Using multistage build to fasten up

Dockerfile

@@ -1,10 +1,24 @@
-# Debian base
-FROM debian:buster
-
+FROM ruby:2.4.6-slim-buster as main-image
 MAINTAINER Sebastian Silva <sebastian@fuentelibre.org>
 
+FROM python:2.7 as gdal-builder
+
 # Install the application.
-RUN apt-get update -qq && apt-get install -y gdal-bin ruby imagemagick ruby-sinatra ruby-kramdown ruby-nokogiri bundler git python-gdal
+RUN apt-get update -qq && \
+    apt-get install -y --no-install-recommends \
+        gdal-bin \
+        python-gdal
+
+FROM main-image
+
+COPY --from=gdal-builder /usr/share /usr/share
+COPY --from=gdal-builder /usr/bin /usr/bin
+
+RUN apt-get update -qq && \
+    apt-get install -y --no-install-recommends \
+        build-essential \
+        git \
+        imagemagick
 
 # Configure ImageMagick
 COPY ./nolimit.xml /etc/ImageMagick-6/policy.xml