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#### 7.2.120 snapshot

`(snapshot CAM-ID FILENAME [FORMAT [XSIZE [YSIZE]]])`
  Save a snapshot of CAM-ID in the FILENAME (a string). The FORMAT argument is optional; it may be "ppmscreen" (the default), "ps", "ppm", "sgi" (on SGI machines), "ppmosmesa" (if built with libOSMesa) or "ppmosglx". A "ppmscreen" snapshot is created by reading the image directly from the given window; the window is popped above other windows and redrawn first, then its contents are written as a PPM format image. A "ppmosmesa" snapshot is drawn by Mesa's software renderer into a memory buffer in RAM. A "ppmosglx" snapshot is rendered into a GLX Pixmap buffer, which is also off-screen but may or may not reside in video RAM. Rendering may or may not be accelerated. The problem with on-screen snapshots is that the window must be mapped and not obscured by other windows. So on-screen snapshots will not work in the background, or when a screen safer is active. With "ps", dumps a Postscript picture representing the view from that window; hidden-surface removal might be incorrect. With "ppm", dumps a PPM-format image produced by geomview's internal software renderer; this may be of arbitrary size. If the FILENAME argument begins with "|", it's interpreted as a `/bin/sh` command to which the PPM or PS data should be piped. Optional XSIZE and YSIZE values are relevant only for "ppm" formats, and render to a window of that size (or scaled to that size, with aspect fixed, if only XSIZE is given)