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Removing color from multiple images

Aug 13, 2011, 03:46 (This post was last modified: Aug 13, 2011 03:55 by Aquilo.)
Post: #1
Removing color from multiple images
Hi All:

I'm rather new here and have been working with Gimp 2.6 for a few months. I have two questions.

1. I am making a .gif with 57 images [black silhouette] with a white background. Is there any way I can remove the background from all of the images at once (like a batch tool) rather than going through each one of them?

2. This may relate to my first question. If I make a change to one image i.e. crop an image and resize it, is there a way to effect that change to all of the images Vs going through each one?

Thanks
Aquilo
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Aug 13, 2011, 18:42 (This post was last modified: Aug 13, 2011 18:45 by Aquilo.)
Post: #2
RE: Removing color from multiple images
(Aug 13, 2011 11:43)ofnuts Wrote:  1) The Gimp Animation Package (aka GAP) (availabel here: http://www.gimp.org/downloads/ ) has a tool to apply a filter to all layers. And what to you want to do is a filter (Color-to-alpha)(*)

2) If you have all your layers/Frames load in an image, image crop and resize aplies to all layers at the same time.

It is also possible to do that outside of Gimp in the finished image. In a GIF, a specific color is designated as being the transparent color, so making the white transparent is just updating the color map. With the Imagemagick toolbox:
Code:
convert opaque.gif -transparent white  transparent.gif

Thanks for your reply Ofnuts;

I installed the GAP add-on and fooled around with it a bit. I think I can get the hang of it in no time. I did notice GIMP saying I needed to install a re-synthesizer. However the only one available was for linux and I don't know how to do a build for Windows.

Also; I installed Imagemagick, but when I opened the .gif file I didn;t have any options available in the menus? I searched for more detailed installation instructions but was unable to find any. While I am sharp with computers I am on the learning curve with Gimp, GAP, Add-ons and Imagemagick's routine atm etc. Can you point me in the right direction for this?

Thanks again
Aquilo
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Aug 15, 2011, 01:19 (This post was last modified: Aug 15, 2011 01:19 by Aquilo.)
Post: #3
RE: Removing color from multiple images
(Aug 13, 2011 19:42)ofnuts Wrote:  ImageMagick is fundamentally a collection of command-line tools, and one of them is "convert" for which you have an example above.

To be honest, I don't use GAP, but I don't think the resynthetizer is necessary for what you are doing.

Thanks for the info Ofnuts;

I took a look at ImageMagick and am completely lost. I was expecting a GUI to use. I understand the command line instructions but IM is a bit more involved than I had anticipated. Reminds me of DOS command-lines Big Grin and felt shivers having to get into that again.
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Sep 28, 2017, 12:56 (This post was last modified: Sep 28, 2017 12:57 by angel0sdh.)
Post: #4
RE: Removing color from multiple images
Load all images as layers in the same file. GMIC -> Colors -> Select-Replace Colors -> Choose the color you want to select. Then choose any color to replace it with and change the opacity to zero. You will have transparency. Be sure to export as png.

Make sure in the GMIC settings that you set the action to apply to All Layers.
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