bmaptool

TLDR

Create a blockmap from image file

$ bmaptool create -o [blockmap.bmap] [source.img]

Copy an image file into sdb

$ bmaptool copy --bmap [blockmap.bmap] [source.img] [/dev/sdb]

Copy a compressed image file into sdb

$ bmaptool copy --bmap [blockmap.bmap] [source.img.gz] [/dev/sdb]

Copy an image file into sdb without using a blockmap

$ bmaptool copy --nobmap [source.img] [/dev/sdb]