将从 URL 提取的图像转换为 base64

Question

每当用户通过 Facebook 登录时，我都会获取他们的 Facebook 个人资料图片。我想将图像从 URL 转换为 Base 64。在确保用户仍然可以在视图（home.view）中看到他们的个人资料图片的同时，最好的方法是什么？目前，我直接引用 URL。

到目前为止，这是我的代码：

facebook.service.js

function FacebookService($http, config) {
      this.getUserPicture = function(userId, token) {
      return $http({
        method: 'GET',
        url: 'https://graph.facebook.com/' + userId + '/picture?type=large&redirect=false'
      })
    }
  }

home.controller.js

function HomeController($scope, $cordovaNativeStorage, FacebookService, $ionicLoading) {
  if (window.cordova) {
    // Get Facebook access token
    $cordovaNativeStorage.getItem("facebookAccessToken").then(function(value) {
      $scope.facebookAccessToken = value

      // Get Facebook user picture (currently stored as a URL, would want to store it as a base 64 string which can be displayed as an image
      FacebookService.getUserPicture($scope.facebookUserData.id).then(function(dataResponse) {
        $scope.facebookUserPicture = dataResponse.data;

        // Save Facebook user picture
        $cordovaNativeStorage.setItem("facebookUserPicture", $scope.facebookUserPicture).then(function() {}, function(error) {
          console.error("Unable to cache user data: " + result);
          $ionicLoading.show({
            template: 'Unable to cache user data',
            duration: 1500
          })
        });
      }, function(error) {
        console.log(error.data.error.message)
      })
    }, function(error) {
      console.log(error.data.error.message)
    })
  }
};

home.view.js

<img class="icon icon-home img-circle" ng-src="{{ facebookUserPicture.data.url }}">

Answer 1

有一种方法可以通过画布（source）来做到这一点：

var convertImgToDataURLviaCanvas = function(url, callback) {
  var img = new Image();

  img.crossOrigin = 'Anonymous';

  img.onload = function() {
    var canvas = document.createElement('CANVAS');
    var ctx = canvas.getContext('2d');
    var dataURL;
    canvas.height = this.height;
    canvas.width = this.width;
    ctx.drawImage(this, 0, 0);
    dataURL = canvas.toDataURL();
    callback(dataURL);
    canvas = null;
  };

  img.src = url;
}

convertImgToDataURLviaCanvas( 'http://some.com/images/1.jpg', function( base64_data ) {
    console.log( base64_data );
} );