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erasepage

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  erasepage Cecil Westerhof <Cecil@decebal.nl> - 2013-07-16 01:58 +0200
    Re: erasepage luser- -droog <mijoryx@yahoo.com> - 2013-07-15 19:53 -0700
    Re: erasepage bugbear <bugbear@trim_papermule.co.uk_trim> - 2013-07-16 10:23 +0100

#1454 — erasepage

The blue book says:
    – erasepage – paint current page white

But in reality it makes the page transparent. (Which in a way is more
logical.) Is this an error in the documentation, or in ghostscript?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#1456

On Monday, July 15, 2013 6:58:25 PM UTC-5, Cecil Westerhof wrote:
> The blue book says:
> 
>     – erasepage – paint current page white
> 
> 
> 
> But in reality it makes the page transparent. (Which in a way is more
> 
> logical.) Is this an error in the documentation, or in ghostscript?
> 

I think that changes with the language level. Postscript (Level) 3
also changes the interpretation of copypage to be the same as showpage.
Try this:

systemdict /.setlanguagelevel known {2 .setlanguagelevel} if

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#1459

Cecil Westerhof wrote:
> The blue book says:
>      – erasepage – paint current page white
>
> But in reality it makes the page transparent. (Which in a way is more
> logical.) Is this an error in the documentation, or in ghostscript?

The blue book is not a spec - it's a tutorial, and a level 1 tutorial at that.
Further, I'm not sure what you mean by transparent, since that's
about the one thing that PostScript (famously) doesn't do.

erasepage – erasepage –
erases the current page by painting it with gray level 1.0 (which is ordinarily white,
but may be some other color if an atypical transfer function has been defined).
The entire page is erased, without reference to the clipping path currently in force.
erasepage affects only the contents of raster memory; it does not modify the
graphics state, nor does it cause a page to be transmitted to the output device.
The showpage operator automatically invokes erasepage after imaging a page.
There are few situations in which a PostScript page description should invoke
erasepage explicitly, since it affects portions of the page outside the current clipping
path. It is usually more appropriate to erase just the area inside the current
clipping path (see clippath). This allows the page description to be embedded
within another, composite page without undesirable effects.
Errors: none
See Also: showpage, fill, clippath

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