celestar@9913: 32bpp and OpenTTD
celestar@9913: =================
celestar@9913: 
celestar@9913: OpenTTD has 32bpp support. This means: OpenTTD still is 8bpp, but it has the
celestar@9913: posibility to override the graphics with 32bpp. This means that it isn't a
celestar@9913: replacement of grf or newgrf, but simply an addition. If you want to use 32bpp
celestar@9913: graphics of a newgrf, you do need the newgrf itself too (with 8bpp graphics).
celestar@9913: 
celestar@9913: 
celestar@9913: The Format
celestar@9913: ----------
celestar@9913: 
celestar@9913: 32bpp images are stored in PNG. They should go in:
celestar@9913:   data/sprites/<grfname>/<SpriteID>.png
celestar@9913: 
celestar@9913: For example, a grfname would be 'openttd' (without .grf, lowercase), and the
celestar@9913: SpriteID 3, to override the 3rd sprite in openttd.grf with a 32bpp version.
celestar@9913: 
celestar@9913: The format of this PNG can be almost anything, but we advise to use RGBA
celestar@9913: format. Alpha-channel is fully supported.
celestar@9913: 
celestar@9913: As the core of OpenTTD is 8bpp, and because you of course want company colours
celestar@9913: in your images, you will need to add a mask for every sprite that needs colour
celestar@9913: remapping. The name is simular as above, only you have to put a 'm' behind the
celestar@9913: SpriteID. This image should be a 8bpp palette image, where the palette is the
celestar@9913: OpenTTD palette. Upon load of the PNG, the mask is loaded too, and overrides
celestar@9913: the RGB (not the Alpha) of the original PNG image, and replacing it with a
celestar@9913: 8bpp color remapped and converted to 32bpp.
celestar@9913: 
celestar@9913: An other thing that OpenTTD needs in your png, is 2 tEXt chunks: x_offs and
celestar@9913: y_offs. This to define the x- and y-offset, of course. Use the tool we supply
celestar@9913: to add this information. Sadly enough most graphical editors trashes those
celestar@9913: chunks upon save, so you have to readd it every time you save your image.
celestar@9913: 
celestar@9913: Your images should be the same as the grf, in size.
celestar@9913: