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Thread: Making part of an existing image partially transparent in GIMP

  1. #1
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    Making part of an existing image partially transparent in GIMP

    Ok, what I want to do in GIMP is turning out to be a little more difficult than usual.
    I can find plenty of tutorials on making parts of images transparent or semi-transparent.
    I can work out how to do this from scratch, creating an image.
    The problem here is I am not creating an image from scratch - I want to take an existing flat image with existing background and remove background and be left with an image (complete with transparent and semi-transparent areas) which I can then save to a PNG or use on any other background I wish.

    To illustrate what I want to do, I have made mockup images below.
    Image 1 shows an image with a black background. I want to remove the black background but leave the image and semi-transparent "rays" intact so they can be placed onto a different background, as in image 2. Note that the "rays" appear over the new background colour.

    image 1


    image 2


    If anyone knows how to achieve this, please ellaborate. Feel free to download and use the above kbblack.png image to explain how to get from image 1 to image 2.

    Thanks
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  2. #2
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    Re: Making part of an existing image partially transparent in GIMP

    Maybe THIS will help?

  3. #3
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    Re: Making part of an existing image partially transparent in GIMP

    Almost, but not quite...

    That method makes areas of the image semi-transparent but unfortunately also retains the black shade from the background, so when it is placed over the top of a new background, instead of the "rays" being a translucent white, they are a dirty grey colour.

    The image below shows the dirty grey effect I can't work out how to avoid -


    This is the exact problem I keep coming up with.

    Is there any other way to extract the black background from the image?
    Last edited by blackdalek; October 16th, 2010 at 07:20 AM.
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  4. #4
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    Re: Making part of an existing image partially transparent in GIMP

    Thats a tuff one, I played around with that image for a while and I can't figure it out. Its hard because it's all one layer. Hopefully someone will be able to figure it out. Heres a couple of helpful links I found for future reference. Hope this is any help at all. I'll keep looking around too. Good luck.

    USER MANUAL

    GIMP CHAT FORUMS

  5. #5
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    Re: Making part of an existing image partially transparent in GIMP

    I've had some success using a combination of desaturate, curves and colour to alpha filters on images where the background is simple like one colour backgrounds.

    Images where the background is more complex, I think removing the background may prove near impossible.

    Thanks bigsmitty64 for helping.
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  6. #6
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    Re: Making part of an existing image partially transparent in GIMP

    No problem, sorry I couldn't be more help!

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