Hello,
I am using bitmap-0.2 [1] to load a Bitmap file [2]. However, the
following sample GHCi session fails for me.
> Prelude Data.Bitmap Data.Bitmap.Pure.File> readBitmap "b.bmp" :: IO (Bitmap
> Word8)
> *** Exception: Data/Bitmap/Internal.hs:(63,17)-(67,15): Non-exhaustive
> patterns in case
I downloaded the sources of bitmap-0.2 from Hackage and modified the
relevant function by appending the last line.
> decodeCType :: CInt -> PixelComponentType
> decodeCType k = case k of
> 1 -> PctWord8
> 2 -> PctWord16
> 3 -> PctWord32
> 4 -> PctFloat
> _ -> error $ "decodeCType: unexpected integer (" ++ show k ++ ")"
With this modification the same GHCi session given above results in
the following error.
> Prelude Data.Bitmap Data.Bitmap.Pure.File> readBitmap "b.bmp" :: IO (Bitmap
> Word8)
> *** Exception: decodeCType: unexpected integer (7077888)
I don't have any idea where 7077888 comes from. Am I doing something
wrong? Is my bitmap corrupted in some way? The number 7077888 has no
apparent significance except that it is a perfect cube [3]. So I guess
this is not a problem with endianness.
In fact as far as I can tell `decodeCType` is only called on
`(PixelComponent t => c_type t)` and `c_type t` only yields integer
values in the (inclusive) range of 1 to 4. That is if I am not missing
some orphaned instance.
Could anyone please enlighten me what is happening and if I am doing
something wrong?
In case this is relevant: I am using bitmap-0.2 from Hackage with GHC
7.4.1 on a 3.2.20 kernel i686 architecture Linux.
Regards,
Alexander Foremny
[1] http://hackage.haskell.org/package/bitmap
[2] https://www.dropbox.com/s/pyutvni9vx6f6mo/b.bmp
[3] http://www.wolframalpha.com/input/?i=7077888
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