Re: NR pdf is larger with current git by 15%

[Masamichi Hosoda]

>>> I've found the documented way to specify Ghostscript devices
>>> without `-sDEVICE=pdfwrite`.  It is using the operator
>>> `selectdevice`.
> 
> Thanks for investigating.  The main question remains why gs produces
> suboptimal results without `selectdevice`.

`selectdevice` is defined in gs_init.ps as follows.

```
/selectdevice
        { finddevice setdevice .setdefaultscreen } bind def
```

`selectdevice` does `setdevice` and then `.setdefaultscreen`.
If we use only `setdevice`, then `.setdefaultscreen` is not done.

I've found that `.setdefaultscreen` is described here.
https://www.ghostscript.com/doc/current/History3.htm#V3.61_Interpreter

Here's a quote.

-------------
Defines a .setdefaultscreen procedure that sets the default halftone screen,
transfer function, and stroke adjustment for the current device.  Changes
selectdevice and setpagedevice so that they call .setdefaultscreen;
setpagedevice calls .setdefaultscreen before calling the Install procedure,
so that Install can set different parameters if it wishes.  Note that
setdevice does not do this.  (gs_init.ps, gs_setpd.ps)
-------------

It seems to set some defaults for the current device.

This means that if we use only `setdevice`, those defaults are not set.
In that case, many drawing operators need to be written,
including the defaults that can be omitted if I understand correctly.