Hi Chris,
On 13.04.2012, at 22:06, Chris Moline wrote:
> Hi, I am slowly working on improving HOpenCV and to support displaying
> IplImages using Gtk I needed pixbufNewFromData. I've attached a patch
> but I'm not sure that I've implemented it correctly. Thanks for your
> time.
+pixbufNewFromData :: Ptr CUChar -> Colorspace -> Bool -> Int -> Int -
> Int -> Int -> IO Pixbuf
+pixbufNewFromData imData cSpace hasAlpha bitsPerSample width height
rowStride
+ = wrapNewGObject mkPixbuf $
+ {#call pixbuf_new_from_data #}
+ imData
+ (fromIntegral . fromEnum $ cSpace)
+ (fromBool hasAlpha)
+ (fromIntegral bitsPerSample)
+ (fromIntegral width)
+ (fromIntegral height)
+ (fromIntegral rowStride)
+ nullFunPtr nullPtr
I think there is a problem here in that you pass a simple pointer to
the C function which takes ownership of the memory. In order for your
program not to crash you have to ensure that the pointer remains valid
until the program exists.
We haven't bound this function since it wasn't clear how you can
always ensure that the passed in data is freed without forcing the
user to commit to a specific way of allocating it (e.g. with
malloc() ). When keeping the function agnostic to the way the buffer
was allocated, it is necessary to pass in a custom free function.
Could you try to change the function as follows:
{#pointer GdkPixbufDestroyNotify as PixbufDestroyNotify#}
foreign import ccall "wrapper" mkPixbufDestroyNotifyPtr :: (Ptr CUChar
-> IO ()) -> IO PixbufDestroyNotify
+pixbufNewFromData :: Ptr CUChar -> PixbufDestroyNotify -> Colorspace -
> Bool -> Int -> Int -> Int -> Int -> IO Pixbuf
+pixbufNewFromData imData free cSpace hasAlpha bitsPerSample width
height rowStride
+ = wrapNewGObject mkPixbuf $
+ {#call pixbuf_new_from_data #}
+ imData
+ (fromIntegral . fromEnum $ cSpace)
+ (fromBool hasAlpha)
+ (fromIntegral bitsPerSample)
+ (fromIntegral width)
+ (fromIntegral height)
+ (fromIntegral rowStride)
+ free nullPtr
I hope this compiles and works :-)
Cheers,
Axel
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