Well after a bit more playing I've got it.
// Project: scaling sprites
// Created: 2015-07-05
// set window properties
SetWindowTitle( "scaling sprites" )
SetWindowSize( 1024, 768, 0 )
// set display properties
SetVirtualResolution( 1024, 768 )
SetOrientationAllowed( 1, 1, 1, 1 )
loadimage(1,"enemyplane.png",1)
type enemyplanestype
xoffset as float
yoffset as float
scale as float
randomspeed as float
endtype
global dim enemyplane[10] as enemyplanestype
for r=1 to 10
enemyplane[r].xoffset=random(0,960)
enemyplane[r].yoffset=random(20,700)
enemyplane[r].scale=random(1,10)/100
enemyplane[r].randomspeed=random(1,2)
createsprite(r,1)
setspriteoffset(r,getspritewidth(r)/2,getspriteheight(r)/2)
next r
do
for s=1 to 10
drawplanes(s)
next s
sync()
loop
function drawplanes(id)
enemyplane[id].scale=(enemyplane[id].scale+enemyplane[id].randomspeed)
setspritescalebyoffset(id,enemyplane[id].scale/200,enemyplane[id].scale/200)
setspritepositionbyoffset(id,enemyplane[id].xoffset,enemyplane[id].yoffset)
if getspritewidth(id)>200
enemyplane[id].xoffset=random(0,960)
enemyplane[id].yoffset=random(20,700)
enemyplane[id].scale=random(1,10)/100
enemyplane[id].randomspeed=random(1,2)
endif
endfunction
I'm not too sure if that is the most economical way to do it but it works.
Happy for some feedback
DBPro is the new Amos (I hope)