Dynagraph images can be saved into files in
a variety of graphics formats. Currently the following
formats are are available:
JPEG,
TIFF,
PNG,
PPM (raw/binary and ASCII),
POSTSCRIPT (grayscale and color rasterized formats)
and
POSTSCRIPT (color vector format).
With the exception of Postscript vector format, graphs are saved as raster images of screen pixels. Raster images are simple and compact, however they are not best suited for resizing or printing on high-resolution printers. The Postscript vector format saves the drawing instructions, not pixels, therefore it can reproduce the image scaled to arbitrary sizes and resolutions. Beware, however, that the Postscript vector files generated by dynagraph can be quite large and may take hours to print on a printer.
Images can be saved either through the command line or through the dynagraph's graphics display's File menu.
Dynagraph does not save images in the GIF format. See the section Why no GIF below.
An image saved via the File->Save menu
is written into a file named dgplot.* in the current
directory, where the .* extension is set to reflect the
format of the saved image according to:
| Format | Extension | |
| JPEG | .jpg | |
| TIFF | .tiff | |
| PNG | .png | |
| PPM (both binary and ascii) | .ppm | |
| Postscript (all formats) | .ps |
Remark: The file name dgplot is built in and
cannot be changed when saving via a menu. See the description of the
savegraph command below if you wish to specify a file name.
savegraph() command
The savegraph() command can be invoked in two
different ways:
savegraph(format);
savegraph(format, filename);
The format argument specifies the format of the saved image.
Select it according to the following table:
| Desired format | The format argument | |
| JPEG | jpg or jpeg | |
| TIFF | tiff | |
| PNG | png | |
| PPM (binary) | ppm or ppm-binary or ppm-raw or ppm6 | |
| PPM (ascii) | ppm-ascii or ppm3 | |
| Postscript (grayscale) | ps or postscript or postscript-gray | |
| Postscript (color) | cps or postscript-color or postscript-colour | |
| Postscript (vector) | vps or postscript-vector |
If savegraph() is invoked with one argument, the
currently displayed graph is saved in a dgplot.* file,
This is equivalent to saving the image via the File->Save
menu.
If savegraph() is invoked with two arguments,
the second argument is taken to be the name of the file to save the image in.
The user is responsible for providing an appropriate filename, e.g.,
mygraph.jpg; dynagraph will not append a .jpg
or any other extension on its own. As always, file names which
involve other than alphanumeric characters must be quoted. See the
section Quoted Strings for details.
The savegraph() command can be called from dynagraph
scripts when executing dynagraph in the non-interactive mode. See Dynagraph Scripts for the description of the
non-interactive mode.
GIF image format is not included in dynagraph due
to a controversial patent issue; see
http://www.gnu.org/philosophy/gif.html
for a description of the problem. It is recommended that the
PNG format be used as a substitute for GIF,
whenever possible. If pressed, you may save the graph in the binary
PPM format, then use one of the many publicly available
programs to convert it to GIF. Two such programs are:
PPM to GIF, apply
netpbm's ppmquant and ppmtogif in a Unix
pipeline, as in:
ppmquant -fs 256 dgplot.ppm | ppmtogif >dgplot.gif