Convert to Colours on Tiff

[Brother Gabriel-Marie]

When I use Image > Convert to Colours on tiff files, it wrecks them - but only if "Use LIBIMAGEQUANT" is enabled in the effect options popup.
You can see my examples.

In my opinion, "Use LIBIMAGEQUANT" seems like a useless option to have if it is going to mess up the graphic.

Also, I don't know if that Convert-to-Colours messes up anything, but afterward, if I run blur on it afterward, the effect is not the same as the Effect Preview.
For this, I ran Convert to Colours without LIBIMAGEQUANT, which seemed to work fine.
Then I went and opened Effects and chose Blur - it's only set to 1 as you can see in my screenshot.

blur on converted version

[xnview]

When I use Image > Convert to Colours on tiff files, it wrecks them - but only if "Use LIBIMAGEQUANT" is enabled in the effect options popup.
You can see my examples.

In my opinion, "Use LIBIMAGEQUANT" seems like a useless option to have if it is going to mess up the graphic.

right

Also, I don't know if that Convert-to-Colours messes up anything, but afterward, if I run blur on it afterward, the effect is not the same as the Effect Preview.
For this, I ran Convert to Colours without LIBIMAGEQUANT, which seemed to work fine.
Then I went and opened Effects and chose Blur - it's only set to 1 as you can see in my screenshot.

yes it's a known issue because blur is applied on preview and not a full image