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上传压缩图片
Dai的博客
Original
1136 people have browsed it
/**
 * 图片压缩,默认同比例压缩
 * @param {Object} f
 *   图片文件
 * @param {Object} obj
 *   obj 对象 有 width, height, quality(0-1)
 * @param {Object} callback
 *   回调函数有一个参数,base64的字符串数据
 */
function coursePptChange(f,obj, callback){
    var MyTest = f.files[0];
    var reader = new FileReader();
    reader.readAsDataURL(MyTest);
    reader.onload = function(theFile) {
        var img = new Image();
        img.src = theFile.target.result;
        img.onload = function(){
            var that = this;
            console.log(that.length);
            // 默认按比例压缩
            var w = that.width,
                h = that.height,
                scale = w / h;
            w = obj.width || w;
            h = obj.height || (w / scale);
            var quality = 0.1;  // 默认图片质量为0.7
            //生成canvas
            var canvas = document.createElement('canvas');
            var ctx = canvas.getContext('2d');
            // 创建属性节点
            var anw = document.createAttribute("width");
            anw.nodeValue = w;
            var anh = document.createAttribute("height");
            anh.nodeValue = h;
            canvas.setAttributeNode(anw);
            canvas.setAttributeNode(anh);
            ctx.drawImage(that, 0, 0, w, h);
            // 图像质量
            if(obj.quality && obj.quality <= 1 && obj.quality > 0){
                quality = obj.quality;
            }
            // quality值越小,所绘制出的图像越模糊
            var base64 = canvas.toDataURL('image/jpeg', quality );
            // 回调函数返回base64的值
            callback(base64);
        }
    };
}
// 调用函数处理图片      
// coursePptChange(this, {
//     // 注意:在pc端可以用绝对路径或相对路径,移动端最好用绝对路径
//     width : 200
// }, function(base){
//     //直接将获取到的base64的字符串,放到一个image标签中就可看到测试后的压缩之后的样式图了
//     console.log(base.length);
//     document.getElementById("faceSrc").src = base;
//     console.log("压缩后:" + base.length / 1024 + " " + base);
// })


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