Actually alpha would be 255 for visible areas, 0 for complete invisibility But yes, that's the technique i used too.
You are right, i was using 1 value coz i am working in 16 bit color mode (1555 bit scheme), for 32 bit color Alpha=0 mean full transparent, alpha=255 mean full opaque.


I've tried to convert that example source to delphi and I cannot get the .data attribute of a PTAUX_RGBImageRec to give me any info...
That is why i hate C language, :roll:, the example was more meaning to show you the opengl commands and parameters that enable the transparent rendering using alpha channel.

For loading and proccesing the bitmap file please check your delphi help about Tbitmap class methods loadfromfile() and scanline property or search for any custom bitmap file loading rutine out there.

tp.