collisions optimization

for 1) this ?

Function RectsOverlap%(x0, y0, w0, h0, x2, y2, w2, h2)
If x0 > (x2 + w2) Or (x0 + w0) < x2 Then Return False
If y0 > (y2 + h2) Or (y0 + h0) < y2 Then Return False
Return True
End Function

for 2 this ?
(stored for each sprite)

local radius# = sqr( ImageWidth(img)*ImageWidth+ImageHeight(Img)*Imageheight)


and for 3 ImagesCollide;-)