[gdal-dev] Blending mode when composing images in a VRT

[Sandro Mani]

Hi

Take the following [1] VRT which composes two images of semitransparent 
polygons on transparent background. Loading this into QGIS, it looks the 
images are not blended together, i.e. in overlapping areas the ARGB 
pixel values of the last image listed in a VRTRasterBand are the ones 
which end up being rendered, see [2]. I haven't found anything regarding 
blending modes in VRT datasets. Is there currently any way to have the 
images blended together?

Thanks
Sandro

[1] https://smani.fedorapeople.org/tmp/vrttest.zip
[2] https://smani.fedorapeople.org/tmp/vrt.png