Pearl REST API capture preview images from channels, inputs, and outputs

The API can return a still preview image for a channel, an input, or an HDMI output. These endpoints return image data directly rather than a JSON envelope, which makes them useful for confidence monitoring and dashboards.

Applies to: Pearl-2, Pearl Mini, Pearl Nexus, Pearl Nano.

Method and path	Returns
`GET /channels/{cid}/preview`	Preview of a channel's program output
`GET /inputs/{sid}/preview`	Preview of a single input source
`GET /outputs/{did}/preview`	Preview of what an HDMI output is showing

Parameters.

Parameter	Applies to	Notes
`resolution`	All three	`widthxheight` (`1920x1080`), a width alone (`1920`), or `auto`. Supplying only a width scales the image to that width and preserves the original aspect ratio
`keep_aspect_ratio`	Channels and inputs	Default `true`
`format`	All three	`jpg` or `png`. Default `jpg`. JPG is the recommended format

The default resolution is auto for channel and input previews, and 1920x1080 for output previews.

GET /api/v2.0/channels/1/preview?resolution=640&format=jpg

The response is image/jpeg or image/png binary data. A request naming a channel, input, or output that does not exist returns 404 with a JSON error body.

Because preview images are generated on demand by the device, poll them at a modest rate in monitoring tools rather than at frame rate.