bug correction  in the 2 layer opacity slider
bug correction  in the 2 layer opacity slider

aabadie/medInria-public,aabadie/medInria-public,NicolasSchnitzler/medInria-public,rdebroiz/medInria-public,rdebroiz/medInria-public,NicolasSchnitzler/medInria-public,aabadie/medInria-public,NicolasSchnitzler/medInria-public,rdebroiz/medInria-public