We study 100 images of early LHC collisions that were recorded by the ATLAS experiment and made
public for outreach purposes, and extract the charged particle multiplicity as a function of
momentum for proton–proton collisions at a centre-of-mass energy of 7 TeV. As these collisions have
already been pre-processed by the ATLAS Collaboration, the particle tracks are visible, but are
available to the public only in the form of low-resolution bitmaps. We describe two separate image
processing methods, one based on the industry-standard OpenCV library and C++, another based on
self-developed algorithms in Python. We present our analysis of the transverse momentum and
azimuthal angle distributions of the particles, in agreement with the literature.