Gpuview

gpuview — GPU-native screen capture + change-feed

Built from the idea: the GPU already has the screen in perfect form, so take frames at the compositor handoff (DXGI IDXGIOutputDuplication) and let the GPU itself tell us which rectangles changed between frames. Instead of "screenshot the whole 4K screen every time and make the model stare at it", watch emits a JSON event stream of dirty regions + small crops — typically >90% less image data for UI monitoring.

How it works

A C# exe (T:\gpuview\gpuview.exe, source in src/gpuview.cs) talks raw COM vtables to D3D11/DXGI: DuplicateOutput → AcquireNextFrame (GPU surface) → CopyResource to a staging texture → Map to CPU → PNG. Dirty rects come from GetFrameDirtyRects; watch then refines those hints with previous-frame pixel diffs so coalesced compositor rectangles become readable changed-content crops. Handles HDR desktops (RGBA16F scRGB → tonemapped sRGB). Per-monitor (mon=N = DXGI output index). frame reports source and nonblack, and retries/falls back rather than silently returning an all-black PNG.

Usage

GV=/home/terp/.config/devin/skills/gpuview/scripts/gpuview.sh

$GV frame [mon]                # one full frame; prints WSL path to PNG -> read it
$GV watch <secs> [mon] [minpx] # JSON event per change: regions + crop PNGs
$GV rebuild                    # recompile exe from src (csc, ~1s)

watch output (one JSON line per event):

{"event":"baseline","path":"T:\\gpuview\\watch_...\\baseline.png","w":3840,"h":2160,"path_wsl":"/mnt/t/gpuview/watch_.../baseline.png"}
{"event":"change","n":3,"t":1820,"raw_regions":2,"raw_area":640100,"refined_area":196352,"regions":[{"x":216,"y":344,"w":944,"h":208,"crop":"T:\\gpuview\\watch_...\\chg_3_0.png","crop_wsl":"/mnt/t/gpuview/watch_.../chg_3_0.png"}]}
{"event":"done","changes":42}

• t = ms since start; raw_area is compositor dirty-rect area; refined_area is the final crop area after previous-frame refinement. minpx filters regions smaller than that pixel area (default 400 — kills cursor blinks). Read crop_wsl directly from WSL.

When to use which eye

• gpuview frame: full-desktop captures, HDR screens, games/video (compositor surface, no GDI black-frame problem for borderless/windowed apps).
• gpuview watch: "tell me when/where the screen changes" — wait for a build to finish, a dialog to pop, a game to reach a menu. Read only the crops.
• screenshot skill shot.sh window: capturing one specific window (incl. occluded/background windows — duplication only sees the visible desktop).
• screenshot skill control.sh: all mouse/keyboard input (gpuview has no hands).

Limits

• Exclusive-fullscreen games may block duplication (DuplicateOutput error) — switch the game to borderless/windowed.
• Captures the desktop output, not hidden windows.
• mon=1 can return black if that output is idle/asleep or on another adapter.
• Protected (DRM) content is blanked by the OS by design.