Screen Capture (`f8.screencap`)¶

No description.

Service class: f8.screencap
Version: 0.0.1
Source directory: f8/screencap
Tags: video, capture, shm

When to Use¶

Use f8.screencap when the graph needs live desktop, monitor, or region capture as a video source.
It is a standard choice for UI vision, screen analysis, game capture, and desktop automation scenarios.
Reach for it when the graph needs to interpret what is currently on the screen.

Common Wiring Patterns¶

A common chain is f8.screencap -> CV / DL / Viz.
While tuning capture area and scale, keep a f8.viz.video branch connected for visual confirmation.
If later modules only care about a small region, crop early rather than feeding a full screen at full rate.

Pitfalls / Gotchas¶

Screen recording permissions, OS security policies, and GPU compatibility are common blockers.
Full-screen high-resolution capture is expensive; reduce area or scale whenever possible.
If only one button, panel, or HUD matters, capture only that region instead of the entire desktop.

Service Reference¶

How to Run¶

win/f8screencap_service.exe

Workdir: ./
Environment overrides: none

Typical Inputs / Outputs¶

Data inputs: none
Data outputs: monitor
Commands: listDisplays, pickDisplay, pickWindow, pickRegion

Service State Fields¶

Name	Access	Required	On Node	Schema	Description
`videoShmName`	`ro`	`true`	`true`	`string`	Shared memory region name
`videoShmEvent`	`ro`	`true`	`false`	`string`	Shared memory event name
`mode`	`rw`	`true`	`false`	`string / enum[display, window, region]`	display\|window\|region
`fps`	`rw`	`true`	`true`	`number`	Capture rate
`displayId`	`ro`	`true`	`false`	`integer`	0..N-1 (see listDisplays)
`windowId`	`ro`	`true`	`false`	`string`	backend-specific (e.g. win32:hwnd:0x... or x11:win:0x...)
`window`	`ro`	`true`	`false`	`object{backend, id, pid, rect, ...}`	Resolved window metadata (best-effort)
`region`	`ro`	`true`	`false`	`object{h, w, x, y}`	Virtual desktop coordinates
`scale`	`ro`	`true`	`false`	`object{h, w}`	Optional output size (0 disables)
`captureRunning`	`ro`	`true`	`false`	`boolean`	Is capture currently running
`lastError`	`ro`	`true`	`false`	`string`	Last error message
`videoWidth`	`ro`	`true`	`true`	`integer`	Width of the video frame in pixels
`videoHeight`	`ro`	`true`	`true`	`integer`	Height of the video frame in pixels
`videoPitch`	`ro`	`true`	`false`	`integer`	Number of bytes per row of the video frame
`active`	`rw`	`true`	`false`	`boolean / default=True`	Service lifecycle state (activate/deactivate).
`svcId`	`ro`	`true`	`false`	`string`	Readonly: current service instance id (svcId).

Key Fields That Matter¶

videoShmName (Video SHM, ro): Shared memory region name Schema: string.
videoShmEvent (Video Event, ro): Shared memory event name Schema: string.
mode (Mode, rw): display|window|region Schema: string / enum[display, window, region].
fps (FPS, rw): Capture rate Schema: number.
displayId (Display ID, ro): 0..N-1 (see listDisplays) Schema: integer.
windowId (Window ID, ro): backend-specific (e.g. win32:hwnd:0x... or x11:win:0x...) Schema: string.
window (Window, ro): Resolved window metadata (best-effort) Schema: object{backend, id, pid, rect, ...}.
region (Region, ro): Virtual desktop coordinates Schema: object{h, w, x, y}.

Service Commands¶

`listDisplays`¶

List displays/monitors (backend-specific)

Show on node: false
Params: none

`pickDisplay`¶

Interactive pick a display (hover highlight + click)

Show on node: true
Params: none

`pickWindow`¶

Interactive pick a window (hover highlight + click)

Show on node: true
Params: none

`pickRegion`¶

Interactive pick a region (click-drag to draw)

Show on node: true
Params: none

Service Data Input Ports¶

None

Service Data Output Ports¶

Name	Required	On Node	Schema	Description
`monitor`	`true`	`false`	`object{active, alive, cpu, error, ...}`	Unified runtime monitor snapshots (health/resource/perf/error).

Operators¶