GIMP Version: 2.8.0
Operating System: Windows
OS Version: Windows 7
GIMP Experience: Beginner Level

---

Hello,

I am a beginner and still learning, so take it easy on me.

I have this logo that I would like to put on the homepage of a site I am designing. The file I have has a white background, but the background of the page is grey, so when I place the logo, I end up with an ugly white box around the logo.

Is it possible to change the background color of the logo to grey so it matches my website background?

Is this a pretty advanced project? Any tips or tutorials or guides would be appreciated! I attached the image to this post.

Thanks!

.

Got Ninja'd , yes I would go that way as well. Copy the layer, add alpha channel, select the white, select invert , select shrink 1 pixel, select invert, Ctl-X or delete , Bin the bottom layer (with the white bg) and save as a png.
I shrunk the selection to get rid of the "whitish" outer pixels, which would probably give a halo effect on a darker back ground. Do experiment with the shrink , if you are using a light grey background you may not have to shrink it.

There's different ways to do this. After you open the image, you might want to Save As so you're working on a duplicate, still have your original, and you can go back to edit if needed. One way is to find the Select By Color tool. It looks like a finger hovering over colors. First, right click on your layer in the layer dialog box then click Add Alpha Channel. That adds transparency for what you're about to do. Now click on the white part in your image. You'll see only the white part is selected. Press Delete on your keyboard. Now you can do two things. You can go to File>Export and save as a PNG. That way you just have your logo with a transparent background. Or you can add a new layer at the bottom of the layer dialog box. You can use the Bucket tool to fill that layer with whatever you want. Click the down arrow, again in the layer dialog so this color layer is at the bottom underneath your logo. Now you can Export in whatever format you prefer.

It seems I've been beaten to the punch twice. Oh well.

What is the difference with "Select/grow" (1px)?

Select white area first Ofnuts. I think that's what is meant here.
Then-
select>invert - (selects colored logo)
select>shrink (1 pixel) (to capture white border if any)
select>invert again to delete the white area.
I would use feather to blend with the bg on your website.

Thankyou soooo much
This method works best for me and I did not know about this.
So quick and easy. Just a few clicks.
Thankyou thankyou !

Hi ofnuts , there is probably very little difference in this case . This is a small and simple image. It is just the way I work , I try to keep the focus on the thing to be altered (the image). Absolutely nothing wrong if you want to do the grow method. But there is a difference I believe in the way that Gimp handles single pixel outlines. If you use the same image and use the shrink and grow methods and overlay them in difference mode you can see the difference. In this case almost unnoticeable, but if you use the different methods in a complex image such as a plasma render the difference is quite noticeable. I came across this effect some time ago when I had unexplained dots of colours in an image. I do not know what causes this discrepancy but I believe it is probably a rounding error somewhere in the pixel maths. Nor do I know which method is the correct outcome of the maths. I suppose both methods are correct depending on your needs.
The difference in the first image is the white outline, the difference in the plasma is the grey dots

Very good example wbool.

Once you have a selection you don't care if it was obtained from the white or else.

Try this:
- create image
- create selection with freehand
- save to channel
- grow N pixels
- save to Channel as Selection #1
- reload original selection
- Invert/Shrink N pixels/Invert
- save to Channel as Selection #2
- create white layer, load selection #1, bucket fill with white
- create white layer, load selection #2, bucket fill with white
- put the top layer in "difference" mode
- try to find a pixel which is not pure black (you can do "new from visible" and play with histogram/threshold)

=> the two selections are identical

.. unless I'm missing something?

i would like to recreate that logo, anybody has an idea how to make an archimedean spiral ?

EDIT: found something here:
http://gimp-handbuch.de/index.php?optio ... &Itemid=91

Thank you so much for all the great responses! I will try those suggestions tonight!

It wasn't too awful long ago that Ofnuts wrote a real nice spiral filter "golden spiral".
http://registry.gimp.org/node/25982

Try that.

thanks Rod, im always a bit anti to installing a script, when you can also do it by hand and learn something, but i will try both ways later when i come back home and report back

Sorry, I forgot to address cleanup. It's already been covered by others, though. Be aware if you use the Color to Alpha method, your logo will have transparency as well. The background color will affect the colors of your logo. There are ways to fix this though. I didn't do any cleanup. That's why it looks a little off.

Because you should not do it that way, you are destroying the anti-aliasing pixels. See here for an explanation.

Oh dear, that was one of those easy looking tasks, that werent that easy at all



I used the method, with the Polar Coordinates, but tweaked the end of the spiral a lot with elliptical selections. That took the most time, until it looked right.
Also i changed the colors a bit. As far as i know, Reiki energy comes from the heart-chakra and has the colors pink, green and golden, thats why i added the golden glow.

The original looks more earthy, my version is very clean.
Maybe it would have been good, to make the spiral as a path and then stroke the path, so that you get varying thickness of the line, but i dont know how do to that.
Also i was too lazy to look for the original font, which again, has a different character, than the one i used.
Dunno, my version has a really different feel, its a bit too "computerized".....

Could you please tell me the ways to fix this problem please Bug Sampson... in case I need to deal with this in the future ?
Please and thankyou !

My usual technique is:
- wand-select the background (and any "closed" areas, like letter loops, if needed).
- grow the selection by one pixel. This adds to the selection the 'anti-aliasing' pixels that make the border of the subject (there are the ones that are important to transform with color-to-alpha) while leaving out of it most of the subject (which we want to keep unchanged)
- apply color-to-alpha.

To simplify this process, I created a script a while back:

http://www.silent9.com/incoming/scripts/transbg.scm

This works if the background is one even colour. There are some sliders to adjust the amount the edges get cleaned up to allow for source images with either sharp of soft edges.

-Rob A>