Segmentation Fault using GRIP to process images in Python

Question

I'm using Python to get images from an IP camera over an ethernet connection, and then process them looking for specific targets. I am using GRIP to generate code to look for the specific targeted areas. (For those unfamiliar with GRIP: it basically offers you a GUI desktop interface where you can see a live video feed and alter parameters until you get the desired output. Then you can auto generate a piece of code—mine is in Python—that will perform that processing 'pipeline' on any image you feed into it in your code).

After extensively debugging my connection code, I finally got a successful working connection that gets the image from the IP camera and send it into the GRIP pipeline. However, the processing of the image is failing, and it's returning a Segmentation Fault, with no indicated line numbers. Here is the pipeline code (auto generated):

import cv2
import numpy
import math
from enum import Enum

class GripPipeline:
    """
    An OpenCV pipeline generated by GRIP.
    """
    
    def __init__(self):
        """initializes all values to presets or None if need to be set
        """

        self.__blur_type = BlurType.Median_Filter
        self.__blur_radius = 19.81981981981982

        self.blur_output = None

        self.__hsv_threshold_input = self.blur_output
        self.__hsv_threshold_hue = [72.84172661870504, 86.31399317406144]
        self.__hsv_threshold_saturation = [199.50539568345323, 255.0]
        self.__hsv_threshold_value = [89.43345323741006, 255.0]

        self.hsv_threshold_output = None

        self.__find_contours_input = self.hsv_threshold_output
        self.__find_contours_external_only = False

        self.find_contours_output = None

        self.__filter_contours_contours = self.find_contours_output
        self.__filter_contours_min_area = 500.0
        self.__filter_contours_min_perimeter = 0.0
        self.__filter_contours_min_width = 0.0
        self.__filter_contours_max_width = 1000.0
        self.__filter_contours_min_height = 0.0
        self.__filter_contours_max_height = 1000.0
        self.__filter_contours_solidity = [0, 100]
        self.__filter_contours_max_vertices = 1000000.0
        self.__filter_contours_min_vertices = 0.0
        self.__filter_contours_min_ratio = 0.0
        self.__filter_contours_max_ratio = 1000.0

        self.filter_contours_output = None


    def process(self, source0):
        """
        Runs the pipeline and sets all outputs to new values.
        """
        # Step Blur0:
        self.__blur_input = source0
        (self.blur_output) = self.__blur(self.__blur_input, self.__blur_type, self.__blur_radius)

        # Step HSV_Threshold0:
        self.__hsv_threshold_input = self.blur_output
        (self.hsv_threshold_output) = self.__hsv_threshold(self.__hsv_threshold_input, self.__hsv_threshold_hue, self.__hsv_threshold_saturation, self.__hsv_threshold_value)

        # Step Find_Contours0:
        self.__find_contours_input = self.hsv_threshold_output
        (self.find_contours_output) = self.__find_contours(self.__find_contours_input, self.__find_contours_external_only)

        # Step Filter_Contours0:
        self.__filter_contours_contours = self.find_contours_output
        (self.filter_contours_output) = self.__filter_contours(self.__filter_contours_contours, self.__filter_contours_min_area, self.__filter_contours_min_perimeter, self.__filter_contours_min_width, self.__filter_contours_max_width, self.__filter_contours_min_height, self.__filter_contours_max_height, self.__filter_contours_solidity, self.__filter_contours_max_vertices, self.__filter_contours_min_vertices, self.__filter_contours_min_ratio, self.__filter_contours_max_ratio)


    @staticmethod
    def __blur(src, type, radius):
        """Softens an image using one of several filters.
        Args:
            src: The source mat (numpy.ndarray).
            type: The blurType to perform represented as an int.
            radius: The radius for the blur as a float.
        Returns:
            A numpy.ndarray that has been blurred.
        """
        if(type is BlurType.Box_Blur):
            ksize = int(2 * round(radius) + 1)
            return cv2.blur(src, (ksize, ksize))
        elif(type is BlurType.Gaussian_Blur):
            ksize = int(6 * round(radius) + 1)
            return cv2.GaussianBlur(src, (ksize, ksize), round(radius))
        elif(type is BlurType.Median_Filter):
            ksize = int(2 * round(radius) + 1)
            return cv2.medianBlur(src, ksize)
        else:
            return cv2.bilateralFilter(src, -1, round(radius), round(radius))

    @staticmethod
    def __hsv_threshold(input, hue, sat, val):
        """Segment an image based on hue, saturation, and value ranges.
        Args:
            input: A BGR numpy.ndarray.
            hue: A list of two numbers the are the min and max hue.
            sat: A list of two numbers the are the min and max saturation.
            lum: A list of two numbers the are the min and max value.
        Returns:
            A black and white numpy.ndarray.
        """
        out = cv2.cvtColor(input, cv2.COLOR_BGR2HSV)
        return cv2.inRange(out, (hue[0], sat[0], val[0]),  (hue[1], sat[1], val[1]))

    @staticmethod
    def __find_contours(input, external_only):
        """Sets the values of pixels in a binary image to their distance to the nearest black pixel.
        Args:
            input: A numpy.ndarray.
            external_only: A boolean. If true only external contours are found.
        Return:
            A list of numpy.ndarray where each one represents a contour.
        """
        if(external_only):
            mode = cv2.RETR_EXTERNAL
        else:
            mode = cv2.RETR_LIST
        method = cv2.CHAIN_APPROX_SIMPLE
        im2, contours, hierarchy =cv2.findContours(input, mode=mode, method=method)
        return contours

    @staticmethod
    def __filter_contours(input_contours, min_area, min_perimeter, min_width, max_width,
                        min_height, max_height, solidity, max_vertex_count, min_vertex_count,
                        min_ratio, max_ratio):
        """Filters out contours that do not meet certain criteria.
        Args:
            input_contours: Contours as a list of numpy.ndarray.
            min_area: The minimum area of a contour that will be kept.
            min_perimeter: The minimum perimeter of a contour that will be kept.
            min_width: Minimum width of a contour.
            max_width: MaxWidth maximum width.
            min_height: Minimum height.
            max_height: Maximimum height.
            solidity: The minimum and maximum solidity of a contour.
            min_vertex_count: Minimum vertex Count of the contours.
            max_vertex_count: Maximum vertex Count.
            min_ratio: Minimum ratio of width to height.
            max_ratio: Maximum ratio of width to height.
        Returns:
            Contours as a list of numpy.ndarray.
        """
        output = []
        for contour in input_contours:
            x,y,w,h = cv2.boundingRect(contour)
            if (w < min_width or w > max_width):
                continue
            if (h < min_height or h > max_height):
                continue
            area = cv2.contourArea(contour)
            if (area < min_area):
                continue
            if (cv2.arcLength(contour, True) < min_perimeter):
                continue
            hull = cv2.convexHull(contour)
            solid = 100 * area / cv2.contourArea(hull)
            if (solid < solidity[0] or solid > solidity[1]):
                continue
            if (len(contour) < min_vertex_count or len(contour) > max_vertex_count):
                continue
            ratio = (float)(w) / h
            if (ratio < min_ratio or ratio > max_ratio):
                continue
            output.append(contour)
        return output


BlurType = Enum('BlurType', 'Box_Blur Gaussian_Blur Median_Filter Bilateral_Filter')

I realize that that is long, however I am less familiar with Python than other languages, so I wanted to offer all of it in the case that someone with much more Python experience might be able to spot some error in it.

Here is my code that I have written to get the image and feed it into the pipeline:

import numpy
import math
import cv2
import urllib.request
from enum import Enum
from GripPipeline import GripPipeline
from networktables import NetworkTable

frame = cv2.VideoCapture('https://10.17.11.1')

pipeline = GripPipeline()

def get_image()
    img_array = numpy.asarray(bytearray(frame.grab()))
    return img_array
while True:
    img = get_image()
    pipeline.process(img) #where the Segmentation Fault occurs

Does anyone have any idea on what could be causing this or how to fix it?

EDIT: It turns out that the error is coming from something in the second line of the process method, but I still don't know what. If anyone sees any flaws in what's being called there please let me know.

Answer 1

Try getting frames as tutorial suggests. Note renaming frame to cap:

cap = cv2.VideoCapture('https://10.17.11.1')

pipeline = GripPipeline()

while True:
    ret, img = cap.read()
    pipeline.process(img)