How to Run Aspose.Slides in Docker

Overview

Aspose.Slides for Python via .NET runs in Linux containers, but the package is a Python wrapper around a bundled .NET Core 3.1 runtime. That runtime needs three native libraries that slim Python images do not ship, and it is particular about their versions. This article gives a Dockerfile that works, explains why each dependency is there, and shows how to add fonts and a license.

A working Dockerfile

FROM python:3.11-slim-bullseye

RUN apt-get update && apt-get install -y --no-install-recommends \
        libgdiplus \
        libicu67 \
        libfontconfig1 \
        fonts-dejavu-core \
    && rm -rf /var/lib/apt/lists/*

RUN pip install --no-cache-dir aspose.slides

WORKDIR /app
COPY app.py .
CMD ["python", "app.py"]

app.py:

import aspose.slides as slides

with slides.Presentation() as presentation:
    slide = presentation.slides[0]
    shape = slide.shapes.add_auto_shape(slides.ShapeType.RECTANGLE, 100, 100, 400, 100)
    shape.text_frame.text = "Created inside a Docker container"
    presentation.save("output.pptx", slides.export.SaveFormat.PPTX)
    presentation.save("output.pdf", slides.export.SaveFormat.PDF)

Build and run:

docker build -t aspose-slides-python .
docker run --rm aspose-slides-python

Why the base image is Debian 11

The aspose.slides wheel bundles a .NET Core 3.1 runtime, and that runtime predates the library versions shipped by current Debian releases. On Debian 12 and 13 the container builds successfully and then fails at the first Presentation() call:

Process terminated. Couldn't find a valid ICU package installed on the system.

The message is misleading — ICU is installed on those images, but it is ICU 72 or 76, and .NET Core 3.1 only recognises older major versions. Debian 12 additionally ships OpenSSL 3, which produces a second failure:

No usable version of libssl was found

python:3.11-slim-bullseye is Debian 11, which provides both versions the bundled runtime expects:

Package	Version on Debian 11	Why it is needed
libgdiplus	6.0.4	GDI+ implementation used for rendering shapes, text, and images
libicu67	67.1	Globalization data. Newer majors are not recognised by .NET Core 3.1
libssl1.1	1.1.1w	Cryptography. Preinstalled on Debian 11; absent from Debian 12+
libfontconfig1	—	Font discovery

libssl1.1 is already present in the base image, so it does not need to be listed in apt-get install.

If you must use a newer base image, set DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1 to bypass the ICU requirement. This disables culture-specific formatting and does not solve the OpenSSL problem, so Debian 11 remains the simpler choice.

Fonts

Slim images contain no fonts at all. Without at least one font installed, text renders as blank boxes in PDF, image, and HTML output. fonts-dejavu-core is a small general-purpose starting point.

To match a presentation’s intended appearance, copy the fonts it uses into the image and point Aspose.Slides at them:

COPY fonts/ /usr/share/fonts/truetype/custom/
RUN fc-cache -f

import aspose.slides as slides

slides.FontsLoader.load_external_fonts(["/usr/share/fonts/truetype/custom/"])

Licensing inside a container

Do not build the license file into the image — anyone who pulls the image gets the license. Mount it at run time instead:

docker run --rm -v /path/on/host:/license aspose-slides-python

import aspose.slides as slides

license = slides.License()
license.set_license("/license/Aspose.Slides.Python.NET.lic")

Without a license the library runs in evaluation mode, which adds a watermark and limits the number of slides processed. See Licensing for details.

Memory

Rendering to PDF or images is more memory-hungry than reading a file. Containers with tight memory limits can be terminated by the OOM killer partway through a conversion, which usually surfaces as the process disappearing without a Python traceback. If that happens, raise the container’s memory limit before investigating the code.