I will give you some temporary solutions that I discovered:
Just wondering if the Roblox Staff has seen this thread, and if a fix is in the works? Not being able to upload optimized PNG images is a big problem.
Upon further research, I believe that 8-bit PNGs are the problem. In the recent past, 8-bit PNGS uploaded fine, but now they lose their transparency, and on some occasions they cannot be uploaded at all.
Repro:
Two PNG images are shown below. One is a 32-bit PNG saved directly from Photoshop. The other is the exact same image, but saved as an 8-bit PNG (with transparency).
I uploaded both images in Studio, and placed them in ImageLabels. You can see the results below. The 32-bit PNG shows the transparency as expected (top image), but the 8-bit PNG shows a solid color instead of the expected transparency (bottom image).
Whenever I upload an image to studio that doesn’t fill up the whole canvas, it gets a black background.
For example, I was uploading this image.
I haven’t been doing UIs for a few days, but last time I did it was working just fine. I haven’t changed any settings or anything since then.
I uploaded this image:
This is what I see when looking at the decal on the website and in studio:
I tried doing it through studio first. Then I tried through the website. Happened both times. Never experienced this until today.
Here is a link to the decal:
Thanks.
I can’t reproduce this when I download your hammer image and upload it to the site. Could you give more details?
If you change a pixel and reupload, is the problem resolved?
See also: How to post a Bug Report
Yes, I tried uploading after changing a pixel. It did the same thing. I don’t know what other details I can give. All I did was upload the image, like normal.
What format is the original file in? Could you upload it to a file sharing site and share a link to it so engineering has the original file? (uploading it into the thread here may have fixed the file and won’t have it reproduce anymore)
The file is png. I hope this works?
And, I also uploaded the image again. Uploading here did not fix it.
For everyone who posted in the thread so far, could you check if this is the issue on your images?
Yep, seems to be. 32 bit images do work just fine, and the 8 bit images are the ones with the issue.
Sorry for all of the issues around uploading images. We are actively looking into this.
Please continue to let us know if converting to 24-bit PNGs (from 8-bit) fixes the issue.
This is a fix for all the images that I had issues with. Oddly, 8-bit image uploads were working fine about a week or so ago. So it must be a recent change on your end, which is causing these problems.
Keep in mind that using 24-bit images results in much larger file sizes, which is the main reason that I prefer using 8-bit images. This is very important when optimizing games for mobile devices. So I am hoping that the 8-bit image uploads will be fixed soon. Thanks!
I’m having a similiar problem.
Uploaded image:
Image that I get after uploading:
This is not the first time I am having this issue.
If you apply color with 1 opacity (completely transparent) it will work completely fine!
Yea mine was definately PNG-8 format when exporting from Adobe Illustrator, I assume that means 8 bit.
This is happening to me too. After resizing and reuploading, it still results to the same glitched texture. 
Experiencing the same problem, I’m trying to upload a simple box but I get a black image on the website.
I made it in pain.net and saved it as a 8-bit PNG
Original Image
Roblox Image
Tried to upload the same image with just some moved pixels etc and I still got the problem
Are 8-bit PNGs with transparency uploaded from before Jan 15 also having problems with black background when rendered in game?
(I know first report on this issue was Jan 17, just padding in case this took some time to surface)
I know I didn’t start encountering my issue until the 16th.
