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Indexed PNG with transparency is embedded but renders invisible #392
Description
Summary
When drawing an indexed/palette PNG with transparency (tRNS) onto an existing PDF page using XGraphics.DrawImage, PDFsharp 6.2.4 or 7.0.0-preview-1 produces an output PDF that contains the image XObject, but the image is not visible when rendered on macOS. If the exact same image is first converted to RGBA PNG, the image renders visibly.
Environment
- PDFsharp: 6.2.4
- Target framework tested: net10.0
- OS tested: macOS
- Renderer used to verify: macOS
sips/ Preview-style rendering
Activity
Write an image's stencil mask only where no soft mask goes (#41)
ThomasHoevel commentedon Sep 28, 2026
As far as I can tell, PDFsharp creates a correct PDF file and Adobe Reader show it correctly, but MacOS Quartz ignores the PDF specification and shows the image incorrectly. We'll discuss what we can do about it.