Bitmap.hs

{-# LANGUAGE DeriveDataTypeable #-}
{-# OPTIONS_HADDOCK hide #-}

-- | Helper functions for rendering bitmaps
module Brillo.Internals.Rendering.Bitmap (
  Rectangle (..),
  BitmapData (..),
  BitmapFormat (..),
  PixelFormat (..),
  RowOrder (..),
  bitmapPath,
  freeBitmapData,
)
where

import Data.Data (Data, Typeable)
import Foreign (ForeignPtr, Ptr, Word8, free)


-- | Represents a rectangular section in a bitmap
data Rectangle
  = Rectangle
  { rectPos :: (Int, Int)
  -- ^ x- and y-pos in the bitmap in pixels
  , rectSize :: (Int, Int)
  -- ^ width/height of the area in pixelsi
  }
  deriving (Show, Read, Eq, Ord, Data, Typeable)


-- | Abstract 32-bit RGBA bitmap data.
data BitmapData
  = BitmapData
  { bitmapDataLength :: Int -- length (in bytes)
  , bitmapFormat :: BitmapFormat
  , bitmapSize :: (Int, Int)
  -- ^ width, height in pixels
  , bitmapCacheMe :: Bool
  , bitmapPointer :: ForeignPtr Word8
  }
  deriving (Eq, Data, Typeable)


{-| Description of how the bitmap is layed out in memory.

  * Prior version of Brillo assumed `BitmapFormat BottomToTop PxABGR`
-}
data BitmapFormat
  = BitmapFormat
  { rowOrder :: RowOrder
  , pixelFormat :: PixelFormat
  }
  deriving (Eq, Data, Typeable, Show, Ord)


{-| Order of rows in an image are either:

  * `TopToBottom` - the top row, followed by the next-lower row and so on.
  * `BottomToTop` - the bottom row followed by the next-higher row and so on.
-}
data RowOrder
  = TopToBottom
  | BottomToTop
  deriving (Eq, Data, Typeable, Show, Ord, Enum, Bounded)


-- | Pixel formats describe the order of the color channels in memory.
data PixelFormat
  = PxRGBA
  | PxABGR
  deriving (Eq, Data, Typeable, Show, Ord, Enum, Bounded)


instance Show BitmapData where
  show _ = "BitmapData"


-- | Generates the point path to display the bitmap centred
bitmapPath :: Float -> Float -> [(Float, Float)]
bitmapPath width height =
  [ (-width', -height')
  , (width', -height')
  , (width', height')
  , (-width', height')
  ]
  where
    width' = width / 2
    height' = height / 2


-- | Frees the allocated memory given to OpenGL to avoid a memory leak
freeBitmapData :: Ptr Word8 -> IO ()
freeBitmapData = free
{-# INLINE freeBitmapData #-}