You could also try this plugin from TIG: OBJ Exporter v3.0 (It’s the one I use)
I am able to create obj file with the last plugin. So far it is the best I have been able to do, though not as good as you earlier showed.
Eventually ! Many thanks to @mihai.s
The dim appearance changed when I modified the accompanying mtl file:
newmtl Image1
Ka 1 1 1
Kd 1 1 1
Ks 0.333 0.333 0.333
Ns 0
d 1
Tr 1
map_Kd sag_Textures/Image1.PNG
#EOF
I changed the Ka, Kd values to 1 1 1. Earlier they were smaller.