com.blockether.spel.visual-diff — com.blockether/spel 0.5.17

Pixel-level screenshot comparison using the pixelmatch algorithm. Runs inside Playwright's Canvas API — no AWT/ImageIO dependency, GraalVM native-image safe.

Based on pixelmatch by Mapbox (ISC license): https://github.com/mapbox/pixelmatch

compare-pages clj

(compare-pages baseline-page current-page & {:as opts})

Screenshot + snapshot + diff in one call. Takes two live Playwright pages, captures screenshots and accessibility snapshots from both, then runs pixel diff with semantic region enrichment.

This is the highest-level diff function — produces fully enriched regions with element labels like "button 'Submit' — content-change".

Options: same as compare-screenshots (threshold, include-aa, etc.)

Returns: same as compare-screenshots, with enriched regions, plus: :baseline-snapshot - accessibility tree of baseline page :current-snapshot - accessibility tree of current page

compare-screenshot-files clj

(compare-screenshot-files baseline-path current-path & opts)

Compare two PNG screenshot files. See compare-screenshots for options.

compare-screenshots clj

(compare-screenshots baseline
                     current
                     &
                     {:keys [threshold include-aa alpha denoise dilate
                             merge-distance diff-path baseline-refs
                             current-refs]
                      :or {threshold 0.1
                           include-aa false
                           alpha 0.5
                           denoise 25
                           dilate 3
                           merge-distance 50}})

Compare two PNG screenshots pixel-by-pixel using the pixelmatch algorithm (YIQ NTSC color space with anti-aliasing detection).

Runs the comparison inside Playwright's Canvas API — no AWT/ImageIO, GraalVM native-image safe.

baseline and current are PNG byte arrays (as returned by page/screenshot).

Options: :threshold — matching threshold 0.0-1.0 (default 0.1, lower = stricter) :include-aa — count anti-aliased pixels as diff (default false) :alpha — red overlay opacity on changed pixels (default 0.5) :denoise — minimum connected-component pixels to keep (default 25) :dilate — dilation radius in pixels before component labeling (default 3) :merge-distance — merge nearby region boxes within this many pixels (default 50) :diff-path — optional path to save the diff image PNG :baseline-refs — snapshot refs map for baseline state (optional, from capture-snapshot :refs) :current-refs — snapshot refs map for current state (optional, from capture-snapshot :refs) When provided, regions are enriched with semantic element labels.

Returns: {:matched true/false :diff-count number of different pixels :total-pixels total pixel count :diff-percent percentage of different pixels (2 decimal places) :width comparison width :height comparison height :regions [{:id n :label "added|removed|content-change" :pixels n :bounding-box {:x n :y n :width n :height n} :element {:ref s :role s :name s :overlap n} :elements [{:ref s :role s :name s :overlap n}] :semantic-label s} ...] :diff-image diff PNG as byte[] :baseline-dimensions {:width w :height h} :current-dimensions {:width w :height h} :dimension-mismatch true/false}

enrich-regions clj

(enrich-regions regions refs)

Enriches diff regions with semantic labels from accessibility snapshot refs.

regions - vector of diff regions from compare-screenshots refs - snapshot refs map from capture-snapshot (:refs key) Format: {e2yrjz {:role button :name Submit :bbox {:x :y :width :height}} ...}

Returns the regions vector with additional keys on each region: :element - best matching element {:ref :role :name :overlap} :elements - all overlapping elements sorted by specificity :semantic-label - human-readable label like button 'Submit' — content-change