Functions.py

import math
import cv2


class ifChar:
    # this function contains some operations used by various function in the code
    def __init__(self, cntr):
        self.contour = cntr

        self.boundingRect = cv2.boundingRect(self.contour)

        [x, y, w, h] = self.boundingRect

        self.boundingRectX = x
        self.boundingRectY = y
        self.boundingRectWidth = w
        self.boundingRectHeight = h

        self.boundingRectArea = self.boundingRectWidth * self.boundingRectHeight

        self.centerX = (self.boundingRectX + self.boundingRectX + self.boundingRectWidth) / 2
        self.centerY = (self.boundingRectY + self.boundingRectY + self.boundingRectHeight) / 2

        self.diagonalSize = math.sqrt((self.boundingRectWidth ** 2) + (self.boundingRectHeight ** 2))

        self.aspectRatio = float(self.boundingRectWidth) / float(self.boundingRectHeight)


class PossiblePlate:

    def __init__(self):
        self.Plate = None
        self.Grayscale = None
        self.Thresh = None

        self.rrLocationOfPlateInScene = None

        self.strChars = ""


# this function is a 'first pass' that does a rough check on a contour to see if it could be a char
def checkIfChar(possibleChar):
    if (possibleChar.boundingRectArea > 80 and possibleChar.boundingRectWidth > 2
            and possibleChar.boundingRectHeight > 8 and 0.25 < possibleChar.aspectRatio < 1.0):

        return True
    else:
        return False


# check the center distance between characters
def distanceBetweenChars(firstChar, secondChar):
    x = abs(firstChar.centerX - secondChar.centerX)
    y = abs(firstChar.centerY - secondChar.centerY)

    return math.sqrt((x ** 2) + (y ** 2))


# use basic trigonometry (SOH CAH TOA) to calculate angle between chars
def angleBetweenChars(firstChar, secondChar):
    adjacent = float(abs(firstChar.centerX - secondChar.centerX))
    opposite = float(abs(firstChar.centerY - secondChar.centerY))

    # check to make sure we do not divide by zero if the center X positions are equal
    # float division by zero will cause a crash in Python
    if adjacent != 0.0:
        angleInRad = math.atan(opposite / adjacent)
    else:
        angleInRad = 1.5708

    # calculate angle in degrees
    angleInDeg = angleInRad * (180.0 / math.pi)

    return angleInDeg