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Groups > comp.lang.postscript > #2565

how do filters work (internally)?

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I've been digging into some pdf tutorials and (old) specs 
(cuz they're shorter) and one major facility that I think
xpost will need in order to handle pdf (whether input or
output) is filters.

So, as usual, I'll just ramble and speculate out loud.
Please jump in if I make a stupid.

Filters seem to require a further degree of polymorphism
from the file operators. Eg. read will need to interface
between two implementations, something like


errcode ps_read (object f){
    if (is_filter(f))
        return filter_read(f);
    else
        return file_read(f);
}


and similarly for write. If other operators like 
readstring and readhexstring are implemented in terms
of read, then no changes to them should be necessary.

And the various available filters are also collected
into a Named Resource, right? So I'll need to beef-up
my implementation of that, too. 

Hm. That's all I've got so far.

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how do filters work (internally)? luser- -droog <mijoryx@yahoo.com> - 2016-05-11 22:47 -0700

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