The html2canvas is a JavaScript library that allows you to capture screenshots or convert HTML elements into a canvas. It essentially takes a snapshot of the DOM (Document Object Model) and renders it onto an HTML5 canvas. This can be particularly useful for various purposes, such as generating screenshots of web pages, creating previews of HTML content, or capturing portions of a webpage for further manipulation.

Background

Some time ago, I utilized the JavaScript library html2canvas for a digital signature project. I implemented html2canvas to generate an image from an HTML format and then embedded that image into a PDF canvas. After testing it with various scenarios, it seems I encountered a slight issue with the generated results from html2canvas when embedded into the PDF canvas. Despite using a document with a background other than white, the obtained results did not meet expectations. The signature background appeared incongruent with the document background. My expectation is that the html2canvas-generated result should have a transparent background to avoid a noticeable color contrast with the document background.

So, what can I do to resolve this issue?

I tried to find a solution to the issues I encountered. Fortunately, I came across a similar case on the Stack Overflow forum. After that, I attempted to integrate some snippets of that code into my digital signature project. I tested various scenarios again, and ultimately, everything met my expectations.

Here’s a basic example of how you might use html2canvas:

// Include the html2canvas library in your HTML file
// <script src="https://html2canvas.hertzen.com/dist/html2canvas.min.js"></script>

// Capture a specific element
let element = document.getElementById("myElement");

html2canvas(element).then(function (canvas) {
    // `canvas` now contains the rendered content of the specified element
    document.body.appendChild(canvas);
});

If you want to set it with a transparent background:

html2canvas(element, {backgroundColor:null}).then(function (canvas) {
    // `canvas` now contains the rendered content of the specified element
    document.body.appendChild(canvas);
});

Conclusion

With html2canvas, you can capture the content of a specific HTML element or the entire page, including styles and images. It works by traversing the DOM, rendering each element onto the canvas, and handling CSS styles and positioning to create an accurate representation of the webpage.

The html2canvas has various combination options that can be utilized to manipulate objects and, of course, can be customized according to the needs of our project. You can find them on this page.

I would love to hear your thoughts on this blog post. Please feel free to share your feedback and comments in the comment section below. Thank you!