gimp cannot read multi-byte pgm files?

unruh

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Feb 13, 2010, 6:11:49 PM2/13/10

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I have some pgm files which have a max value of 4095 (ie 12 bits, which
uses 2 bytes to store). But gimp complains that it cannot read a pgm
file with more that 255 levels (8 bit) abnd that the pnm filter does not
support it.
(PNM image Message Invalid maximum value\Gimp message
Opening '/tmp/dark.pgm' failed:
PNM Image plug-in could not open image)

The header of the file is
P5
1920 1080
#Fri Feb 12 17:33:33 2010
4095
......
(The dots are the start of the data)

Since multibyte pgm are part of the standard, what is the problem?
(http://netpbm.sourceforge.net/doc/pgm.html)
Surely gimp is newer that 2000 when the 2 byte format apparently came in.

Note that convert ( from ImageMagic) does seem to work, so if necessary
I could always use convert to get it into some format gimp does
understand.

Thanks

(gimp 2.4.7)

sid

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Feb 15, 2010, 12:50:06 PM2/15/10

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unruh wrote:

Well I clicked on your link which downloaded and opened the file in
KolourPaint. Saved it from there onto the desktop and right clicked open
with gimp and it opened without complaint?

Mandriva 2010, gimp 2.6.7

--
sid
RLU 300284
2010

furlan

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Feb 15, 2010, 2:25:43 PM2/15/10

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Thanks for the update on this. I was able to get the file via Firefox. I
also tried to open it via the GIMP w/ the same result as the OP. I just
snagged KolourPaint and installed it and will try it in that
application...

It opened and all I see is BLACK.

ciao,
f

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unruh

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Feb 15, 2010, 2:53:24 PM2/15/10

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I suspect that KolourPaint saved it in a different format.
Do
head filename
on the file that KolourPaint saved and post it please.

>>
>> Mandriva 2010, gimp 2.6.7
>
> Thanks for the update on this. I was able to get the file via Firefox. I
> also tried to open it via the GIMP w/ the same result as the OP. I just
> snagged KolourPaint and installed it and will try it in that
> application...
>
> It opened and all I see is BLACK.

It was a picture taken with the camera with the lens cap on. There
should be a few pixels which are not quite black (ie if you increase the
brightness, you should see a few pixels poke up and eventually a mottled
noise floor. The noise floor has pixel brightness values of about 20 out
of 4095. The maximum brightness of any single pixel is about 700 out of
4095.

Michael Soibelman

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Mar 11, 2010, 12:53:31 AM3/11/10

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On Mon, 15 Feb 2010 17:50:06 +0000, sid wrote:

Yes but when saving Kolourpaint gives a warning that (re)saving in this
format (pgm) may reduce the number of colors ! This is why Gimp no
longer has a problem opening the file as the number of colors no longer
exceeds the maximum that Gimp allows...

OSIS (or so it seems)

Perhaps the previous poster didn't get/see this warning but I suspect
that is what happened. Also, it's likely kolourpaint uses ImageMagick as
a backend to convert/read the file in...and then export it.

When looking at the image properties in Gimp I see this:

1920 x 1080 pixels
72 ppi
Grayscale
2.0 MB
PNM (not pgm)

That's AFTER saving from kolourpaint.