
    var images = this.getImages(zoom, leftBase, rightBase);
    var im;

    for (var i = 0; i < images.length; i++) {
	im = images[i];
	if (!(im.parentNode && im.parentNode.parentNode)) {
	    im.style.cssText = "position: absolute; left: " + (100 * ((im.startBase - leftBase) / blockWidth)) + "%; width: " + (100 * (im.baseWidth / blockWidth)) + "%; top: 0px; height: " + zoom.height + "px;";
            block.appendChild(im);
	}
    }

    return zoom.height;
};

ImageTrack.prototype.startZoom = function(destScale, destStart, destEnd) {
    this.tileToImage = {};
    this.getImages(this.getZoom(destScale), destStart, destEnd);
};

ImageTrack.prototype.endZoom = function(destScale, destBlockBases) {
    Track.prototype.clear.apply(this);
};

ImageTrack.prototype.clear = function() {
    Track.prototype.clear.apply(this);
    this.tileToImage = {};
};

ImageTrack.prototype.transfer = function(sourceBlock, destBlock) {
    if (!(sourceBlock && destBlock)) return;

    var children = sourceBlock.childNodes;
    var destLeft = destBlock.startBase;
    var destRight = destBlock.endBase;
    var im;
    for (var i = 0; i < children.length; i++) {
	im = children[i];
	if ("startBase" in im) {
	    //if sourceBlock contains an image that overlaps destBlock,
	    if ((im.startBase < destRight)
		&& ((im.startBase + im.baseWidth) > destLeft)) {
		//move image from sourceBlock to destBlock
		im.style.left = (100 * ((im.startBase - destLeft) / (destRight - destLeft))) + "%";
		destBlock.appendChild(im);
	    } else {
		delete this.tileToImage[im.tileNum];
	    }
	}
    }
};

/*

Copyright (c) 2007-2009 The Evolutionary Software Foundation

Created by Mitchell Skinner <mitch_skinner@berkeley.edu>

This package and its accompanying libraries are free software; you can
redistribute it and/or modify it under the terms of the LGPL (either
version 2.1, or at your option, any later version) or the Artistic
License 2.0.  Refer to LICENSE for the full license text.

*/