enabledirectinput 1

Graphics 800,600,0,2
Global temporary=CreateImage(800,600) ;<<<WICHTIG!

image=CreateImage(400,300,1)
SetBuffer ImageBuffer(image)
For i=1 To 100
  Color Rand(255),Rand(255),Rand(255)
  Oval Rand(-50,350),Rand(-50,250),Rand(10,100),Rand(10,100),1
Next

ClsColor 0,0,255

While Not KeyHit(1)
  x2=x1
  y2=y1
  x1=MouseX()
  y1=MouseY()
  If x1<>x2 Or y1<>y2 Then
    SetBuffer BackBuffer()
    ClsColor 0,0,255
    Cls
    drawscaled image,BackBuffer(),0,0,x1,y1
    Flip
  EndIf
Wend

WaitKey()
FreeImage temporary
FreeImage image
End


;---------------------------------------------------------------------
Function drawscaled(src,dest,x,y,width,height)
  src_width  =ImageWidth (src)
  src_height =ImageHeight(src)
  src_buffer =ImageBuffer(src)
  tmp_buffer =ImageBuffer(temporary)
  div_x#     =Float#(src_width) /Float#(width)
  div_y#     =Float#(src_height)/Float#(height)
  If width=0 Or height=0 Or src_width=0 Or src_height=0 Then Return

  SetBuffer tmp_buffer
  ClsColor 0,0,0
  Cls

  For i=0 To width-1
    CopyRect i*div_x#,0,1,src_height,i,0,src_buffer,tmp_buffer
  Next

  For i=0 To height-1
    CopyRect 0,i*div_y#,width,1,x,y+i,tmp_buffer,dest
  Next
End Function