我正在使用 HTML5 画布并在那里放置两个图像,但我面临一个问题,即一个图像已加载并在 chrome 中可见,但另一个图像仅在 mozilla 中可见,但在刷新后。我不知道为什么会发生这种情况,因为我是画布新手。
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var x = 0;
var y = 0;
var width = 900;
var height = 700;
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, x, y, width, height);
};
imageObj.src = 'http://img13.deviantart.net/1550/i/2011/353/4/2/mobile_game_background_by_disnie-d4jmr8r.jpg';
var startImageObj = new Image();
startImageObj.onload = function() {
context.drawImage(startImageObj, (canvas.width-startImageObj.width)/2, (canvas.height-startImageObj.height)/2)
};
startImageObj.src = 'http://assets.halfbrick.com/yc/v3/images/button-play.png';
<canvas id="canvas" width="900" height="700"></canvas>
fiddle https://jsfiddle.net/cfucxet7/1/
As onload https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/Attribute/image.onload事件是异步的,请确保play-button
正在设置在onload-handler
of the base-image
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var x = 0;
var y = 0;
var width = 900;
var height = 700;
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, x, y, width, height);
var startImageObj = new Image();
startImageObj.onload = function() {
context.drawImage(startImageObj, (canvas.width - startImageObj.width) / 2, (canvas.height - startImageObj.height) / 2)
};
startImageObj.src = 'https://d30y9cdsu7xlg0.cloudfront.net/png/5670-200.png';
};
imageObj.src = 'http://img13.deviantart.net/1550/i/2011/353/4/2/mobile_game_background_by_disnie-d4jmr8r.jpg';
<canvas id="canvas" width="900" height="700"></canvas>
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