Load image from url and draw to HTML5 Canvas

问题:

I am having trouble loading an image from a url in javascript. The code below works, but I don't want to have to have the image loaded from html. I want to load the image from a url using pure javascript.

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = document.getElementById("imImageId");
ctx.drawImage(img, 0, 0);

回答1:

Simple, just create an image object in JavaScript, set the src, and wait for the load event before drawing.

Working Example:

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = new Image();
img.onload = function() {
    ctx.drawImage(img, 0, 0);
};
img.src = 'https://cdn.sstatic.net/stackexchange/img/logos/so/so-icon.png';

<canvas id="myCanvas"></canvas>

回答2:

Easy as this...

var img=new Image();
img.onload=start;
img.src="myImage.png";
function start(){
    ctx.drawImage(img,0,0);
}