You probably have to reupload the decal as mentioned earlier.
Sorry for the bump, but it appears that 2 years later it still isnât fixed.
New uploads?
Yep, this tutorial was made only 2 months ago, if it was fixed there would be no need for the tutorial. I havenât really experienced this issue as I donât work with UI often, but I was having some weird outline problems with small images only a few weeks ago.
bumping. Iâve been using decals for a build, and these black outlines are a nuisance.
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Is there any idea when this will be fixed? Itâs annoying how my loading icon has a black outline around it.
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This is fixed, the site no longer mangles the color of transparent pixels. You will need to make sure your source image is correct. If you have black transparent pixels next to an opaque color, that will still have a black outline. The site doesnât do any kind of fancy color correction if thatâs what youâre wondering, thatâs intentional.
See:
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The problem in OP is still not fixed as you said yourself that the site doesnât do any correcting so you still have to manually correct everything yourself.
Please read again what I said. You are meant to correct this yourself. File a feature request if you think the site should re-encode transparent pixels to have the colors of the nearest opaque pixels, itâs off-topic here.
This bug report was, based on the responses here, about the site re-encoding all the transparent pixels to be black transparent instead, which guaranteed that black outlines would be present on the image.
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Almost 6 years later and still no fix 
Before anyone tries to link me to any of these
Please note, these DO NOT fix the problem on mobile. While UI looks clean and crisp on PC, testing on mobile still shows they black outlines. I believe this is a bug tho, as it did fix on mobile when I used PixelFix, and the UI was looking clean and crisp. But when I play tested the next day, it was back to the old ugly black outlines. Still same images, so I donât know whatâs going on with the rendering or something but ye.
This video was taken when I had fixed the UI with PixelFix. As you can see, the buttons and their icons donât have the black outlines.
Then the next day I join and Iâm greeted with the ugly black outlined UI again
The button images in studio are referencing the PixelFix images, so I donât know if images get their quality ruined after a few hours after upload or what. But this bug still isnât fixed 
making UI for mobile a near impossible feat sorry, I should say GOOD looking UI a near impossible feat
I have some further proof this is still an issue. Image1 shows robux icons taken before the pixelfix (with time stamp)
Image2 shows it after pixelfix (taken 2 minutes after previous image)
Then this last image shows me on a few hours later (3 hours after I did the pixelfix) and the images have reverted to black outlines
Can we please get some word that this issue is being taken seriously? Really hindering my games progress
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This annoying thing, itâs making doing some waves on my game impossible. Just look at this.
Whatâs up with that line on top? It looks super bad.
When are we getting a fix for this? Im tired of using pixelfix for all my images. I just want to make UI, not do image processing for every icon I upload
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Bumping this up again, because with the images uploaded having Bilinear Interpolation, the only alternative is to scale the image down to the exact offset, however, doing so would cut the imageâs quality. It has been years since this issue has been brought up and many of us are all looking forward to a fix.
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Itâs funny how long this thread has existed and the initial problem STILL hasnât been fixed. Iâve been dealing with this issue over and over. I use photoshop and the plugins recommended in the tutorial by Quenty are outdated now.
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Bumping this up ONCE AGAIN. I still have the same issue even when using Pixelfix⌠this is starting to be a joke, when will this be fixed? Roblox is concentrating on graphics and real looks but wont fix this issue.
Hi everyone,
Apologies for any confusion this may have had in the past, and for the delayed response. We have discussed this internally. We do not support premultiplied alpha, and at this time donât have any plans to enhance the image processing system to support. Any potential solution is complex and may create multiple other issues as a byproduct.
We recommend using the offline solutions that others have suggested in the post.
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I just want to add that us developers canât fix this issue in all situations. This is still very much an issue regardless of how easy these fixes are made. This isnât an issue on other programs and even other engines.
This even affects images rendered by the engine (ViewportFrames)! In the case of ViewportFrames developers have little to no control of the resulting image, so we canât avoid or fix this issue at all, we rely on a fix to the engine to make it display the image âproperlyâ.
10 year anniversary for this problem
The situation with this problem today for me as a developer:
It doesnât affect all people wanting to upload images to Roblox, because some image editors properly set the color of nearby fully transparent pixels.
However I personally still use an image editor that, for some reason, sets all the 100% transparent pixels to black and if I upload them to Roblox I get that black outline we all know for a long time now. Of course Iâve solved this problem by using a program to additionally process my images before I upload them to Roblox - this program sets the invisible pixels to the color of their nearest visible pixels and it solves the black outline problem to a very respectable degree.
Sometimes I forget to additionally process my images after Iâve exported them from my image editing software and I end up seeing the black outline time to time.
By now there are several programs like that, Iâm posting one of them here.
Why wouldnât Roblox just do this image processing in-studio (on my machine) before uploading images as an asset?
Iâm not sure how prevalent are image editors that still set invisible pixels to a single color today, but if they are then itâs likely that a lot of developers could be running into this problem to this day. Iâm really curious whether this sort of image preprocessing before uploading would impact image quality or mess with support for certain special images.
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