I am having trouble with -compose copy_opacity.
Test:
IM 6.7.6.9beta: (transparency not showing)
convert logo: -resize 50% logo2.png

convert logo2.png -fill black -opaque white -fill white +opaque black logo2mask.png

convert logo2.png logo2mask.png -alpha off -compose copy_opacity -composite logo2trans2.png

IM 6.7.4.10 (same input images as above) (transparency showing fine)
im6 convert logo2.png logo2mask.png -alpha off -compose copy_opacity -composite logo2trans1.png
