Normal Blend black outs base image

[fazal-e-majid]

I've two images (given below) and I want to blend them using NormalBlend.

Background

Blend Image

After applying Normal Blend like so:

var background = PictureInput(imageName: "sBackground.jpg")
var blendImage = PictureInput(imageName: "front.jpg")

var transformOperation = TransformOperation()
transformOperation.transform = Matrix4x4(getScaledCGAffineTransform( ) )

var normalBlend = NormalBlend()

background.addTarget(normalBlend, atTargetIndex: 0)

blendImage.addTarget(transformOperation)
transformOperation.addTarget(normalBlend, atTargetIndex: 1)

normalBlend.addTarget(renderView)

background.processImage()
blendImage.processImage()

I get this result :

But this is not what I want and expect. Instead I want my result to be like this:

@BradLarson , @joshbernfeld if you could help me please.
Thank you very much.