Support bitmap color blend when render cue.

[peerless2012]

[REQUIRED] Use case description

I'm developing ass/ssa render use libass for Meida3, the libass will produce a alpha bitmap, I create a ALPHA_8 bitmap and put it to Cue, when render the bitmap in SubtitlePainter, I need to blend some color when draw the bitmap.

Proposed solution

Add a bitmapColor field in Cue, and set the bitmapColor to bitmapPaint in SubtitlePainter.

Alternatives considered

• When I put ALPHA_8 bitmap in cue, it will occur un error, see Cue encode error when use bitmap and config is ALPHA_8. #2054
• I notices thant bitmap will be compress to png file, and decode it when use, I think, in my situation pass the bitmap directly will be great.

I also noticed that, compress bitmap to png is to fix a bug

• Split Cue.toBundle into serializable and binder-based variants
• Error when textTrackTranscodingEnabled is set to true

[icbaker]

I'm afraid we don't plan to modify Cue to support this level of custom integration.

[peerless2012]

I can make a PR for this.

[icbaker]

I'm afraid we wouldn't merge a PR for this either.

[peerless2012]

But the Effect can't use to render subtitle.

And this feature will make bitmap from AGRB_8888 to ALPHA_8, and save 3/4 memory usage.

Without this feature, I have to use ARGB_8888 for each bitmap, the performance is so bad.

[peerless2012]

Currently, I add a AssSubtitleParser to parse ass data and a AssSubtitleParserFactory to use my own SubtitleParser.

When parse ass time data, i can get bitmap, then set the output bitmap to output.

The bitmap is ARGB_8888 for now, because I can't extend Subtitle render logic. And I think the blend color for bitmap is also a simple and common feature which not just for me.