UIBezierPath Warped Shadow for RubyMotion, idea from http://nscookbook.com/2013/01/ios-programming-recipe-10-adding-a-shadow-to-uiview/

warpshadow.rb

# =================================
# = Warped shadow for any CGLayer =
# =================================
def warpShadow(rect, offset)
  size = rect.size
  path = UIBezierPath.bezierPath
 
  # Top/Right:  ````|
  path.moveToPoint([offset, offset]) 
  path.addLineToPoint([size.width - offset, offset])
  path.addLineToPoint([size.width - (offset * 0.75), size.height + offset])
 
  # Bottom/Left:  |.-`-.
  path.addQuadCurveToPoint([offset * 0.75, size.height + offset],
       controlPoint:[size.width / 2.0, size.height - offset])
  path.closePath
  
  path.CGPath
end

# ---------------------------------------------------------------------------------------
# Example: http://shell.reverse.net/~dphase/sshots/warpshadow.png
# Source:

box = UIView.alloc.initWithFrame([[30,30],[400,75]]).tap do |v|
  v.backgroundColor     = 0x6c8ea3.uicolor(0.8)
  v.layer.shadowOffset  = CGSizeZero # Set zero since offset is handled by warpShadow method
  v.layer.shadowColor   = :black.uicolor.cgcolor
  v.layer.shadowOpacity = 0.5
  v.layer.shadowRadius  = 1.25
  v.layer.shadowPath    = warpShadow(v.layer.bounds, 5) # Params are current layer and offset
end
    
view << box

Example screenshot:

http://shell.reverse.net/~dphase/sshots/warpshadow.png