Transparent Background Not Totally Transparent?

atlanta43 · **Joined:** Aug 11, 2016 **Posts:** 49

GIMP Version: 2.8.14
Operating System: Windows
GIMP Experience: New User

I'm having a lot of trouble making transparent backgrounds and I'm not sure why? This acorn (below) was on a white background and I made it transparent - or thought I did? But when it's placed on the aqua background, you can see the 'greenish' haze so it's only partly transparent. I've read multiple tutorials and still have this problem - but only sometimes. Can anybody tell direct me to a tutorial that will help me do this right or have any idea about what I'm doing wrong?

Thanks in advance.

dinasset · **Posted:** Wed Sep 14, 2016 9:54 am **(#2)**

to understand the problem, attach the xcf file not the jpg

bilbo9955 · **Joined:** Jul 11, 2010 **Posts:** 349

I've had that problem too. To fix it I took the main layer, ran "alpha-to selection", inverted selection, than hit the delete button.

atlanta43 · **Joined:** Aug 11, 2016 **Posts:** 49

I figured this out, finally - and learned something new and wonderful from an ancient tutorial. You experienced GIMP users probably already know this but there are many who probably don't so I'm happy to share ...

When we make a background transparent, there are almost always stray pixels along the edges and they are almost always in different colors and don't give a crisp, clean edge. I've spent lots of time cleaning up edges and, in fact, just read a tut from a supposedly very experienced user who said that's just an inevitable part of removing backgrounds.

BUT, all you have to do is Select > Grow *before* you make the background transparent. That command moves the edges in a bit and removes those pesky pixels. The number of pixels to grow depends on the size of the image. I've been doing images that are about 500 pixels and "1" is plenty. You will have to experiment. I am really thrilled to have learned this. No more pixel cleanup!

dinasset · **Posted:** Fri Sep 16, 2016 3:26 pm **(#5)**

thanks for sharing this info, Atlanta!
(BTW, do you call yourself Atlanta because you live in Atlanta-Georgia?)

atlanta43 · **Joined:** Aug 11, 2016 **Posts:** 49

dinasset: sorry - I missed your question. And yes, I live in metro Atlanta. Great place to live except in July and August when it's 1000 degrees out with 100% humidity. :-)

dinasset · **Posted:** Sat Nov 05, 2016 1:50 pm **(#7)**

Thanks.
I asked the question because I've been in Atlanta for a couple of weeks many years ago...nice place!

Rod · **Joined:** May 16, 2010 **Posts:** 16136

I actually just wrote a script that does exactly what you said. Removes a solid color from a background utilizing color to alpha.
You can find it here.
viewtopic.php?f=9&t=14833