updated

docker/Dockerfile

@@ -57,11 +57,14 @@ apt-get update \
 && if [ "$(uname -m)" = "armv7l" ]; then \
     ln -s /usr/lib/arm-linux-gnueabihf/libz.so /usr/lib/ \
     && ln -s /usr/lib/arm-linux-gnueabihf/libjpeg.so /usr/lib/ \
-; fi
+; fi \
+&& rm -rf /var/lib/apt/lists/*
 
 RUN printf "deb http://httpredir.debian.org/debian stretch-backports main non-free\ndeb-src http://httpredir.debian.org/debian stretch-backports main non-free" > /etc/apt/sources.list.d/backports.list \
 			&& apt-get update \
-			&& apt-get install -t stretch-backports -y tesseract-ocr tesseract-ocr-deu
+			&& apt-get install -t stretch-backports -y libtesseract-dev libleptonica-dev liblept5 tesseract-ocr tesseract-ocr-deu \
+      && apt-get autoremove -y --purge \
+      && rm -rf /var/lib/apt/lists/*
 
 ####
 # builder_image - This image builds the Python package and is discarded afterwards