PGPLOT: PNG file format
PNG (Portable Network Graphics) is a widely supported format for
raster graphics. For full information, see the PNG web page. PGPLOT can
create PNG files with up to 8 bits per pixel (256 colors), with either
an opaque or a transparent background.
In order to compile the PGPLOT PNG driver, and to run programs that
include this driver, you need libpng
, zlib
,
and supporting header files, which are available through the PNG web
page.
- Device type code
-
/PNG
/TPNG
(transparent background)
- Default file name
-
pgplot.png
For multi-page plots PGPLOT creates
additional files. PGPLOT appends an underscore and the page number to
the file name for the second and subsequent pages. If the supplied
file name is ``-'', the output is sent to the standard output stream,
so that it can, for example, be piped into a viewing program. This
will only work for single-page plots.
- Default view surface dimensions
-
850 by 680 pixels (nominally 10.0 by 8.0 inches)
These defaults can be overridden by specifying environment
variables, or by calling routine PGPAP. The maximum size is limited
only by available memory.
- Resolution
-
PGPLOT assumes that the device resolution is 85 pixels/inch, but the
actual resolution will vary depending on the display device.
- Color capability
-
Color indices 0-255 are accepted, with standard defaults for color
indices 0-15. If the color representation of a color index is changed,
it affects all pixels drawn in that color on the current page.
- Input capability
- None.
- Environment variables
-
PGPLOT_PNG_WIDTH
: width of image in pixels (default 850)
PGPLOT_PNG_HEIGHT
: height of image in pixels (default 680)
- File format
- PNG files are binary files.
- Author
- Pete Ratzlaff, pratzlaff@cfa.harvard.edu (March 1999).
Tim Pearson, California Institute of Technology,
tjp·astro.caltech.edu
Copyright © 1995-2005 California Institute of Technology