Detect Face

Mix.install([
  {:req, "~> 0.5"},
  {:evision, "~> 0.2"},
  {:kino, "~> 0.14"}
])

Download model

prefix = "https://github.com/opencv/opencv/raw/master/data/haarcascades"

frontal_face_model_path = "frontal_face_model.xml"

"#{prefix}/haarcascade_frontalface_default.xml"
|> Req.get!(connect_options: [timeout: 300_000], into: File.stream!(frontal_face_model_path))

eye_model_path = "eye_model.xml"

"#{prefix}/haarcascade_eye.xml"
|> Req.get!(connect_options: [timeout: 300_000], into: File.stream!(eye_model_path))

profile_face_model_path = "profile_face_model.xml"

"#{prefix}/haarcascade_profileface.xml"
|> Req.get!(connect_options: [timeout: 300_000], into: File.stream!(profile_face_model_path))

Load models

frontal_face_model = Evision.CascadeClassifier.cascadeClassifier(frontal_face_model_path)

eye_model = Evision.CascadeClassifier.cascadeClassifier(eye_model_path)

profile_face_model = Evision.CascadeClassifier.cascadeClassifier(profile_face_model_path)

Download image

img =
  "https://upload.wikimedia.org/wikipedia/en/7/7d/Lenna_%28test_image%29.png"
  |> Req.get!()
  |> Map.get(:body)
  |> Evision.imdecode(Evision.Constant.cv_IMREAD_COLOR())

Detect frontal face

face_rect_list = Evision.CascadeClassifier.detectMultiScale(frontal_face_model, img)

draw_rects = fn img, rect_list ->
  Enum.reduce(rect_list, img, fn rect, drawed_mat ->
    {left, top, width, height} = rect

    Evision.rectangle(
      drawed_mat,
      {left, top},
      {left + width, top + height},
      {255, 0, 0},
      thickness: 4
    )
  end)
end

draw_rects.(img, face_rect_list)

{face_rect_list, number_of_detections} =
  Evision.CascadeClassifier.detectMultiScale2(frontal_face_model, img)

hd(number_of_detections)

{face_rect_list, reject_levels, level_weights} =
  Evision.CascadeClassifier.detectMultiScale3(frontal_face_model, img, outputRejectLevels: true)

Detect eyes

eye_rect_list = Evision.CascadeClassifier.detectMultiScale(eye_model, img)

draw_rects.(img, eye_rect_list)

Evision.CascadeClassifier.detectMultiScale2(eye_model, img)

Evision.CascadeClassifier.detectMultiScale3(eye_model, img, outputRejectLevels: true)

Detect profile face

profile_face_rect_list = Evision.CascadeClassifier.detectMultiScale(profile_face_model, img)

Evision.flip(img, 1)

profile_face_rect_list =
  img
  |> Evision.flip(1)
  |> then(&Evision.CascadeClassifier.detectMultiScale(profile_face_model, &1))

img
|> Evision.flip(1)
|> draw_rects.(profile_face_rect_list)