dom-to-image vs html2canvas
Web Page Screenshot Libraries
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Web Page Screenshot Libraries

Web Page Screenshot Libraries are tools that allow developers to capture visual representations of web pages or specific elements within them. These libraries can generate images or PDFs of the rendered content, which can be useful for creating thumbnails, saving user-generated content, or implementing features like sharing and printing. They work by rendering the HTML and CSS of a page or element and converting it into a bitmap image. dom-to-image focuses on converting DOM nodes to images, while html2canvas captures the visual representation of a web page or element by rendering it in a canvas.

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dom-to-image010,781-3378 years agoMIT
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Feature Comparison: dom-to-image vs html2canvas

Image Generation

  • dom-to-image:

    dom-to-image generates images from specific DOM elements, allowing for more control over what is captured. It supports various formats, including PNG and JPEG, and can handle SVGs, text, and styles.

  • html2canvas:

    html2canvas captures the visual representation of a web page or element by rendering it in a canvas. It captures the entire layout, including backgrounds, images, and text, but may have limitations with certain CSS properties.

CSS Support

  • dom-to-image:

    dom-to-image has good support for inline styles, background images, and SVGs. It can handle most CSS properties, but complex animations and certain pseudo-elements may not be captured accurately.

  • html2canvas:

    html2canvas supports a wide range of CSS properties, including backgrounds, borders, and shadows. However, it may struggle with some advanced CSS features, such as filters, gradients, and animations.

Customization

  • dom-to-image:

    dom-to-image allows for more customization, such as specifying the image format, quality, and dimensions. It also provides options for excluding certain elements or styles during the capture process.

  • html2canvas:

    html2canvas offers limited customization options, primarily related to the rendering process. Developers can adjust the scale, use a proxy for cross-origin images, and set a background color, but overall customization is more limited compared to dom-to-image.

Cross-Origin Support

  • dom-to-image:

    dom-to-image handles cross-origin images by using CORS (Cross-Origin Resource Sharing) headers. It requires the images to be served with the appropriate CORS headers to be captured accurately.

  • html2canvas:

    html2canvas also supports cross-origin images, but it requires the images to have CORS enabled. If CORS is not configured, the library will not be able to access the images, leading to potential security issues.

Ease of Use: Code Examples

  • dom-to-image:

    dom-to-image provides a simple API for converting DOM elements to images. Here’s a quick example:

    import { toPng } from 'dom-to-image';
const node = document.getElementById('my-node');
toPng(node)
  .then((dataUrl) => {
    const img = new Image();
    img.src = dataUrl;
    document.body.appendChild(img);
  })
  .catch((error) => {
    console.error('Error generating image:', error);
  });
  • html2canvas:

    html2canvas captures screenshots of web pages or elements. Here’s an example:

    import html2canvas from 'html2canvas';
const element = document.getElementById('my-element');
hl2canvas(element)
  .then((canvas) => {
    document.body.appendChild(canvas);
  })
  .catch((error) => {
    console.error('Error capturing screenshot:', error);
  });

How to Choose: dom-to-image vs html2canvas

  • dom-to-image:

    Choose dom-to-image if you need to convert specific DOM elements into images, especially if you require support for SVGs, text, and styles. It is ideal for generating images from smaller, well-defined parts of a web page.

  • html2canvas:

    Choose html2canvas if you want to capture a screenshot of an entire web page or a large section, including complex layouts and backgrounds. It is more suitable for capturing the overall appearance of a page.

Similar Npm Packages to dom-to-image

dom-to-image is a JavaScript library that allows developers to convert DOM elements into images. This can be particularly useful for generating images from HTML content, such as charts, graphs, or any other visual representation of data. By using dom-to-image, developers can easily create PNG or JPEG images from their web applications, enabling features like downloadable content or sharing visual data.

While dom-to-image provides a straightforward solution for converting DOM elements to images, there are several alternatives available that offer similar functionalities. Here are a few notable options:

  • html-to-image is a library that allows you to convert HTML nodes into images. It supports various output formats, including PNG and JPEG, and is designed to be simple to use. html-to-image is particularly useful for developers looking for a lightweight solution that can easily integrate into their projects. It also provides options for customizing the output, such as setting image quality and background color.

  • html2canvas is another popular library that enables developers to take "screenshots" of web pages or specific DOM elements. Unlike dom-to-image, which directly converts DOM elements to images, html2canvas renders the elements onto a canvas and then generates an image from that canvas. This approach allows for more complex rendering scenarios, such as capturing styles and effects that may not be easily translated to an image format. html2canvas is widely used for its flexibility and ability to capture a wide range of visual content.

  • screenshot-desktop is a library that captures screenshots of the entire desktop or specific application windows. While it is not limited to web applications like the other libraries mentioned, it can be useful for developers looking to capture images from their desktop environment. This library is particularly relevant for Electron applications or scenarios where capturing the entire screen is necessary.

For a detailed comparison of these packages, check out the following link: Comparing dom-to-image vs html-to-image vs html2canvas vs screenshot-desktop.

Similar Npm Packages to html2canvas

html2canvas is a popular JavaScript library that allows developers to take "screenshots" of web pages or specific elements within a page by rendering them as canvas elements. This library is particularly useful for creating visual representations of web content, enabling features such as saving web pages as images, generating thumbnails, or creating visual reports. By converting HTML elements into canvas, html2canvas provides a straightforward way to capture and manipulate web content in a visually appealing manner.

While html2canvas is a powerful tool for capturing web content, there are alternatives available that offer similar functionality. One notable alternative is:

  • dom-to-image is a library that allows you to convert DOM nodes into images. It provides a simple API to generate PNG or JPEG images from HTML elements, making it a great alternative to html2canvas. dom-to-image supports various features, such as customizing image dimensions, adding background colors, and handling SVG elements. If you are looking for a lightweight solution to convert DOM elements into images without the additional overhead of canvas manipulation, dom-to-image is an excellent choice.

To see how html2canvas compares with dom-to-image, check out the comparison: Comparing dom-to-image vs html2canvas.

README for dom-to-image

DOM to Image

Build Status

What is it

dom-to-image is a library which can turn arbitrary DOM node into a vector (SVG) or raster (PNG or JPEG) image, written in JavaScript. It's based on domvas by Paul Bakaus and has been completely rewritten, with some bugs fixed and some new features (like web font and image support) added.

Installation

NPM

npm install dom-to-image

Then load

/* in ES 6 */
import domtoimage from 'dom-to-image';
/* in ES 5 */
var domtoimage = require('dom-to-image');

Bower

bower install dom-to-image

Include either src/dom-to-image.js or dist/dom-to-image.min.js in your page and it will make the domtoimage variable available in the global scope.

<script src="path/to/dom-to-image.min.js" />
<script>
  domtoimage.toPng(node)
  //...
</script>

Usage

All the top level functions accept DOM node and rendering options, and return promises, which are fulfilled with corresponding data URLs.
Get a PNG image base64-encoded data URL and display right away:

var node = document.getElementById('my-node');

domtoimage.toPng(node)
    .then(function (dataUrl) {
        var img = new Image();
        img.src = dataUrl;
        document.body.appendChild(img);
    })
    .catch(function (error) {
        console.error('oops, something went wrong!', error);
    });

Get a PNG image blob and download it (using FileSaver, for example):

domtoimage.toBlob(document.getElementById('my-node'))
    .then(function (blob) {
        window.saveAs(blob, 'my-node.png');
    });

Save and download a compressed JPEG image:

domtoimage.toJpeg(document.getElementById('my-node'), { quality: 0.95 })
    .then(function (dataUrl) {
        var link = document.createElement('a');
        link.download = 'my-image-name.jpeg';
        link.href = dataUrl;
        link.click();
    });

Get an SVG data URL, but filter out all the <i> elements:

function filter (node) {
    return (node.tagName !== 'i');
}

domtoimage.toSvg(document.getElementById('my-node'), {filter: filter})
    .then(function (dataUrl) {
        /* do something */
    });

Get the raw pixel data as a Uint8Array with every 4 array elements representing the RGBA data of a pixel:

var node = document.getElementById('my-node');

domtoimage.toPixelData(node)
    .then(function (pixels) {
        for (var y = 0; y < node.scrollHeight; ++y) {
          for (var x = 0; x < node.scrollWidth; ++x) {
            pixelAtXYOffset = (4 * y * node.scrollHeight) + (4 * x);
            /* pixelAtXY is a Uint8Array[4] containing RGBA values of the pixel at (x, y) in the range 0..255 */
            pixelAtXY = pixels.slice(pixelAtXYOffset, pixelAtXYOffset + 4);
          }
        }
    });

All the functions under impl are not public API and are exposed only for unit testing.

Rendering options

filter

A function taking DOM node as argument. Should return true if passed node should be included in the output (excluding node means excluding it's children as well). Not called on the root node.

bgcolor

A string value for the background color, any valid CSS color value.

height, width

Height and width in pixels to be applied to node before rendering.

style

An object whose properties to be copied to node's style before rendering. You might want to check this reference for JavaScript names of CSS properties.

quality

A number between 0 and 1 indicating image quality (e.g. 0.92 => 92%) of the JPEG image. Defaults to 1.0 (100%)

cacheBust

Set to true to append the current time as a query string to URL requests to enable cache busting. Defaults to false

imagePlaceholder

A data URL for a placeholder image that will be used when fetching an image fails. Defaults to undefined and will throw an error on failed images

Browsers

It's tested on latest Chrome and Firefox (49 and 45 respectively at the time of writing), with Chrome performing significantly better on big DOM trees, possibly due to it's more performant SVG support, and the fact that it supports CSSStyleDeclaration.cssText property.

Internet Explorer is not (and will not be) supported, as it does not support SVG <foreignObject> tag

Safari is not supported, as it uses a stricter security model on <foreignObject> tag. Suggested workaround is to use toSvg and render on the server.`

Dependencies

Source

Only standard lib is currently used, but make sure your browser supports:

Tests

Most importantly, tests depend on:

  • js-imagediff, to compare rendered and control images

  • ocrad.js, for the parts when you can't compare images (due to the browser rendering differences) and just have to test whether the text is rendered

How it works

There might some day exist (or maybe already exists?) a simple and standard way of exporting parts of the HTML to image (and then this script can only serve as an evidence of all the hoops I had to jump through in order to get such obvious thing done) but I haven't found one so far.

This library uses a feature of SVG that allows having arbitrary HTML content inside of the <foreignObject> tag. So, in order to render that DOM node for you, following steps are taken:

  1. Clone the original DOM node recursively

  2. Compute the style for the node and each sub-node and copy it to corresponding clone

    • and don't forget to recreate pseudo-elements, as they are not cloned in any way, of course

  3. Embed web fonts

    • find all the @font-face declarations that might represent web fonts

    • parse file URLs, download corresponding files

    • base64-encode and inline content as data: URLs

    • concatenate all the processed CSS rules and put them into one <style> element, then attach it to the clone

  4. Embed images

    • embed image URLs in <img> elements

    • inline images used in background CSS property, in a fashion similar to fonts

  5. Serialize the cloned node to XML

  6. Wrap XML into the <foreignObject> tag, then into the SVG, then make it a data URL

  7. Optionally, to get PNG content or raw pixel data as a Uint8Array, create an Image element with the SVG as a source, and render it on an off-screen canvas, that you have also created, then read the content from the canvas

  8. Done!

Things to watch out for

  • if the DOM node you want to render includes a <canvas> element with something drawn on it, it should be handled fine, unless the canvas is tainted - in this case rendering will rather not succeed.

  • at the time of writing, Firefox has a problem with some external stylesheets (see issue #13). In such case, the error will be caught and logged.

Authors

Anatolii Saienko, Paul Bakaus (original idea)

License

MIT

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