Dockerfile for Python3 and OpenCV - python-3.x

Question

I need to have a Dockerfile with Python3 and the latest version of OpenCV. The Dockerfile I have written is described below:
FROM ubuntu
#Install OpenCV
RUN apt-get update &&\
apt-get install -y cmake
RUN apt-get install -y gcc g++
RUN apt-get install -y python3-dev python3-numpy
# To support GUI features
RUN apt-get install -y libavcodec-dev libavformat-dev libswscale-dev
# To support GTK 2
RUN apt-get install -y libgtk2.0-dev
# To support GTK 3
RUN apt-get install -y libgtk-3-dev
#Optional dependencies
RUN apt-get install -y libpng-dev
RUN apt-get install -y libjpeg-dev
RUN apt-get install -y libopenexr-dev
RUN apt-get install -y libtiff-dev
RUN apt-get install -y libwebp-dev
# Clone OpenCV repo
RUN apt-get install -y git
RUN git clone https://github.com/opencv/opencv.git
#Compile
RUN mkdir /opencv/build && \
cd /opencv/build
RUN cmake ..
RUN make
However, when i run it, it gives me the following error with cmake.
Step 17/27 : RUN cmake ..
---> Running in 3dca32df2036
CMake Error: The source directory "/" does not appear to contain CMakeLists.txt.
Specify --help for usage, or press the help button on the CMake GUI.
The command '/bin/sh -c cmake ..' returned a non-zero code: 1
Do you know what am i doing wrong?

Answer 1

You just need to chain the last RUN instructions:
#Compile
RUN mkdir /opencv/build && \
cd /opencv/build && \
cmake .. && \
make
Explanation:
A RUN statement creates a new image layer and executes the specified shell command. This means that each RUN statement will run the command in a separate shell, so the current directory from the previous RUN will not be preserved (you can see that the CMake current directory is / by looking closely at the error message).
You can find more info about RUN statement in the Docker documentation and I also recommend reading Best practices for writing Dockerfiles.