Saving and Recording

CDFViewer writes three kinds of output. It saves still images of the current figure, records videos of an animation, and prints a command-line string that reproduces the whole session. All three are available as REPL commands and as the Save, Record, and Export buttons of the menu window.

Saving figures

savefig writes the current figure as a PNG.

CDFViewer> savefig filename=temperature.png
[ Info: Saved figure to temperature.png

Three options control the output.

filename sets the output path, and the .png extension is added if missing.
px_per_unit multiplies the resolution. A value of 2 doubles the pixel resolution at the same figure layout, for print-quality output.
overwrite decides what a name already taken means (see Writing over an earlier file).

Without a filename, a name is derived automatically. All three stay set until you change them, so the Save button of the menu writes with whatever you gave last.

Recording videos

record sweeps the play dimension once and writes a video. The format follows the extension (.mp4, .mkv, .webm, or .gif).

CDFViewer> record filename=temperature.mp4, framerate=30

Four options control the recording.

filename sets the output path, and the extension selects the codec.
framerate sets the frames per second (default 30).
range restricts the recorded frames, e.g. range=1:12.
overwrite decides what a name already taken means (see Writing over an earlier file).

The animated dimension is set with pdim (or the Play dropdown). See Animation and Playback.

Writing over an earlier file

A name that is already taken is written over, and a line on stderr says so. Both outputs are composed in a temporary file and moved into place only once they are complete, so a render or a recording that fails halfway never costs you the file that was there.

Overwriting is what a re-run wants. Recording waves.mp4 a second time after changing the plot leaves the newer take under the name you gave it, rather than parking it in waves(1).mp4 and leaving everything pointed at the name – a docs page, a script, a player you left open – showing the older one.

Pass overwrite=false for the other behaviour: the taken name is left alone and the output goes to the next free waves(1).mp4, waves(2).mp4, and so on. This is worth having when saving a series of views by hand under one name.

CDFViewer> record filename=waves.mp4, overwrite=false

Batch mode with `--savefig` and `--record`

Both outputs also work non-interactively, without opening any window. Pass a complete plot description on the command line together with --savefig or --record, and CDFViewer renders, writes the file, and exits.

cdfviewer demo.nc -v temperature -x lon -y lat -p heatmap \
    --savefig -s 'filename="temperature.png", px_per_unit=2'

cdfviewer demo.nc -v temperature -x lon -y lat -p heatmap -a time \
    --record -s 'filename="temperature.mp4", framerate=25'

This makes CDFViewer usable in scripts and batch jobs, for example to render a figure for every file of a model run.

Reproducing a session with `export`

After interactively tuning a plot, export prints the command line that recreates the current state, including the variable, axes, plot type, fixed indices, keyword arguments, and even the current axis limits.

CDFViewer> export
┌ Info: Commandline Arguments:
└ -vtemperature -xlon -ylat -pheatmap --dims=time=6 -atime --kwargs='colormap=:balance, title="Air temperature", limits=(-180.0, 175.0, -87.5, 87.5)' --saveoptions='filename="temperature.png"'

Paste the printed arguments after cdfviewer to jump straight back to this view, or combine them with --savefig for batch rendering.

On a map the limits come out in longitude and latitude, the coordinates you would type yourself, rather than in the metres the projection works in. A view that no pair of meridians and parallels describes, one zoomed out past the edge of its projection or straddling the ±180° seam, is exported without its limits and reopens on the whole field.