Measure size of objects in an image using OpenCV

The project provides a script to read an image and based on the dimensions of a reference object find the dimensions of other objects in a scene. The reference object must be the leftmost object in the scene. In sample images given, a box of dimension 2cm x 2cm is taken as a reference object.

For any other reference object provide actual width of the object. (change line 59 in file 'init.py')

Constraints

1. Shadow effect: use dark braground
2. Object boundry: use contrasting background

Getting Started

Prerequisites

Python 3 Pip OpenCV Numpy

Installing

For python and pip installation follow this blog

1. For windows https://www.howtogeek.com/197947/how-to-install-python-on-windows/
2. For Linux https://docs.python-guide.org/starting/install3/linux/

Other prerequisites:

• pip install numpy
• pip install opencv-python

Algorithm

1. Image pre-processing

• Read an image and convert it it no grayscale
• Blur the image using Gaussian Kernel to remove un-necessary edges
• Edge detection using Canny edge detector
• Perform morphological closing operation to remove noisy contours

2. Object Segmentation

• Find contours
• Remove small contours by calculating its area (threshold used here is 100)
• Sort contours from left to right to find the reference objects

3. Reference object

• Calculate how many pixels are there per metric (centi meter is used here)

4. Compute results

• Draw bounding boxes around each object and calculate its height and width

Results

Authors

• Shashank Sharma

Acknowledgments

• https://www.pyimagesearch.com/