Jacobo Aragunde Pérez 372388b7ed
Support rendering transparent bitmaps in presentations. (#990)
* Support rendering transparent bitmaps in presentations.

Add PictureShape.getAlpha() method and implementations for HSLF and
XSLF. Then make use of it in DrawPictureShape to apply the right alpha
value to the picture being drawn.

Fixed a bug in BitmapImageRenderer that considered alpha value 0 as
"fully opaque", when it means "fully transparent" instead.

Finally, added a test for this feature in TestDrawPictureShape for XSLF.
A test for HSLF could not be created because it was not possible to
generate a test file with today's tools; MS Office removes the
bitmap transparency effect when saving as .ppt, and LibreOffice blends
it into the bitmap.

* Address reviewer comments.

* Add comment about default alpha value.

* Prevent NPE in XSLFPictureShape.getAlpha().

* Change wording in comments to avoid the word "percentage".

* Use static vars for extreme alpha values.
2026-01-17 13:47:09 +01:00
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2025-07-30 18:54:05 +01:00