truelight@7392: 32bpp and OpenTTD
truelight@7392: =================
truelight@7392: 
truelight@7392: OpenTTD has 32bpp support. This means: OpenTTD still is 8bpp, but it has the
truelight@7392: posibility to override the graphics with 32bpp. This means that it isn't a
truelight@7392: replacement of grf or newgrf, but simply an addition. If you want to use 32bpp
truelight@7392: graphics of a newgrf, you do need the newgrf itself too (with 8bpp graphics).
truelight@7392: 
truelight@7392: 
truelight@7392: The Format
truelight@7392: ----------
truelight@7392: 
truelight@7392: 32bpp images are stored in PNG. They should go in:
truelight@7392:   data/sprites/<grfname>/<SpriteID>.png
truelight@7392: 
truelight@7392: For example, a grfname would be 'openttd' (without .grf, lowercase), and the
truelight@7392: SpriteID 3, to override the 3rd sprite in openttd.grf with a 32bpp version.
truelight@7392: 
truelight@7392: The format of this PNG can be almost anything, but we advise to use RGBA
truelight@7392: format. Alpha-channel is fully supported.
truelight@7392: 
truelight@7392: As the core of OpenTTD is 8bpp, and because you of course want company colours
truelight@7392: in your images, you will need to add a mask for every sprite that needs colour
truelight@7392: remapping. The name is simular as above, only you have to put a 'm' behind the
truelight@7392: SpriteID. This image should be a 8bpp palette image, where the palette is the
truelight@7392: OpenTTD palette. Upon load of the PNG, the mask is loaded too, and overrides
truelight@7392: the RGB (not the Alpha) of the original PNG image, and replacing it with a
truelight@7392: 8bpp color remapped and converted to 32bpp.
truelight@7392: 
truelight@7392: An other thing that OpenTTD needs in your png, is 2 tEXt chunks: x_offs and
truelight@7392: y_offs. This to define the x- and y-offset, of course. Use the tool we supply
truelight@7392: to add this information. Sadly enough most graphical editors trashes those
truelight@7392: chunks upon save, so you have to readd it every time you save your image.
truelight@7392: 
truelight@7392: Your images should be the same as the grf, in size.
truelight@7392: