Hi,

we have the following PDF Rendering Issue.

Issue Description
I am experiencing a rendering issue when using PDFium SDK to render PDF pages. Specifically, the font in the rendered output appears almost completely transparent, with only faint outlines of the text visible. This issue does not occur when viewing the same PDF document with Adobe Acrobat.

Technical Details
Using Pdfium.NET SDK version: 4.99.2704
Implementation: The issue occurs when calling PdfPage.Render(PdfBitmap, int, int, int, int, PageRotate, RenderFlags) method. RenderFlags are FPDF_ANNOT | FPDF_LCD_TEXT
Programming Language: C#

Attachments
Original PDF document ( original_document.pdf (60kb) downloaded 2 time(s).)

Screenshot of page rendered by Adobe Acrobat - text appears normal and fully visible
adobe_rendering.png (7kb) downloaded 2 time(s).

Screenshot of the same page rendered by PDFium - text appears almost transparent with only outlines visible
pdfium_rendering.png (4kb) downloaded 2 time(s).


Expected Behavior
The text should be rendered with proper opacity and appearance, matching the output as seen in Adobe Acrobat.

Actual Behavior
Text is rendered almost completely transparent with only faint outlines visible, making the content practically unreadable.

Additional Information
The PdfBitmap ist generated with isUseAlpha = true and FillRect with white as color. Afterwards it is displayed in a WPF application by creating a BitmapSource.
The document has more pages with sensible data, so I extracted a page only with non sensible data, but this issue affects all text in the document consistently.


Please advise on how to resolve this font rendering issue. I need the PDFium output to match the quality and appearance of the Adobe rendering.

Thank you for your assistance.