tcl/tk only exports the canvas as a PS (Postscript) file. In this function,
the magick package is used to read the postscript file and render it
to an image file based upon the suffix supplied in the filename argument.
canvas_save(canvas, filename, ps_density = NULL, ...)a tic_ui 'canvas' element.
where the image should be saved. The image suffix will be
used as the format argument to the call to magick::image_write()
DPI. Resolution to postscript document. This corresponds to
the density argument in magick::image_read(). Default: NULL
means to use whatever magick package defaults to.
all other arguments passed to magick::image_write()
Other canvas:
canvas_arc(),
canvas_clear(),
canvas_image(),
canvas_line(),
canvas_oval(),
canvas_plot(),
canvas_polygon(),
canvas_rect(),
canvas_text(),
tic_canvas()