El dl 10 de 05 de 2010 a les 08:02 +0200, en/na bob va escriure:
> Hi all.
> I'm trying to edit an jpg image I've downloaded from the net.
> This image:
> http://creativenerds.co.uk/wp-content/uploads/2009/04/twitter-icos.jpg
> As you can see, the image has a white background.
> I want to isolate one of the illustrations and remove the white background.
> First I use the scalpal tool to isolate one of the illustrations. Then I use
> either the select tool or the erasor to remove the white. Instead of getting
> transparent area as a result, I get a grey.
> (What is happening here)
> To get around this, I first save the image as a png, then give the image a
> background layer with a random colour, save the image as an xcf and close the
> image. Then I open the xcf. 
> Again, I try to erase the white in order to get a transparent area. Again, I
> get an grey as a result.
> Obviously, I'm running into the boundaries of my understanding of image
> formats here.
> I'd love to know why I'm getting these results.

JPG don't has transparencies, so GIMP opens them withouth alpha channel.

> I'd also like to know how I can remove the white area and get transaparency
> without closing and re-opening the image.

Add alpha channel as suggested, then use the magic wand to select the
wite then edit->cut and you are done.

But if you want more quality, then zoom to 800 or more, look at the
white in the edges and continue adding a layer mask (transfering the
alpha channel already created, then carefully paint the edges of the
object in the main layer with the same color as the neighbour pixels, so
the wite don't show in the edges.

Hope this helps.

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