Make Bluray subtitle background transparent

[picrade]

I have a Bluray movie where subtitles are in a box with black background.
Is there a way to make the background transparent by modifying just the SUP file?

[Ghitulescu]

I asked (http://forum.doom9.org/showthread.php?t=170327)this last time at least one year ago (http://forum.doom9.org/showpost.php?p=1678925&postcount=1291), no useful answer.

I hope you'll have a better luck (http://forum.doom9.org/showpost.php?p=1599816&postcount=1221).

[picrade]

I used the steps that was given in one of your links, BD to DVD to BD conversion, and it worked.
The background is now transparent but the subtitles look flat because there is no shadow or outline.
This process loses some colors because the palette is reduced from BD 256 colors to DVD 16 colors.

I am thinking of doing it "manually".
1) Export BD subtitles as 256 color PNG images and an xml file.
Is there a program to do this?
BDSupEdit can export subtitles as PNG but they are 24 bit color.
Also it exports the whole frame, 1920x1080, not just the subtitle.

2) Make the background color of the PNG image transparent in some graphic utility??

3) Make new BD SUP with the xml file and the new images.

Of course this process is not practical for doing subtitles one by one.
Perhaps it can be made into a batch process.

[Ghitulescu]

I used the steps that was given in one of your links, BD to DVD to BD conversion, and it worked.
The background is now transparent but the subtitles look flat because there is no shadow or outline.
This process loses some colors because the palette is reduced from BD 256 colors to DVD 16 colors.

That was the problem I raised - some colours went lost. Thus the solution was not good.

[Sm3n]

Maybe SubtitleEdit can do it. It is able to recreate the sup I believe I did once.
Maybe you can remove background before making new one.

[Ghitulescu]

Nikse is busy now to make his program able to "read the mind" of its users in what OCR is concerned. :)