  Social media images, curated or casual, have become a crucial component of
communicating situational information and emotions during health crises.
Despite its prevalence and significance in informational dissemination and
emotional connection, there lacks a comprehensive understanding of visual
crisis communication in the aftermath of a pandemic which is characterized by
uncertain local situations and emotional fatigue. To fill this gap, this work
collected 345,423 crisis-related posts and 65,376 original images during the
Xi'an COVID-19 local outbreak in China, and adopted a mixed-methods approach to
understanding themes, goals, and strategies of crisis imagery. Image clustering
captured the diversity of visual themes during the outbreak, such as text
images embedding authoritative guidelines and ``visual diaries'' recording and
sharing the quarantine life. Through text classification of the post that
visuals were situated in, we found that different visual themes highly
correlated with the informational and emotional goals of the post text, such as
adopting text images to convey the latest policies and sharing food images to
express anxiety. We further unpacked nuanced strategies of crisis image use
through inductive coding, such as signifying authority and triggering empathy.
We discuss the opportunities and challenges of crisis imagery and provide
design implications to facilitate effective visual crisis communication.
