Coloring Textures

Many blocks and items in vanilla change their texture color depending on where they are or what properties they have, such as grass. Models support specifying “tint indices” on faces, which are integers that can then be handled by IBlockColors and IItemColors. See the wiki for information on how tint indices are defined in vanilla models.

IBlockColor/IItemColor

Both of these are single-method interfaces. IBlockColor takes a BlockState, an (nullable) IBlockDisplayReader, and a (nullable) BlockPos. IItemColor takes an ItemStack. Both of them take an int parameter tintIndex, which is the tint index of the face being colored. Both of them return an int, a color multiplier. This int is treated as 4 unsigned bytes, alpha, red, green, and blue, in that order, from most significant byte to least. For each pixel in the tinted face, the value of each color channel is (int)((float) base * multiplier / 255.0), where base is the original value for the channel, and multiplier is the associated byte from the color multiplier. Note that blocks do not use the alpha channel. For example, the grass texture, untinted, looks white and gray. The IBlockColor and IItemColor for grass return color multipliers with low red and blue components, but high alpha and green components, (at least in warm biomes) so when the multiplication is performed, the green is brought out and the red/blue diminished.

If an item inherits from the builtin/generated model, each layer (“layer0”, “layer1”, etc.) has a tint index corresponding to its layer index.

Creating Color Handlers

IBlockColors need to be registered to the BlockColors instance of the game. BlockColors can be acquired through ColorHandlerEvent$Block, and an IBlockColor can be registered by BlockColors#register. Note that this does not cause the BlockItem for the given block to be colored. BlockItems are items and need to be colored with an IItemColor.

@SubscribeEvent
public void registerBlockColors(ColorHandlerEvent.Block event){
    event.getBlockColors().register(myIBlockColor, coloredBlock1, coloredBlock2, ...);
}

IItemColors need to be registered to the ItemColors instance of the game. ItemColors can be acquired through ColorHandlerEvent$Item, and an IItemColor can be registered by ItemColors#register. This method is overloaded to also take Blocks, which simply registers the color handler for the item Block#asItem (i.e. the block’s BlockItem).

@SubscribeEvent
public void registerItemColors(ColorHandlerEvent.Item event){
    event.getItemColors().register(myIItemColor, coloredItem1, coloredItem2, ...);
}