toDataURL() 返回不正确的 url

Question

我正在尝试从我的流星驱动的网站创建一个页面的 pdf。该页面包含相当多的样式和一些 d3 图表。我添加了chipcastledotcom:jspdf 和new3rs:html2canvas 来实现我的目标。

我的计划是使用 html2canvas 和 jsPDF 的 .addImage() 函数将图表添加到 pdf 中。作为实现目标的第一步，我尝试在网页（徽标）中获取现有图像，将其绘制到新创建的画布元素上，然后在 html2canvas 内部调用 canvas.toDataURL('image/jpg')，然后我将其用作 jsPDF 的 @ 的参数987654327@ 功能。

最终，徽标图像将被我通过将 d3 图表转换为 img 元素创建的图像替换。我的问题是生成了pdf，但图像是空白的。

我认为这不是图像的负载问题，因为在我以网站用户的身份调用 pdf 生成之前，图像在网页上清晰可见。

我得到的数据网址如下。 我从toDataURL() 返回的数据网址末尾的= 对我来说看起来不太正确（尽管我真的不知道会发生什么）：

data:image/png;base64,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

对于这个问题或我对toDataURL() 不了解的问题是否有修复/解决方法？

这是一个 jsfiddle（完美运行），它展示了我想要完成的工作：https://jsfiddle.net/jdcast/tqfdkusp/。

请注意，我偶然发现了这个关于类似/相同问题的先前 SO 问题，但它似乎没有解决方案：canvas.toDataURL() not working properly

谢谢！

Answer 1

Html2canvas 有时不适用于在 DOM 中有很多元素的 HTML（它支持的元素数量有限制）。因为它解析整个 DOM 元素。

在这种情况下 canvas.toDataURL() 总是返回空白图像。