Does writing the Geocoded Exif information degenerate Jpeg files ?

[Trouncewalk]

I understand that each time you open and re-save a Jpeg image you
degrade the image (generation loss). Even something as simple as a
"rotate" can cause generation loss. Some programs like Pain Shop Pro 8
offer a "lossless rotation" feature where it can rotate the image
without degrading the image.

When gpicsync writes the exif info to a Jpeg image does it do it with
out adding a generation loss to the image?

Thanks.

[francois...@gmail.com]

Hello Trouncewalk,

The image data are not modified so there is no loss of quality. The
only thing which is modified is the invisible image header which
contain the metadata (ie informations about the file).

To read and write in the header I use EXIFTool which is a very mature
tool/library:
http://www.sno.phy.queensu.ca/~phil/exiftool/

Anyway always keep the default "backup picture" option so you'll
always have a copy of your original pictures (ie without header/
metadata change)

Bye

francois

[Trouncewalk]

Thanks for your answer. I appreciate it. And thanks for gpicsync...
it's a great little program.
Thanks.

On Jul 9, 10:49 am, "francois.schn...@gmail.com"

[bw]

On 9 Jul., 11:49, "francois.schn...@gmail.com"

<francois.schn...@gmail.com> wrote:
> Hello Trouncewalk,
>
> The image data are not modified so there is no loss of quality. The
> only thing which is modified is the invisible image header which
> contain the metadata (ie informations about the file).

Francois, I can observer that when geotagging Canon CR2 file, the size
of the preview image is reduced drastically.
Does someone else observer the same effect?

bernhard

[francois...@gmail.com]

>
> Francois, I can observer that when geotagging Canon CR2 file, the size
> of the preview image is reduced drastically.
> Does someone else observer the same effect?
>
> bernhard

According to the author of EXIFTool:

"""
Re: Writing JPG metadata, and image quality
Writing meta information with exiftool is lossless. The image data
itself is simply copied over to the modified file, byte for byte. This
applies to all image types: JPEG, RAW, etc.

- Phil
"""
Source: http://www.cpanforum.com/threads/5632

I've tested on this CR2 file provided by a user and tagged both with
and without geonames:
http://code.google.com/p/gpicsync/issues/detail?id=9&can=1&q=cr2

I didn't notice any problem (just 1 k difference in size which
correspond the header, in the example going from 7208 k to 7207 k, not
a drastic change of size).

GPicSync applies the same command to the JPG and to the RAW files.

francois

[Richard Barnes]

I noticed this with the first version that worked with CR2 files. I ran a
batch last week with v1.06 and didn't notice the effect viewing the pix in
Breezebrowser. (Then again, I haven't found any program that will show me
the embedded GPS info in a CR2 file either!)

Richard Barnes

www.pbase.com/rbarnes11