graphical user interface (GUI), and there are few, if any, graphics file
formats that cannot be manipulated when using Linux. These programs can
be called in Perl scripts, shell scripts, or command-line pipes to support
many types of complex format-conversion and image-manipulation tasks.
See the man pages for the ppm, pbm, pnm, and pgm families of commands.
Also see the man page for the convert command, which is part of the
extremely capable ImageMagick suite of programs.Sometimes, a file you want to manipulate in some way is in a format that
cannot be used by either your graphics application or the final application.
The solution is to convert the image file—sometimes through several formats.
The convert utility from ImageMagick is useful, as is the netpbm family
of utilities. If it is not already installed, you can easily install ImageMagick
from the Ubuntu repositories; the netpbm tools are always installed by
default.
convert is super simple to use from the command line. Here is an example:
Click here to view code image
matthew@seymour~:$ convert image.gif image.png
The convert utility converts between image formats recognized by
ImageMagick. You can also manipulate color depth and size during the
conversion process. You can use ImageMagick to append images, surround
them with borders, add labels, rotate and shade them, and perform other
manipulations well suited to scripting. Other commands associated with
ImageMagick include display, animate, identify, and import. The
application supports more than 130 different image formats (all listed in the
man page for ImageMagick).
The netpbm tools are installed by default because they compose the
underpinnings of graphics format manipulation. The man page for each image
format lists related conversion utilities; the number of those utilities gives you
some indication of the way each format is used and shows how one is built on
another:
ppm—The man page for ppm, the portable pixmap file format, lists 47
conversion utilities related to ppm. This makes sense because ppm is
considered the lowest common denominator for color image files. It is
therefore often used as an intermediate format.
pgm—The man page for pgm, the portable graymap file format, lists 22
conversion utilities. This makes sense because pgm is the lowest
common denominator for grayscale image files.