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Show HN: I created snapDOM to capture DOM nodes as images with exceptional speed

(github.com)

107 points

by tinchox622 hours ago |
39 comments
upvoteby Sephr23 minutes ago|
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Awesome! I was making exactly this library 13 years ago but only made it as far as creating CSS and other asset inlining+normalization tools before I ran into a few major roadblocks.

The most significant roadblock was that drawing SVG <foreignObject> with inline subresources (data: and blob: URIs) tainted canvases in Chrome and Safari, and this was partially resolved in 2019[1].

Notably, some issues still remain but apparently it's now workable. As is apparent from snapDOM, completely accurate CSS normalization is still an unsolved problem.

While I'm excited to see the HTML-in-foreignObject use case mature, it is also important to point out that the Media Capture API now has the ability to capture individual elements natively in Chrome[2].

1. https://issues.chromium.org/issues/41054640#comment49

2. https://developer.mozilla.org/en-US/docs/Web/API/CropTarget/...

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upvoteby streptomycin21 hours ago|
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I've been using html2canvas for a long time in https://play.basketball-gm.com/ so I gave your library a try. It was much slower (I know your README has benchmarks saying the opposite so idk) and the result looked a lot worse.

html2canvas: https://i.imgur.com/zfSwNR1.png

snapdom: https://i.imgur.com/FxowTzp.png

Also I recommend putting the npm package name clearly in your README. I guess I don't really know what other people are doing these days, but I think most people are like me and consume packages like this from npm rather than a <script> tag.

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upvoteby tinchox621 hours ago|
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Thank you for testing it out and sharing the screenshots!

I’ve run some performance tests using Vitest Bench, and SnapDOM was faster. I also created a few manual demos, and SnapDOM won in both speed and accuracy.

That said, I still need to run more real-world tests. So, thanks again for your help!

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upvoteby hirako200020 hours ago|
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How can svg be faster, and especially more accurate (lets throw some IMG or CSS shadows for fun) than canvas?
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upvoteby kaoD19 hours ago|
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You can embed HTML in an SVG via foreignObject. Seems like that's exactly what the library is doing[0].

Whether that's faster or more reliable, I don't know. Seems likely to render different depending on where you view the SVG (especially out of browsers).

[0]: https://github.com/search?q=repo%3Azumerlab%2Fsnapdom%20fore...

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upvoteby tinchox621 hours ago|
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I added to README the npm / yarn reference. Thanks!
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upvoteby jdiff21 hours ago|
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Capturing HTML as scalable SVGs is huge, how do you manage condensing all of CSS and its quirks into an SVG? Do you only support a subset of styling properties and rely on the browser to calculate layouts for you?
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upvoteby tinchox621 hours ago|
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I was upset about the size of generated svg file because at first all styles were inlined in each element. So I created a function to make mini css classes (.c1, c2, c3,...) So the final size is quite small.
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upvoteby krebby21 hours ago|
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How does this compare to something like the the Media Capture API? Looks like this uses `canvas.toDataURL()` which can be slow to serialize compared to `toBlob` or `canvas.captureStream(0).getVideoTracks()`

I've been using CropTarget.fromElement with a CaptureController: https://gist.github.com/akre54/e93ab2ce27999aecb109e38085f2e...

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upvoteby tinchox620 hours ago|
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Hi! Insaw this API when I was starting to work on snapDOM but I thought it was not ok for my needs so I discarded it. Regarding other API it would be great if View Transitions API could exposed the old view in a future
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upvoteby krebby20 hours ago|
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What were your needs that the API didn't meet?
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upvoteby tinchox619 hours ago|
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It requires user intervention and doesn't work for me.
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upvoteby streptomycin21 hours ago|
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Looks cool, somebody should make a package that puts a nice API around it. However seems that those APIs are only in Chrome now, not Firefox or Safari.
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upvoteby krebby20 hours ago|
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IMO it's simple enough to just write directly without library code.

For most cases, the Element Capture or Region Capture API should be sufficient: https://developer.mozilla.org/en-US/docs/Web/API/Screen_Capt...

Demos: https://mdn.github.io/dom-examples/screen-capture-api/elemen... https://mdn.github.io/dom-examples/screen-capture-api/region...

If you need cross-browser compatibility (and can't just use a canvas) then yeah html2canvas is the way to go

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upvoteby streptomycin14 hours ago|
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idk, your code is 170 lines, html2canvas and similar are 1 line to use.
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upvoteby tinchox618 hours ago|
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I tested it on Chrome, Firefox and Safari
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upvoteby simonw14 hours ago|
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Tiny feature request: snapdom.toJpg(el) appears to return a JPEG image where the background color for any transparent areas is set to black - it would be useful to be able to set that to another color (I needed it to be white).
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upvoteby tinchox611 hours ago|
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No problem! May you open an issue on the repo?
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upvoteby ashishact20 hours ago|
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Image in the readme would really be helpful. In fact anytime there is a visual output it makes sense to put an image. Thanks for creating this though - Will give it a try for an upcoming project.
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upvoteby tinchox618 hours ago|
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Thank you for the suggestion!
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upvoteby G_o_D12 hours ago|
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It doesnt load, snapdom dont appear in my devtools had to copy paste script

Plus it just struck at pending promise dont work

Plus css is messed up, i cant call it a snapshot, if it dont look same

domtoimage lib works for me and is fast whole html body node captured within second

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upvoteby darrenf19 hours ago|
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I’ve been writing a browser extension recently, and part of the functionality I want is to export part of a view as an image, shareable for the socials. I wanted to use html2canvas, but the docs explicitly advise against using it in a browser extension. Would snapDOM be suitable for inclusion in an extension?
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upvoteby genewitch6 hours ago|
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Firefox has screenshot that auto-picks elements, or you can click and drag a crop, or you can save the whole page. That and ad nauseam are the reason I use firefox; that singlefile also works is great (single html file dump of a web page, somehow).
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upvoteby tinchox618 hours ago|
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Sincerely, I don't know if snapdom would work on a browser extension. I've never tested it on this scenery
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upvoteby 17 hours ago|
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deleted
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upvoteby maxloh20 hours ago|
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Maybe add a function to convert to PDF? I've always dreamed of converting an element or the document body to a long-scrolling PDF. I tried to implement it with Playwright Python, but I had no luck. The resulting PDF height is messed up.
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upvoteby tinchox618 hours ago|
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Its a bit out of scope right now, but I thing it would be possible using some external libraries such as jsPDF or svg2pdf.js
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upvoteby rs18619 hours ago|
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How does this compare with https://www.npmjs.com/package/dom-to-image-more?
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upvoteby tinchox618 hours ago|
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It is pretty the same idea. There are many good solutions like dom-to-imge-more: the battle tested html2canvas, dom-to-image, modern-screenshot, etc. SnapDom is focused on avoiding long-taks whenever is possible because was designed to a zoomble UI engine that needs the capture doesnt affect the transition. But this is the first public version and there many things to adjust.
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upvoteby braebo19 hours ago|
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I found puppeteer or playwright to be good at this with their screenshot method. I made a cli tool for this recently that worked quite well.
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upvoteby tinchox619 hours ago|
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Yes they are so good. But in my case I need to work only on the client side
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upvoteby badmonster21 hours ago|
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Does snapDOM support capturing elements with CSS animations in their current frame, or does it only capture static states?
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upvoteby tinchox621 hours ago|
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Yes it capture elements with css animations in theirr current frame. It isnt't work for animted gifs. And I have to test js animations engines
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upvoteby imvetri4 hours ago|
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How does it work
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upvoteby nikeee20 hours ago|
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Does it work with some DOM polyfill in Node.js?
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upvoteby tinchox620 hours ago|
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Not tested yet
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upvoteby andrewstuart21 hours ago|
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Screenshots on the GitHub would be great.
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upvoteby Eduard21 hours ago|
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Not only screenshots, but also actual results. As I understand the short description, this tool allows to transform a website's current visual state into an SVG.
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upvoteby andrewstuart21 hours ago|
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Why not do it at the back end where you can literally snapshot node to png.
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