Trouble installing opencv in docker container using pip

Question

I want to build a python docker container that has scikit-learn, opencv, and numpy. Unfortunately, I couldn't find a pre-built container that contained all these, but I did find the one below that contains numpy and scikit-learn.

https://hub.docker.com/r/frolvlad/alpine-python-machinelearning/

I still needed to install opencv, so within my docker file I included a RUN pip install opencv-python. However, I keep on getting the error below:

Could not find a version that satisfies the requirement opencv-python (from version: ) No matching distribution found for opencv-python

Every single thing I have read online says that a pip install opencv-python will work, but it isn't working for me for some reason. Is it a problem with the python package maybe?

Any help is appreciated

Also, I will include my full Dockerfile below, I am aiming to use openFaas, which is a serverless framework, so my Dockerfile might look odd:

FROM frolvlad/alpine-python-machinelearning

RUN apk update
RUN apk upgrade

# Alternatively use ADD https:// (which will not be cached by Docker builder)
RUN apk --no-cache add curl \
    && echo "Pulling watchdog binary from Github." \
    && curl -sSL         
https://github.com/openfaas/faas/releases/download/0.8.0/fwatchdog > /usr/bin/fwatchdog \
    && chmod +x /usr/bin/fwatchdog \
    && apk del curl --no-cache

# Add non root user
RUN addgroup -S app && adduser -S -g app app
RUN chown app /home/app

RUN pip install -U pip

USER app

ENV PATH=$PATH:/home/app/.local/bin

WORKDIR /home/app/

RUN pip install opencv-python

RUN mkdir -p function
RUN touch ./function/__init__.py
WORKDIR /home/app/function/
RUN pip install --user app opencv-python

WORKDIR /home/app/
COPY function           function

ENV fprocess="python index.py"

HEALTHCHECK --interval=1s CMD [ -e /tmp/.lock ] || exit 1

CMD ["fwatchdog"]

Answer 1

I've just run into this issue as well. It turns out that this is not working because opencv-python does not have any prebuilt wheels for Alpine (the distribution you're using as your base docker image).

The conversation in this issue on the opencv-python package explains why this happens in greater detail. The TL;DR is: if you really need to use Alpine, you can try forcing the installation of the manylinux wheel for opencv-python, but this can break. Your best option if you need to keep Alpine is to build the module from source. Since you are running this on OpenFAAS, I suspect you will want to keep your size low, so building from source may be a good option for you.

If you're not attached to Alpine, I would suggest moving to a different base docker image. If you're not sure which image to use as your base, I would recommend python:3.7-slim, since it will come with Python already installed (substitute 3.7 for whichever version you are using, but really. . . 3.7 is nice). With this container, you can simply run pip install opencv-python numpy scipy to have all three of your desired packages installed. The rest of your Dockerfile should work mostly unmodified; you will just need to install/uninstall curl using apt instead of apk.