[SciPy-User] FreeImage <-> numpy IO wrappers

[Sebastian Haase]

Zach,
Thanks for the reply,

I have looked at the sourceforge - few comments:

- is there currently only one person behind FreeImage ?
- it seems there are some problems with 64 bit windows - apparently
related to inline assembly...
- the discussion group seems not very responsive / active -- might
also of course mean that it mostly "just works" ;-)
- the "who uses FreeImage" list seems really quite long - but then PIL
is probably also used by many ...

How large is the DLL actually ?

Thanks,
Sebastian


On Wed, May 12, 2010 at 7:10 PM, Zachary Pincus <zachary.pincus at yale.edu> wrote:
>> Do you know if FreeImage does anything via memory-mapping ? I'm mostly
>> interested in TIFF-memmap, which exists according to libtif, but I
>> have now idea how useful it is .....  (I need memmap for GB-size
>> multipage images)
>
> I don't know a ton about how memmapping works, but check out these
> functions from FreeImage:
>
>> FreeImage_OpenMemory
>> DLL_API FIMEMORY *DLL_CALLCONV FreeImage_OpenMemory(BYTE *data
>> FI_DEFAULT(0), DWORD
>> size_in_bytes FI_DEFAULT(0));
>>
>> Open a memory stream. The function returns a pointer to the opened
>> memory stream.
>> When called with default arguments (0), this function opens a memory
>> stream for read / write
>> access. The stream will support loading and saving of FIBITMAP in a
>> memory file (managed
>> internally by FreeImage). It will also support seeking and telling
>> in the memory file.
>> This function can also be used to wrap a memory buffer provided by
>> the application driving
>> FreeImage. A buffer containing image data is given as function
>> arguments data (start of the
>> buffer) and size_in_bytes (buffer size in bytes). A memory buffer
>> wrapped by FreeImage is
>> read only. Images can be loaded but cannot be saved.
>
>> FreeImage_LoadFromHandle
>> DLL_API FIBITMAP *DLL_CALLCONV
>> FreeImage_LoadFromHandle(FREE_IMAGE_FORMAT fif,
>> FreeImageIO *io, fi_handle handle, int flags FI_DEFAULT(0));
>>
>> FreeImage has the unique feature to load a bitmap from an arbitrary
>> source. This source
>> might for example be a cabinet file, a zip file or an Internet
>> stream. Handling of these arbitrary
>> sources is not directly handled in the FREEIMAGE.DLL, but can be
>> easily added by using a
>> FreeImageIO structure as defined in FREEIMAGE.H.
>> FreeImageIO is a structure that contains 4 function pointers: one to
>> read from a source, one
>> to write to a source, one to seek in the source and one to tell
>> where in the source we currently
>> are. When you populate the FreeImageIO structure with pointers to
>> functions and pass that
>> structure to FreeImage_LoadFromHandle, FreeImage will call your
>> functions to read, seek
>> and tell in a file. The handle-parameter (third parameter from the
>> left) is used in this to
>> differentiate between different contexts, e.g. different files or
>> different Internet streams.
>
> With the first, I think you could just pass the void* pointer returned
> from memmapping a file; with the second, I think you could wrap a
> memmapped file with a file-like interface (implemented in python
> callbacks, even). Not sure, of course, if that will work OK... Might
> be easier to work with wrappers to libtiff directly?
>
> Zach
>
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