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[GIMP] Removing White Backgrounds.

PostPosted: Fri Jun 25, 2010 6:43 am
by TheSaxlad
Can anyone enlighten me on how to remove the white background from pictures on gimp?

Re: Removing White BAckgrounds.

PostPosted: Fri Jun 25, 2010 7:15 am
by ManBungalow
TheSaxlad wrote:Can anyone enlighten me on how to remove the white background from pictures on gimp?

When you create the image, simply choose to fill with transparency as so:
Image
(You'll need to select 'Advanced Options' first, of course).

Or if you've got a white background on a layered image you are already working on, just delete the white background layer..

Re: Removing White BAckgrounds.

PostPosted: Sun Jun 27, 2010 6:19 am
by TheSaxlad
Sorry I mean when you copy and paste a picture with a white background...

Re: Removing White BAckgrounds.

PostPosted: Sun Jun 27, 2010 7:28 am
by thenobodies80
Select "colors menu" --> "color to alpha"

http://docs.gimp.org/2.6/en/plug-in-colortoalpha.html

Re: Removing White BAckgrounds.

PostPosted: Sun Jun 27, 2010 7:36 am
by natty dread
I don't know if GIMP has a "curves" tool that can map one channel to another through a dynamic curve, but that's how I always do these things in paint.net when I need transparency. I take the curves tool, select input channel = luminosity and output channel = alpha. Then if I want black to be transparent I set the curve so that 0 = 0 and 1-255 = 255. If I want white to be transparent I'll set 255=0 and 0-254=255. If I want a smooth transition from transparent to black I'll just make a straight line from 0 to 255 so that 255=0 and 0=255.

If I set the input channel to "hue" I can make any colour or combination of colours transparent.

The curves tool is very powerful, again not sure if GIMP has this but if it doesn't then it sucks...