Tracing an OpenCV tutorial app with OpenCensus Python

traced-opencv-example.py

#!/usr/bin/env python3

"""
Copyright 2018, OpenCensus Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
u may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""
     
import os

# OpenCV stuff
import cv2
import numpy as np
from matplotlib import pyplot as plt

# Tracing
from opencensus.trace.samplers import always_on
from opencensus.trace.exporters import stackdriver_exporter
from opencensus.trace.exporters.transports.background_thread import BackgroundThreadTransport
from opencensus.trace.tracer import Tracer

def createAveraged(tracer, img):
    with tracer.span(name='createAveraged') as span:
        span.add_annotation('Creating Kernel')
        kernel = np.ones((5, 5), np.float32)/25
        span.add_annotation('Finished creating Kernel')
        span.add_annotation('Creating averaged image')
        dst = cv2.filter2D(img, -1, kernel)
        span.add_annotation('Finished creating averaged image')
        return dst

def drawBeforeAndAfterImages(tracer, plt, before, after):
    with tracer.span(name='drawBeforeAndAfterImages') as span:
        span.add_annotation('Starting to write original image')
        plt.subplot(121)
        plt.imshow(before)
        plt.title('Original')
        plt.xticks([])
        plt.yticks([])
        span.add_annotation('Finished writing original image')

        span.add_annotation('Starting to write averaged image')
        plt.subplot(122)
        plt.imshow(after)
        plt.title('Averaging')
        plt.xticks([])
        plt.yticks([])
        span.add_annotation('Finished writing averaged image')

def retrieveImage(tracer, path):
    with tracer.span(name='imread') as span:
        span.add_annotation('Starting imread')
        img = cv2.imread(path)
        span.add_annotation('Finished imread')
        return img

def main():
    # Create the tracer
    exporter = stackdriver_exporter.StackdriverExporter(
            project_id=os.environ.get('TRACED_CV_PROJECTID', 'census-demos'),
            transport=BackgroundThreadTransport)
    tracer = Tracer(sampler=always_on.AlwaysOnSampler(), exporter=exporter)

    with tracer.span(name='Visualize image'):
        img = retrieveImage(tracer, 'opencensus-logo.png')
        dst = createAveraged(tracer, img)
        drawBeforeAndAfterImages(tracer, plt, img, dst)

    plt.show()
    
if __name__ == '__main__':
    main()