ObjectTransparent property

此 API 条目保留标识符、签名、代码块和 PDF 术语的原始形式。

Indicates whether a page object participates in PDF transparency — either through a non-opaque fill/stroke alpha or through a non-Normal blend mode — and therefore needs compositing rather than simple painter's-algorithm rendering.

PDF 1.4 introduced the Transparency Imaging Model (PDF 32000-1 § 11), which lets any page object specify a graphics-state alpha (ca/CA) and a blend mode (BM in the ExtGState dictionary). ObjectTransparent returns True if PDFium detected either of these on the object at Index, meaning the renderer cannot simply overpaint and must allocate an isolated compositing buffer for the object.

This is the per-object analogue of Transparent, which reports whether the whole current page contains any transparent content. Use it when you want to flatten only the costly portions of a page, audit incoming PDFs for print-shop pipelines that do not understand transparency, or speed up custom rendering by short-circuiting compositing for the majority of objects that are fully opaque.

The result reflects the object's own graphics state at insertion time. Mutating the object (for example through native FPDFPageObj_SetFillColor with a non-255 alpha) only changes the reported value after UpdatePage and ReloadPage have rebuilt the cached page.

• Image objects whose source data contains an alpha channel (soft mask / SMask) also report True.
• An object can be partially behind a transparent neighbour and still report False — the property describes the object itself, not how it is composited with siblings.
• Wraps PDFium's FPDFPageObj_HasTransparency and is intentionally cheap to call inside loops over ObjectCount.
• The reported value is independent of PageRotation, page scaling, or the current rendering DPI.

ObjectCount, ObjectType, ObjectBounds, Transparent