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365 lines
10 KiB
JavaScript
365 lines
10 KiB
JavaScript
/*
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* JavaScript Load Image
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* https://github.com/blueimp/JavaScript-Load-Image
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*
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* Copyright 2011, Sebastian Tschan
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* https://blueimp.net
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*
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* Licensed under the MIT license:
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* http://www.opensource.org/licenses/MIT
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*/
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/* global define, URL, webkitURL, FileReader */
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;(function ($) {
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'use strict'
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// Loads an image for a given File object.
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// Invokes the callback with an img or optional canvas
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// element (if supported by the browser) as parameter:
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function loadImage (file, callback, options) {
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var img = document.createElement('img')
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var url
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img.onerror = function (event) {
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return loadImage.onerror(img, event, file, callback, options)
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}
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img.onload = function (event) {
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return loadImage.onload(img, event, file, callback, options)
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}
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if (loadImage.isInstanceOf('Blob', file) ||
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// Files are also Blob instances, but some browsers
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// (Firefox 3.6) support the File API but not Blobs:
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loadImage.isInstanceOf('File', file)) {
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url = img._objectURL = loadImage.createObjectURL(file)
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} else if (typeof file === 'string') {
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url = file
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if (options && options.crossOrigin) {
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img.crossOrigin = options.crossOrigin
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}
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} else {
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return false
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}
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if (url) {
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img.src = url
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return img
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}
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return loadImage.readFile(file, function (e) {
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var target = e.target
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if (target && target.result) {
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img.src = target.result
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} else if (callback) {
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callback(e)
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}
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})
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}
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// The check for URL.revokeObjectURL fixes an issue with Opera 12,
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// which provides URL.createObjectURL but doesn't properly implement it:
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var urlAPI = (window.createObjectURL && window) ||
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(window.URL && URL.revokeObjectURL && URL) ||
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(window.webkitURL && webkitURL)
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function revokeHelper (img, options) {
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if (img._objectURL && !(options && options.noRevoke)) {
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loadImage.revokeObjectURL(img._objectURL)
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delete img._objectURL
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}
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}
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loadImage.isInstanceOf = function (type, obj) {
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// Cross-frame instanceof check
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return Object.prototype.toString.call(obj) === '[object ' + type + ']'
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}
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loadImage.transform = function (img, options, callback, file, data) {
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callback(loadImage.scale(img, options, data), data)
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}
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loadImage.onerror = function (img, event, file, callback, options) {
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revokeHelper(img, options)
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if (callback) {
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callback.call(img, event)
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}
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}
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loadImage.onload = function (img, event, file, callback, options) {
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revokeHelper(img, options)
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if (callback) {
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loadImage.transform(img, options, callback, file, {})
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}
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}
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// Transform image coordinates, allows to override e.g.
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// the canvas orientation based on the orientation option,
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// gets canvas, options passed as arguments:
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loadImage.transformCoordinates = function () {
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return
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}
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// Returns transformed options, allows to override e.g.
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// maxWidth, maxHeight and crop options based on the aspectRatio.
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// gets img, options passed as arguments:
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loadImage.getTransformedOptions = function (img, options) {
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var aspectRatio = options.aspectRatio
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var newOptions
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var i
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var width
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var height
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if (!aspectRatio) {
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return options
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}
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newOptions = {}
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for (i in options) {
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if (options.hasOwnProperty(i)) {
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newOptions[i] = options[i]
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}
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}
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newOptions.crop = true
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width = img.naturalWidth || img.width
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height = img.naturalHeight || img.height
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if (width / height > aspectRatio) {
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newOptions.maxWidth = height * aspectRatio
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newOptions.maxHeight = height
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} else {
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newOptions.maxWidth = width
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newOptions.maxHeight = width / aspectRatio
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}
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return newOptions
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}
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// Canvas render method, allows to implement a different rendering algorithm:
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loadImage.renderImageToCanvas = function (
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canvas,
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img,
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sourceX,
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sourceY,
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sourceWidth,
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sourceHeight,
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destX,
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destY,
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destWidth,
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destHeight
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) {
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canvas.getContext('2d').drawImage(
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img,
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sourceX,
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sourceY,
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sourceWidth,
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sourceHeight,
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destX,
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destY,
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destWidth,
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destHeight
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)
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return canvas
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}
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// Determines if the target image should be a canvas element:
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loadImage.hasCanvasOption = function (options) {
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return options.canvas || options.crop || !!options.aspectRatio
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}
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// Scales and/or crops the given image (img or canvas HTML element)
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// using the given options.
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// Returns a canvas object if the browser supports canvas
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// and the hasCanvasOption method returns true or a canvas
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// object is passed as image, else the scaled image:
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loadImage.scale = function (img, options, data) {
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options = options || {}
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var canvas = document.createElement('canvas')
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var useCanvas = img.getContext ||
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(loadImage.hasCanvasOption(options) && canvas.getContext)
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var width = img.naturalWidth || img.width
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var height = img.naturalHeight || img.height
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var destWidth = width
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var destHeight = height
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var maxWidth
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var maxHeight
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var minWidth
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var minHeight
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var sourceWidth
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var sourceHeight
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var sourceX
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var sourceY
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var pixelRatio
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var downsamplingRatio
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var tmp
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function scaleUp () {
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var scale = Math.max(
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(minWidth || destWidth) / destWidth,
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(minHeight || destHeight) / destHeight
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)
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if (scale > 1) {
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destWidth *= scale
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destHeight *= scale
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}
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}
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function scaleDown () {
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var scale = Math.min(
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(maxWidth || destWidth) / destWidth,
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(maxHeight || destHeight) / destHeight
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)
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if (scale < 1) {
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destWidth *= scale
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destHeight *= scale
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}
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}
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if (useCanvas) {
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options = loadImage.getTransformedOptions(img, options, data)
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sourceX = options.left || 0
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sourceY = options.top || 0
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if (options.sourceWidth) {
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sourceWidth = options.sourceWidth
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if (options.right !== undefined && options.left === undefined) {
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sourceX = width - sourceWidth - options.right
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}
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} else {
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sourceWidth = width - sourceX - (options.right || 0)
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}
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if (options.sourceHeight) {
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sourceHeight = options.sourceHeight
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if (options.bottom !== undefined && options.top === undefined) {
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sourceY = height - sourceHeight - options.bottom
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}
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} else {
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sourceHeight = height - sourceY - (options.bottom || 0)
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}
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destWidth = sourceWidth
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destHeight = sourceHeight
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}
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maxWidth = options.maxWidth
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maxHeight = options.maxHeight
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minWidth = options.minWidth
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minHeight = options.minHeight
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if (useCanvas && maxWidth && maxHeight && options.crop) {
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destWidth = maxWidth
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destHeight = maxHeight
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tmp = sourceWidth / sourceHeight - maxWidth / maxHeight
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if (tmp < 0) {
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sourceHeight = maxHeight * sourceWidth / maxWidth
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if (options.top === undefined && options.bottom === undefined) {
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sourceY = (height - sourceHeight) / 2
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}
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} else if (tmp > 0) {
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sourceWidth = maxWidth * sourceHeight / maxHeight
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if (options.left === undefined && options.right === undefined) {
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sourceX = (width - sourceWidth) / 2
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}
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}
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} else {
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if (options.contain || options.cover) {
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minWidth = maxWidth = maxWidth || minWidth
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minHeight = maxHeight = maxHeight || minHeight
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}
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if (options.cover) {
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scaleDown()
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scaleUp()
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} else {
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scaleUp()
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scaleDown()
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}
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}
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if (useCanvas) {
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pixelRatio = options.pixelRatio
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if (pixelRatio > 1) {
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canvas.style.width = destWidth + 'px'
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canvas.style.height = destHeight + 'px'
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destWidth *= pixelRatio
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destHeight *= pixelRatio
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canvas.getContext('2d').scale(pixelRatio, pixelRatio)
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}
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downsamplingRatio = options.downsamplingRatio
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if (downsamplingRatio > 0 && downsamplingRatio < 1 &&
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destWidth < sourceWidth && destHeight < sourceHeight) {
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while (sourceWidth * downsamplingRatio > destWidth) {
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canvas.width = sourceWidth * downsamplingRatio
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canvas.height = sourceHeight * downsamplingRatio
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loadImage.renderImageToCanvas(
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canvas,
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img,
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sourceX,
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sourceY,
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sourceWidth,
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sourceHeight,
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0,
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0,
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canvas.width,
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canvas.height
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)
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sourceWidth = canvas.width
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sourceHeight = canvas.height
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img = document.createElement('canvas')
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img.width = sourceWidth
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img.height = sourceHeight
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loadImage.renderImageToCanvas(
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img,
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canvas,
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0,
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0,
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sourceWidth,
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sourceHeight,
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0,
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0,
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sourceWidth,
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sourceHeight
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)
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}
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}
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canvas.width = destWidth
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canvas.height = destHeight
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loadImage.transformCoordinates(
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canvas,
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options
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)
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return loadImage.renderImageToCanvas(
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canvas,
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img,
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sourceX,
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sourceY,
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sourceWidth,
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sourceHeight,
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0,
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0,
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destWidth,
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destHeight
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)
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}
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img.width = destWidth
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img.height = destHeight
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return img
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}
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loadImage.createObjectURL = function (file) {
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return urlAPI ? urlAPI.createObjectURL(file) : false
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}
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loadImage.revokeObjectURL = function (url) {
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return urlAPI ? urlAPI.revokeObjectURL(url) : false
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}
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// Loads a given File object via FileReader interface,
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// invokes the callback with the event object (load or error).
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// The result can be read via event.target.result:
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loadImage.readFile = function (file, callback, method) {
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if (window.FileReader) {
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var fileReader = new FileReader()
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fileReader.onload = fileReader.onerror = callback
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method = method || 'readAsDataURL'
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if (fileReader[method]) {
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fileReader[method](file)
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return fileReader
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}
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}
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return false
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}
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if (typeof define === 'function' && define.amd) {
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define(function () {
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return loadImage
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})
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} else if (typeof module === 'object' && module.exports) {
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module.exports = loadImage
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} else {
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$.loadImage = loadImage
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}
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}(window))
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