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/*

* JavaScript Load Image 1.3.1

* https://github.com/blueimp/JavaScript-Load-Image

*

* Copyright 2011, Sebastian Tschan

* https://blueimp.net

*

* iOS image scaling fixes based on

* https://github.com/stomita/ios-imagefile-megapixel

*

* Licensed under the MIT license:

* http://www.opensource.org/licenses/MIT

*/

/*jslint nomen: true, bitwise: true */

/*global window, document, URL, webkitURL, Blob, File, FileReader, define */

(function ($) {

'use strict';

// Loads an image for a given File object.

// Invokes the callback with an img or optional canvas

// element (if supported by the browser) as parameter:

var loadImage = function (file, callback, options) {

var img = document.createElement('img'),

url,

oUrl;

img.onerror = callback;

img.onload = function () {

if (oUrl && !(options && options.noRevoke)) {

loadImage.revokeObjectURL(oUrl);

}

callback(loadImage.scale(img, options));

};

if ((window.Blob && file instanceof Blob) ||

// Files are also Blob instances, but some browsers

// (Firefox 3.6) support the File API but not Blobs:

(window.File && file instanceof File)) {

url = oUrl = loadImage.createObjectURL(file);

// Store the file type for resize processing:

img._type = file.type;

} else {

url = file;

}

if (url) {

img.src = url;

return img;

}

return loadImage.readFile(file, function (e) {

var target = e.target;

if (target && target.result) {

img.src = target.result;

} else {

callback(e);

}

});

},

// The check for URL.revokeObjectURL fixes an issue with Opera 12,

// which provides URL.createObjectURL but doesn't properly implement it:

urlAPI = (window.createObjectURL && window) ||

(window.URL && URL.revokeObjectURL && URL) ||

(window.webkitURL && webkitURL);

// Detects subsampling in JPEG images:

loadImage.detectSubsampling = function (img) {

var iw = img.width,

ih = img.height,

canvas,

ctx;

if (iw * ih > 1024 * 1024) { // only consider mexapixel images

canvas = document.createElement('canvas');

canvas.width = canvas.height = 1;

ctx = canvas.getContext('2d');

ctx.drawImage(img, -iw + 1, 0);

// subsampled image becomes half smaller in rendering size.

// check alpha channel value to confirm image is covering edge pixel or not.

// if alpha value is 0 image is not covering, hence subsampled.

return ctx.getImageData(0, 0, 1, 1).data[3] === 0;

}

return false;

};

// Detects vertical squash in JPEG images:

loadImage.detectVerticalSquash = function (img, ih) {

var canvas = document.createElement('canvas'),

ctx = canvas.getContext('2d'),

data,

sy,

ey,

py,

alpha;

canvas.width = 1;

canvas.height = ih;

ctx.drawImage(img, 0, 0);

data = ctx.getImageData(0, 0, 1, ih).data;

// search image edge pixel position in case it is squashed vertically:

sy = 0;

ey = ih;

py = ih;

while (py > sy) {

alpha = data[(py - 1) * 4 + 3];

if (alpha === 0) {

ey = py;

} else {

sy = py;

}

py = (ey + sy) >> 1;

}

return (py / ih) || 1;

};

// Renders image to canvas while working around iOS image scaling bugs:

// https://github.com/blueimp/JavaScript-Load-Image/issues/13

loadImage.renderImageToCanvas = function (img, canvas, width, height) {

var iw = img.width,

ih = img.height,

ctx = canvas.getContext('2d'),

vertSquashRatio,

d = 1024, // size of tiling canvas

tmpCanvas = document.createElement('canvas'),

tmpCtx,

dw,

dh,

dx,

dy,

sx,

sy;

ctx.save();

if (loadImage.detectSubsampling(img)) {

iw /= 2;

ih /= 2;

}

vertSquashRatio = loadImage.detectVerticalSquash(img, ih);

tmpCanvas.width = tmpCanvas.height = d;

tmpCtx = tmpCanvas.getContext('2d');

dw = Math.ceil(d * width / iw);

dh = Math.ceil(d * height / ih / vertSquashRatio);

dy = 0;

sy = 0;

while (sy < ih) {

dx = 0;

sx = 0;

while (sx < iw) {

tmpCtx.clearRect(0, 0, d, d);

tmpCtx.drawImage(img, -sx, -sy);

ctx.drawImage(tmpCanvas, 0, 0, d, d, dx, dy, dw, dh);

sx += d;

dx += dw;

}

sy += d;

dy += dh;

}

ctx.restore();

tmpCanvas = tmpCtx = null;

};

// Scales the given image (img or canvas HTML element)

// using the given options.

// Returns a canvas object if the browser supports canvas

// and the canvas option is true or a canvas object is passed

// as image, else the scaled image:

loadImage.scale = function (img, options) {

options = options || {};

var canvas = document.createElement('canvas'),

width = img.width,

height = img.height,

scale = Math.max(

(options.minWidth || width) / width,

(options.minHeight || height) / height

);

if (scale > 1) {

width = Math.ceil(width * scale);

height = Math.ceil(height * scale);

}

scale = Math.min(

(options.maxWidth || width) / width,

(options.maxHeight || height) / height

);

if (scale < 1) {

width = Math.ceil(width * scale);

height = Math.ceil(height * scale);

}

if (img.getContext || (options.canvas && canvas.getContext)) {

canvas.width = width;

canvas.height = height;

if (img._type === 'image/jpeg') {

loadImage

.renderImageToCanvas(img, canvas, width, height);

} else {

canvas.getContext('2d')

.drawImage(img, 0, 0, width, height);

}

return canvas;

}

img.width = width;

img.height = height;

return img;

};

loadImage.createObjectURL = function (file) {

return urlAPI ? urlAPI.createObjectURL(file) : false;

};

loadImage.revokeObjectURL = function (url) {

return urlAPI ? urlAPI.revokeObjectURL(url) : false;

};

// Loads a given File object via FileReader interface,

// invokes the callback with the event object (load or error).

// The result can be read via event.target.result:

loadImage.readFile = function (file, callback) {

if (window.FileReader && FileReader.prototype.readAsDataURL) {

var fileReader = new FileReader();

fileReader.onload = fileReader.onerror = callback;

fileReader.readAsDataURL(file);

return fileReader;

}

return false;

};

if (typeof define === 'function' && define.amd) {

define(function () {

return loadImage;

});

} else {

$.loadImage = loadImage;

}

}(this));