Properly handle InputTransparentColor when dealing with Holes in mosaics

Description

When setting an inputTransparentColor, there are cases where the output image doesn't contain transparency.
As an instance if you request an area inside the mosaic bbox for which no granules exist, you may get an opaque result filled by background color.
We should improve that

Environment

None

Assignee

Daniele Romagnoli

Reporter

Daniele Romagnoli

Triage

None

Components

Fix versions

Affects versions

Priority

Medium
Configure