rubidium@9628: 32bpp and OpenTTD
rubidium@9628: =================
rubidium@9628: 
rubidium@9628: OpenTTD has 32bpp support. This means: OpenTTD still is 8bpp, but it has the
rubidium@9628: posibility to override the graphics with 32bpp. This means that it isn't a
rubidium@9628: replacement of grf or newgrf, but simply an addition. If you want to use 32bpp
rubidium@9628: graphics of a newgrf, you do need the newgrf itself too (with 8bpp graphics).
rubidium@9628: 
rubidium@9628: 
rubidium@9628: The Format
rubidium@9628: ----------
rubidium@9628: 
rubidium@9628: 32bpp images are stored in PNG. They should go in:
rubidium@9628:   data/sprites/<grfname>/<SpriteID>.png
rubidium@9628: 
rubidium@9628: For example, a grfname would be 'openttd' (without .grf, lowercase), and the
rubidium@9628: SpriteID 3, to override the 3rd sprite in openttd.grf with a 32bpp version.
rubidium@9628: 
rubidium@9628: The format of this PNG can be almost anything, but we advise to use RGBA
rubidium@9628: format. Alpha-channel is fully supported.
rubidium@9628: 
rubidium@9628: As the core of OpenTTD is 8bpp, and because you of course want company colours
rubidium@9628: in your images, you will need to add a mask for every sprite that needs colour
rubidium@9628: remapping. The name is simular as above, only you have to put a 'm' behind the
rubidium@9628: SpriteID. This image should be a 8bpp palette image, where the palette is the
rubidium@9628: OpenTTD palette. Upon load of the PNG, the mask is loaded too, and overrides
rubidium@9628: the RGB (not the Alpha) of the original PNG image, and replacing it with a
rubidium@9628: 8bpp color remapped and converted to 32bpp.
rubidium@9628: 
rubidium@9628: An other thing that OpenTTD needs in your png, is 2 tEXt chunks: x_offs and
rubidium@9628: y_offs. This to define the x- and y-offset, of course. Use the tool we supply
rubidium@9628: to add this information. Sadly enough most graphical editors trashes those
rubidium@9628: chunks upon save, so you have to readd it every time you save your image.
rubidium@9628: 
rubidium@9628: Your images should be the same as the grf, in size.
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