https://bugs.documentfoundation.org/show_bug.cgi?id=169934
Bug ID: 169934
Summary: Transparency is lost when applying a duotone filter to
images in Excel files
Product: LibreOffice
Version: 26.2.0.0 alpha0+ master
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Printing and PDF export
Assignee: [email protected]
Reporter: [email protected]
Description:
When exporting an Excel document to PDF using the command-line option
`--convert-to pdf`, images that have a duotone filter applied lose their
transparency. In the resulting PDF, the affected images appear fully opaque
instead of preserving their original transparency.
Steps to Reproduce:
1. Prepare an Excel file that contains an image with a duotone filter applied.
2. Export it using: `soffice --headless --convert-to pdf filename.xlsx`
3. Open the generated PDF.
Actual Results:
The transparency of the duotone-filtered image is lost, and the image is
rendered as fully opaque in the PDF output.
Expected Results:
Transparency should be preserved when exporting duotone-filtered images to PDF.
Reproducible: Always
User Profile Reset: No
Additional Info:
The issue appears to originate from the duotone conversion logic in
`BitmapDuoToneFilter::execute()`.
The alpha channel is not propagated to the output color, causing the resulting
bitmap to lose transparency.
A minimal fix is shown below:
diff --git a/vcl/source/bitmap/BitmapDuoToneFilter.cxx
b/vcl/source/bitmap/BitmapDuoToneFilter.cxx
index 2dd10459e242..d0bb35cf6863 100644
--- a/vcl/source/bitmap/BitmapDuoToneFilter.cxx
+++ b/vcl/source/bitmap/BitmapDuoToneFilter.cxx
@@ -41,10 +41,12 @@ Bitmap BitmapDuoToneFilter::execute(Bitmap const& rBitmap)
const
BitmapColor aColor = pReadAcc->GetColor(y, x);
sal_uInt8 nLuminance = aColor.GetLuminance();
BitmapColor aResultColor(
+ ColorAlphaTag::ColorAlpha,
lcl_getDuotoneColorComponent(nLuminance, aColorOne.GetRed(),
aColorTwo.GetRed()),
lcl_getDuotoneColorComponent(nLuminance, aColorOne.GetGreen(),
aColorTwo.GetGreen()),
- lcl_getDuotoneColorComponent(nLuminance, aColorOne.GetBlue(),
aColorTwo.GetBlue()));
+ lcl_getDuotoneColorComponent(nLuminance, aColorOne.GetBlue(),
aColorTwo.GetBlue()),
+ aColor.GetAlpha());
pWriteAcc->SetPixel(y, x, aResultColor);
}
}
--
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