POV-Ray : Newsgroups : povray.bugreports : transmit does not work with image maps : Re: transmit does not work with image maps Server Time
23 Jun 2024 06:32:58 EDT (-0400)
  Re: transmit does not work with image maps  
From: Kenneth
Date: 21 Apr 2024 12:40:00
Message: <web.66253f7ee419c9f791c33a706e066e29@news.povray.org>
When using 'transmit all' with typical jpeg and png images, there is an
unfortunate mix of flaws in both official v3.7.0 and in the v3.8 betas--
different kinds of problems in each, especially with alpha-channel images.
See this related post from December 2022 (with some function solutions further
down in the post)...

https://news.povray.org/povray.binaries.images/thread/%3Cweb.63ac0323f59cfc766631b53a9334df62%40news.povray.org%3E/?mto
p=438912

and this one from 2016...
https://news.povray.org/povray.binaries.images/thread/%3C569528cc%241%40news.povray.org%3E/

According to POV-ray's  documentation, transmit all ...some value... *should*
work correctly even on non-GIF images. I have successfully used it many times in
the distant past. But currently, this  is the situation:

In 'official' v3.7.0, it does work correctly with typical 24-bit .jpeg's and
png's -- but has an odd problem with 32-bit alpha-channel images that already
have a mask, where the 'invisible' parts of the alpha mask start showing up as
the image's complementary colors instead. (Developer Christoph Lipka fixed that
particular flaw back in 2016, in one of the ongoing v3.71 development releases
that 'piggy-backed' on v3.7.)

But in the v3.8 beta releases, something changed--  transmit all  is completely
*ignored*, when used with typical 24-bit images. However, it DOES
work correctly if those images are re-saved as 32-bit .png. I currently use the
free paint.net app to do this-- it creates a 'dummy' alpha channel, which is
apparently needed now. Images with an *actual* alpha channel also behave
properly. (If the #version in the scene is changed to 3.7 instead of 3.8, the
behavior is the same as using v3.7.0 itself: transmit all  works as advertised
on typical 24-bit images...but with the prior 32-bit alpha-channel problem.)


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