Strange behavior in scaling an image

Can anyone tell me the difference between

self.image = Fox::FXJPGImage.new(app, io.read).scale(100,100,1)

and

self.image = Fox::FXJPGImage.new(app, io.read)
self.image.scale(100,100,1)

???

The former makes the image appear like a point, such as it wasn’t
loaded, while the latter makes it scaling in the right way.