vgx11: fix translate offset
Address issue #179 by translating the image to (0,-h) so (0,0) is at the bottom-left corner for the X11 backend.
go test ./... will skip the X11 test if $DISPLAY is not defined.
Address issue #179 by translating the image to (0,-h) so (0,0) is at the bottom-left corner for the X11 backend.
go test ./... will skip the X11 test if $DISPLAY is not defined.