fix(pdf): BEHIND_CONTENT watermark opacity no longer bleeds into page content#159
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… content The watermark renderer set its low-alpha graphics state inside a prepended content stream without a save/restore pair. PDFBox's resetContext flag only isolates APPEND streams, so the alpha constant leaked into the original page stream and washed out every element on the page. Wrap the watermark drawing in q/Q. Regression test renders a solid shape under a BEHIND_CONTENT watermark and asserts the fill samples at full strength while the watermark keeps its own low-alpha ExtGState.
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Problem
A
BEHIND_CONTENTwatermark renders through a PREPEND content stream. The renderer set the watermark opacity via ExtGState there without aq/Qpair — and PDFBox'sresetContextflag only isolates APPEND streams. The low alpha constant leaked into the original page stream, washing out the entire page (everything rendered at the watermark's opacity, except elements that set their own alpha).Since
DocumentWatermarkdefaults tolayer = BEHIND_CONTENT, every document using a default watermark was affected. Found while verifying the feature-catalog render: the whole page was ghosted except the translucency demo chips.Fix
PdfWatermarkRenderer.applynow wraps the watermark drawing insaveGraphicsState()/restoreGraphicsState().Tests
PdfWatermarkStateIsolationTest: renders a solid navy shape under aBEHIND_CONTENTwatermark at opacity 0.05, asserts the shape centre samples at full strength (pixel check) and the watermark still carries its low-alpha ExtGState. Verified the test fails on the unfixed renderer and passes with the fix.