您可以使用FormData对象获取表单的值，然后将画布的Blob版本附加到FormData中。

该斑点将被服务器视为文件。

不幸的是，所有浏览器仍然不支持本机canvas.toBlob()方法，甚至值得，所有实现都不相同。
现在，所有主要的浏览器都支持toBlob方法，并且您可以在mdn上为较旧的浏览器找到一个 polyfill。

// the function to create and send our FormData
var send = function(form, url, canvas, filename, type, quality, callback) {

  canvas.toBlob(function(blob){
    var formData = form ? new FormData(form) : new FormData();
    formData.append('file', blob, filename);

    var xhr = new XMLHttpRequest();
    xhr.onload = callback;
    xhr.open('POST', url);
    xhr.send(formData);

    }, type, quality);
};

// How to use it //

var form = document.querySelector('form'),   // the form to construct the FormData, can be null or undefined to send only the image
  url = 'http://example.com/upload.php',     // required, the url where we'll send it
  canvas = document.querySelector('canvas'), // required, the canvas to send
  filename = (new Date()).getTime() + '.jpg',// required, a filename
  type = 'image/jpeg',                       // optional, the algorithm to encode the canvas. If omitted defaults to 'image/png'
  quality = .5,                              // optional, if the type is set to jpeg, 0-1 parameter that sets the quality of the encoding
  callback = function(e) {console.log(this.response);}; // optional, a callback once the xhr finished

send(form, url, canvas, filename, type, quality, callback);

PHP方面将是：

if ( isset( $_FILES["file"] ) ){
    $dir = 'some/dir/';
    $blob = file_get_contents($_FILES["file"]['tmp_name']);
    file_put_contents($dir.$_FILES["file"]["name"], $blob);
    }