How to convert <=8bit to 32bit with transparency

[ClausWARE]

How can I convert PNGs with <= 8 bits and transparent color to 32 bit PNGs with aplha transparency by batch processing?

In my attempts, XnView can only convert to 24bit and XnViewMP loses the transparency despite 32 bits.

Specifying the pallet index for the aplha transparency is not really useful because the index is different for each image, which should be taken over automatically.

Have I overlooked anything?

[XnTriq]

Welcome to the forum, ClausWARE.

It seems that 8-bit PNGs with index transparency can only be converted manually to 32-bit PNGs with alpha channel transparency.
With the exception of Add alpha, there's no command for increasing the color depth to 32-bit in XnView Classic's batch processing. The same goes for XnViewMP's and XnConvert's Change color depth action: If set to 32 bits, existing single color transparency is lost and replaced by a uniform alpha channel.

PNG test suites:

• schaik.com
  • http://www.schaik.com/pngsuite2011/tbbn3p08.png
  • http://www.schaik.com/pngsuite2011/tbgn3p08.png
  • http://www.schaik.com/pngsuite2011/tbwn3p08.png
  • http://www.schaik.com/pngsuite2011/tbyn3p08.png
  • http://www.schaik.com/pngsuite2011/tm3n3p02.png
  • http://www.schaik.com/pngsuite2011/tp1n3p08.png
• libpng.org
  • http://www.libpng.org/pub/png/PngSuite/tbbn3p08.png
  • http://www.libpng.org/pub/png/PngSuite/tbgn3p08.png
  • http://www.libpng.org/pub/png/PngSuite/tbwn3p08.png
  • http://www.libpng.org/pub/png/PngSuite/tbyn3p08.png
  • http://www.libpng.org/pub/png/PngSuite/tp0n3p08.png
  • http://www.libpng.org/pub/png/PngSuite/tp1n3p08.png