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在做webapp时候，遇到一个需要做双指放大的功能，需求是：一张带有坐标的图片上有固定的点，需要点击这些坐标上的点进入相应的商品，并且需要对这一块进行双指可以缩放，双击缩放；

一开始是自己写监听touch事件进行处理，但是再缩放的时候，偶尔出现卡顿闪烁，用户体验不很好，后来采用插件

pinch-zoom GitHub地址： 

所以就简单写了一个demo；用于测试一下，顺便练习一下；

需要使用的图片 图片w:800px,h:560px;

图上红块为点击点，固定坐标，使用插件，方便处就是不用处理定位的块；它会随着缩放自动变换，这样就可以绑定事件进行一系列的操作；

事件点击后

附上

pinch-zoom.umd.js

(function (global, factory) {    if (typeof define === "function" && define.amd) {        define(['exports'], factory);    } else if (typeof exports !== "undefined") {        factory(exports);    } else {        var mod = {            exports: {}        };        factory(mod.exports);        global.PinchZoom = mod.exports;    }})(this, function (exports) {    'use strict';    Object.defineProperty(exports, "__esModule", {        value: true    });    /*            PinchZoom.js        Copyright (c) Manuel Stofer 2013 - today            Author: Manuel Stofer (mst@rtp.ch)        Version: 2.2.0            Permission is hereby granted, free of charge, to any person obtaining a copy        of this software and associated documentation files (the "Software"), to deal        in the Software without restriction, including without limitation the rights        to use, copy, modify, merge, publish, distribute, sublicense, and/or sell        copies of the Software, and to permit persons to whom the Software is        furnished to do so, subject to the following conditions:            The above copyright notice and this permission notice shall be included in        all copies or substantial portions of the Software.            THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR        IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,        FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE        AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER        LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,        OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN        THE SOFTWARE.        */    // polyfills    if (typeof Object.assign != 'function') {        // Must be writable: true, enumerable: false, configurable: true        Object.defineProperty(Object, "assign", {            value: function assign(target, varArgs) {                // .length of function is 2                if (target == null) {                    // TypeError if undefined or null                    throw new TypeError('Cannot convert undefined or null to object');                }                var to = Object(target);                for (var index = 1; index < arguments.length; index++) {                    var nextSource = arguments[index];                    if (nextSource != null) {                        // Skip over if undefined or null                        for (var nextKey in nextSource) {                            // Avoid bugs when hasOwnProperty is shadowed                            if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {                                to[nextKey] = nextSource[nextKey];                            }                        }                    }                }                return to;            },            writable: true,            configurable: true        });    }    if (typeof Array.from != 'function') {        Array.from = function (object) {            return [].slice.call(object);        };    }    // utils    var buildElement = function buildElement(str) {        // empty string as title argument required by IE and Edge        var tmp = document.implementation.createHTMLDocument('');        tmp.body.innerHTML = str;        return Array.from(tmp.body.children)[0];    };    var triggerEvent = function triggerEvent(el, name) {        var event = document.createEvent('HTMLEvents');        event.initEvent(name, true, false);        el.dispatchEvent(event);    };    var definePinchZoom = function definePinchZoom() {        /**         * Pinch zoom         * @param el         * @param options         * @constructor         */        var PinchZoom = function PinchZoom(el, options) {            this.el = el;            this.zoomFactor = 1;            this.lastScale = 1;            this.offset = {                x: 0,                y: 0            };            this.initialOffset = {                x: 0,                y: 0            };            this.options = Object.assign({}, this.defaults, options);            this.setupMarkup();            this.bindEvents();            this.update();            // The image may already be loaded when PinchZoom is initialized,            // and then the load event (which trigger update) will never fire.            if (this.isImageLoaded(this.el)) {                this.updateAspectRatio();                this.setupInitialOffset();            }            this.enable();        },            sum = function sum(a, b) {            return a + b;        },            isCloseTo = function isCloseTo(value, expected) {            return value > expected - 0.01 && value < expected + 0.01;        };        PinchZoom.prototype = {            defaults: {                tapZoomFactor: 2,                zoomOutFactor: 1.3,                animationDuration: 300,                maxZoom: 4,                minZoom: 0.5,                draggableUnzoomed: true,                lockDragAxis: false,                use2d: true,                zoomStartEventName: 'pz_zoomstart',                zoomUpdateEventName: 'pz_zoomupdate',                zoomEndEventName: 'pz_zoomend',                dragStartEventName: 'pz_dragstart',                dragUpdateEventName: 'pz_dragupdate',                dragEndEventName: 'pz_dragend',                doubleTapEventName: 'pz_doubletap',                verticalPadding: 0,                horizontalPadding: 0            },            /**             * Event handler for 'dragstart'             * @param event             */            handleDragStart: function handleDragStart(event) {                triggerEvent(this.el, this.options.dragStartEventName);                this.stopAnimation();                this.lastDragPosition = false;                this.hasInteraction = true;                this.handleDrag(event);            },            /**             * Event handler for 'drag'             * @param event             */            handleDrag: function handleDrag(event) {                var touch = this.getTouches(event)[0];                this.drag(touch, this.lastDragPosition);                this.offset = this.sanitizeOffset(this.offset);                this.lastDragPosition = touch;            },            handleDragEnd: function handleDragEnd() {                triggerEvent(this.el, this.options.dragEndEventName);                this.end();            },            /**             * Event handler for 'zoomstart'             * @param event             */            handleZoomStart: function handleZoomStart(event) {                triggerEvent(this.el, this.options.zoomStartEventName);                this.stopAnimation();                this.lastScale = 1;                this.nthZoom = 0;                this.lastZoomCenter = false;                this.hasInteraction = true;            },            /**             * Event handler for 'zoom'             * @param event             */            handleZoom: function handleZoom(event, newScale) {                // a relative scale factor is used                var touchCenter = this.getTouchCenter(this.getTouches(event)),                    scale = newScale / this.lastScale;                this.lastScale = newScale;                // the first touch events are thrown away since they are not precise                this.nthZoom += 1;                if (this.nthZoom > 3) {                    this.scale(scale, touchCenter);                    this.drag(touchCenter, this.lastZoomCenter);                }                this.lastZoomCenter = touchCenter;            },            handleZoomEnd: function handleZoomEnd() {                triggerEvent(this.el, this.options.zoomEndEventName);                this.end();            },            /**             * Event handler for 'doubletap'             * @param event             */            handleDoubleTap: function handleDoubleTap(event) {                var center = this.getTouches(event)[0],                    zoomFactor = this.zoomFactor > 1 ? 1 : this.options.tapZoomFactor,                    startZoomFactor = this.zoomFactor,                    updateProgress = function (progress) {                    this.scaleTo(startZoomFactor + progress * (zoomFactor - startZoomFactor), center);                }.bind(this);                if (this.hasInteraction) {                    return;                }                this.isDoubleTap = true;                if (startZoomFactor > zoomFactor) {                    center = this.getCurrentZoomCenter();                }                this.animate(this.options.animationDuration, updateProgress, this.swing);                triggerEvent(this.el, this.options.doubleTapEventName);            },            /**             * Compute the initial offset             *             * the element should be centered in the container upon initialization             */            computeInitialOffset: function computeInitialOffset() {                this.initialOffset = {                    x: -Math.abs(this.el.offsetWidth * this.getInitialZoomFactor() - this.container.offsetWidth) / 2,                    y: -Math.abs(this.el.offsetHeight * this.getInitialZoomFactor() - this.container.offsetHeight) / 2                };            },            /**             * Determine if image is loaded             */            isImageLoaded: function isImageLoaded(el) {                if (el.nodeName === 'IMG') {                    return el.complete && el.naturalHeight !== 0;                } else {                    return Array.from(el.querySelectorAll('img')).every(this.isImageLoaded);                }            },            setupInitialOffset: function setupInitialOffset() {                if (this._initialOffsetSetup) {                    return;                }                this._initialOffsetSetup = true;                this.computeInitialOffset();                this.offset.x = this.initialOffset.x;                this.offset.y = this.initialOffset.y;            },            /**             * Max / min values for the offset             * @param offset             * @return {Object} the sanitized offset             */            sanitizeOffset: function sanitizeOffset(offset) {                var elWidth = this.el.offsetWidth * this.getInitialZoomFactor() * this.zoomFactor;                var elHeight = this.el.offsetHeight * this.getInitialZoomFactor() * this.zoomFactor;                var maxX = elWidth - this.getContainerX() + this.options.horizontalPadding,                    maxY = elHeight - this.getContainerY() + this.options.verticalPadding,                    maxOffsetX = Math.max(maxX, 0),                    maxOffsetY = Math.max(maxY, 0),                    minOffsetX = Math.min(maxX, 0) - this.options.horizontalPadding,                    minOffsetY = Math.min(maxY, 0) - this.options.verticalPadding;                return {                    x: Math.min(Math.max(offset.x, minOffsetX), maxOffsetX),                    y: Math.min(Math.max(offset.y, minOffsetY), maxOffsetY)                };            },            /**             * Scale to a specific zoom factor (not relative)             * @param zoomFactor             * @param center             */            scaleTo: function scaleTo(zoomFactor, center) {                this.scale(zoomFactor / this.zoomFactor, center);            },            /**             * Scales the element from specified center             * @param scale             * @param center             */            scale: function scale(_scale, center) {                _scale = this.scaleZoomFactor(_scale);                this.addOffset({                    x: (_scale - 1) * (center.x + this.offset.x),                    y: (_scale - 1) * (center.y + this.offset.y)                });                triggerEvent(this.el, this.options.zoomUpdateEventName);            },            /**             * Scales the zoom factor relative to current state             * @param scale             * @return the actual scale (can differ because of max min zoom factor)             */            scaleZoomFactor: function scaleZoomFactor(scale) {                var originalZoomFactor = this.zoomFactor;                this.zoomFactor *= scale;                this.zoomFactor = Math.min(this.options.maxZoom, Math.max(this.zoomFactor, this.options.minZoom));                return this.zoomFactor / originalZoomFactor;            },            /**             * Determine if the image is in a draggable state             *             * When the image can be dragged, the drag event is acted upon and cancelled.             * When not draggable, the drag event bubbles through this component.             *             * @return {Boolean}             */            canDrag: function canDrag() {                return this.options.draggableUnzoomed || !isCloseTo(this.zoomFactor, 1);            },            /**             * Drags the element             * @param center             * @param lastCenter             */            drag: function drag(center, lastCenter) {                if (lastCenter) {                    if (this.options.lockDragAxis) {                        // lock scroll to position that was changed the most                        if (Math.abs(center.x - lastCenter.x) > Math.abs(center.y - lastCenter.y)) {                            this.addOffset({                                x: -(center.x - lastCenter.x),                                y: 0                            });                        } else {                            this.addOffset({                                y: -(center.y - lastCenter.y),                                x: 0                            });                        }                    } else {                        this.addOffset({                            y: -(center.y - lastCenter.y),                            x: -(center.x - lastCenter.x)                        });                    }                    triggerEvent(this.el, this.options.dragUpdateEventName);                }            },            /**             * Calculates the touch center of multiple touches             * @param touches             * @return {Object}             */            getTouchCenter: function getTouchCenter(touches) {                return this.getVectorAvg(touches);            },            /**             * Calculates the average of multiple vectors (x, y values)             */            getVectorAvg: function getVectorAvg(vectors) {                return {                    x: vectors.map(function (v) {                        return v.x;                    }).reduce(sum) / vectors.length,                    y: vectors.map(function (v) {                        return v.y;                    }).reduce(sum) / vectors.length                };            },            /**             * Adds an offset             * @param offset the offset to add             * @return return true when the offset change was accepted             */            addOffset: function addOffset(offset) {                this.offset = {                    x: this.offset.x + offset.x,                    y: this.offset.y + offset.y                };            },            sanitize: function sanitize() {                if (this.zoomFactor < this.options.zoomOutFactor) {                    this.zoomOutAnimation();                } else if (this.isInsaneOffset(this.offset)) {                    this.sanitizeOffsetAnimation();                }            },            /**             * Checks if the offset is ok with the current zoom factor             * @param offset             * @return {Boolean}             */            isInsaneOffset: function isInsaneOffset(offset) {                var sanitizedOffset = this.sanitizeOffset(offset);                return sanitizedOffset.x !== offset.x || sanitizedOffset.y !== offset.y;            },            /**             * Creates an animation moving to a sane offset             */            sanitizeOffsetAnimation: function sanitizeOffsetAnimation() {                var targetOffset = this.sanitizeOffset(this.offset),                    startOffset = {                    x: this.offset.x,                    y: this.offset.y                },                    updateProgress = function (progress) {                    this.offset.x = startOffset.x + progress * (targetOffset.x - startOffset.x);                    this.offset.y = startOffset.y + progress * (targetOffset.y - startOffset.y);                    this.update();                }.bind(this);                this.animate(this.options.animationDuration, updateProgress, this.swing);            },            /**             * Zooms back to the original position,             * (no offset and zoom factor 1)             */            zoomOutAnimation: function zoomOutAnimation() {                if (this.zoomFactor === 1) {                    return;                }                var startZoomFactor = this.zoomFactor,                    zoomFactor = 1,                    center = this.getCurrentZoomCenter(),                    updateProgress = function (progress) {                    this.scaleTo(startZoomFactor + progress * (zoomFactor - startZoomFactor), center);                }.bind(this);                this.animate(this.options.animationDuration, updateProgress, this.swing);            },            /**             * Updates the aspect ratio             */            updateAspectRatio: function updateAspectRatio() {                this.setContainerY(this.container.parentElement.offsetHeight);            },            /**             * Calculates the initial zoom factor (for the element to fit into the container)             * @return {number} the initial zoom factor             */            getInitialZoomFactor: function getInitialZoomFactor() {                var xZoomFactor = this.container.offsetWidth / this.el.offsetWidth;                var yZoomFactor = this.container.offsetHeight / this.el.offsetHeight;                return Math.min(xZoomFactor, yZoomFactor);            },            /**             * Calculates the aspect ratio of the element             * @return the aspect ratio             */            getAspectRatio: function getAspectRatio() {                return this.el.offsetWidth / this.el.offsetHeight;            },            /**             * Calculates the virtual zoom center for the current offset and zoom factor             * (used for reverse zoom)             * @return {Object} the current zoom center             */            getCurrentZoomCenter: function getCurrentZoomCenter() {                var offsetLeft = this.offset.x - this.initialOffset.x;                var centerX = -1 * this.offset.x - offsetLeft / (1 / this.zoomFactor - 1);                var offsetTop = this.offset.y - this.initialOffset.y;                var centerY = -1 * this.offset.y - offsetTop / (1 / this.zoomFactor - 1);                return {                    x: centerX,                    y: centerY                };            },            /**             * Returns the touches of an event relative to the container offset             * @param event             * @return array touches             */            getTouches: function getTouches(event) {                var rect = this.container.getBoundingClientRect();                var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;                var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft;                var posTop = rect.top + scrollTop;                var posLeft = rect.left + scrollLeft;                return Array.prototype.slice.call(event.touches).map(function (touch) {                    return {                        x: touch.pageX - posLeft,                        y: touch.pageY - posTop                    };                });            },            /**             * Animation loop             * does not support simultaneous animations             * @param duration             * @param framefn             * @param timefn             * @param callback             */            animate: function animate(duration, framefn, timefn, callback) {                var startTime = new Date().getTime(),                    renderFrame = function () {                    if (!this.inAnimation) {                        return;                    }                    var frameTime = new Date().getTime() - startTime,                        progress = frameTime / duration;                    if (frameTime >= duration) {                        framefn(1);                        if (callback) {                            callback();                        }                        this.update();                        this.stopAnimation();                        this.update();                    } else {                        if (timefn) {                            progress = timefn(progress);                        }                        framefn(progress);                        this.update();                        requestAnimationFrame(renderFrame);                    }                }.bind(this);                this.inAnimation = true;                requestAnimationFrame(renderFrame);            },            /**             * Stops the animation             */            stopAnimation: function stopAnimation() {                this.inAnimation = false;            },            /**             * Swing timing function for animations             * @param p             * @return {Number}             */            swing: function swing(p) {                return -Math.cos(p * Math.PI) / 2 + 0.5;            },            getContainerX: function getContainerX() {                return this.container.offsetWidth;            },            getContainerY: function getContainerY() {                return this.container.offsetHeight;            },            setContainerY: function setContainerY(y) {                return this.container.style.height = y + 'px';            },            /**             * Creates the expected html structure             */            setupMarkup: function setupMarkup() {                this.container = buildElement('
   
');                this.el.parentNode.insertBefore(this.container, this.el);                this.container.appendChild(this.el);                this.container.style.overflow = 'hidden';                this.container.style.position = 'relative';                this.el.style.webkitTransformOrigin = '0% 0%';                this.el.style.mozTransformOrigin = '0% 0%';                this.el.style.msTransformOrigin = '0% 0%';                this.el.style.oTransformOrigin = '0% 0%';                this.el.style.transformOrigin = '0% 0%';                this.el.style.position = 'absolute';            },            end: function end() {                this.hasInteraction = false;                this.sanitize();                this.update();            },            /**             * Binds all required event listeners             */            bindEvents: function bindEvents() {                var self = this;                detectGestures(this.container, this);                window.addEventListener('resize', this.update.bind(this));                Array.from(this.el.querySelectorAll('img')).forEach(function (imgEl) {                    imgEl.addEventListener('load', self.update.bind(self));                });                if (this.el.nodeName === 'IMG') {                    this.el.addEventListener('load', this.update.bind(this));                }            },            /**             * Updates the css values according to the current zoom factor and offset             */            update: function update(event) {                if (this.updatePlaned) {                    return;                }                this.updatePlaned = true;                window.setTimeout(function () {                    this.updatePlaned = false;                    this.updateAspectRatio();                    if (event && event.type === 'resize') {                        this.computeInitialOffset();                    }                    if (event && event.type === 'load') {                        this.setupInitialOffset();                    }                    var zoomFactor = this.getInitialZoomFactor() * this.zoomFactor,                        offsetX = -this.offset.x / zoomFactor,                        offsetY = -this.offset.y / zoomFactor,                        transform3d = 'scale3d(' + zoomFactor + ', ' + zoomFactor + ',1) ' + 'translate3d(' + offsetX + 'px,' + offsetY + 'px,0px)',                        transform2d = 'scale(' + zoomFactor + ', ' + zoomFactor + ') ' + 'translate(' + offsetX + 'px,' + offsetY + 'px)',                        removeClone = function () {                        if (this.clone) {                            this.clone.parentNode.removeChild(this.clone);                            delete this.clone;                        }                    }.bind(this);                    // Scale 3d and translate3d are faster (at least on ios)                    // but they also reduce the quality.                    // PinchZoom uses the 3d transformations during interactions                    // after interactions it falls back to 2d transformations                    if (!this.options.use2d || this.hasInteraction || this.inAnimation) {                        this.is3d = true;                        removeClone();                        this.el.style.webkitTransform = transform3d;                        this.el.style.mozTransform = transform2d;                        this.el.style.msTransform = transform2d;                        this.el.style.oTransform = transform2d;                        this.el.style.transform = transform3d;                    } else {                        // When changing from 3d to 2d transform webkit has some glitches.                        // To avoid this, a copy of the 3d transformed element is displayed in the                        // foreground while the element is converted from 3d to 2d transform                        if (this.is3d) {                            this.clone = this.el.cloneNode(true);                            this.clone.style.pointerEvents = 'none';                            this.container.appendChild(this.clone);                            window.setTimeout(removeClone, 200);                        }                        this.el.style.webkitTransform = transform2d;                        this.el.style.mozTransform = transform2d;                        this.el.style.msTransform = transform2d;                        this.el.style.oTransform = transform2d;                        this.el.style.transform = transform2d;                        this.is3d = false;                    }                }.bind(this), 0);            },            /**             * Enables event handling for gestures             */            enable: function enable() {                this.enabled = true;            },            /**             * Disables event handling for gestures             */            disable: function disable() {                this.enabled = false;            }        };        var detectGestures = function detectGestures(el, target) {            var interaction = null,                fingers = 0,                lastTouchStart = null,                startTouches = null,                setInteraction = function setInteraction(newInteraction, event) {                if (interaction !== newInteraction) {                    if (interaction && !newInteraction) {                        switch (interaction) {                            case "zoom":                                target.handleZoomEnd(event);                                break;                            case 'drag':                                target.handleDragEnd(event);                                break;                        }                    }                    switch (newInteraction) {                        case 'zoom':                            target.handleZoomStart(event);                            break;                        case 'drag':                            target.handleDragStart(event);                            break;                    }                }                interaction = newInteraction;            },                updateInteraction = function updateInteraction(event) {                if (fingers === 2) {                    setInteraction('zoom');                } else if (fingers === 1 && target.canDrag()) {                    setInteraction('drag', event);                } else {                    setInteraction(null, event);                }            },                targetTouches = function targetTouches(touches) {                return Array.from(touches).map(function (touch) {                    return {                        x: touch.pageX,                        y: touch.pageY                    };                });            },                getDistance = function getDistance(a, b) {                var x, y;                x = a.x - b.x;                y = a.y - b.y;                return Math.sqrt(x * x + y * y);            },                calculateScale = function calculateScale(startTouches, endTouches) {                var startDistance = getDistance(startTouches[0], startTouches[1]),                    endDistance = getDistance(endTouches[0], endTouches[1]);                return endDistance / startDistance;            },                cancelEvent = function cancelEvent(event) {                event.stopPropagation();                event.preventDefault();            },                detectDoubleTap = function detectDoubleTap(event) {                var time = new Date().getTime();                if (fingers > 1) {                    lastTouchStart = null;                }                if (time - lastTouchStart < 300) {                    cancelEvent(event);                    target.handleDoubleTap(event);                    switch (interaction) {                        case "zoom":                            target.handleZoomEnd(event);                            break;                        case 'drag':                            target.handleDragEnd(event);                            break;                    }                } else {                    target.isDoubleTap = false;                }                if (fingers === 1) {                    lastTouchStart = time;                }            },                firstMove = true;            el.addEventListener('touchstart', function (event) {                if (target.enabled) {                    firstMove = true;                    fingers = event.touches.length;                    detectDoubleTap(event);                }            });            el.addEventListener('touchmove', function (event) {                if (target.enabled && !target.isDoubleTap) {                    if (firstMove) {                        updateInteraction(event);                        if (interaction) {                            cancelEvent(event);                        }                        startTouches = targetTouches(event.touches);                    } else {                        switch (interaction) {                            case 'zoom':                                target.handleZoom(event, calculateScale(startTouches, targetTouches(event.touches)));                                break;                            case 'drag':                                target.handleDrag(event);                                break;                        }                        if (interaction) {                            cancelEvent(event);                            target.update();                        }                    }                    firstMove = false;                }            });            el.addEventListener('touchend', function (event) {                if (target.enabled) {                    fingers = event.touches.length;                    updateInteraction(event);                }            });        };        return PinchZoom;    };    var PinchZoom = definePinchZoom();    exports.default = PinchZoom;});