capture_screenshot

Capture a PNG screenshot of a sketch, multiple sketches, or the workspace viewport — the verification step in the create→capture→analyze→fix loop.

Input Schema

Parameter	Type	Required	Description
`target`	`'selected'` \| `'sketch'` \| `'workspace'` \| `'viewport'`	no	What to capture (default: `'selected'`)
`sketchId`	string	no	Required when `target` is `'sketch'`
`width`	number	no	Output image width in pixels (default: sketch canvas width)
`height`	number	no	Output image height in pixels (default: sketch canvas height)
`seed`	number	no	Override seed for this capture only (doesn't mutate sketch state)
`params`	object	no	Override params for this capture only (doesn't mutate sketch state)
`format`	`'png'` \| `'base64'`	no	Output format (default: `'base64'`)
`savePath`	string	no	If provided, save PNG to this path in addition to returning

Output Shape

{
  "success": true,
  "target": "selected",
  "sketchId": "noise-grid",
  "width": 1200,
  "height": 1200,
  "seed": 42,
  "image": "data:image/png;base64,iVBORw0KGgo...",
  "savedTo": null
}

For target: 'workspace', returns a composite image of all visible artboards at their canvas positions. For target: 'viewport', returns what's currently visible in the viewport at the current zoom level.

Side Effects

If savePath provided: writes PNG file to disk
Does not mutate sketch state (seed/param overrides are temporary)

Error Cases

Condition	Error
`target` is `'selected'` but nothing selected	`"No sketch is currently selected"`
`target` is `'sketch'` but no `sketchId`	`"sketchId is required when target is 'sketch'"`
`sketchId` not found in workspace	`"Sketch not found: 'bad-id'"`
Renderer fails to produce frame	`"Renderer error for 'noise-grid': [error message]"`
No workspace open	`"No workspace is currently open"`

Golden Path Example

Request:

{
  "target": "selected",
  "seed": 99999
}

Response:

{
  "success": true,
  "target": "selected",
  "sketchId": "noise-grid",
  "width": 1200,
  "height": 1200,
  "seed": 99999,
  "image": "data:image/png;base64,iVBORw0KGgo...",
  "savedTo": null
}