: unexpected white box
convert -size 1x1 xc:blue ^
-filter point -virtual-pixel tile -define distort:viewport=250x150+0+0 -distort SRT 0 +repage ^
( rose: -rotate 10 -geometry +50+50 ) -composite ^
out_1.png

: shows size of white box to be 250x150
convert -size 1x1 xc:blue ^
-filter point -virtual-pixel tile -define distort:viewport=250x150+0+0 -distort SRT 0 +repage ^
+duplicate -append +duplicate +append ^
( rose: -rotate 10 -geometry +50+50 ) -composite ^
out_2.png

: works when rose is not rotated
convert -size 250x150 xc:blue ^
-filter point -virtual-pixel tile -define distort:viewport=250x150+0+0 -distort SRT 0 +repage ^
( rose: -geometry +50+50 ) -composite ^
out_3.png

: works when background is not tiled
convert -size 250x150 xc:blue ^
( rose: -rotate 10 -geometry +50+50 ) -composite ^
out_4.png

ImageMagick 6.8.8-1 Q16 x64 on Windows 7
EDIT: Subject