Use higher colour depth R16 sprites in D2k.

[pchote]

The OG D2k shipped with a graphics option to use 8-bit or 16-bit sprites:

• The "8-bit" option is the R8 that we're all familiar with; indexed sprites that (with a couple of exceptions) used a single global palette.
• The "16-bit" option (R16) actually mainly still used indexed sprites (to support player remapping) but every frame defined its own individual palette to reduce colour banding. The terrain did use real 16-bit sprites.

This PR completes the transition towards supporting non-paletted sprites as a first-class feature by switching D2k over to these higher colour sprites. The 16-bit and embedded-palette frames are converted to 32-bit when loaded, and remapped to player colours using the ColorShift logic.

The main disruption is that we did not previously install or download the R16 assets, so the content must be reinstalled. I have followed the example from the first time we did this by installing the new asset set to a v3 subdirectory that is independent from the v2 used by current installs. OpenRA/OpenRAWebsiteV3#52 will need to be merged before the downloads will work.

The actual visual improvements are subtle, and mainly visible in the explosion effects and sidebar icons. The quickest way to get an overview of the improvements is to use the --dump-sequence-sheets utility command before and after, then blink between the two versions.

[pchote]

I tagged a test build for anyone who wants to try this (but remember that the asset download still requires the website PR to be merged)

https://github.com/pchote/OpenRA/releases/tag/devtest-20231206

[Porenutak]

Required patch 1.06 is not on any ISO and cant be downloaded. Manual extraction of 1.06 into V3 folder also dont work. Is there any other option here?

[pchote]

Options:

1. Install gruntmods d2k and use that as the assets source
2. Nag people to merge the OpenRAWeb PR
3. Manually extract d2k-quickinstall-v3.zip into Content/d2k/v3

[Porenutak]

Do we know from where .tpm tiles origins are? because some will need update to r16.
If they are community made Im certain there will be R16 equivalent somewhere.
sand platform:

Rock-Rock tiles are mostly fine:

difference between r8/16 sand is most visible:

[Porenutak]

I found R16 Rocktiles:
https://forum.dune2k.com/topic/29942-release-rock-tileset/
SandPlatform will be easy to fix by hand.

I will add them in my own PR.

[PunkPun]

merged OpenRA/OpenRAWebsiteV3#52

and a crash

Exception of type `System.NullReferenceException`: Object reference not set to an instance of an object.
   at OpenRA.Renderer.Dispose() in OpenRA/OpenRA.Game/Renderer.cs:line 537
   at OpenRA.Game.Run() in OpenRA/OpenRA.Game/Game.cs:line 896
   at OpenRA.Game.InitializeAndRun(String[] args) in OpenRA/OpenRA.Game/Game.cs:line 313
   at OpenRA.Launcher.Program.Main(String[] args) in OpenRA/OpenRA.Launcher/Program.cs:line 32

a bit later I got

[pchote]

Fixed the quickinstall download sha1 (it had incorrectly duplicated the patch106 hash) and rebased.

I'm not able to reproduce the "mirror not available" or NRE errors.

[PunkPun]

LGTM

[PunkPun]

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