Transparency Problems

[jay]

I use gimp primarily for editing textures for game models, and I've been having problems exporting with a transparent background, no matter what i do the background always comes out either black or white. I've followed a bunch of tutorials around the alpha channels and exporting with a transparent background and nothing seems to work. The background shows up in all image viewers I've tried and in vtfedit, the program I need to get the images to work in the source engine.

For my purposes I need everything but a small part of the image file to be completely transparent otherwise you get the problem I've been having where half the model goes either black or white. Any chance someone can tell me exactly how they successfully create images with fully transparent backgrounds? Failing at this has eaten up far to much of my time now, so any help would be much appreciated. Running gimp GIMP 2.8.18 in case that's in any way relevant.

[rich2005]

What format are you using to export your image?

Some viewers / browsers do not honour transparency anyway and will show transparency as white or black rather than the usual checker pattern.

A quick search and does this make any sense.

https://developer.valvesoftware.com/wiki/GIMP
https://github.com/Artfunkel/gimp-vtf/releases
https://developer.valvesoftware.com/wiki/Decals_in_GIMP

[Blighty]

As Rich asked, what format are you using for export? jpg does not support transparency, png does.

[rich2005]

If it is for a game, there is a good chance that the format is tga.

and as an example of how different file viewers show a transparent file

[jay]

I've tried both png and tga, with the same results. I read somewhere that tga can't support transparency but png does, then other sources working with the source engine seem to lean towards tga.

[rich2005]

(11-01-2017, 08:30 PM)jay Wrote: I've tried both png and tga, with the same results.  I read somewhere that tga can't support transparency but png does, then other sources working with the source engine seem to lean towards tga.

Sorry, not into games, so up to you to try the possibilities in the vagaries of your game engine

png & tga are not the only formats to support transparency. Discounting gif as poor quality and tif with a clipping mask as too complicated

The alpha channel is a mask so there will be 'something' remaining

For png, and the png export settings. Try turning off the Save colour values from transparent pixels screenshot https://i.imgur.com/c9KOuxd.jpg

For tga, only one option and I have seen this before. Turn off the run-length-encoding (RLE) compression. https://i.imgur.com/NMaMt5O.jpg

Do not discount bmp, there is a transparency option in Advanced Options -> 16bit . 
Unlikely but sometimes Do not write colour space information needs to be checked. https://i.imgur.com/Coza0wm.jpg

All three show with an image viewer as having transparency: https://i.imgur.com/moEoiuM.jpg