I used to use category icons with a transparent background (especially useful when having both light and dark mode versions). Now I always get a white background. I realized that when I download an old icon (that still works) it is PNG. But when I download the newly uploaded (PNG) icon, it downloads as JPEG. I would consider this a bug as I think it makes no sense to convert those icons to JPEG. I have full control over what I am uploading, unlike in forum posts where I can imagine it can be useful. EDIT: This worked Problem with category image transparency. I did not find it at first. But what has changed recently? My png_to_jpg setting was on 95, so changed to 100 and it started working. But why now?

[图片] tvavrda: But when I download the newly uploaded (PNG) icon, it downloads as JPEG. [图片] tvavrda: My png_to_jpg setting was on 95, so changed to 100 and it started working. But why now? It looks like your issue is solved but I took a quick look into this anyway. From looking at the code the png is converted to a jpg (which doesn’t support transparency) if the site setting value for png_to_jpg_quality is less than 100. I agree that there is room to improve the usability around these settings as it could be more intuitive. The easiest solution is to keep the site setting at 100 to prevent any image conversion. There are a couple of other pitfalls too, if the image was pasted or if the png dimensions are very large (ie. greater than 1280 * 720). In both scenarios it will be converted to a jpg too.

This change should prevent needing to use any workaround in future. Now site assets bypass the PNG to JPG conversion: https://github.com/discourse/discourse/pull/40975

类别图标转换为JPEG

产品支持

davidb (David B) 2026 年6 月 17 日 11:27 5

此次更改应可避免将来需要采用任何变通方法。现在，站点资产将绕过 PNG 到 JPG 的转换：

话题		回复	浏览量
Problem with category image transparency Product Support	10	1715	2021 年3 月 5 日
Png converts to Jpg no matter what! Product Support	12	1541	2021 年3 月 17 日
Very small PNGs are inappropriately converted to JPGs Bug	22	2259	2018 年11 月 23 日
PNG with transparency getting converted to JPG after uploads Product Support	7	1906	2022 年4 月 5 日
Why default to converting PNG to JPG? Feature	22	4688	2025 年8 月 7 日

类别图标转换为JPEG

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