1.24 class camera

A camera delivers video from a camera, e.g., a webcam, as an image. camera->open starts the camera. Each new frame is copied into the same camera<-image, so a bitmap that displays this image shows the video, and camera<-message is executed:

new(C, camera),
send(Window, display, bitmap(C?image)),
send(C, open).

The image is replaced by the frame, so its size is the size of the frames. If camera<-texture is an sdl_texture, the frames go there instead. They keep the format of the camera and an sdl_layer shows them in an sdl_window without converting them on the CPU, which is much cheaper for large frames. The user may have to give permission to use the camera. Until this is decided, camera<-status is waiting.

See also

- display<-cameras
- class image
- class sdl_texture

1.24.1 Instance variables

camera <- name: name*

The name of the camera, as in display<-cameras. @nil uses the first camera.

camera <- image: image

The last frame.

camera <- status: {closed,waiting,open,denied}

Whether the camera delivers frames: waiting while the user has to decide whether the application may use the camera and denied if the user refused.

camera <-> message: code*

Executed with the camera as argument for each new frame.

camera <-> status_message: code*

Executed with the camera and the new camera<-status when it changes.

camera <-> texture: sdl_texture*

If not @nil, the frames are copied into this texture rather than into camera<-image, keeping their format. Motion JPEG frames are decoded.

camera <-> writer: video_writer*

If not @nil, each frame is also appended to this video_writer. The frames get the time of the camera, starting at the next frame of the writer. The writer is reset to @nil if appending fails.

1.24.2 Send methods

camera ->initialise: name=[name]

Create for the named camera or, if omitted, the first camera. The camera is not opened.

camera ->open: size=[size]

Start delivering frames. If size is given, the camera uses the size it supports that is closest: the same size or else the smallest larger size, using the highest frame rate. Otherwise the camera chooses, often its largest size. Large frames take time to process. Fails with a report if there is no such camera.

camera ->close:

Stop delivering frames.

camera ->sdl_test_frame: width=int, height=int, colour=colour, format=[{yuy2,mjpg}]

For testing only. Deliver a frame of the given size and colour in the YUY2 (default) or Motion JPEG format of cameras.

1.24.3 Get methods

camera <-sizes: -> chain

New chain with the sizes the camera supports, smallest first.