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In this post on main, when the PNG file is shown implicitly (one has to open a new tab to see it), the color scheme seems to be reversed (bright $\leftrightarrow$ dark).

The same file looks perfectly fine when done inline (or reference style but explicitly displayed).

Please see my screen grab below (done inline style to avoid ambiguity).

enter image description here

Evidence shows that this "feature" persists when the same file is downloaded and reuploaded (duh), and it's not just my computer but a Google Chrome issue.

I understand there are numerous image encoding practices and not just a few standards, but is this considered a bug?

If the info is relevant, I'm running Google Chrome "Version $79.0.3945.130$ (Official Build) ($64$-bit)" on a Windows $10$ Home edition "Version $1903$ OS build $18362.657$". At this point I haven't felt the need to ask how the original image was generated.

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After checking the PNG file, I can now confirm most of the image is indeed transparent: everything except the geometric objects.

Some navigators seem to have problems showing a standalone image file (i.e. not embedded in a web page) which has transparency.

On Windows:

  • Correctly shown: Firefox 73, Internet Explorer 11, Edge
  • Black background: Google Chrome, Vivaldi

I think we can consider this a bug of the navigator.

It will not harm in web pages, only when showing a standalong image file, which happens quite often on MSE as newcomers seem to have a hard time importing images. It will likely only happen with images produced by software (plots, drawing), not with photos.

The solution is quite simple: either imbed the image in the web page, as should generally be done, or edit the image file: MS Paint replaces transparency with a white background, which is usually the right thing - but MS Photos fails and opens the image with a dark background too.

It's quite disturbing. PNG was invented more than 20 years ago. I remember back then graphics software did not often handle transparency very well (but some did). But having such a bug in navigators and OS software in 2020 is bewildering. Having to rely on MS Paint as a last resort is even more so.

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  • $\begingroup$ I just tried uploading a PNG with transparency and the image was converted to a JPG after rendering the PNG on a white background. Since a PNG without transparency is brought through as a PNG, I imagine that the devs have "fixed" this by converting PNGs with transparency to JPGs. $\endgroup$
    – robjohn Mod
    Nov 29, 2020 at 18:16
  • $\begingroup$ @robjohn JPEG isn't well suited to drawings usually. Does the image suffer from lossy compression? $\endgroup$
    – Jean-Claude Arbaut
    Nov 29, 2020 at 23:24

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