diff --git a/Graphics/DrawingCombinators.hs b/Graphics/DrawingCombinators.hs --- a/Graphics/DrawingCombinators.hs +++ b/Graphics/DrawingCombinators.hs @@ -8,7 +8,7 @@ -- -- Maintainer : Luke Palmer -- Stability : experimental --- Portability : needs GADTs and rank n types +-- Portability : tested on GHC only -- -- Drawing combinators as a functional interface to 2D graphics using OpenGL. -- @@ -19,25 +19,24 @@ -- Whenever possible, a /denotational semantics/ for operations in this library -- is given. Read @[[x]]@ as \"the meaning of @x@\". -- --- Intuitively, an "Image" @a@ is an infinite plane of pairs of colors /and/ --- @a@\'s. The colors are what are drawn on the screen when you "render", and --- the @a@\'s are what you can recover from coordinates using "sample". The +-- Intuitively, an 'Image' @a@ is an infinite plane of pairs of colors /and/ +-- @a@\'s. The colors are what are drawn on the screen when you 'render', and +-- the @a@\'s are what you can recover from coordinates using 'sample'. The -- latter allows you to tell, for example, what a user clicked on. -- -- The following discussion is about the associated data. If you are only -- interested in drawing, rather than mapping from coordinates to values, you --- can ignore the following and just use @mappend@ and @mconcat@ (Data.Monoid) --- to overlay images. +-- can ignore the following and just use 'mappend' and 'mconcat' to overlay images. -- -- Wrangling the @a@\'s -- the associated data with each \"pixel\" -- is done --- using the "Functor", "Applicative", and "Monoid" instances. +-- using the 'Functor', 'Applicative', and 'Monoid' instances. -- --- The primitive @Image@s such as "circle" and "text" all return @Image Any@ --- objects. "Any" is just a wrapper around "Bool", with @(||)@ as its monoid +-- The primitive @Image@s such as 'circle' and 'text' all return @Image Any@ +-- objects. 'Any' is just a wrapper around 'Bool', with @(||)@ as its monoid -- operator. So e.g. the points inside the circle will have the value @Any -- True@, and those outside will have the value @Any False@. Returning @Any@ -- instead of plain @Bool@ allows you to use @Image@s as a monoid, e.g. --- "mappend" to overlay two images. But if you are doing anything with +-- 'mappend' to overlay two images. But if you are doing anything with -- sampling, you probably want to map this to something. Here is a drawing -- with two circles that reports which one was hit: -- @@ -67,6 +66,7 @@ , Sprite, openSprite, sprite -- * Text , Font, openFont, text, textWidth + , Monoid(..), Any(..) ) where @@ -97,7 +97,7 @@ -- > [[Image a]] = R2 -> (Color, a) -- -- The semantics of the instances are all consistent with /type class morphism/. --- I.e. Functor, Applicative, and Monoid act point-wise, using the "Color" monoid +-- I.e. Functor, Applicative, and Monoid act point-wise, using the 'Color' monoid -- described below. data Image a = Image { dRender :: Renderer , dPick :: Picker a @@ -146,7 +146,7 @@ dRender d identity mempty --- |Like "render", but clears the screen first. This is so +-- |Like 'render', but clears the screen first. This is so -- you can use this module and pretend that OpenGL doesn't -- exist at all. clearRender :: Image a -> IO () @@ -242,7 +242,7 @@ -- | A Bezier curve given a list of control points. It is a curve -- that begins at the first point in the list, ends at the last one, -- and smoothly interpolates between the rest. It is the empty --- image ("mempty") if zero or one points are given. +-- image ('mempty') if zero or one points are given. bezierCurve :: [R2] -> Image Any bezierCurve controlPoints = rendererImage $ \tr _ -> do -- todo check at least 4 points? @@ -272,27 +272,26 @@ Colors -------------} --- | Color is defined in the usual computer graphics sense, of +-- | Color is defined in the usual computer graphics sense: -- a 4 vector containing red, green, blue, and alpha. -- --- The Monoid instance is given by alpha transparency blending, --- so: --- --- > mempty = Color 1 1 1 1 --- > mappend c@(Color _ _ _ a) c' = a*c + (1-a)*c' +-- The Monoid instance is given by alpha composition, described +-- at @http:\/\/lukepalmer.wordpress.com\/2010\/02\/05\/associative-alpha-blending\/@ -- --- Where multiplication is componentwise. In the semantcs the --- values @zero@ and @one@ are used, which are defined as: +-- In the semantcs the values @zero@ and @one@ are used, which are defined as: -- -- > zero = Color 0 0 0 0 -- > one = Color 1 1 1 1 -data Color = Color R R R R +data Color = Color !R !R !R !R + deriving (Eq,Show) instance Monoid Color where - mempty = Color 1 1 1 1 - mappend (Color r g b a) (Color r' g' b' a') = Color (i r r') (i g g') (i b b') (i a a') + mempty = Color 0 0 0 0 + mappend (Color r g b a) (Color r' g' b' a') = Color (i r r') (i g g') (i b b') γ where - i x y = a*x + (1-a)*y + γ = a + a' - a * a' + i | γ == 0 = \_ _ -> 0 -- imples a = a' = 0 + | otherwise = \x y -> (a*x + (1-a)*a'*y)/γ -- | Modulate two colors by each other. -- diff --git a/graphics-drawingcombinators.cabal b/graphics-drawingcombinators.cabal --- a/graphics-drawingcombinators.cabal +++ b/graphics-drawingcombinators.cabal @@ -4,7 +4,7 @@ have to go into the deep, dark world of imperative stateful programming just to draw stuff. It supports 2D only (for now), with support drawing geometry, images, and text. -Version: 1.1.1 +Version: 1.2.0 Stability: experimental Synopsis: A functional interface to 2D drawing in OpenGL License: BSD3