# bs.py
# Method:
# 0 - MOG2
# 1 - dynamic approach
#
# Kim Salmi, kim.salmi(at)iki(dot)fi
# http://tunn.us/arduino/falldetector.php
# License: GPLv3

# BackgroundSubtractorMOG2([history, varThreshold[, bShadowDetection]]) -> <BackgroundSubtractorMOG2 object>
# http://docs.opencv.org/2.4/modules/video/doc/motion_analysis_and_object_tracking.html#backgroundsubtractormog2

import cv2
import settings

class Bs:
	def __init__(self):
		self.settings = settings.Settings()
		self.method = self.settings.bsMethod

		if self.method == 0:
			self.fgbg = cv2.BackgroundSubtractorMOG2(self.settings.MOG2history, 
				self.settings.MOG2thresh, self.settings.MOG2shadow)
			self.foregroundMask = None

		if self.method == 1:
			self.backgroundFrame = None
			self.frameCount = 1

	def updateBackground(self, frame):
		if self.method == 0:
			self.foregroundMask = self.fgbg.apply(frame, self.foregroundMask, 
				self.settings.MOG2learningRate)

		if self.method == 1:
			alpha = (1.0/self.frameCount)
			if self.backgroundFrame is None:
				self.backgroundFrame = frame
			self.backgroundFrame = cv2.addWeighted(frame, alpha, 
				self.backgroundFrame, 1.0-alpha, 0)
			self.frameCount += 1

	def compareBackground(self, frame):
		if self.method == 0:
			return self.foregroundMask

		if self.method == 1:
			self.frameDelta = cv2.absdiff(self.backgroundFrame, frame)
			self.foregroundMask = cv2.threshold(self.frameDelta, 
				self.settings.thresholdLimit, 255, cv2.THRESH_BINARY)[1]
			return self.foregroundMask

	def deleteBackground(self):
		if self.method == 0:
			self.foregroundMask = None

		if self.method == 1:
			self.backgroundFrame = None

	def resetBackgroundIfNeeded(self, frame):
		if self.method == 0:
			if self.foregroundMask is None:
				self.foregroundMask = self.fgbg.apply(frame)

		if self.method == 1:
			if self.backgroundFrame is None:
				self.updateBackground(frame)
				self.frameCount = 1