从base 64字符串绘制Canvas图片时出错 [英] Error when drawing Canvas Picture from base 64 String

问题描述

我想将base64字符串绘制到画布bur中，我总是会收到错误

I want to draw a base64 String into a canvas bur I always get the error

TypeError：CanvasRenderingContext2D.drawImage的参数1可能不会转换为以下任何一个：HTMLImageElement，HTMLCanvasElement，HTMLVideoElement。

TypeError: Argument 1 of CanvasRenderingContext2D.drawImage could not be converted to any of: HTMLImageElement, HTMLCanvasElement, HTMLVideoElement.

我用google搜索了，但是我仍然不知道我在做什么

I did google it, but I still don't know what I did wrong.

var canvas = document.createElement('canvas');
document.body.appendChild(canvas);
var ctx = canvas.getContext("2d");
var data =  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAIAAAACDbGyAAAAAXNSR0IArs4c6QAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9oMCRUiMrIBQVkAAAAZdEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAADElEQVQI12NgoC4AAABQAAEiE+h1AAAAAElFTkSuQmCC";
ctx.drawImage(data, 0, 0);

Here's a fiddle.

推荐答案

drawImage 希望其第一个参数是图像，视频或画布（即 HTMLImageElement ， HTMLVideoElement 或 HTMLCanvasElement ），而不是字符串。

drawImage expects its first argument to be an image, video, or canvas (i.e., HTMLImageElement, HTMLVideoElement, or HTMLCanvasElement), not a string.

您需要构造一个新图像，然后为该图像对象提供一个新图像base64源。加载图像后，您可以将图像添加到画布中：

You need to construct a new image, and then supply that new image object with your base64 source. Once the image loads, you can add the image to your canvas:

var img = new Image();
img.src = "data:image/png;base64,iVBORw0KGgoAAAANSUh...";
img.onload = function() {
    ctx.drawImage(img, 0, 0);
}

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