GIMP vs. TIFF B/W Pack Bit CCITT Group 4 (2D) FAX
Mazi
B/W Pack Bit CCITT Group 4 (2D) FAX format? I have lots of document
that I would like to digitize using a scanner and save them on a CD
media. So far, I scanned them @ 600x600DPI and they are saved under
TIFF B/W Pack Bit CCITT Group 4 (2D) FAX format. However, there are
some files that I need to do some retouch/rotate and GIMP-1.2.4 could
not save it back with the same TIFF B/W Pack Bit CCITT Group 4 (2D)
FAX format (or may be I just don't know how) and the saved files
become 20x the size of their original files. The reason I want to save
it under TIFF B/W Pack Bit CCITT Group 4 (2D) FAX format is mainly
because I find this format gives the best quality and compression for
a B/W text document..
Thanks.
Phil Harper
well, i'm afraid i can't answer your question, but is it worth trying
PNG as a replacement, especially if these scans are true black and
white(not greyscale) the compression should be pretty good, in fact
it's pretty good even if it's just greyscale, give it a try, i've
never had good results with TIFF personally, but then, i don't use
anything that specialises in the format.
Mazi
wrote:
The scanned file is pure B/W @600x600 DPI. I tried your suggestion and
the created PNG file is about 1.2MB in size where as the original TIFF
B/W Pack Bit CCITT Group 4 (2D) FAX format is about 88KB in size. As
you can see, the PNG file is still about 13x larger than the TIFF B/W
with Pack Bit CCITT Group 4 (2D) FAX format file. A conversion like
this is definitely out of question.
Michael Schumacher
> The scanned file is pure B/W @600x600 DPI. I tried your suggestion and
> the created PNG file is about 1.2MB in size where as the original TIFF
> B/W Pack Bit CCITT Group 4 (2D) FAX format is about 88KB in size. As
> you can see, the PNG file is still about 13x larger than the TIFF B/W
> with Pack Bit CCITT Group 4 (2D) FAX format file. A conversion like
> this is definitely out of question.
Did you convert the PNG to 1bit indexed or did you save it as RGB?
Michael
--
schumamls Netzpl@zle: http://schumaml.gmxhome.de
Mazi
1bit. The original file is in a B/W Pack Bit CCITT Group 4 (2D) FAX
format (I believe it is a 1bit/pixel).
Olivier Ripoll
> I just did "save as" and there is no option to convert the PNG to
> 1bit. The original file is in a B/W Pack Bit CCITT Group 4 (2D) FAX
> format (I believe it is a 1bit/pixel).
>
Image->Colors->indexed
then choose a 1 bit palette
then save.
Regards,
Olivier.
Marc 'BlackJack' Rintsch
> I just did "save as" and there is no option to convert the PNG to
> 1bit. The original file is in a B/W Pack Bit CCITT Group 4 (2D) FAX
> format (I believe it is a 1bit/pixel).
Usually GIMP should tell you in the window title what format the Image has
(RGB, grayscale or indexed). I suspect loading such a TIFF results in a
grayscale image!?
You have to convert it before saving with Image->Mode->Indexed... (or
ALT+i) to an indexed image with 1 Bit Palette (and maybe without
dithering) and then save it as PNG.
Ciao,
Marc 'BlackJack' Rintsch
Mazi
Thanks for the information. However, the saved PNG file (237,49 Bytes)
is still about 2.7x larger than the original B/W Pack Bit CCITT Group
4 (2D) FAX format (88,904 Bytes). BTW, I also did try to save the
converted 1 bit pixel image in TIFF pack bit and it yielded the file
with a much larger size, i.e. 943,096 Bytes. I opened this TIFF file
using imaging software made by Kodak found in my Win2k Adv Server (I
believe this software comes with Windows 2K) and found the TIFF file
was save in an uncompress 256 color format. Then, I converted the file
to a 1 bit/pixel and saved it with CCITT Group 4 (2d) Fax compression
format and the file size becomes 140,492 Bytes.
Mazi
I did exactly what you had mentioned above and the saved files are
usually at least > 2x of original TIFF in a B/W Pack Bit CCITT Group 4
(2D) FAX format. I thought the extra Bytes are due to the edit;
however, I tried just load the original file, convert it to
1bit/pixel, and saved in PNG with a file > 2x larger than original
file. I am hoping someone will be able to guide me to save the file in
TIFF B/W Pack Bit CCITT Group 4 (2D) FAX format.
Olivier Ripoll
>
> Thanks for the information. However, the saved PNG file (237,49 Bytes)
> is still about 2.7x larger than the original B/W Pack Bit CCITT Group
> 4 (2D) FAX format (88,904 Bytes). BTW, I also did try to save the
> converted 1 bit pixel image in TIFF pack bit and it yielded the file
> with a much larger size, i.e. 943,096 Bytes. I opened this TIFF file
> using imaging software made by Kodak found in my Win2k Adv Server (I
> believe this software comes with Windows 2K) and found the TIFF file
> was save in an uncompress 256 color format. Then, I converted the file
> to a 1 bit/pixel and saved it with CCITT Group 4 (2d) Fax compression
> format and the file size becomes 140,492 Bytes.
CCITT fax 4 format is specially optimised for faxes in two colours, so PNG
won't beat it at this game, clearly
Here is a test I did with a scanned image, after converting it to B&W. The
soft used is Irfan Viewer for Windows (I think it works quite well in
Wine), but XNview gives the same results (slightly better) and also exists
on Unices.
Tiff:
without compression: 184 KiB
with lzw compression: 19 KiB
with packbits compression: 34 KiB
with joeg compression: 302 KiB
with zip compression: 17 KiB
now the three formats specially done for B&W
with huffmanRLE: 27KiB
with CCITT fax 3: 28KiB
with CCITT fax 4: 8KiB
PNG : 15 KiB
What to conclude?
1- PNG is from far the best of all-purpose formats here. But for a pure
B&W image, better is to use the CCITT fax 4 format
2- Jpeg is one of the best formats around the world in compression, but of
course not for a B&W image
3- Use Xnview or Irfan viewer for your problem.
Regards,
Olivier.
Mazi
Thank you very much, Olivier. Just one more question: Does Irfan
viewer support B/W Pack Bit CCITT Group 4 (2D) FAX format file to save
the pure B/W image? My scanned files are all pure B/W (2 levels)
images.
Olivier Ripoll
The three formats, amomg which FAX 4, that are tested under the sentence "now
the three formats specially done for B&W" are only B&W. That's why I said PNG
is the best of all purpose format, because only fax 4 beats it, but cannot do
colour images.
Regards,
Olivier.
PS: Irfan is windows only (wine may be useful), but Xnview exists on both
Windows and Linux.
Mazi
You did not seem to answer my question: Does Irfan View support a B/W
Pack Bit CCITT Group 4 (2D) FAX format file in saving? BTW, all my
scanned document files are in B/W; therefore, PNG is not a good choice
if I can have B/W Pack Bit CCITT Group 4 (2D) FAX format file
supported under GIMP. However, AFAIK it looks like GIMP does not
support this B/W Pack Bit CCITT Group 4 (2D) FAX format unless someone
can proof me wrong ... :)
Olivier Ripoll
>
> You did not seem to answer my question: Does Irfan View support a B/W
> Pack Bit CCITT Group 4 (2D) FAX format file in saving?
>The soft used is Irfan Viewer for Windows
>[...]
>now the three formats specially done for B&W
>[...]
>with CCITT fax 4: 8KiB
in the last to previous message, and
>The three formats, amomg which FAX 4, that are tested under the sentence
>"now the three formats specially done for B&W"
>are only B&W.
in my previous message.
Sincerely,
Olivier.
Mazi
patience to reponse to my posts.