feat(screenshot): Add threaded JPEG screenshots on F11 without game stalls

[bobtista]

Summary

Implements compressed JPEG screenshots (F11) that don't stall the game, addressing issues with the current F12 BMP screenshot functionality.

Closes #1555

Adds a new screenshot function using the stb_image_write library with background threading:

• F11 - New compressed JPEG screenshot (no stalling, ~600KB files)
• F12 - Original BMP screenshot (still works if lossless needed)

Notes

• stb_image-write is public domain licensed, single-header, zero compilation needed
• Captures frame buffer on main thread (~1-2ms)
• Spawns detached thread for JPEG compression and disk I/O
• Uses std::shared_ptr for safe memory management across threads
• JPEG quality set to 90 (excellent quality, 10x compression)
• Works for both Generals and Zero Hour

Testing

• Screenshots save correctly with both F11(jpg) and F12(original bmp)
• No game stalling during screenshot with F11
• Files appear in correct directory with sequential numbering
  

[Stubbjax]

Some initial thoughts:

• Keep variants of the same function to a single hotkey; instead toggle image format via a new setting in Options.ini
• Apply image compression / quality via a new setting in Options.ini
• Can we consolidate this logic in core instead of repeating the implementation twice?

[xezon]

Agree with Stubbjax.

JPG 90 is big file. Better make it default 80.

Replace BMP screenshot with PNG screenshot. PNG is lossless compressed and always better than BMP.

Make F12 take JPG 80 screenshot. Make CTRL+F12 take PNG screenshot. Make JPG Quality adjustable.

Remove the old BMP code(s) and only use the new code for screenshot.

[xezon]

Regarding Github formatting:

When you write

Addresses #1555

Then it will not close this report when this is merged.

Please read up on it here:
https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#closing-multiple-issues

[bobtista]

Some initial thoughts:

• Keep variants of the same function to a single hotkey; instead toggle image format via a new setting in Options.ini
• Apply image compression / quality via a new setting in Options.ini
• Can we consolidate this logic in core instead of repeating the implementation twice?

RE moving logic to core, I moved what I could to core - but there are a lot more files that need to be moved to core before this can be moved there eg WWVegas/WW3D2/*

[Skyaero42]

Will this cause a key conflict as F12 is already in use.
Or is it the intention to take both JPG and PNG screenshots?

[bobtista]

The intention is to use ctrl + f12 for png and f12 for jpg, though to your point, maybe the regular f12 should be png as it's lossless?

[xezon]

Regular F12 for PNG would be more in line with lossless BMP, HOWEVER, most players will want to take JPG screenshots first because these will compress much smaller and are far better for archiving and sending around the internet.

PNG screenshots are more for artists that want to create artwork and similar.

[bobtista]

Ok I went with F12: JPG and CTRL+F12: PNG

[OmniBlade]

I think pinning to a specific tag or commit is the way forward, otherwise you risk changes to upstream breaking the build, supply chain attacks and such.

Some efforts have been made to move dependencies to vcpkg which might be a better approach. At the very least I'd suggest adding a find command to try and find the module first (from vcpkg or alternatively package managers), then fall back on the fetch content method if not found?

[bobtista]

Done