rpi_fb_capture v0.3.0 RpiFbCapture View Source

Capture the Raspberry Pi's frame buffer

Link to this section Summary

Types

dithering()

format()

option()

Functions

backend(server)

Return the name of the active capture backend

capture(server, format)

Capture the screen in the specified format.

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

save(server, path, format \\ :ppm)

Helper method for saving a screen capture to a file

set_dithering(server, algorithm)

Set dithering algorithm.

set_mono_threshold(server, threshold)

Adjust the value that pixels are on for monochromatic conversion.

start_link(args \\ [])

Start up the capture process

stop(server)

Stop the capture process

Link to this section Types

dithering()

dithering() :: :none | :floyd_steinberg | :sierra | :sierra_2row | :sierra_lite

format()

format() :: :ppm | :rgb24 | :rgb565 | :mono | :mono_column_scan

option()

option() ::
  {:width, non_neg_integer()}
  | {:height, non_neg_integer()}
  | {:display, non_neg_integer()}

Link to this section Functions

backend(server)

backend(GenServer.server()) :: String.t()

Return the name of the active capture backend

Example backend names:

"sim" for the simulator
"dispmanx" for the Raspberry Pi
"unknown" if the backend hasn't reported its name

capture(server, format)

capture(GenServer.server(), format()) ::
  {:ok, RpiFbCapture.Capture.t()} | {:error, atom()}

Capture the screen in the specified format.

Formats include:

:ppm - PPM-formatted data
:rgb24 - Raw 24-bit RGB data 8-bits R, G, then B
:rgb565 - Raw 16-bit data 5-bits R, 6-bits G, 5-bits B
:mono - Raw 1-bpp data
:mono_column_scan - Raw 1-bpp data, but scanned down columns

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

save(server, path, format \\ :ppm)

save(GenServer.server(), Path.t(), format()) :: :ok | {:error, atom()}

Helper method for saving a screen capture to a file

Example:

iex> {:ok, cap} = RpiFbCapture.start_link()
iex> RpiRbCapture(cap, "/tmp/capture.ppm")
:ok

set_dithering(server, algorithm)

set_dithering(GenServer.server(), dithering()) :: :ok | {:error, atom()}

Set dithering algorithm.

Algorithms include:

:none - No dithering applied
:floyd_steinberg - Floyd–Steinberg
:sierra - Sierra (also called Sierra-3)
:sierra_2row - Two-row Sierra
:sierra_lite - Sierra Lite

set_mono_threshold(server, threshold)

set_mono_threshold(GenServer.server(), byte()) :: :ok | {:error, atom()}

Adjust the value that pixels are on for monochromatic conversion.

The threshold should be 8-bits. The capture buffer is rgb565, so the threshold will be reduced to 5 or 6 bits for the actual comparisons.

start_link(args \\ [])

start_link([option()]) :: :ignore | {:error, any()} | {:ok, pid()}

Start up the capture process

NOTE: The Raspberry Pi capture hardware has limitations on the window size. In general, capturing the whole display is fine. Keeping the width as a multiple of 16 appears to be good.

Options:

:width - the width of the capture window (0 for the display width)
:height - the height of the capture window (0 for the display width)
:display - which display to capture (defaults to 0)

stop(server)

stop(GenServer.server()) :: :ok

Stop the capture process