-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 DR0ID wrote: > Perhaps you should write a convert script that removes the alphachannel > and replaces it with a colorkey of your choice. The main problem will be > what do you do with half transparent pixels? e.g. pixel where the alpha > value is between 0 and 255.
I have done this; in case anyone else wants it, it's a line of ImageMagick code, as follows: convert -compose Over -fill "rgb(255, 0, 255)" \ -draw "color 0,0 reset" $1 -draw "image Over 0,0 0,0 '$1'" \ +matte $2 (where $1 is the name of the input file and $2 the name of the output file). (255, 0, 255) is magenta and doesn't often come up in the game I'm working on. As for half-transparent pixels, I tell my artist not to make them :) but maybe subtracting the alpha would be a good solution too. (I'm not sure how to do that in ImageMagick though.) However, because it potentially could collide with a color in an image in the game, I save the colorkey to a separate file. Actually, for a given file foo.png I check for a file foo.inf which contains a statement like: colorkey = True # this means take the colorkey from the top-left pixel, as Greg Ewing suggests colorkey = (x, y) # colorkey is a pixel at (x, y) colorkey = (r, g, b) # colorkey is (r, g, b) colorkey = False # no colorkey; this is the default If no foo.inf file is found, complain, and assume colorkey = False. Even in this engine, per-pixel alpha may be needed for some graphics. This system was grown, not designed, and if I were to redo it, I think I would make colorkey = (255, 0, 255) the default, as you suggest, because almost all of the images use that as the colorkey, with colorkey = False available in case per-pixel alpha is needed. But as it is, I just have a ton of .inf files floating around my graphics directory. > From the set_alpha() documentation: > "If the Surface contains per pixel alphas, setting the alpha value to > None will disable the per pixel transparency." > > But I dont know what dolor this pixels will have afterwards. My guess would be that it would strip the alpha channel entirely: (255, 0, 0, 127) would become (255, 0, 0). > Greg Ewing schrieb: >> Probably you could just throw away the alpha channel >> and use the colour of the top left pixel as the >> colorkey. This really doesn't work if you have a rectangular image with a hole in the center or something like that. It's tricky to characterize what kinds of images you'll have in your game before you have them, and if you want reasonably generic image loading code, you have to make some guesses. Ethan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFG6h4BhRlgoLPrRPwRAhMSAKCLYSa/Pq6U+p1u9xCSk9vhX2nXNwCdF0Fa QL/KwXKZ4A/9mHVmb9Fx094= =olAO -----END PGP SIGNATURE-----
