mui配合jpgtobase64.js压缩正文

本示例代码，为我爱模板网在项目中使用的，mui拍照或从相册选择照片，并且对照片进行1倍压缩，最终得到base64为图片地址的代码。这里的图片压缩，用的是jpgtobase64.js插件(点击下载)，它的原理很简单，就是利用html5的canvas，将图片放到canvas画布上，再进行缩放得到结果，代码已经在文章末尾提供。废话不多说，直接上代码：

---

<script src="js/mui.min.js"></script>
<script src="js/jpgtobase64.js"></script>
<script>
var photo; //用以接收图片最终地址

//弹出选择拍照还是从相册获取
document.querySelector('#upload').addEventListener('tap', function(){
    var buttonTit = [{ 
        title: "拍照" 
    }, { 
        title: "从手机相册选择" 
    }];
    plus.nativeUI.actionSheet({ 
            title: "上传图片", 
            cancel: "取消", 
            buttons: buttonTit 
        }, function(b) { /*actionSheet 按钮点击事件*/ 
            switch (b.index) { 
                case 0: 
                    break; 
                case 1: 
                    getImage(); /*拍照*/ 
                    break; 
                case 2: 
                    galleryImg();/*打开相册*/ 
                    break; 
                default: 
                    break; 
        } 
    })
})

//拍照
function getImage(){
    var cmr = plus.camera.getCamera(1); //获取后面的摄像头
    cmr.captureImage(function(p) {
        //拍照成功，返回路径 p，但是不是绝对路径
        //通过p，读取图片文件
        plus.io.resolveLocalFileSystemURL(p, function(entry) {
            //entry为获取的文件，.file()方法可以获取该文件的文件名、大小等信息，返回包含文件信息的对象
            entry.file(function (file) {
                //alert("getFile:" + JSON.stringify(file));
                var fileReader = new plus.io.FileReader(); //开启读取文件
                fileReader.readAsDataURL(file, 'utf-8');   //将文件数据对象信息file进行url base64编码
                fileReader.onloadend = function (evt) {
                    //压缩图片
                    convertImgToBase64(evt.target.result, function (retImg) {
                        photo = retImg;
                        document.querySelector('.uploaded-imgs').innerHTML += '<span><img src="'+photo+'"></span>';
                    });
                }
            })
        }, function(e) {
            alert(e.message);
        }); 
    },function(e) {}, {
        filename: "_doc/camera/" 
    }); //拍照
}

//从相册选择
function galleryImg(){
    plus.gallery.pick(function(e){
        for(var i in e.files){
            var fileSrc = e.files[i];
            //压缩图片
            convertImgToBase64(fileSrc, function (retImg) {
                photo = retImg;
                document.querySelector('.uploaded-imgs').innerHTML += '<span><img src="'+photo+'"></span>';
            });
        }
    }, function (e) {
        console.log( "取消选择图片" );
    },{
        filter: "image", 
        multiple: true, 
        maximum: 1, 
        system: false, 
        onmaxed: function() {
            plus.nativeUI.alert('最多只能选择1张图片');
        } 
    });
}
</script>





function convertImgToBase64(url, callback, outputFormat) {
    var canvas = document.createElement('CANVAS');
    var ctx = canvas.getContext('2d');
    var img = new Image;
    img.crossOrigin = 'Anonymous';
    img.onload = function () {
        var width = img.width;
        var height = img.height;
        // 按比例压缩1倍
        var rate = (width < height ? width / height : height / width) / 1;
        canvas.width = width * rate;
        canvas.height = height * rate;
        ctx.drawImage(img, 0, 0, width, height, 0, 0, width * rate, height * rate);
        var dataURL = canvas.toDataURL(outputFormat || 'image/png');
        callback.call(this, dataURL);
        canvas = null;
    };
    img.src = url;
}