Question

我想将Base64中编码的PNG图像加载到canvas元素。我有这段代码：

<html>
<head>
</head>
<body>
<canvas id="c"></canvas>
<script type="text/javascript">

var canvas = document.getElementById("c");
var ctx = canvas.getContext("2d");

data =  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAIAAAACDbGyAAAAAXNSR0IArs4c6QAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9oMCRUiMrIBQVkAAAAZdEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAADElEQVQI12NgoC4AAABQAAEiE+h1AAAAAElFTkSuQmCC";

ctx.drawImage(data, 0, 0);

</script>
</body>
</html>

在Chrome 8中，我收到错误：Uncaught TypeError: Type error

在Firefox的Firebug中：“对象的类型与对象关联的参数的预期类型不兼容”代码：“17”

因为base64是我在GIMP中制作的5x5px黑色PNG方块，并在GNU / Linux程序base64中将其转换为base64。

Answer 1

通过它的外观你需要实际传递drawImage像这样的图像对象

var canvas = document.getElementById("c");
var ctx = canvas.getContext("2d");

var image = new Image();
image.onload = function() {
  ctx.drawImage(image, 0, 0);
};
image.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAIAAAACDbGyAAAAAXNSR0IArs4c6QAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9oMCRUiMrIBQVkAAAAZdEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAADElEQVQI12NgoC4AAABQAAEiE+h1AAAAAElFTkSuQmCC";

<canvas id="c"></canvas>

我在chrome中尝试过它并且工作正常。

Answer 2

杰里夫的答案很好，除了一个缺陷。

onload事件应该在src之前设置。有时src可以立即加载，永远不会发起onload事件。

（就像Totty.js指出的那样。）

var canvas = document.getElementById("c");
var ctx = canvas.getContext("2d");

var image = new Image();
image.onload = function() {
    ctx.drawImage(image, 0, 0);
};
image.src = "data:image/  png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAIAAAACDbGyAAAAAXNSR0IArs4c6QAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9oMCRUiMrIBQVkAAAAZdEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAADElEQVQI12NgoC4AAABQAAEiE+h1AAAAAElFTkSuQmCC";

Base64 PNG数据到HTML5画布

2 个答案: