openseadragon/src/tile.js

/*
 * OpenSeadragon - Tile
 *
 * Copyright (C) 2009 CodePlex Foundation
 * Copyright (C) 2010-2013 OpenSeadragon contributors
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of CodePlex Foundation nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

(function( $ ){

/**
 * @class Tile
 * @memberof OpenSeadragon
 * @param {Number} level The zoom level this tile belongs to.
 * @param {Number} x The vector component 'x'.
 * @param {Number} y The vector component 'y'.
 * @param {OpenSeadragon.Point} bounds Where this tile fits, in normalized
 *      coordinates.
 * @param {Boolean} exists Is this tile a part of a sparse image? ( Also has
 *      this tile failed to load? )
 * @param {String} url The URL of this tile's image.
 * @param {CanvasRenderingContext2D} context2D The context2D of this tile if it
 * is provided directly by the tile source.
 */
$.Tile = function(level, x, y, bounds, exists, url, context2D) {
    /**
     * The zoom level this tile belongs to.
     * @member {Number} level
     * @memberof OpenSeadragon.Tile#
     */
    this.level   = level;
    /**
     * The vector component 'x'.
     * @member {Number} x
     * @memberof OpenSeadragon.Tile#
     */
    this.x       = x;
    /**
     * The vector component 'y'.
     * @member {Number} y
     * @memberof OpenSeadragon.Tile#
     */
    this.y       = y;
    /**
     * Where this tile fits, in normalized coordinates
     * @member {OpenSeadragon.Rect} bounds
     * @memberof OpenSeadragon.Tile#
     */
    this.bounds  = bounds;
    /**
     * Is this tile a part of a sparse image? Also has this tile failed to load?
     * @member {Boolean} exists
     * @memberof OpenSeadragon.Tile#
     */
    this.exists  = exists;
    /**
     * The URL of this tile's image.
     * @member {String} url
     * @memberof OpenSeadragon.Tile#
     */
    this.url     = url;
    /**
     * The context2D of this tile if it is provided directly by the tile source.
     * @member {CanvasRenderingContext2D} context2D
     * @memberOf OpenSeadragon.Tile#
     */
    this.context2D = context2D;
    /**
     * Is this tile loaded?
     * @member {Boolean} loaded
     * @memberof OpenSeadragon.Tile#
     */
    this.loaded  = false;
    /**
     * Is this tile loading?
     * @member {Boolean} loading
     * @memberof OpenSeadragon.Tile#
     */
    this.loading = false;

    /**
     * The HTML div element for this tile
     * @member {Element} element
     * @memberof OpenSeadragon.Tile#
     */
    this.element    = null;
    /**
     * The HTML img element for this tile.
     * @member {Element} imgElement
     * @memberof OpenSeadragon.Tile#
     */
    this.imgElement = null;
    /**
     * The Image object for this tile.
     * @member {Object} image
     * @memberof OpenSeadragon.Tile#
     */
    this.image      = null;

    /**
     * The alias of this.element.style.
     * @member {String} style
     * @memberof OpenSeadragon.Tile#
     */
    this.style      = null;
    /**
     * This tile's position on screen, in pixels.
     * @member {OpenSeadragon.Point} position
     * @memberof OpenSeadragon.Tile#
     */
    this.position   = null;
    /**
     * This tile's size on screen, in pixels.
     * @member {OpenSeadragon.Point} size
     * @memberof OpenSeadragon.Tile#
     */
    this.size       = null;
    /**
     * The start time of this tile's blending.
     * @member {Number} blendStart
     * @memberof OpenSeadragon.Tile#
     */
    this.blendStart = null;
    /**
     * The current opacity this tile should be.
     * @member {Number} opacity
     * @memberof OpenSeadragon.Tile#
     */
    this.opacity    = null;
    /**
     * The distance of this tile to the viewport center.
     * @member {Number} distance
     * @memberof OpenSeadragon.Tile#
     */
    this.distance   = null;
    /**
     * The visibility score of this tile.
     * @member {Number} visibility
     * @memberof OpenSeadragon.Tile#
     */
    this.visibility = null;

    /**
     * Whether this tile is currently being drawn.
     * @member {Boolean} beingDrawn
     * @memberof OpenSeadragon.Tile#
     */
    this.beingDrawn     = false;
    /**
     * Timestamp the tile was last touched.
     * @member {Number} lastTouchTime
     * @memberof OpenSeadragon.Tile#
     */
    this.lastTouchTime  = 0;
};

/** @lends OpenSeadragon.Tile.prototype */
$.Tile.prototype = {

    /**
     * Provides a string representation of this tiles level and (x,y)
     * components.
     * @function
     * @returns {String}
     */
    toString: function() {
        return this.level + "/" + this.x + "_" + this.y;
    },

    // private
    _hasTransparencyChannel: function() {
        return !!this.context2D || this.url.match('.png');
    },

    /**
     * Renders the tile in an html container.
     * @function
     * @param {Element} container
     */
    drawHTML: function( container ) {
        if (!this.cacheImageRecord) {
            $.console.warn(
                '[Tile.drawHTML] attempting to draw tile %s when it\'s not cached',
                this.toString());
            return;
        }

        if ( !this.loaded ) {
            $.console.warn(
                "Attempting to draw tile %s when it's not yet loaded.",
                this.toString()
            );
            return;
        }

        //EXPERIMENTAL - trying to figure out how to scale the container
        //               content during animation of the container size.

        if ( !this.element ) {
            this.element                              = $.makeNeutralElement( "div" );
            this.imgElement                           = this.cacheImageRecord.getImage().cloneNode();
            this.imgElement.style.msInterpolationMode = "nearest-neighbor";
            this.imgElement.style.width               = "100%";
            this.imgElement.style.height              = "100%";

            this.style                     = this.element.style;
            this.style.position            = "absolute";
        }
        if ( this.element.parentNode != container ) {
            container.appendChild( this.element );
        }
        if ( this.imgElement.parentNode != this.element ) {
            this.element.appendChild( this.imgElement );
        }

        this.style.top     = this.position.y + "px";
        this.style.left    = this.position.x + "px";
        this.style.height  = this.size.y + "px";
        this.style.width   = this.size.x + "px";

        $.setElementOpacity( this.element, this.opacity );
    },

    /**
     * Renders the tile in a canvas-based context.
     * @function
     * @param {Canvas} context
     * @param {Function} drawingHandler - Method for firing the drawing event.
     * drawingHandler({context, tile, rendered})
     * where <code>rendered</code> is the context with the pre-drawn image.
     * @param {Number} [scale=1] - Apply a scale to position and size
     * @param {OpenSeadragon.Point} [translate] - A translation vector
     */
    drawCanvas: function( context, drawingHandler, scale, translate ) {

        var position = this.position.times($.pixelDensityRatio),
            size     = this.size.times($.pixelDensityRatio),
            rendered;

        if (!this.context2D && !this.cacheImageRecord) {
            $.console.warn(
                '[Tile.drawCanvas] attempting to draw tile %s when it\'s not cached',
                this.toString());
            return;
        }

        rendered = this.context2D || this.cacheImageRecord.getRenderedContext();

        if ( !this.loaded || !rendered ){
            $.console.warn(
                "Attempting to draw tile %s when it's not yet loaded.",
                this.toString()
            );

            return;
        }

        context.save();

        context.globalAlpha = this.opacity;

        if (typeof scale === 'number' && scale !== 1) {
            // draw tile at a different scale
            position = position.times(scale);
            size = size.times(scale);
        }

        if (translate instanceof $.Point) {
            // shift tile position slightly
            position = position.plus(translate);
        }

        //if we are supposed to be rendering fully opaque rectangle,
        //ie its done fading or fading is turned off, and if we are drawing
        //an image with an alpha channel, then the only way
        //to avoid seeing the tile underneath is to clear the rectangle
        if (context.globalAlpha === 1 && this._hasTransparencyChannel()) {
            //clearing only the inside of the rectangle occupied
            //by the png prevents edge flikering
            context.clearRect(
                position.x + 1,
                position.y + 1,
                size.x - 2,
                size.y - 2
            );
        }

        // This gives the application a chance to make image manipulation
        // changes as we are rendering the image
        drawingHandler({context: context, tile: this, rendered: rendered});

        context.drawImage(
            rendered.canvas,
            0,
            0,
            rendered.canvas.width,
            rendered.canvas.height,
            position.x,
            position.y,
            size.x,
            size.y
        );

        context.restore();
    },

    /**
     * Get the ratio between current and original size.
     * @function
     * @return {Float}
     */
    getScaleForEdgeSmoothing: function() {
        var context;
        if (this.cacheImageRecord) {
            context = this.cacheImageRecord.getRenderedContext();
        } else if (this.context2D) {
            context = this.context2D;
        } else {
            $.console.warn(
                '[Tile.drawCanvas] attempting to get tile scale %s when tile\'s not cached',
                this.toString());
            return 1;
        }
        return context.canvas.width / (this.size.x * $.pixelDensityRatio);
    },

    /**
     * Get a translation vector that when applied to the tile position produces integer coordinates.
     * Needed to avoid swimming and twitching.
     * @function
     * @param {Number} [scale=1] - Scale to be applied to position.
     * @return {OpenSeadragon.Point}
     */
    getTranslationForEdgeSmoothing: function(scale, canvasSize, sketchCanvasSize) {
        // The translation vector must have positive values, otherwise the image goes a bit off
        // the sketch canvas to the top and left and we must use negative coordinates to repaint it
        // to the main canvas. In that case, some browsers throw:
        // INDEX_SIZE_ERR: DOM Exception 1: Index or size was negative, or greater than the allowed value.
        var x = Math.max(1, Math.ceil((sketchCanvasSize.x - canvasSize.x) / 2));
        var y = Math.max(1, Math.ceil((sketchCanvasSize.y - canvasSize.y) / 2));
        return new $.Point(x, y).minus(
            this.position
                .times($.pixelDensityRatio)
                .times(scale || 1)
                .apply(function(x) {
                    return x % 1;
                })
        );
    },

    /**
     * Removes tile from its container.
     * @function
     */
    unload: function() {
        if ( this.imgElement && this.imgElement.parentNode ) {
            this.imgElement.parentNode.removeChild( this.imgElement );
        }
        if ( this.element && this.element.parentNode ) {
            this.element.parentNode.removeChild( this.element );
        }

        this.element    = null;
        this.imgElement = null;
        this.loaded     = false;
        this.loading    = false;
    }
};

}( OpenSeadragon ));