Native camera discovery and capture-mode helpers.

moonbit

native

camera

capture

Download zip

Author

justjavac

Version

0.1.3

License

MIT

Repository

github.com/justjavac/moonbit-camera

Last updated

3 months ago

Downloads

justjavac/ffi0.2.4

#justjavac/camera

Native-only camera discovery helpers for MoonBit.

fn main {
  for device in @camera.CameraDevice::list() {
    println(device.label())
  }
}

Run examples with --target native:

moon run src/examples/list_cameras --target native
moon run src/examples/parse_listing --target native

CameraDevice

source

pub(all) struct CameraDevice {
  id : String
  name : String
  facing : Facing
  mode : CaptureMode
  torch : Bool
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

A camera device descriptor returned by the native discovery helpers.

The descriptor is intentionally small and portable: id is stable within one parsed listing, name preserves the native display name, facing is a best effort hint, mode is the known or default capture mode, and torch reports whether torch-style illumination is expected to be available.

impl Show for CameraDevice

fn output(self : CameraDevice, logger : &Logger) -> Unit

source

Formats a camera device for logs and snapshots.

The representation includes id, native name, facing hint, mode, and torch metadata. It is intended for diagnostics and snapshot tests rather than compact UI copy.

CameraDevice::is_high_definition

source

fn CameraDevice::is_high_definition(self : CameraDevice) -> Bool

Whether the device default mode should be treated as HD.

This checks the normalized default mode and returns true for devices whose default capture dimensions are at least 1280x720.

Example

test {
  let device = @camera.CameraDevice::{
    id: "camera-0",
    name: "HD Camera",
    facing: External,
    mode: { width: 1280, height: 720, fps: 30, pixel_format: Mjpeg },
    torch: false,
  }
  inspect(device.is_high_definition(), content="true")
}

CameraDevice::label

source

fn CameraDevice::label(self : CameraDevice) -> String

Produce a concise device label for camera pickers.

The label uses facing:name so UI code can display predictable values while still preserving the native device name exactly as reported.

Example

test {
  let device = @camera.CameraDevice::{
    id: "camera-0",
    name: "USB Camera",
    facing: External,
    mode: { width: 1280, height: 720, fps: 30, pixel_format: Mjpeg },
    torch: false,
  }
  inspect(device.label(), content="external:USB Camera")
}

CameraDevice::list

source

fn CameraDevice::list() -> Array[CameraDevice]

List camera devices visible to the current native platform.

Discovery is intentionally lightweight: the backend uses platform APIs to enumerate camera names and turns them into portable descriptors. Applications that need negotiated frame formats can use these descriptors as a first discovery pass before opening a platform-specific capture session.

Example

test {
  for device in @camera.CameraDevice::list() {
    ignore(device.label())
  }
}

CameraDevice::parse_listing

source

fn CameraDevice::parse_listing(output : String) -> Array[CameraDevice]

Parse a native camera listing into camera descriptors.

Each non-empty line is treated as one camera name. Native platform APIs usually omit capture modes at this discovery stage, so parsed devices receive a conservative 1280x720@30 MJPEG default mode and torch=false.

Example

test {
  let devices = @camera.CameraDevice::parse_listing(
    "Front Camera\nUSB Camera\n",
  )
  inspect(devices.length(), content="2")
  inspect(devices[0].label(), content="front:Front Camera")
  inspect(devices[1].label(), content="external:USB Camera")
}

CameraDevice::supports_low_latency_preview

source

fn CameraDevice::supports_low_latency_preview(self : CameraDevice) -> Bool

Whether the default mode is suitable for low-latency preview.

A device is considered low-latency friendly when its normalized default mode runs at 60 frames per second or above.

Example

test {
  let device = @camera.CameraDevice::{
    id: "camera-0",
    name: "Fast Camera",
    facing: External,
    mode: { width: 640, height: 480, fps: 60, pixel_format: Yuy2 },
    torch: false,
  }
  inspect(device.supports_low_latency_preview(), content="true")
}

CaptureMode

source

pub(all) struct CaptureMode {
  width : Int
  height : Int
  fps : Int
  pixel_format : PixelFormat
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

A concrete camera capture mode with dimensions, frame rate, and pixel format.

The values are intended to describe a usable preview or capture stream. Use CaptureMode::normalize before performing arithmetic with user-provided or native data, because platform APIs can report incomplete mode information.

impl Show for CaptureMode

fn output(self : CaptureMode, logger : &Logger) -> Unit

source

Formats a capture mode for logs and snapshots.

The representation includes every field so tests can snapshot the complete negotiated or default mode. For UI labels, prefer composing the individual fields with PixelFormat::name.

CaptureMode::frame_interval_ms

source

fn CaptureMode::frame_interval_ms(self : CaptureMode) -> Int

Return the capture interval in milliseconds for one frame.

The mode is normalized before the calculation, so an invalid fps value is treated as 1. The result uses integer milliseconds because native preview schedulers usually accept whole millisecond delays.

Example

test {
  let mode = @camera.CaptureMode::{
    width: 1280,
    height: 720,
    fps: 25,
    pixel_format: Mjpeg,
  }
  inspect(mode.frame_interval_ms(), content="40")
}

CaptureMode::normalize

source

fn CaptureMode::normalize(self : CaptureMode) -> CaptureMode

Normalize a camera capture mode into a safe baseline.

Width, height, and frames per second are clamped to at least 1, while the pixel format is preserved. This keeps downstream frame timing and layout calculations from dividing by zero or producing negative sizes.

Example

test {
  let mode = @camera.CaptureMode::{
    width: 0,
    height: -720,
    fps: 0,
    pixel_format: Nv12,
  }.normalize()
  inspect(mode.width, content="1")
  inspect(mode.height, content="1")
  inspect(mode.fps, content="1")
}

Facing

source

pub(all) enum Facing {
  Front
  Back
  External
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

Camera lens placement as reported or inferred from the native device name.

Native discovery APIs do not always expose a normalized facing field, so the package infers this value from common device names when necessary. Use it as a UI hint rather than as a hardware guarantee.

impl Show for Facing

fn output(self : Facing, logger : &Logger) -> Unit

source

Formats a facing value for logs and snapshots.

The output intentionally matches the enum constructor name. This keeps test snapshots compact while preserving enough detail to distinguish front, back, and external devices during debugging.

Facing::name

source

fn Facing::name(self : Facing) -> String

Return the stable label for camera placement.

The label is lowercase and intended for UI copy, logs, and serialized metadata where the enum constructor name would be too MoonBit-specific. Values are stable across releases unless the enum itself changes.

Example

test {
  inspect(@camera.Facing::Back.name(), content="back")
}

PixelFormat

source

pub(all) enum PixelFormat {
  Mjpeg
  Yuy2
  Nv12
  Rgba
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

Pixel formats commonly reported by native camera stacks and preview APIs.

Discovery currently returns a conservative default format because platform APIs often separate device enumeration from stream negotiation. Applications that open a capture session can replace this with the negotiated format.

impl Show for PixelFormat

fn output(self : PixelFormat, logger : &Logger) -> Unit

source

Formats a pixel format value for logs and snapshots.

The output is the MoonBit constructor name, which is useful for developer diagnostics. Use PixelFormat::name when a lowercase user-facing or serialized label is needed.

PixelFormat::name

source

fn PixelFormat::name(self : PixelFormat) -> String

Return the stable label for a pixel format.

The label is lowercase and mirrors common native camera terminology such as mjpeg, yuy2, and nv12. Use it when printing modes or exposing device metadata to configuration files.

Example

test {
  inspect(@camera.PixelFormat::Nv12.name(), content="nv12")
}

Source Files

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camera

#justjavac/camera

#CameraDevice

#CameraDevice::is_high_definition

Example

#CameraDevice::label

Example

#CameraDevice::list

Example

#CameraDevice::parse_listing

Example

#CameraDevice::supports_low_latency_preview

Example

#CaptureMode

#CaptureMode::frame_interval_ms

Example

#CaptureMode::normalize

Example

#Facing

#Facing::name

Example

#PixelFormat

#PixelFormat::name

Example

Source Files

CameraDevice

CameraDevice::is_high_definition

CameraDevice::label

CameraDevice::list

CameraDevice::parse_listing

CameraDevice::supports_low_latency_preview

CaptureMode

CaptureMode::frame_interval_ms

CaptureMode::normalize

Facing

Facing::name

PixelFormat

PixelFormat::name