Created attachment 162469 [details]
Image transparency get lost in Writer

Description:
I'm using LibreOffice 7.0.0.1.beta1 in the China locale and finding a very strange bug. I'll try to be as clear as possible in the description.
New spreadsheet document on LibreOffice 7.0.0.1.beta1,then insert picture,and set 
Transparency value,finally Save as Docx and open with LibreOffice 7.0.0.1.beta1,the transparency value is lost.

Steps to Reproduce:
1.New LibreOffice Writer text document.
2.Insert picture in png format.
3.Right-click the upper picture -> Properties -> Transparency -> set Transparency value -> OK
4.Save as OfficeOpenXML (*.docx) or Word2007-365 (*.docx) format.
5.Open the document with LibreOffice 7.0.0.1.beta1 again.
6.Picture transparency lost.

Actual Results:
The transparency value is lost.

Expected Results:
Transparency value remains unchanged.

Reproducible: 
Always

Additional Info:
Version: 7.0.0.0.beta1 (x64)
Build ID: 94f789cbb33335b4a511c319542c7bdc31ff3b3c
Environment:CPU threads: 12; OS: Windows 10.0 Build 18363; 
User Interface: UI render:Skia/Vulkan; VCL: win
Locale: zh-CN (zh_CN); UI: zh-CN
Misc:   Calc: threaded