[solved] Problem: transparent background eliminated in exported PNG

purehunter · **Joined:** Apr 11, 2026 **Posts:** 3

GIMP Version: 3.2.2
Operating System: Windows
GIMP Experience: Intermediate Level

List any ERROR messages you received:
Operation not supported

Hi!
I have a strange behavior with the current GIMP version 3.2.2:
I'm unable to export a PNG image with transparency (Alpha channel exists and transparency is visible in the opened image). Tried every option in the export menu. The exported image has always a black BG. When exporting the same image as GIF, the transparency persists as expected. Tested with several images.

The simplest way to reproduce it: open a PNG image with a transparent BG. Export it as PNG.
Result: When pressing the "Export" button, there is a small error message in the bottom line: "Operation not supported". The export-file will be created, but the image has a black BG now.

Any idea would be appreciated.

Wallace · **Posted:** Sun Apr 12, 2026 8:28 am **(#2)**

If the Image mode is RGB, with an
Alpha channel, and you still get “Operation not supported”.

it’s almost likely a GIMP 3.2.2 bug.

quietreader · **Joined:** Apr 11, 2024 **Posts:** 306

This has been reported as a bug already:
https://gitlab.gnome.org/GNOME/gimp/-/issues/16159

TeaMouse · **Joined:** Jan 01, 2026 **Posts:** 507

Looking in your image Layer pallette is the layer name showing bold letters, if so, this means that you are working with no Alpha Channels in your mage. Do this....

1. Check the image mode to make sure you are working in RBG MODE
2. Right click the image in the layer pallette to add a Alpha Channel
If it doesn't have them, the option will be in bold letters. Click it.

When the Alpha Channels are missing in a PNG file, it doesn't know what you are doing with those pixels, so it treats that information with a default setting of sold black pixels.

Think of a PNG file like this, there are 4 internal layers or channels working together to create an image, (the alpha channel as a whole). Each pixel has 4 values to it, (0 - 255), zero meaning none.

1 for the opacity channel
1 for the red channel
1 for the blue channel
1 for the green channel

Without these four values, you can not create transparent pixels, meaning all unsign pixel channel values in the saving process will be saved with a value of zero, because there is no information for each channel available, it is missing in your PNG file, I suggest you look up what are color channels and how they work in digital imaging and how they relate to one another for more understanding. This should fix your problem, if everything is working properly. Good Luck.

In Gimp 3.2,2., they made a slight change in how it opens files.

Rod · **Joined:** May 16, 2010 **Posts:** 16114

After you open the export As dialog, and then exporting as PNG, after the PNG Export Dialog appears, try unchecking Save Background Color. You still get the warnings but the file maintains it's transparency. It did for me anyways.

TeaMouse · **Joined:** Jan 01, 2026 **Posts:** 507

Here is a file to see if you are exporting a PNG with transparency in it.
This file a TIFF file with no Alpha Channel and it was created in Indexed Mode.

Once you open it, look in the layer palette, you will see the layer name in bold letters, this means there
is no alpha Channel. Right click the image in the layers palette and add alpha channel, then go to image from
the main tool bar and change the image mode to RGB.
If it is left in index mode, it will have a colored background, when opened in other photo editing programs.
But not All.

Next select the fuzzy select tool by pressing the U key. Next using the fuzzy select tool, select an
area outside the whale and delete it. Then Press Ctrl + Shift + E, to export as a PNG. Here are
the settings I'm using and I have no problems.

Attachment:

PNG-Demo-01.png [ 54.46 KiB | Viewed 5133 times ]

If the image you open isn't using alpha channel, it will not apply one. I just posted 22 new Photo Frames in PNG
with no problems at all, with no error messages. Try following my step with the file posted.

Attachment:

Whale - Cartoon 1.zip [7.86 KiB]
Downloaded 35 times

purehunter · **Joined:** Apr 11, 2026 **Posts:** 3

Hi together,

thanks for your suggestions!
With the shown Export-Dialog from @TeaMouse I got it working:
the "Pixel format" was the problem. I did not touch that in previous tries as I assumed it has to do with color depth and let it in the default state "8 bpc RGB" which should be good to get a small file-size for the icon I worked with. Now I changed that to "Automatic" as seen in the Export-Dialog from TeaMouse. And -hooray!- it's working! :tyspin

Thank you all!

To be honest, I have no clue what this different setting does in the background as the file size remains the same.

purehunter · **Joined:** Apr 11, 2026 **Posts:** 3

quietreader wrote:

This has been reported as a bug already:
.../GNOME/gimp/-/issues/16159

For me this error message disappears, if I check the "Save color profile" checkbox in the export dialog. This increases the file size in my case from 19.5kiB to 19.8kiB. But in both cases the exported image appears identically.

All checkboxes of the export dialog are unchecked by default.