Safe Haskell	None
Language	GHC2021

SDL3.Sys.Bindgen.Camera

Description

Video capture for the SDL library.

This API lets apps read input from video sources, like webcams. Camera devices can be enumerated, queried, and opened. Once opened, it will provide SDL_Surface objects as new frames of video come in. These surfaces can be uploaded to an SDL_Texture or processed as pixels in memory.

Several platforms will alert the user if an app tries to access a camera, and some will present a UI asking the user if your application should be allowed to obtain images at all, which they can deny. A successfully opened camera will not provide images until permission is granted. Applications, after opening a camera device, can see if they were granted access by either polling with the SDL_GetCameraPermissionState() function, or waiting for an SDL_EVENT_CAMERA_DEVICE_APPROVED or SDL_EVENT_CAMERA_DEVICE_DENIED event. Platforms that don't have any user approval process will report approval immediately.

Note that SDL cameras only provide video as individual frames; they will not provide full-motion video encoded in a movie file format, although an app is free to encode the acquired frames into any format it likes. It also does not provide audio from the camera hardware through this API; not only do many webcams not have microphones at all, many people from streamers to people on Zoom calls will want to use a separate microphone regardless of the camera. In any case, recorded audio will be available through SDL's audio API no matter what hardware provides the microphone.

Camera gotchas

Consumer-level camera hardware tends to take a little while to warm up, once the device has been opened. Generally most camera apps have some sort of UI to take a picture (a button to snap a pic while a preview is showing, some sort of multi-second countdown for the user to pose, like a photo booth), which puts control in the users' hands, or they are intended to stay on for long times (Pokemon Go, etc).

It's not uncommon that a newly-opened camera will provide a couple of completely black frames, maybe followed by some under-exposed images. If taking a single frame automatically, or recording video from a camera's input without the user initiating it from a preview, it could be wise to drop the first several frames (if not the first several seconds worth of frames!) before using images from a camera. This is a unique ID for a camera device for the time it is connected to the system, and is never reused for the lifetime of the application.

If the device is disconnected and reconnected, it will get a new ID.

The value 0 is an invalid ID.

See also: sDL_GetCameras

Since: 3.2.0

Synopsis

newtype SDL_CameraID = SDL_CameraID {
- unwrap :: Uint32
}
data SDL_Camera
data SDL_CameraSpec = SDL_CameraSpec {
- format :: SDL_PixelFormat
- colorspace :: SDL_Colorspace
- width :: CInt
- height :: CInt
- framerate_numerator :: CInt
- framerate_denominator :: CInt
}
newtype SDL_CameraPosition = SDL_CameraPosition {
- unwrap :: CUInt
}
pattern SDL_CAMERA_POSITION_UNKNOWN :: SDL_CameraPosition
pattern SDL_CAMERA_POSITION_FRONT_FACING :: SDL_CameraPosition
pattern SDL_CAMERA_POSITION_BACK_FACING :: SDL_CameraPosition
newtype SDL_CameraPermissionState = SDL_CameraPermissionState {
- unwrap :: CInt
}
pattern SDL_CAMERA_PERMISSION_STATE_DENIED :: SDL_CameraPermissionState
pattern SDL_CAMERA_PERMISSION_STATE_PENDING :: SDL_CameraPermissionState
pattern SDL_CAMERA_PERMISSION_STATE_APPROVED :: SDL_CameraPermissionState

Documentation

newtype SDL_CameraID Source #

C declaration: SDL_CameraID, defined at SDL3/SDL_camera.h 95:16

Constructors

SDL_CameraID
Fields unwrap :: Uint32

Instances

Instances details

Bits SDL_CameraID Source #

Instance details