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Hi all,

I'm new to GIMP--trying to learn some basic skills to create game models.

I was following a tutorial based in photoshop but I cannot seem to find out how to get the same result in GIMP.

Basically, I am trying to use an alpha layer/channel to export a picture that is transparent except for a grass clump that is colored green over the alpha layer. So the picture looks like a solid green rectangle, but is actually a green blade of grass.

Problem is, I cannot get the alpha layer to work. I can't follow the tutorial as it is in photoshop, and random videos on-line haven't helped.

What can I do to achieve this effect in GIMP?

(Here is the tutorial: , from 08:40 - 09:30)
(I have also attached my practice file as a TGA)
(Nov 26, 2012 00:29)ofnuts Wrote: [ -> ]"Alpha" is a channel (the A in RGBA) and not a "layer" so I don't quite understand what you want to do... The alpha channel of a layer can be edited using a "layer mask". It is possible to save a channel to file.

But I don't understand what your output should look like...


Thanks for the reply.

What I'm trying to create is a 2D blade of grass as in this tutorial ( , from 08:40 - 09:30 only). The output will be white blades of grass with black background (then a green layer over it) so that when I import into a 3D modeling program, only green blades of grass show.

I understand that in an alpha channel, black is transparent and white is opaque. Thus my image's background is black and the grass blades are white. Problem is, I cannot seem to use alpha channels to achieve this in GIMP.
I did look at (some of) that video, the saving bit was sort of glossed over.

But should be possible in Gimp

Make your green layer as a separate image.
Add a white layer mask to this image, make sure that this is 'active' - click in the layer mask, active has a white border not active has a black border, not obvious when it is all white.

Using the "grass image", copy to the clipboard.

Move back to the green image and paste into the image (ie layer mask). Initially it is as a floating layer, anchor this to fix it into the layer mask.

Now you want it as a targa file, go to export, put in the filename including the .tga suffix.

Everything in one screenshot. The targa file is shown in Imagemagick display, transparency is ok.
Thanks for the detailed response Rich,

I was able to save the file with transparency exactly how I wanted. Even if the workflow was a lot different from photoshop, GIMP did the trick Smile
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