Hello,
Author of Data.Bitmap here. The issue is caused by the fact that Data.Bitmap does *not* support
bmp files at all. This should be clear from the documentation. The functions you tried to used use
their own file format, which a really very simple format; they are only added for simple experimentation.
(again, this is explicit in the docs). The same documentation points to the stb-image [1] package,
which supports loading of some common formats (png, jpg, bmp).
In general, I suggest that with package-specific question, unless it is a widely used package,
mail the maintainer directly; you have better chance to get an answer that way.
Regards,
Balazs
[1] http://hackage.haskell.org/package/stb-image
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
