如何从画布精灵中删除模糊

Question

我有一段代码可以从一段文本中创建一个精灵。

var getPicture = function(message){
  var canvas = document.createElement('canvas');
  var context = canvas.getContext('2d');
  var fontSize = 10;
  context.font = fontSize + "px Times New Roman";
  var measurements = context.measureText(message);
  canvas.width = measurements.width + 10;
  canvas.height = fontSize + 2;
  context.fillText(message, 0, 10);

  return canvas;
};

var getLabel = function(message){
  var texture = new THREE.Texture(getPicture(message));
  texture.minFilter = THREE.LinearFilter;
  texture.needsUpdate = true;
  var spriteMaterial = new THREE.SpriteMaterial({map: texture});
  var sprite = new THREE.Sprite(spriteMaterial);
  return sprite;
};

但不幸的是，精灵看起来像这样：

如何在场景中获得清晰的文字？