function imgPreview(config) {var width = config.width || 200;var height = config.height || 200;return {/*** ie9- 预览图片* @param {type} input_file ,$('input[type=file]') 或者 $('input[type=file]')[0]* @param {type} callback 回掉参数为，$(居中的图片)* @returns {interval}*/iePreview: function(input_file, callback) {$(input_file).select();$(input_file).blur();var src = document.selection.createRange().text;if (/.+\.(jpg|gif|png)$/.test(src) === false) {alert('not image!');return;}var imgitem = $('<div></div>').appendTo('body');var f = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + src + "' , sizingMethod= 'image' )";imgitem.css({filter: f,display: 'none',width: '1px',height: '1px'});var itval = setInterval(function() {var w = imgitem.width();if (w !== 1) {window.clearInterval(itval);var boxWidth = width;var boxHeight = height;var zoom = imgPreview.calcZoom({boxWidth: boxWidth,boxHeight: boxHeight,imgWidth: imgitem.width(),imgHeight: imgitem.height()});var fn = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + src + "' , sizingMethod= 'scale' )";var out = $('<div></div>').css(zoom).css({'filter': fn,display: 'block'});callback(out);imgitem.remove();}},16);},/*** html5 objecturl 预览* @param {type} input_file ,$('input[type=file]') 或者 $('input[type=file]')[0]* @param {type} callback 回掉参数为，$(居中的图片)* @returns {undefined}*/canvasPreview: function(input_file, callback) {var files = $(input_file).prop('files');$.each(files,function(index, val) {var img = new Image();img.src = window.URL.createObjectURL(val);img.onload = function() {window.URL.revokeObjectURL(img.src);var boxWidth = width;var boxHeight = height;var zoom = imgPreview.calcZoom({boxWidth: boxWidth,boxHeight: boxHeight,imgWidth: img.naturalWidth,imgHeight: img.naturalHeight});//var canvas = document.createElement( 'canvas' );//canvas.width = parseInt(zoom.width);//canvas.height = parseInt(zoom.height);////var ctx = canvas.getContext("2d");//ctx.drawImage(img, 0,0,canvas.width, canvas.height);//var out = $(canvas).css(zoom);//canvas裸压缩成像质量太差，如果要高质量压缩请参考 https://github.com/mailru/FileAPIvar out = $(img).css(zoom);callback(out);};});},preview: function() {if (document.body.filters) {this.iePreview.apply(this, arguments);} else if (window.HTMLCanvasElement) {this.canvasPreview.apply(this, arguments);}}};
}imgPreview.calcZoom = function(param) {var boxw = param.boxWidth;var boxh = param.boxHeight;var imgw = param.imgWidth;var imgh = param.imgHeight;var out = {width: '0px',height: '0px',marginLeft: '0px',marginRight: '0px',marginTop: '0px',marginBottom: '0px'};if (boxw / boxh > imgw / imgh) {out.height = boxh;out.width = imgw / imgh * boxh;out.marginLeft = (boxw - out.width) / 2;out.marginRight = boxw - out.marginLeft - out.width;} else {out.width = boxw;out.height = imgh / imgw * boxw;out.marginTop = (boxh - out.height) / 2;out.marginBottom = boxh - out.marginTop - out.height;}return out;
};