[Image-SIG] python PIL 16-bit tiff files

[Fredrik Lundh]

I'm afraid you need to rebuild the _imaging module; the patch touches
libImaging/Unpack.c too (without that, you can only read big-endian 48-bit
RGB files; that is, files that start with MM instead of II).

</F>

On Sun, Apr 25, 2010 at 5:53 PM, Dan Blacker <dan.blacker at googlemail.com>wrote:

> Hi Fredrik,
>
> Thanks for taking a look at this, I have downloaded the latest PIL source
> and installed it, and replaced the TiffImagePlugin.py that was in pyShared
> with the latest one.
>
> When running my script, I no longer get errors when reading my 16-bit tiff
> file in.
>
> I do however now get an error when I try and convert and make a grayscale
> copy of my file, in the middle of my script. (this should be 8bit):
>
> *  File "16bittest.py", line 147, in <module>
>     im1 = im0.convert ("L", dither=Image.NONE)
>   File "/usr/lib/python2.6/dist-packages/PIL/Image.py", line 654, in
> convert
>     self.load()
>   File "/usr/lib/python2.6/dist-packages/PIL/ImageFile.py", line 180, in
> load
>     d = Image._getdecoder(self.mode, d, a, self.decoderconfig)
>   File "/usr/lib/python2.6/dist-packages/PIL/Image.py", line 374, in
> _getdecoder
>     return apply(decoder, (mode,) + args + extra)
> ValueError: unknown raw mode*
>
> Am I missing a value to pass into convert() to tell it to make an 8bit
> file?
>
> Thanks,
>
>
>
> On 25 April 2010 13:48, Fredrik Lundh <fredrik at pythonware.com> wrote:
>
>> Oops, that patch was broken, due to pilot error.  Here's an incremental
>> fix:
>>
>> http://hg.effbot.org/pil-2009-raclette/changeset/c3fb89aa181e
>>
>> Alternatively, just grab the latest PIL/TiffImagePlugin.py and
>> libImaging/Unpack.c and drop them on top of the existing versions.
>>
>> </F>
>>
>> On Sun, Apr 25, 2010 at 1:07 PM, Fredrik Lundh <fredrik at pythonware.com>
>> wrote:
>> > This isn't really a full solution, but the following patch at least
>> > allows PIL to read 3x16-bit RGB TIFF files, converting them on the fly
>> > to 24-bit RGB.  Note that it requires new binaries to handle little
>> > endian (intel) files:
>> >
>> > http://hg.effbot.org/pil-2009-raclette/changeset/45c2debe0fc3
>> >
>> > Unfortunately, your sample use "contiguous" pixel storage, which makes
>> > the descriptor manipulation tricks I mentioned harder to implement
>> > efficiently for PIL 1.1.7.  I played a bit with libtiff's tiffcp
>> > utility to see if that could be used as a preprocessor (which is
>> > otherwise a great way to handle more "obscure" TIFF flavours), but at
>> > least the version I have doesn't handle 16-bit images well either.  I
>> > need to think a bit more about this, I think...
>> >
>> > </F>
>> >
>> > On Thu, Apr 22, 2010 at 10:57 PM, Fredrik Lundh <fredrik at pythonware.com>
>> wrote:
>> >> Oh, missed that there was one in your first post.  I'm a bit busy
>> >> right now, but I'll take a look when I find some spare time.
>> >>
>> >> </F>
>> >>
>> >> On Thu, Apr 22, 2010 at 10:56 PM, Fredrik Lundh <
>> fredrik at pythonware.com> wrote:
>> >>> On Tue, Apr 13, 2010 at 10:52 AM, Dan Blacker
>> >>> <dan.blacker at googlemail.com> wrote:
>> >>>> Hey guys,
>> >>>>
>> >>>> Thanks for your input,
>> >>>>
>> >>>> The image is only of a tiny cropped area of a long strip of color
>> kodachrome
>> >>>> film - I will send a better example with some more color in it when I
>> get a
>> >>>> chance.
>> >>>>
>> >>>> I was under the impression that PIL handled 16 bit images
>> (experimentally)
>> >>>> but does this only apply to 16-bit grayscale images?
>> >>>>
>> >>>> Am I going up a dead end trying to read my images with PIL?
>> >>>
>> >>> The current PIL release only supports 8 and 32-bit/pixel internal
>> >>> storage; that's enough to hold e.g. RGB triplets or 32-bit signed
>> >>> integers, but not 3x16 bit pixels.  I'd love to support more storage
>> >>> formats (machines are a lot bigger now than when the internal,
>> >>> intentionally very simple storage model was designed) including HDR
>> >>> formats (float16 etc), but rearchitecting the internals without
>> >>> breaking all existing code is a pretty big project...
>> >>>
>> >>> There is some limited support for 16-bit storage, by packing two
>> >>> pixels per 32-bit storage unit, but not all operations support this
>> >>> (it's mainly intended to support working with huge, memory mapped
>> >>> single-layer images, such as satellite data).
>> >>>
>> >>> There are some non-standard tricks that may help you with your
>> >>> specific case, though.  All codecs do things in two steps; the first
>> >>> is to identify the file format and build a descriptor of where the
>> >>> image data is in the file (the "tile" map).  The second step then
>> >>> loads pixel data on demand, using that descriptor.  You might be able
>> >>> to tweak the descriptor before loading the image, to load one layer at
>> >>> a time.  Do you have any samples?
>> >>>
>> >>> </F>
>> >>>
>> >>
>> >
>>
>
>
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