as hinted in my last email, Gem seems to have different hardcoded ideas about what RGBA means (esp. on OSX)
the main confusion is about which "type" to use: GL_UNSIGNED_INT_8_8_8_8_REV vs GL_UNSIGNED_INT_8_8_8_8 the solution seems to be simple (_REV on ppc, normal on i686) but it seems to be done inconsistently in the source code, thus resulting in all the alpha problems marius has reported.
i have created a wiki-page that tries to explain the technical implementation of Gem's standard colorspaces, which can be found at http://gem.iem.at/documentation/GemWiki/ColorSpace
i have filled this page to my best knowledge, but i would be glad if somebody who knows what they are doing could have a look at it and confirm (or correct) everything (esp. those lines marked with "?")
fgmasdr IOhannes