[dvh]

If I wanted a non-downloadable image I would make it from 1px wide/tall colored divs.

[dorkwood]

I thought this is what it was going to be! Another method would be to generate a plane with the same number of vertices as pixels, store the pixel color values as an attribute, and then render the mesh to a canvas.

[dvh]

You can right-click canvas and save it as image.

[dorkwood]

Oh, you're right! I guess you'd have to disable the context menu too.

[alpaca128]

Which doesn't help either because in the Inspect view you can just click "Screenshot node" on the HTML element.

[dorkwood]

I'm learning a lot today.

[MildlySerious]

Pretty sure that was actually used in emails at some point, just with tables, to get around email clients not loading images.

[Karellen]

Email clients generally don't load external images. The majority should still display images that are sent as part of a multipart/mixed message though, and those should take up significantly less space than thousands of divs/tds and color attributes.

[masswerk]

I actually used this to generate graphs in JS/HTML in the 1990s. :-)

[can16358p]

Out of curiosity, how was the performance (of course normalized to performance of that era)?

[masswerk]

Here's a somewhat older approach splitting charts into linear runs of 1x1 images, which has some statistics at the bottom of each chart:

https://www.masswerk.at/demospace/relayWeb_en/chartset.htm

(Or see https://www.masswerk.at/demospace/relayWeb_en/welcome.htm and select "charts". Total time for calculations and rendering was then in the about 1 sec range. The real problem for using this in production was that these charts could be printed on Windows with Postscript printers only. I think, this was eventually fixed in Windows 98 SE.)