ModuleJuicyPixels-3.3.8Haskell2010

Codec.Picture.Jpg.Internal.FastIdct

Module providing a fast implementation of IDCT

inverse two dimensional DCT, Chen-Wang algorithm (cf. IEEE ASSP-32, pp. 803-816, Aug. 1984) 32-bit integer arithmetic (8 bit coefficients) 11 mults, 29 adds per DCT sE, 18.8.91

coefficients extended to 12 bit for IEEE1180-1990 compliance sE, 2.1.94

this code assumes >> to be a two's-complement arithmetic right shift: (-2)>>1 == -1 , (-3)>>1 == -2

1 type
3 values

PackageJuicyPixels-3.3.8
Exports4
LanguageHaskell2010
LicenceBSD-3-Clause
SourceFastIdct.hs

typetype MutableMacroBlock s a = STVector s a

Macroblock that can be transformed.

valuefastIdct :: MutableMacroBlock s Int16 -> ST s (MutableMacroBlock s Int16)

Algorithm to call to perform an IDCT, return the same block that the one given as input.

valuemutableLevelShift

:: MutableMacroBlock s Int16
-> ST s (MutableMacroBlock s Int16)

Perform a Jpeg level shift in a mutable fashion.

valuecreateEmptyMutableMacroBlock :: (Storable a, Num a) => ST s (MutableMacroBlock s a)

Create a new macroblock with the good array size