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zoom-levels.js
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zoom-levels.js
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(function($) {
'use strict';
if (!$.version || $.version.major < 2) {
throw new Error('This version of OpenSeadragonZoomLevels requires OpenSeadragon version 2.0.0+');
}
$.Viewer.prototype.zoomLevels = function(options) {
if (!this.zoomLevelsInstance || options) {
options = options || {};
options.viewer = this;
this.zoomLevelsInstance = new $.ZoomLevels(options);
}
return this.zoomLevelsInstance;
};
/**
* @class ZoomLevels
* @classdesc Allows restricting the image zoom to specific levels
* @memberof OpenSeadragon
* @param {Object} options
*/
$.ZoomLevels = function(options) {
var self = this;
$.extend(true, self, {
// internal state properties
viewer: null,
// options
levels: [],
}, options);
sortZoomLevels(options.levels);
var viewport = self.viewer.viewport;
var zoom;
self.viewer.addHandler('zoom', function(e) {
if (zoom !== e.zoom) {
zoom = e.zoom;
if (zoom !== viewport.getHomeZoom()) {
if (zoom < viewport.zoomSpring.current.value) {
zoom = self.getLowerZoomLevel(zoom);
} else if (zoom > viewport.zoomSpring.current.value) {
zoom = self.getUpperZoomLevel(zoom);
}
}
if (zoom !== e.zoom) {
e.zoom = zoom;
viewport.zoomTo(zoom, e.refPoint, e.immediately);
}
}
});
};
$.extend($.ZoomLevels.prototype, /** @lends OpenSeadragon.ZoomLevels.prototype */ {
/**
* Only used for fixed zoom levels. See zoomLevels in {@link OpenSeadragon.Options}.
* @function
* @param {Number} zoom - The desired zoom level
* @return {Number} The proper zoom level.
*/
getUpperZoomLevel: function(zoom) {
if ($.isArray(this.levels) && this.levels.length) {
var viewport = this.viewer.viewport;
var imageZoom = viewport.viewportToImageZoom(zoom);
zoom = viewport.imageToViewportZoom(this.levels[this.levels.length - 1]);
for (var i = 0; i < this.levels.length; i++) {
if (this.levels[i] > imageZoom) {
zoom = viewport.imageToViewportZoom(this.levels[i]);
break;
}
}
return Math.min(
zoom,
viewport.getMaxZoom()
);
}
return zoom;
},
/**
* Only used for fixed zoom levels. See zoomLevels in {@link OpenSeadragon.Options}.
* @function
* @param {Number} zoom - The desired zoom level
* @return {Number} The proper zoom level.
*/
getLowerZoomLevel: function(zoom) {
if ($.isArray(this.levels) && this.levels.length) {
var viewport = this.viewer.viewport;
var imageZoom = viewport.viewportToImageZoom(zoom);
zoom = viewport.imageToViewportZoom(this.levels[0]);
for (var i = this.levels.length - 1; i >= 0; i--) {
if (this.levels[i] < imageZoom) {
zoom = viewport.imageToViewportZoom(this.levels[i]);
break;
}
}
return Math.max(
zoom,
viewport.getMinZoom()
);
}
return zoom;
},
});
/**
* Sort zoom levels (if there are any) in numeric, ascending order
* @function
* @return {undefined}
*/
function sortZoomLevels(levels) {
if ($.isArray(levels)) {
levels.sort(function(a, b) {
// numeric, ascending
return a - b;
});
}
}
})(OpenSeadragon);