On Fri, 2008-09-26 at 01:36 +0800, Tsai, Dung-Bang (???) wrote:

I'm using gimp to deal with my photos which are made of DSLR. These ttif files have embedded exif information, and every time I save these files; it seems that the exif information will be stripped. I have done some tests on jpeg files; gimp will not strip the exif information. How can I correctly deal with the exif in tiff by using gimp?

I can't say if the TIFF file plugin supports this or not but there are some options on how to deal with the situation if it doesn't. First, load the TIFF images and then save them in JPEG at 100% quality. Technically that should be equivalent to TIFF since no compression is performed but I can't guarantee that.

To convert back to TIFF you can use ImageMagick's convert tool. According to this discussion:
http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=11600 convert will retain EXIF data. This is true as long as you're simply converting formats and not resizing (such as creating thumbnails). Converting file formats is as simple as

convert file.jpg file.tif

By the way, if I save these tiff images as another files, will gimp also strip the icc profile?
(ps, will gimp strip the icc profile in jpeg?)

I looked at using ICC profiles last month in an article I did for Linux Format magazine but I don't think I checked if the profiles were retained when saved. I think I assumed (bad idea) that they were. You'll simply have to try it and see. GIMP does support retaining ICC profiles when you open files that contain them. You're typically queried when you open the file if you want to keep it over convert it to GIMP's built in profile.

When will the gimp support the 16bit per channel color depth?

When it's ready. :-)

Actually, integration of the GEGL libraries is underway and a first release with GEGL support is due in the next release (due out "soon" but one can never assume when soon might arrive). I don't know if 16 bit channels are to be included in the next release (though I don't believe they are), but one of the purposes of integrating GEGL was to allow for higher color depths. So it should be in either the next release or one of the releases soon after that.

On Fri, 2008-09-26 at 02:14 +0800, Tsai, Dung-Bang (???) wrote:

As far as I know, baseline jpeg is alway lossy; only JPEG-LS supports lossless image saving. So, does it mean that if I save file at 100% quality, gimp will use JPEG-LS?

Don't know - you'd have to look at the source to figure that out or ask on gimp-developer.

Also, I will also check that if your ideal will work or not. I'm worried about that gimp can not even read the exif in the tiff file such that your approach will not work at all.

I wasn't that impressed with the TIFF file plugin though I use it to save lossless screenshots for articles. If you are worried it doesn't read the exif data you can try converting to JPEG first using ImageMagick and then loading it that way. I believe the JPEG plugin supports the EXIF data. Again, since I don't use EXIF much I'm not positive of any of this. You simply have to try it and find out.

Hi,

On Fri, 2008-09-26 at 01:36 +0800, Tsai, Dung-Bang (???) wrote:

I'm using gimp to deal with my photos which are made of DSLR. These ttif files have embedded exif information, and every time I save these files; it seems that the exif information will be stripped.

The GIMP TIFF plug-in lacks support for Exif information. It should not be too difficult to add basic support to it. Basic means that the TIFF loader attaches the Exif information to the image and the TIFF writer writes any attached Exif data back to the file. If this is important for you, then I suggest that you add this functionality to the TIFF plug-in. If you need help, feel free to ask technical questions on the gimp-developer mailing-list.

I have done some tests on jpeg files; gimp will not strip the exif information.

That is correct. The JPEG plug-in has the functionality that is missing in the TIFF plug-in. I suggest that you have a look at the source code of the JPEG plug-in to find out how the JPEG plug-in deals with Exif. The TIFF plug-in should do something similar.

By the way, if I save these tiff images as another files, will gimp also strip the icc profile?
(ps, will gimp strip the icc profile in jpeg?)

No, if I remember correctly, both plug-ins read and write ICC profiles.

Sven

Michael J. Hammel píše v ?t 25. 09. 2008 v 11:57 -0600:

To convert back to TIFF you can use ImageMagick's convert tool. According to this discussion:
http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=11600 convert will retain EXIF data. This is true as long as you're simply converting formats and not resizing (such as creating thumbnails). Converting file formats is as simple as

convert file.jpg file.tif

I am afraid that this might be true only for MS Windows. I tried on linux (ubuntu 8.04 amd64):

$ convert orig_with_exif_and_icc.jpg test.tif

The test.tif has only the ICC profile embedded, Exif is lost. This might be caused by libtiff library, which is different on the systems.

I do not have any TIFF file with Exif, so cannot test what happens on conversions.

On linux, support for creating Exif metadata is quite limited - I personally use it only for JPEGs. Also exiftool's man page reads, that it can only read or write, but not create Exif in TIFF images.

By the way, if I save these tiff images as another files, will gimp also strip the icc profile?
(ps, will gimp strip the icc profile in jpeg?)

I looked at using ICC profiles last month in an article I did for Linux Format magazine but I don't think I checked if the profiles were retained when saved. I think I assumed (bad idea) that they were. You'll simply have to try it and see. GIMP does support retaining ICC profiles when you open files that contain them. You're typically queried when you open the file if you want to keep it over convert it to GIMP's built in profile.

GIMP retains the ICC profile in TIFF.

Best regards,

Milan Knizek knizek (dot) confy (at) volny (dot) cz http://www.milan-knizek.net - about linux and photography

Unfortunately exiv2 does not write to tiff files yet...

This would give you a work around... copy the EXIF back in after editing.

http://www.hugsan.com/EXIFutils/

* stephen moss [09-26-08 07:55]:

Unfortunately exiv2 does not write to tiff files yet...

This would give you a work around... copy the EXIF back in after editing.

http://www.hugsan.com/EXIFutils/

But, Phil Harvey's excellent exiftool will,

http://www.sno.phy.queensu.ca/~phil/exiftool/