If you create a Python module called "myext" (source code below) that exports a Python function "average", you can do your own image processing as follows, in a Scorpion Python script tool:

import arr,myext

im = GetImageMatr('1')
r,c = im.dim()
format = im.elemtype()
p = arr.getArrDataPointer(im)
avg = myext.average(p,r,c,format)
# avg now contains your result...

For instructions on how to create a Python module, please consult the Python docs, or "Python Essential Reference" by David M. Beazley, where you will find detailed documentation on how to create a Python extension. Below you will find the source code for the "myext" module, written in C. The "image processing" is done in the routine average, which gets a pointer to the image data. The routine _average is the Python interface.

myext.h

/**************************************************************************
* myext.h
* 
* Skeleton Python extension
**************************************************************************/

#include "Python.h"

#define byte unsigned char

myext.c

/**************************************************************************
* myext.c
* 
* Skeleton Python extension
**************************************************************************/

#define DLL_PREFIX __declspec(dllexport)

#include "myext.h"

// c image processing routine...

static double average(byte *image,int rows,int cols)
{
  double sum = 0;
  int n = rows*cols;
  int i;
  for (i=0;i<n;i++) sum += *image++;
  return sum/n;
}

// python callable methods

static PyObject *_average(PyObject *self,PyObject *args)
{
  int rows;
  int cols;
  char *format;
  byte *image;
  if (!PyArg_ParseTuple(args,"iiis",&image,&rows,&cols,&format))
    return NULL;
  if (strcmp(format,"uint8")) {
    PyErr_SetString(PyExc_TypeError,"Non-supported image format. Must be 'uint8'");
    return NULL;
  }
  return Py_BuildValue("d",average(image,rows,cols));
}

// module methods table
static struct PyMethodDef myext_methods[] = {
  // DLL exports
  {"average",_average,METH_VARARGS},
  // sentinel
  {NULL, NULL}
};

DLL_PREFIX void initmyext()
{
  PyObject *m;
  m = Py_InitModule("myext", myext_methods);
}