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

[Dan Blacker]

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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