Flaming Pear Solidify with the GIMP

Hi All,

Has anyone successfully used the Flaming Pear Solidify filter in the GIMP?

I'm using the GIMP for Windows v2.2.13.

I read Robin Wood's excellent tutorial "Making a Perfect Alpha Channel, with No White Halo" which can be found here: http://www.robinwood.com/Catalog/Technical/SL-Tuts/SLTutSet.html

Thanks to Tor Lillqvist's PSPI plugin, you can use these filters in GIMP: http://www.gimp.org/~tml/gimp/win32/pspi.html

So I have everything installed, and some of Flaming Pear's other free filters work, but the Solidify filter gives me an error message when I try to use it:

"Needs Transparency: This filter cannot operate on the image's background. Use it on a layer with transparent regions".

Here's what I've tried:
copying the background to a new layer, deleting the original background.
adding an Alpha Channel to the original image.
adding a separate transparency layer.

Any help is appreciated. I'm pretty new to this kind of graphics editing.

Thanks,

Joe Vandeperck

Use the Solidify filter on a layer that contains opaque parts and transparent parts both. If the layer is fully opaque of fully transparent, then the filter can't do anything.

Its purpose is takes the edges of the opaque areas, and extrude them to fill the transparent areas, thus "solidifying" the layer but filling in the holes in it. Make sense?

Thanks for the reply Chosen Few.

I made a single layer with both transparency and opaque, but get the same error. Attached is a zip file with a .tga of the image I am testing with. Would you expect it to work with Solidify as it is?

I'm not sure if I'm doing something wrong, or if the filter simply won't work with GIMP. I don't have Photoshop to test with.

Thanks for your help; it is much appreciated.

-JV

I don't have to open the file to tell you that it's not going to work with Solidify. The fact that it's a TGA is enough. Solidify works against the transparency of individual layers, and TGA images have no layers.

The TGA image itself is completely opaque, always. If it contains an alpha channel, many programs, including SL, will read the data in that channel as a transparency map, but it doesn't automatically mean transparency in its own right, and it certainly doesn't mean layer transparency. Ultimately a channel is just a channel, nothing more than a grayscale image. Layer transparency and alpha transparency are two entirely different things.

If you want Solidify to work, use it on an individual layer that contains some opaque parts and some visible transparent parts. Whatever's going on on the alpha channel is none of Solidify's concern. All it cares about is what's happening on the individual layer to which it's applied.

I think the problem here may be that GIMP seems to rely on visible transparency. The reason I still don't have a GIMP tutorial in my transparency guide is I haven't been able to figure out how to get it to create an alpha channel without using visible transparency as its starting point. That's a tremendous handicap. I'd be amazed if it can't be done, but I'll be damned if I can figure out how.

And it might very well be that that particular filter just doesn't work with GIMP. I'm not really in a position to try it out since I don't have GIMP on this machine, but if I get a chance, I'll give it a try on my old computer.

Thanks again.

Yes, I was working under the assumption that Alpha = Transparency. Some tutorials I've read don't seem to make a distinction between Alpha and Layer Transparency.

I'll pursue another method, other than using the Solidify filter, to get rid of the halo using GIMP. I saw mention of using a Guassian Blur technique to achieve similar results.

It's often stated that the GIMP is just as powerful as Photoshop, but obviously there are some key differences when you get into the finer details.

Thanks very much for your insight.

-JV

I fixed it for you. What you should have done was duplicate the background layer and load your alpha channel as a selection. Invert the selection and clear it so that you end up with just the olive and branch with the rest of the layer transparent. Fill the background layer with black so you can easily evaluate the transparency of the new layer against it. Touch up the transparency on the top layer until it's nice and clean with no stray pixels remaining of the white background, then run solidify on it. Your alpha channel had to be expanded by 2 pixels to get a clean result. That's why you were picking up so much of the white background.

I guess this is probably a stupid question... but here goes.

Why would anyone bother with an alpha channel in GIMP? Why not just start out with a transparent background, and then if you need various opacities (like, say, for a sheer silk sleeve) just fill/paint/whatever using the opacity level in the Tools Options menu? I've been doing it for a while, and haven't really noticed any difference in whether or not I even HAVE an alpha channel. Am I not seeing some basic fundamental thing here?

Thanks,

Oryx

Oryx, you're confusing layer transparency with overall image transparency. They're two different things.

SL uses TGA files as its source material for generating textures with transparency, and sinceTGA's have no layers, they cannot have any layer-specific properties, including layer transparency. The transparency data in a TGA is channel 4, the alpha channel, nothing else.

If you want transparency in your SL texture, you NEED an alpha channel in your TGA. It matters not whether your image was created in GIMP or in any other program. A TGA is a TGA is a TGA.

And just so your aware, all painting programs have layer-specific and tool-specific opacity settings, just like GIMP has.

Okay, I think I get it. I just tested it right quick;

File/New
Advanced - Fill with Transparency

Seems to automatically create an alpha channel? Anything I do to the image after that gets added to the alpha channel and can be saved as a TGA, imported to SL, and comes out transparent... but I never actually edited the alpha on my own, or created it. Is this an okay way to do this, if I want to get proficient, or is it sort of cheating, and I should make my own alpha channels?

Oryx

It's an okay way to do it, but it's not a great way to do it. By letting the alpha channel create itself automatically like that, you often end up with a haloing effect around the edges of the opaque parts, just as Joe described in the original post here. In order to eliminate that halo, you need to be able to separate the alpha channel creation process from the layer transparency, but unfortunately, I haven't been able to figure out how to do that in GIMP.

That separation is a very simple thing to do in Photoshop or Paintshop Pro, so I'd be really surprised if it truly cannot be done in GIMP. Assuming the procedure does exist, there's no obvious way to get to it, I'm afraid. I'm really hoping a GIMP expert will appear here and shed some light on this some day.

what about this?

Say you have two layers; a white background, and a white second layer. Select a square region in the second layer and fill it in with whatever color. Then under the Select menu, choose 'save to channel'. Then select the white surrounding area and cut it. Doesn't this create a perfect alpha channel? Or is there still a halo that I'm not seeing?

Okay I just reread the entire alpha channels thread (beautiful tutorials, btw) and I understand what I was doing wrong re: halos, etc. Easy peasy. The GIMP is basically the same as all those other programs. Now I'm going to have to be obsessive compulsive and eyeball all my clothes for halos LOL. I actually learned a LOT in the last hour... thanks!

You know, I've been playing with the Gimp for a couple of days now, TRYING to get a white halo to appear, and I only successfully did it once, and now I can't remember what I did. When I finally did get a white halo, I said "oooh NOW I know what they're talking about," and then promptly forgot which steps I took to get the dreaded halo in the first place.

I know I'm a really bad lazy person for doing it this way, but I swear up and down that I've NEVER gotten a white halo on clothing (or anything else for that matter) using this procedure when creating a new file:

File/Create
Advanced: Fill with: Transparency


Gimp automatically creates the alpha this way, and while I've been reading everything that all the smart people say (that this is probably not a good idea), I've never had an issue with halos, even at the 1024 level.

*shrug* Dunno!