https://bugs.documentfoundation.org/show_bug.cgi?id=172744
Bug ID: 172744
Summary: XLSX: OOXML clrChange transparency is applied
incorrectly
Product: LibreOffice
Version: 25.8.4.2 release
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: filters and storage
Assignee: [email protected]
Reporter: [email protected]
Description:
The attached XLSX contains a clrChange filter, but LibreOffice does not apply
it correctly.
The image has the following clrChange filter:
```
<a:clrChange>
<a:clrFrom>
<a:srgbClr val="FFFFFF"/>
</a:clrFrom>
<a:clrTo>
<a:srgbClr val="FFFFFF">
<a:alpha val="0"/>
</a:srgbClr>
</a:clrTo>
</a:clrChange>
```
This filter is intended to make the color #FFFFFF (white) transparent.
However, the rendering result differs between Microsoft Excel, LibreOffice
25.8, and LibreOffice 26.8.
Microsoft Excel: Correct behavior. Only the white circle becomes transparent.
LibreOffice 25.8: Pixels with blue = 255 become transparent, so blue, cyan, and
magenta are also transparent.
LibreOffice 26.8: Pixels with alpha = 255 become transparent, causing the
entire image to become transparent.
The expected behavior is to match Microsoft Excel, where only pixels with the
color #FFFFFF are affected by the clrChange filter.
The behavior changed in 26.2 (or later): instead of making pixels with blue ==
255 transparent, pixels with alpha == 255 become transparent, causing the
entire image to disappear.
Steps to Reproduce:
1. Open the attached XLSX file in LibreOffice.
2. Observe the image displayed in the worksheet.
Actual Results:
The clrChange effect is applied incorrectly. The entire image becomes
transparent instead of only the white pixels (#FFFFFF).
Expected Results:
The clrChange effect should match Microsoft Excel. Only pixels with the color
#FFFFFF should become transparent, while all other colors should remain
unchanged.
Reproducible: Always
User Profile Reset: No
Additional Info:
This may be related to Bug 171484, since both involve incorrect handling of the
clrChange effect, but this issue occurs during document rendering/import rather
than PDF export.
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