Fix class/module. Add spec

lib/libfacedetection/facedetect.rb

@@ -0,0 +1,47 @@
+module Libfacedetection
+  module FaceDetection
+    require 'ruby-vips'
+    require 'ffi'
+
+    LIB_FACEDETECTION_MAX_SIZE = 400.0
+
+    extend self
+
+    # vips_img: Vips::Image
+    def detect_faces(vips_img)
+      scale =
+      if vips_img.width > vips_img.height
+        LIB_FACEDETECTION_MAX_SIZE / vips_img.width
+      else
+        LIB_FACEDETECTION_MAX_SIZE / vips_img.height
+      end
+      # convert RGB -> BGR
+      rgb_bands = vips_img.bandsplit
+      bgr = Vips::Image.bandjoin([rgb_bands[2], rgb_bands[1], rgb_bands[0]])
+      # resize to a smaller size - libfacedetection works with smaller images
+      # or perhaps a larger one, but results are not guaranteed to be better
+      resized = bgr.resize(scale)
+
+      mem = resized.write_to_memory
+      ptr = FFI::MemoryPointer.from_string(mem)
+      faces = Libfacedetection.detect_libfacedetection_image_data(ptr.address, resized.width, resized.height)
+      faces.map do |face|
+        scale_face(face, scale)
+      end
+    end
+
+    private
+
+    def scale_face(face, scale)
+      face[:x] = (face[:x] / scale).round
+      face[:y] = (face[:y] / scale).round
+      face[:width] = (face[:width] / scale).round
+      face[:height] = (face[:height] / scale).round
+      face[:landmarks] = face[:landmarks].map do |landmark|
+        [(landmark[0] / scale).round, (landmark[1] / scale).round]
+      end
+      face
+    end
+  end
+
+end

libfacedetection.gemspec

@@ -26,6 +26,8 @@ Gem::Specification.new do |spec|
   spec.extensions = ["Cargo.toml"]
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "gem-compiler"
+  spec.add_development_dependency "ruby-vips"
+  spec.add_development_dependency "ffi"
   spec.required_rubygems_version = Gem::Requirement.new(">= 3.4.0") if spec.respond_to? :required_rubygems_version=
   # spec.add_development_dependency "rake-compiler-dock", "~> 1.2.2"
 

src/lib.rs

@@ -165,16 +165,16 @@ fn features() -> Result<RArray> {
 
 #[magnus::init]
 fn init(ruby: &magnus::Ruby) -> Result<()> {
-    let class = ruby.define_class("Libfacedetection", ruby.class_object())?;
-    class.define_method("detect_opencv", magnus::function!(pub_detect_opencv, 1))?;
-    class.define_method(
+    let module = ruby.define_module("Libfacedetection")?;
+    module.define_module_function("detect_opencv", magnus::function!(pub_detect_opencv, 1))?;
+    module.define_module_function(
         "detect_libfacedetection",
         magnus::function!(pub_detect_libfacedetection, 1),
     )?;
-    class.define_method(
+    module.define_module_function(
         "detect_libfacedetection_image_data",
         magnus::function!(pub_detect_libfacedetection_image_data, 3),
     )?;
-    class.define_method("features", magnus::function!(features, 0))?;
+    module.define_module_function("features", magnus::function!(features, 0))?;
     Ok(())
 }

tests/test_detection.rb

@@ -0,0 +1,14 @@
+gem 'libfacedetection'
+require 'libfacedetection'
+require 'libfacedetection/facedetect'
+
+require 'minitest/autorun'
+
+class FaceDetectionTest < Minitest::Test
+  def test_facedetection
+    result = Libfacedetection::FaceDetection.detect_faces(Vips::Image.new_from_file(File.expand_path("female.webp", __dir__)))
+    assert_instance_of(Array, result)
+    assert_equal(1, result.count)
+    assert(result[0][:confidence] > 90)
+  end
+end