Graphics.Text.PCF

Rendering bitmap text with pcf-font is easy. Consider a program for rendering text into a PNG:

import Codec.Picture.Png
import Codec.Picture.Types
import Data.List
import Graphics.Text.PCF
import System.Environment

-- | USAGE: program <font.pcf> <output.png> <text>
main :: IO ()
main = do
    [input_file, output_file, text] <- getArgs
    pcf <- either fail return =<< loadPCF input_file
    case renderPCFText pcf text of
        Just (w, h, image_data) ->
            writePng output_file (Image w h image_data :: Image Pixel8)
        Nothing ->
            putStrLn "ERROR: Unable to render input text."

Decoding

loadPCF :: FilePath -> IO (Either String PCF)

Load a PCF font file. File should not be compressed (e.g. ".pcf.gz" extension).

decodePCF :: ByteString -> Either String PCF

Decode a PCF font from an in-memory ByteString.

Rendering

renderPCFText

Arguments

:: PCF

Font to render with

-> String

Text to render

-> Maybe (Int, Int, Vector Word8)

Just width, height, and rendering; Nothing if an unrenderable character is encountered

Generate a vector of black and white pixels from a PCF font and a string.

getPCFGlyph :: PCF -> Char -> Maybe PCFGlyph

Extract a single glyph bitmap from a PCF font.

getPCFGlyphPixel

Arguments

:: PCFGlyph

-> Int

X

-> Int

Y

-> Bool

True if pixel at (x,y) is opaque; False if pixel at (x,y) is transparent or (x,y) is out of the glyph's bounds

Calculate the color of a pixel in a glyph given its (x,y) coordinates.

foldPCFGlyphPixels

Arguments

:: PCFGlyph

-> (Int -> Int -> Bool -> a -> a)

Function that takes x, y, pixel value at (x,y), and an accumulator, returning a modified accumulator

-> a

Initial accumulator

-> a

Scan over every pixel in a glyph, constructing some value in the process.

Metadata

getPCFProps :: PCF -> [(ByteString, Either ByteString Int)]

List key-value pairs found in PCF properties table.

getGlyphStrings :: PCF -> [ByteString]

Types

data PCF

Container of tables extracted from a PCF font file.

data PCFGlyph

Container of a single glyph bitmap and its metadata.

Constructors

PCFGlyph

Fields

• glyph_metrics :: Metrics
• glyph_char :: Char

  Unicode character corresponding to glyph

• glyph_width :: Int

  Pixel width of glyph once rendered

• glyph_height :: Int

  Pixel height of glyph once rendered

• glyph_pitch :: Int

  Number of bytes in each bitmap row

• glyph_bitmap :: ByteString

  glyph_height rows of glyph_pitch bytes containing the glyph's bitmap image starting from the left-most bit and ending at the glyph_width bit in each row

Instances

Show PCFGlyph

Methods

showsPrec :: Int -> PCFGlyph -> ShowS

show :: PCFGlyph -> String

showList :: [PCFGlyph] -> ShowS

data Metrics

Constructors

Metrics

Fields

• metrics_left_sided_bearings :: Int16
• metrics_right_sided_bearings :: Int16
• metrics_character_width :: Int16
• metrics_character_ascent :: Int16
• metrics_character_descent :: Int16
• metrics_character_attributes :: Int16

Instances

Eq Metrics

Methods

(==) :: Metrics -> Metrics -> Bool

(/=) :: Metrics -> Metrics -> Bool