how to reverse video of the bitmap image?

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3 total messages Started by zzang Sun, 03 Jan 1993 14:16

#5872

Author: zzang
Date: Sun, 03 Jan 1993 14:16

13 lines
659 bytes

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"?

Thanks very much in advance!

--zhuo

Re: how to reverse video of the bitmap image?

#5874

Author: Ben Goren
Date: Sun, 03 Jan 1993 19:12

3 lines
475 bytes

Is there anything wrong with {1 exch sub}settransfer?

b&

Re: how to reverse video of the bitmap image?

#5873

Author: Glenn Reid
Date: Sun, 03 Jan 1993 20:18

29 lines
1386 bytes

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.

--
 Glenn Reid        		NeXTmail: glenn@rightbrain.com
 RightBrain Software		415-326-2974 (NeXTfax 326-2977)
 Palo Alto, California		Electronic Frontier Foundation, member #054

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