How to save PNG file transparency in automatic thumbnail generation?

I have tried to add png photos with transparency but first they changed to jpg, then I changed the default extension to png, but I still got the same result an image without transparency, which is different from the orginal one that has been uploded.


Omeka always generates jpeg thumbnails, which don’t have an alpha channel and so can’t represent transparency.

Switching the default extension around should result in pngs getting made, but you’d have to go further if you wanted to hack “correct” png thumbnails in. Because we generate jpegs, we do things like flatten the image onto a white background to prevent weird colors from appearing where there were transparent sections. You’d have to remove that stuff from the ImageMagick commands that are being run.

Hello, many thanks, but I’m a little stuck in here, I do not know in which direction to go. I would really appreciate if you could guide me a little bit more into removing stuff from ImageMagick commands, I tried but i was not able to find any lead.

Thank you.

We don’t really support alternative thumbnail formats so I don’t want to delve too far into details, but you’ll be looking at editing the ExternalImageMagick strategy. It builds up arguments to convert, and you’ll probably need to get rid of usages of -background white and -flatten at least.