我遇到了一个小错误，它似乎表明当您传入图像数据作为其源时，在图像完全加载之前调用了 onload 函数。
这是 HTML
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js" type="text/javascript"></script>
</head>
<body>
<canvas id='finalImage'></canvas>
</body>
</html>
这是 JavaScript:
var canvas = document.createElement('canvas');
var context = canvas.getContext('2d');
var image = new Image();
image.onload = function() {
// I've also put a console.log here at one point, and it does get called.
context.drawImage(image, 0, 0, canvas.width, canvas.height);
};
image.src = "data:image/jpeg;base64,/9j/4QNMR..."; // cut for sanity.
var outputCanvas = $("#finalImage")[0];
var outputContext = outputCanvas.getContext('2d');
// If I uncomment this line, the image is drawn.
//context.drawImage(image, 0, 0, canvas.width, canvas.height);
// If I change canvas to image, its also drawn, which means it is being loaded.
// But it seems to indicate to me that onload gets called too early.
outputContext.drawImage(canvas, 0, 0);
Here is the link to the JSFiddle. .
如果您发现它有什么问题，请告诉我，因为现在已经弄乱了它很长时间了。
谢谢!
最佳答案
outputContext.drawImage(canvas, 0, 0); 在 context.drawImage(image, 0, 0, canvas.width, canvas.height); 之前调用保证outputContext绘制到canvas之后就是将其放入onload函数
var canvas = document.createElement('canvas');
var context = canvas.getContext('2d');
var image = new Image();
var outputCanvas = $("#finalImage")[0];
var outputContext = outputCanvas.getContext('2d');
image.onload = function() {
// I've also put a console.log here at one point, and it does get called.
context.drawImage(image, 0, 0, canvas.width, canvas.height);
outputContext.drawImage(canvas, 0, 0);
};
image.src = "data:image/jpeg;base64,/9j/4QNMR..."; // cut for sanity.
关于javascript - 当我传入图像数据字符串(基数 64)时，图像加载似乎被提前调用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13908327/