gimp cannot read multi-byte pgm files?

unruh

unread,

Feb 13, 2010, 6:11:49 PM2/13/10

to

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)

furlan

unread,

Feb 14, 2010, 5:14:02 AM2/14/10

to

Does 2.6.7 act the same way? Which OS?

Is the file that you are working on available online?

ciao,
f

--
aa #2301
"I'd take the awe of understanding over the awe of ignorance any day"
--Douglas Adams

unruh

unread,

Feb 14, 2010, 12:53:41 PM2/14/10

to

Yes. Mandriva Linux 2010.0

>
> Is the file that you are working on available online?

sure,
ftp.theory.physics.ubc.ca/outgoing/dark.pgm

It is 4MB.
It is a dark photo by a camera I am testing, so do not expect to see
anything.

Here is another possibility

-----------------------------------------------------
P5
2 2
4095
aabbccdd
------------------------
(no terminating carriage return at the end)

which does not work with gimp but does with convert from imagemagic.
While there appears to be some dispute with byte order, the netpgm seems
to be pretty standard (most significant byte first).

furlan

unread,

Feb 15, 2010, 3:16:44 AM2/15/10

to

Hmmm, I can't seem to get it:

Connecting to ftp.theory.physics.ubc.ca|142.103.234.23|:80... connected.
HTTP request sent, awaiting response... 200 No headers, assuming HTTP/0.9
Length: unspecified
Saving to: `dark.pgm'

100%[======================================>] 21 --.-K/s in 0s

2010-02-15 03:13:20 (2.00 MB/s) - Read error at byte 21 (Connection reset
by peer).Giving up.

It did that repeatedly. I used wget. It looks like the workaround may be
the way to go though. You would think that the GIMP would be able to
read it though.

sid

unread,

Feb 15, 2010, 12:50:06 PM2/15/10

to

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

unruh

unread,

Feb 15, 2010, 3:10:42 PM2/15/10

to

It is an ftp file, not an html file
I guess I should have written
ftp://ftp.theory.physics.ubc.ca/outgoing/dark.pgm

wget is trying to interpret it as an html file, which will fail
miserably.

For the small example above, if I convert it to a .png file with
convert, and look at that in gimp, you see 4 pixels in various shades of
grey.
If you try it in gimp directly, it does not open at all-- invalid max
value.

furlan

unread,

Feb 16, 2010, 5:40:45 PM2/16/10

to

I find that weird as i know that I've used it the past w/ ftp. In any
case I have gotten it via Firefox. It doesn't open in my version of the
GIMP either. I'll try the conversion that you suggest.