Graphics.Rendering.TrueType.STB

This is a wrapper around Sean Barrett's TrueType font rasterizer code. The original can be found at http://nothings.org/stb/stb_truetype.h. The version of stb-truetype used here is 0.3.

Documentation

newtype TrueType

A TrueType font file (containing maybe multiple font sets) loaded into memory.

Constructors

TrueType ByteString

data Offset

A font offset inside a TrueType font file.

Instances

Eq Offset

Ord Offset

Show Offset

data Font

data Glyph

A glyph inside a font.

Instances

Eq Glyph

Ord Glyph

Show Glyph

Initialization

loadTTF :: FilePath -> IO TrueType

withTTF :: FilePath -> (TrueType -> IO a) -> IO a

enumerateFonts :: TrueType -> IO [Offset]

Enumerates the fonts found in a TrueType file. Often there is only one, but there may be more.

initFont :: TrueType -> Offset -> IO Font

findGlyph :: Font -> Char -> IO (Maybe Glyph)

Note: this is cached.

Font metrics

type Unscaled = Int

data HorizontalMetrics a

Constructors

HMetrics

Fields

advanceWidth :: a

leftSideBearing :: a

Instances

Functor HorizontalMetrics

Show a => Show (HorizontalMetrics a)

data VerticalMetrics a

ascent is the coordinate above the baseline the font extends; descent is the coordinate below the baseline the font extends (i.e. it is typically negative) lineGap is the spacing between one row's descent and the next row's ascent... so you should advance the vertical position by ascent - descent + lineGap

Constructors

VMetrics

Fields

ascent :: a

descent :: a

lineGap :: a

Instances

Functor VerticalMetrics

Show a => Show (VerticalMetrics a)

data BoundingBox a

The convention is BBox (x0,y0) (x1,y1).

Constructors

BBox (a, a) (a, a)

Instances

Show a => Show (BoundingBox a)

lineAdvance :: Num a => VerticalMetrics a -> a

As calculated by (ascent - descent + lineGap).

verticalSize :: Num a => VerticalMetrics a -> a

As calculated by (ascent - descent).

scaleForPixelHeight :: VerticalMetrics Unscaled -> Float -> Float

getFontVerticalMetrics :: Font -> IO (VerticalMetrics Unscaled)

getGlyphHorizontalMetrics :: Font -> Glyph -> IO (HorizontalMetrics Unscaled)

getGlyphKernAdvance :: Font -> Glyph -> Glyph -> IO Unscaled

This is not yet implemented in stb_truetype; it always returns 0.

getGlyphBoundingBox :: Font -> Glyph -> IO (BoundingBox Unscaled)

Bitmaps

type Scaling = (Float, Float)

data Bitmap

A 8-bit grayscale bitmap.

Constructors

Bitmap

Fields

bitmapSize :: (Int, Int)

bitmapPtr :: ForeignPtr Word8

newBitmap :: (Int, Int) -> IO Bitmap

withBitmap :: Bitmap -> (Int -> Int -> Ptr Word8 -> IO a) -> IO a

flipBitmap :: Bitmap -> IO Bitmap

Flips the bitmap vertically (leaving the original unchanged)

type BitmapOfs = (Int, Int)

An offset (for example the pivot of the glyph)

getGlyphBitmapBox :: Font -> Glyph -> Scaling -> IO (BoundingBox Int)

Returns the size of the bitmap (in pixels) needed to render the glyph with the given scaling.

The box is centered around the glyph origin; so the bitmap width is x1-x0, height is y1-y0, and location to place the bitmap top left is (leftSideBearing*scale,y0). Note that the bitmap uses y-increases-down, but the shape uses y-increases-up, so the results of getGlyphBitmapBox and getGlyphBoundingBox are inverted.

newGlyphBitmap :: Font -> Glyph -> Scaling -> IO (Bitmap, BitmapOfs)

Creates a new bitmap just enough to fit the glyph with the given scaling, and renders the glyph into it. The offset returned is the offset in pixel space from the glyph origin to the top-left of the bitmap (so it's almost always negative).

renderGlyphIntoBitmap' :: Font -> Glyph -> Scaling -> Bitmap -> BitmapOfs -> IO ()

The offset is the top-left corner of the bounding box of the glyph, and must be nonnegative (otherwise nothing will happen).

renderGlyphIntoBitmap :: Font -> Glyph -> Scaling -> Bitmap -> BitmapOfs -> IO ()

The offset is the origin of the glyph. If the glyph extends from the bitmap in the positive direction, it is clipped; however, if it extends in the negative direction, no drawing will happen!

bitmapArray :: Bitmap -> IO (UArray (Int, Int) Word8)

NOTE: because of the way Haskell indexes rectangular arrays, the resulting array is indexed with (y,x), as opposed to what you would expect.

bitmapFloatArray :: Bitmap -> IO (UArray (Int, Int) Float)

Cached glyph storage

data CachedBitmap

Note: the metrics are scaled!

Constructors

CBM Bitmap BitmapOfs (HorizontalMetrics Float)

data BitmapCache

A "bitmap cache".

bmcVerticalMetrics :: BitmapCache -> VerticalMetrics Float

Note: these metrics are scaled!

bmcScaling :: BitmapCache -> Scaling

newBitmapCache :: Font -> Bool -> (Float, Float) -> IO BitmapCache

Creates a new cache where glyph bitmaps with the given scaling will be stored. The second argument is whether the resulting bitmaps should be flipped vertically or not (this is useful with OpenGL).

getCachedBitmap :: BitmapCache -> Char -> IO (Maybe CachedBitmap)

Fetches a rendered glyph bitmap from the cache (rendering it first if it was not present in the cache before).