[pstricks] Ghostscript 9.53 transparency operators

Alexander Grahn A.Grahn at hzdr.de
Tue Mar 30 16:05:01 CEST 2021


On Tue, Mar 30, 2021 at 02:48:50PM +0200, Herbert Voss wrote:

  >
  >Am 30.03.21 um 14:17 schrieb Alexander Grahn:
  >> the new PostScript transparency operators in Ghostscript are still not
  >> used, despite the definitions at the top of pstricks.pro.
  >>
  >> The warning
  >>
  >>     **** WARNING: .setopacityalpha is deprecated (as of 9.53.0) and will be removed in a future release
  >>     **** See .setfillconstantalpha/.setalphaisshape for the improved solution
  >>
  >> written to the terminal multiple times indicates that old operators are still
  >> being used.
  >
  >Alexander,
  >
  >this is not really true: the _old_ operators are _not_ used. If there is 
  >a gs version > 9.52
  >pstricks.pro defines it's own .setopacityalpha

I am afraid this is not the case, otherwise the Ghostscript (9.53.3) warning,
as listed above, would not be shown. With my proposed fix, on the other hand,
.setopacityalpha /is/ redefined using the new operators which makes the warning
disappear.

  >and uses the old definitions for old
  >gs versions.  The warnings are wrong in this case, but GhostScript has 
  >no check for
  >this.
  >
  >If I run your example with MiKTeX's up-to-date mgs.exe (9.25) I'll get
  >
  >
  >Error: /undefined in --load--
  >Operand stack:
  >    .setfillconstantalpha.bak   .setfillconstantalpha
  >

Ok. I did not claim my fix would work with obsolete GS versions, but with the
new one, 9.53.*, it definitely does. Therefore my request to revise the current
pstricks.pro.

Another way to demonstrate that old .setopacityalpha is still being used is
dvisvgm. Dvisvgm 2.11+, as contained in TL21-pretest, implements (only) the
new transparency operators for DVI to SVG conversion. Without my
proposed fix, no transparency is produced in the SVG output. But it is
produced with the fix enabled. (Of course, dvisvgm must be told to use
libgs.so.9.53. Dvisvgm option --libgs or environment var LIBGS may help
here.)

Therefore, I kindly ask you, Herbert, to revise the code for gs-9.53 in
pstricks.pro. Otherwise, transparency does not work with Dvisvgm, for
example.


Alexander

  >
  >The reason why I still use the old function names is the fact that the
  >PSTricks code must not be changed.
  >
  >And the warnings will go away hopefully for 9.54
  >
  >Herbert
  >
  >
  >--
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