Tune SikuliX image-matching similarity and handle multi-DPI screen differences
domain: sikulix.com · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Wrap reference images in a Pattern and explicitly set similarity, e.g. Pattern("btn.png").similar(0.95), rather than relying on the library's implicit 0.7 default for reliable click targets
Capture reference images with minimal background, keeping non-unique surrounding pixels below roughly 20% of the image area to avoid false-positive matches
Don't treat very high similarity thresholds (0.98+) as a blanket safety net on images with large flat/solid-color regions — SikuliX can report near-perfect similarity for visually different solid-color areas
When the same script must run on machines with different screen size/DPI, capture and store DPI-specific image sets and select the right set at startup rather than assuming images scale
For remote/virtualized targets with mismatched DPI, drive the automation over a fixed-resolution VNC session so captured and runtime images match
Known gotchas
SikuliX image matching is not DPI-aware — the same UI at a different scale factor is a genuinely different image, and matching degrades or fails outright rather than warning you
Similarity scores near the top of the range can still false-positive on images that are mostly a single flat color, since per-pixel similarity math doesn't capture that a button visually differs
High-resolution/4K displays substantially slow down full-screen image search; scoping searches to a smaller Region instead of the whole screen matters more as resolution increases
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