#!/usr/bin/env python
# GainEstimater.py
#   Copyright (C) 2006 CCLRC, Graeme Winter
#
#   This code is distributed under the BSD license, a copy of which is 
#   included in the root directory of this package.
# 
# A module to estimate the GAIN for a detector based on a number of images
# from a sweep. Will generate a GAIN value from a number of images in that 
# sweep and collect the average.
#
# Will also include some test code to estimate the error on that average.

import os
import sys
import exceptions
import math

if not os.environ.has_key('XIA2_ROOT'):
    raise RuntimeError, 'XIA2_ROOT not defined'
if not os.environ.has_key('XIA2CORE_ROOT'):
    raise RuntimeError, 'XIA2CORE_ROOT not defined'

if not os.environ['XIA2_ROOT'] in sys.path:
    sys.path.append(os.path.join(os.environ['XIA2_ROOT']))

from Wrappers.XIA.Diffdump import Diffdump

def gain(image):
    '''Get the gain from an image.'''

    dd = Diffdump()
    dd.set_image(image)
    return dd.gain()

def generate_gain(image_list):
    '''Get the mean and standard deviation in gain from a list
    of images.'''

    gains = []
    for image in image_list:
        gains.append(gain(image))
    
    sum = 0.0
    for g in gains:
        sum += g
    mean = sum / len(gains)

    sd = 0.0
    for g in gains:
        sd += (g - mean) * (g - mean)
    sd = math.sqrt(sd / len(gains))

    return mean, sd

if __name__ == '__main__':
    
    directory = os.path.join(os.environ['XIA2_ROOT'],
                             'Data', 'Test', 'Images')

    if len(sys.argv) == 1:
        
        print gain(os.path.join(directory, '12287_1_E1_001.img'))
        print gain(os.path.join(directory, '12287_1_E1_090.img'))
        
        print generate_gain([os.path.join(directory, '12287_1_E1_001.img'),
                             os.path.join(directory, '12287_1_E1_090.img')])


    else:

        print generate_gain(sys.argv[1:])
