環境

Raspberry Pi 3B
Raspbian: 2019-04-08-raspbian-stretch (デスクトップ環境)
OpenCV 3.4.6 (ラズパイ3にOpenCV3/4を簡単に導入より)

手順

ラズパイ等の準備 ... (省略)

サンプルで使用する画像データ取得

pi@raspberrypi:~ $ # Sample Data
pi@raspberrypi:~ $ wget -q https://github.com/opencv/opencv/raw/master/samples/data/box.png
pi@raspberrypi:~ $ wget -q https://github.com/opencv/opencv/raw/master/samples/data/box_in_scene.png

--feature=briskにて

pi@raspberrypi:~ $ python3 /usr/local/share/OpenCV/samples/python/find_obj.py --feature=brisk box.png box_in_scene.png

Feature-based image matching sample.

Note, that you will need the https://github.com/opencv/opencv_contrib repo for SIFT and SURF

USAGE
  find_obj.py [--feature=<sift|surf|orb|akaze|brisk>[-flann]] [ <image1> <image2> ]

  --feature  - Feature to use. Can be sift, surf, orb or brisk. Append '-flann'
			   to feature name to use Flann-based matcher instead bruteforce.

  Press left mouse button on a feature point to see its matching point.

using brisk
img1 - 1662 features, img2 - 2786 features
matching...
50 / 52  inliers/matched
Done
pi@raspberrypi:~ $

その他

--feature=sirfや--feature=surf

ここで配布しているラズパイ向けパッケージでは、ビルドに含まれていないのでエラーとなります。

(-213:The function/feature is not implemented) This algorithm is patented and is excluded in this configuration; Set OPENCV_ENABLE_NONFREE CMake option and rebuild the library in function 'create'

ぐーぐる先生翻訳:

(-213：機能/機能は実装されていません) このアルゴリズムは特許取得済みで、この構成では除外されています。 OPENCV_ENABLE_NONFREE CMakeオプションを設定し、関数 'create'でライブラリを再構築します

実行例

pi@raspberrypi:~ $ python3 /usr/local/share/OpenCV/samples/python/find_obj.py --feature=sift box.png box_in_scene.png

Feature-based image matching sample.

Note, that you will need the https://github.com/opencv/opencv_contrib repo for SIFT and SURF

USAGE
  find_obj.py [--feature=<sift|surf|orb|akaze|brisk>[-flann]] [ <image1> <image2> ]

  --feature  - Feature to use. Can be sift, surf, orb or brisk. Append '-flann'
			   to feature name to use Flann-based matcher instead bruteforce.

  Press left mouse button on a feature point to see its matching point.

Traceback (most recent call last):
  File "/usr/local/share/OpenCV/samples/python/find_obj.py", line 195, in <module>
	main()
  File "/usr/local/share/OpenCV/samples/python/find_obj.py", line 154, in main
	detector, matcher = init_feature(feature_name)
  File "/usr/local/share/OpenCV/samples/python/find_obj.py", line 32, in init_feature
	detector = cv.xfeatures2d.SIFT_create()
cv2.error: OpenCV(3.4.6) /home/pi/opencv_contrib-3.4.6/modules/xfeatures2d/src/sift.cpp:1205: error: (-213:The function/feature is not implemented) This algorithm is patented and is excluded in this configuration; Set OPENCV_ENABLE_NONFREE CMake option and rebuild the library in function 'create'

pi@raspberrypi:~ $

OPENCV_ENABLE_NONFREEは今度ためしてみようかと思いますが、公に配布はどうなんでしょう？