Plantuml.com's images (/png/ or /img/) won't insert in Google Docs anymore

[fuhrmanator]

I'm the dev for plantuml-gizmo and users opened an issue yesterday about images not being inserted: fuhrmanator/plantuml-gizmo#2

I tested this further and found that inserting any images into Google Docs (even by hand) that come from a PlantUML.com URL, e.g., https://www.plantuml.com/plantuml/png/SoWkIImgAStDuNBAJrBGjLDmpCbCJbMmKiX8pSd9vt98pKi1IW80 result in invalid images.

Debugging further, in Chrome if I open https://www.plantuml.com/plantuml/png/SoWkIImgAStDuNBAJrBGjLDmpCbCJbMmKiX8pSd9vt98pKi1IW80 and try to save it to disk, it suggests it's a .webp format and won't let me save it as a PNG. Perhaps this has always been like that, but it's strange.

Has something changed in the format of the images on PlantUML.com?

[arnaudroques]

Has something changed in the format of the images on PlantUML.com?

Hi, no change on our side: those images are still PNG images.
This is really weird.

[fuhrmanator]

Debugging further, in Chrome if I open https://www.plantuml.com/plantuml/png/SoWkIImgAStDuNBAJrBGjLDmpCbCJbMmKiX8pSd9vt98pKi1IW80 and try to save it to disk, it suggests it's a .webp format and won't let me save it as a PNG. Perhaps this has always been like that, but it's strange.

@arnaudroques can you explain why that happens (why it's not a .png format)? I also tried in Firefox. I don't have another (local) server to try with, to see if it does the same.

[fuhrmanator]

I dumped the blob info received inside the add-on (running on Google's server), and I see the following:

bytes = 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The first 4 bytes (82,73,70,70) are ASCII for RIFF. I'm guessing the next 4 are a length, and then I see the next 4 are 87,69,66,80 which translates in ASCII to WEBP.

Either Google allowed this before (as a PNG) and is not allowing it now, or something has changed in the encoding of the images.

My "Save as..." in Chrome of the image at https://www.plantuml.com/plantuml/png/SoWkIImgAStDuNBAJrBGjLDmpCbCJbMmKiX8pSd9vt98pKi1IW80 also yields a WEBP format on my computer, yields a file with the same RIFF and WEBP header (it's not a PNG). Notepad++ shows the bytes:

Using PlantUML on my local machine, I generate and save the same source to a PNG, and I get a true PNG (again viewed with Notepad++):

[fuhrmanator]

Some more facts that I hope can help to get to the bottom of things:

• I see another dev tried to use WEBP back in 2020, but it didn't work (Google hasn't supported WEBP format for some time): https://webapps.stackexchange.com/questions/148397/how-to-insert-a-webp-image-into-a-document

• The errors began at some time on Sunday, 22 January 2023, according to the logs in Google's Cloud console:
  

[fuhrmanator]

I asked ChatGPT 😄

Could it be the server started optimizing things without us realizing it?

[arnaudroques]

Thanks for your investigation!
So we confirm that the issue is on our side: our hoster is now doing on-the-fly image optimization and is converting PNG image to WEBP automatically. We are trying to disable this behaviour.

[fuhrmanator]

exifinfo.org shows the images are correct (PNG) again on the /img/ URLs of PlantUML.com.

Thanks for your help!