What file format should you use to save the results of your work, and
should you resize it? The answers depend on what you intend to use the
image for.
If you intend to open the image in GIMP again for further work,
you should save it in GIMP's native XCF format (i. e., name it
something.xcf), because this is the only format that guarantees
that none of the information in the image is lost.
If you intend to print the image on paper, you should avoid
shrinking the image, except by cropping it. The reason is that
printers are capable of achieving much higher dot resolutions than
video monitors---600 to 1400 dots per inch for typical printers,
as compared to 72 to 100 dots per inch for monitors. A 3000 x 5000
image looks huge on a monitor, but it only comes to about 5 inches
by 8 inches on paper at 600 dpi. There is usually no good reason
to expand
the image either: you can't increase the true resolution that way,
and it can always be scaled up at the time it is printed. As for
the file format, it will usually be fine to use JPEG at a quality
level of 75 to 85. In rare cases, where there are large swaths of
nearly uniform color, you may need to set the quality level even
higher or use a lossless format such as TIFF instead.
If you intend to display the image on screen or project it with a
video projector, bear in mind that the highest screen resolution
for most commonly available systems is 1600 x 1200, so there is
nothing to gain by keeping the image larger than that. For this
purpose, the JPEG format is almost always a good choice.
If you want to put the image on a web page or send it by email, it
is a good idea to make every effort to keep the file size as small
as possible. First, scale the image down to the smallest size that
makes it possible to see the relevant details (bear in mind that
other people may be using different sized monitors and/or
different monitor resolution settings). Second, save the image as
a JPEG file. In the JPEG save dialog, check the option to
“Preview in image window”
, and then adjust the Quality slider to the lowest level that
gives you acceptable image quality. (You will see in the image the
effects of each change.) Make sure that the image is zoomed at 1:1
while you do this, so you are not misled by the effects of
zooming.
See the File Formats
section for more information.
4.6.2.
Printing Your Photos
[This needs to be written.]
4.6.3.
EXIF Data
Modern digital cameras, when you take a picture, add information to
the data file about the camera settings and the circumstances under
which the picture was taken. This data is included in JPEG or TIFF
files in a structured format called EXIF. For JPEG files, GIMP is
capable of maintaining EXIF data, if it is built appropriately: it
depends on a library called
“libexif”
, which may not be available on all systems. If GIMP is built with
EXIF support enabled, then loading a JPEG file with EXIF data, and
resaving the resulting image in JPEG format, will cause the EXIF data
to be preserved unchanged. This is not, strictly speaking, the right
way for an image editor to handle EXIF data, but it is better than
simply removing it, which is what earlier versions of GIMP did.
If you would like to see the contents of the EXIF data, you can
download from the registry an
Exif Browser plug-in
.
If you are able to build and install it on your system, you can
access it as Filters->Generic->Exif Browser from the image menu. (See
Installing New Plug-ins
for help.)
Published under the terms of the GNU General Public License
