Huang Xin
1.9 KiB
name, description, metadata
| name | description | metadata | ||||||
|---|---|---|---|---|---|---|---|---|
| ios-widget-cover-bright-edge-line | iOS reading widget cover sometimes had a bright hairline at the right edge from fractional resize; round target to whole pixels |
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iOS reading-widget book covers sometimes showed a bright hairline along the right edge (Android widget never did). Fixed in PR #4950, src-tauri/plugins/tauri-plugin-native-bridge/ios/Sources/ReadingWidgetWriter.swift writeThumbnail.
Root cause: the downsample target was fractional:
CGSize(width: image.size.width * scale, height: image.size.height * scale) with scale = 240 / longEdge. For portrait covers the height (longEdge) lands on a whole pixel but the width is fractional. UIGraphicsImageRenderer allocates a whole-pixel buffer (rounds the size up), while image.draw(in:) fills only the exact fractional rect — so when the fractional width rounds up, the rightmost pixel column is only partially covered → semi-transparent (e.g. alpha 225 instead of 255). jpegData has no alpha, so that column flattens to a visible bright line. Intermittent ("sometimes") because it only bites when the fractional part rounds up; portrait-specific because width is the fractional edge.
Fix: round both dimensions to whole pixels so draw-rect == pixel-buffer and every edge pixel is fully covered:
CGSize(width: (image.size.width * scale).rounded(), height: (image.size.height * scale).rounded()).
Verified with a faithful CoreGraphics repro (same rasterization as UIKit): 453x680 cover gave edge alpha 225 before, 255 after; all sizes 255 after. Android (mobile-reading-widgets ReadingWidgetStore.kt) is immune because it scales to a fixed integer 240x360 and center-crops.
No checked-in Swift test: the plugin Package.swift has no wired test target and the code is UIKit-only.