🚀 go-pugleaf

zzang writes
> Hello,
> can someone tell me how to reverse video of the image?
> for example,
> 
> /data <....> def
> 8 8 1 [8 0 0 8 0 0] {data} image showpage
> 
> now how to reverse video the above image without
> change the "data"?

The simplest way is to precede the code with this:

{ 1 exch sub } settransfer

You should probably put "gsave" and "grestore" around it to keep this
from affecting the rest of your document.  Also, you might want to
be more careful to concatenate the transfer function with the existing
one, sorta like this (see Green Book for more detail):

[ currenttransfer /exec load 1 /exch load /sub load ] cvx settransfer

Note: this only works with black-and-white images, which your example
happens to be.  There is an analogous approach for colorimage.

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 Glenn Reid        		NeXTmail: glenn@rightbrain.com
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