Xpra: Ticket #1713: black and white mode

We already have "png/L" support, but we could add a global black-and-white mode to try to save bandwidth:

jpeg supports TJPF_GRAY
all the video encoders would need a csc step
webp would need csc too

I'm not sure this will save enough bandwidth: the self-tuning video encode heuristics normally switch to YUV420P for video, and that already reduces the space taken by the colours to 33% or less of the bitstream. For non-video, it may allow us to use a lossless encoding more often than we would otherwise.

Wed, 27 Dec 2017 19:26:55 GMT - Antoine Martin: milestone changed

milestone changed from 2.3 to future

I don't see the point:

many things don't degrade well
none of the video encoders take grayscale as input
the cost of chroma is a small overhead (just a 33% with YUV420P - worst case scenario - often less if the video encoder interpolates chroma and luma)
the cost of a single lossless refresh dwarfs any savings we might have made at that point - best to make efficient use of the encodings we have than to invent new ones

Sun, 23 Sep 2018 06:50:34 GMT - Antoine Martin: status, milestone changed

status changed from new to assigned
milestone changed from future to 2.5

Let's give it a go: libyuv does have a ARGBGrayTo function we can use for video and webp codecs.

Thu, 22 Nov 2018 08:55:16 GMT - Antoine Martin: milestone changed

milestone changed from 2.5 to 3.1

All the encoding related tickets are scheduled for 3.1

Wed, 20 Mar 2019 05:06:15 GMT - Antoine Martin: milestone changed

milestone changed from 3.1 to 4.0

Milestone renamed

Sat, 21 Sep 2019 12:28:45 GMT - Antoine Martin: milestone changed

milestone changed from 4.0 to 4.1

Thu, 11 Jun 2020 15:37:26 GMT - Antoine Martin: status changed; resolution set

status changed from assigned to closed
resolution set to fixed

Updates:

r26698 adds grayscale as a valid encoding option, ie:
```
xpra attach --encoding=grayscale
```

(also works from the tray menu)

r26699 supports grayscale mode for 'jpeg' and 'webp' via pillow
r26700 supports grayscale with video modes (via ARGBGrayTo)

Fri, 14 Aug 2020 10:18:39 GMT - Antoine Martin:

Fixups in r27138.

Sat, 23 Jan 2021 05:31:47 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1713