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 BlockColors and ItemColors. See the wiki for information on how tint indices are defined in vanilla models.

BlockColor/ItemColor

Both of these are single-method interfaces. BlockColor takes a BlockState, a (nullable) BlockAndTintGetter, and a (nullable) BlockPos. ItemColor 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 BlockColor and ItemColor 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

BlockColors need to be registered to the BlockColors instance of the game. BlockColors can be acquired through RegisterColorHandlersEvent$Block, and an BlockColor can be registered by #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 ItemColor.

@SubscribeEvent
public void registerBlockColors(RegisterColorHandlersEvent.Block event){
  event.register(myBlockColor, coloredBlock1, coloredBlock2, ...);
}

ItemColors need to be registered to the ItemColors instance of the game. ItemColors can be acquired through RegisterColorHandlersEvent$Item, and an ItemColor can be registered by #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(RegisterColorHandlersEvent.Item event){
  event.register(myItemColor, coloredItem1, coloredItem2, ...);
}