You overwrite all of your inputs with constant parameters, so no matter what is passed in, you always do the same thing. You should generally only assign to the parameters if you detect that the parameter is missing.
Your call to dataterm() should be passing in all three parameters.
You do not happen to show the code for inellipse(). You should be sure to check whether it takes an image data array (as most routines do), or if it takes an image file name (which is what you are passing in.)
Note: you should never name a variable "image" as that interferes with using the image() graphics routine.
