1.canvas转换为dataURL (从canvas获取dataURL)

var dataurl = canvas.toDataURL('image/png');

var dataurl2 = canvas.toDataURL('image/jpeg', 0.8);

2.File对象转换为dataURL、Blob对象转换为dataURL

function readBlobAsDataURL(blob, callback) {    var a = new FileReader();    a.onload = function(e) {callback(e.target.result);};    a.readAsDataURL(blob);}//example:readBlobAsDataURL(blob, function (dataurl){    console.log(dataurl);});readBlobAsDataURL(file, function (dataurl){    console.log(dataurl);});

3.dataURL转换为Blob对象、dataURL转换为File对象

function dataURLtoBlob(dataurl) {    var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],        bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);    while(n--){        u8arr[n] = bstr.charCodeAt(n);    }    return new Blob([u8arr], {type:mime});}function dataURLtoFile(dataurl, filename) {    var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],        bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);    while(n--){        u8arr[n] = bstr.charCodeAt(n);    }    return new File([u8arr], filename, {type:mime});}//test:var blob = dataURLtoBlob('data:text/plain;base64,YWFhYWFhYQ==');var file = dataURLtoFile('data:text/plain;base64,YWFhYWFhYQ==', 'test.txt');

4.dataURL图片数据绘制到canvas

var img = new Image();
img.onload = function(){canvas.drawImage(img);
};
img.src = dataurl;

5.File,Blob的图片文件数据绘制到canvas

readBlobAsDataURL(file, function (dataurl){    var img = new Image();    img.onload = function(){        canvas.drawImage(img);    };    img.src = dataurl;});

6.Canvas转换为Blob对象并使用Ajax发送

var dataurl = canvas.toDataURL('image/png');var blob = dataURLtoBlob(dataurl);//使用ajax发送var fd = new FormData();fd.append("image", blob, "image.png");var xhr = new XMLHttpRequest();xhr.open('POST', '/server', true);xhr.send(fd);