Installing OpenCV got easier

OpenCV is undoubtedly the unmatched de facto standard library for computer vision. Not only does it provide a near complete set of vision algorithms, the set of primitive graphics functions it provides to manipulate images makes it essential to many of our projects.

OpenCV being used when building a Keras CNN model

Installing the latest version of OpenCV used to be hard. The pre-built binaries available was never up to the tasks we wanted. Compiling from source was an option, but was tedious and time consuming.

Then, we got the anaconda versions of OpenCV from Conda-Forge, which we could simply install using,

conda install -c conda-forge opencv

Now, things are going to be simpler, as Anaconda native OpenCV packages are now available.

Using Multiple Cameras with OpenCV

As you know, OpenCV is capable of reading from any connected camera in your system, whether it's a built-in webcam (in a laptop) or a USB connected one.

But what if, you wanted to read from more than one cam at the same time?

Can OpenCV handle it?

OpenCV accessing 2 cameras at once

Yes, it can!

It's quite simple. Here's how to do it.

Track any object in a video with Dlib Correlation Trackers

Training an object detector is bit of a complicated task. You need to have a proper training dataset with the relevant bounding boxes, and then use something like a HOG feature extractor with a SVM classifier for the detection - such as the Dlib Object Detection classes (link).

But that's a lot of work if you just need to track an object across a limited number of frames, or just need to detect motion or direction of movement. For that, we can easily use the Correlation Trackers feature in Dlib.

Object Tracking

See it in action,

Object Tracking in Action

Correlation Trackers - as their name suggests - works by correlating a set of pixels from one frame to the next.

Let's see how to build it.

Need More Fonts on OpenCV?

OpenCV has a built-in simple function to add text on your images - the cv2.putText() function. With just one line of code, you can add text anywhere on the image. You just need to specify the position, colour, scale (font size), and which the font to use as the minimum parameters.

 cv2.putText(image,  
           text_to_show,  
           (20, 40),  
           fontFace=cv2.FONT_HERSHEY_SIMPLEX,  
           fontScale=1,  
           color=(255, 255, 255))  

OpenCV also gives you a choice from a handful of fonts - all variants of the "Hershey" font.

But, there may come a point where you want more fonts. Have you wished that you could use a specific True Type or Open Type font on OpenCV?

The good news is, it's possible.

True Type Fonts working on OpenCV

Snapchat like Image Overlays with Dlib, OpenCV, and Python

You're probably familiar with Snapchat, and it's filters feature where you can put some cool and funny image overlays on your face images. As computer vision enthusiasts, we typically look at applications like these, and try to understand how it's done, and whether we can build something similar.

It turns out, we can make our own application with Snapchat like image overlays using Python, OpenCV, and Dlib.

Snapchat like Image Overlays with Dlib, OpenCV, and Python

So, how do we build it?

1. We'll first load the Webcam feed using OpenCV.
2. We'll load an image (in our example, and image for the 'eye') to be used as the overlay.
3. Use Dlib's face detection to localize the faces, and then use facial landmarks to find where the eyes are.
4. Calculate the size and the position of the overlay for each eye.
5. Finally, place the overlay image over each eye, resized to the correct size.

Let's start.

Wink Detection using Dlib and OpenCV

A couple of weeks ago, I was going through a tutorial for eye blink detection by Adrian at PyImageSearch. It was an excellent tutorial, which explained the use of Eye Aspect Ratio (EAR) in order to detect when an eye gets closed. Then, few weeks back, I was having a chat with Shirish Ranade, a reader of this blog and a fellow computer vision and machine learning enthusiast, on whether we can perform an action by winking at the computer. So, I decided to try out a code to detect winking.

Wink Detection Running with Dlib and OpenCV

It's an interesting idea to perform an action or a task just by winking at your computer. It can be thought as a form of gesture detection or facial expression detection as well. So, here's how you can build your own 'wink' detector for it.

We start by importing all the necessary packages,

 import numpy as np  
 import cv2  
 import dlib  
 from scipy.spatial import distance as dist  

OpenCV 3.2 and Dlib 19.4 Packages Now Available from Conda-Forge

Anaconda is an asset for us Machine Learning enthusiasts. Not only does it have the ability to create fully isolated Python environments, its pre-built packages for many operating systems and architectures helps you to spend less time setting up, and more time doing actual machine learning stuff.

In some scenarios, to get some Python packages to work in certain environments, getting them from Anaconda was the only way that worked. If you tried installing Dlib or OpenCV 3 on Windows 64-Bit, then you know the effort it takes to get them setup, if it wasn't for Anaconda.

OpenCV and Dlib working perfectly together, thanks to Conda

If you check my posts on Installing Dlib on Anaconda Python on Windows, and Installing OpenCV 3 on Anaconda Python 3.5 on Windows, you know how easy it is to use conda to install them on Python 3.5 64-Bit on Windows.

But there was a catch: The Anaconda registry only had OpenCV 3.1 and Dlib 19.0 - not the latest versions.

Extracting individual Facial Features from Dlib Face Landmarks

If you remember, in my last post on Dlib, I showed how to get the Face Landmark Detection feature of Dlib working with OpenCV. We saw how to use the pre-trained 68 facial landmark model that comes with Dlib with the shape predictor functionality of Dlib, and then to convert the output of into a numpy array to use it in an OpenCV context. We were able to get all 68 feature points on to our face image.

Dlib detecting the 68 Face Landmarks

The 68 feature points which the Dlib model detects include the Jawline of the face, left and right eyes, left and right eyebrows, the nose, and the mouth. So, what if you only want to detect few of those features on a face? E.g. you may only want to detect the positions of the eyes and the nose. Is there a way to extract only few of the features from the Dlib shape predictor?

There is actually a very simple way to do that. Here’s how.

Installing OpenCV 3 on Anaconda Python 3.5 on Windows

If you checked my last post, you know that TensorFlow now officially works on Windows. This was really exciting to me, since I was using a Linux machine for my TensorFlow experiments, I had to switch between the Linux and Windows for my other tasks. Now, I should be able to perform some of those experiments on Windows as well. (I would still switch to Linux for more processor intensive deep learning models). So, I decided to set everything up on Windows again.

I've been using OpenCV 3 on Anaconda Python 3.5 on Linux. (Check out my guide on Installing OpenCV from source on Anaconda Python on Ubuntu 16.10 if you are trying to install on Linux). But on Windows, I've previously only tried OpenCV on Python 2.7. Since the OpenCV Downloads page has pre-built binaries for OpenCV 3 (version 3.2 being latest), I thought the installation would be straightforward.

I downloaded and ran the OpenCV 3.2 installer (which just extracts OpenCV to a directory of your choosing), set the OPENCV_DIR environment variable, add the bin dir in OpenCV to the PATH, and finally copy the cv2.pyd file to the site-packages directory in my Anaconda environment. I fired up the Anaconda environment, and tried loading cv2 in Python. But I got the following error,

 (tensorflow) C:\>python  
 Python 3.5.2 |Continuum Analytics, Inc.| (default, Jul 5 2016, 11:41:13) [MSC v  
 .1900 64 bit (AMD64)] on win32  
 Type "help", "copyright", "credits" or "license" for more information.  
 >>> import cv2  
 Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
 ImportError: DLL load failed: The specified module could not be found.  

Installing OpenCV from source on Anaconda Python on Ubuntu 16.10

I recently switched to Linux for my Machine Learning experiments, and I did a post on How to install Keras and Anaconda Python on Ubuntu 16.10.

Now, I wanted to install OpenCV on Ubuntu also. Since OpenCV does not have a pre-built package for Linux, it meant I had to compile OpenCV from source.

OpenCV 3.1 running on Lubuntu 16.10

Adrian of PyImageSearch has recently done a post about how to compile OpenCV on Ubuntu 16.04 using virtualenv. I followed his steps as a base, but had to make numerous adjustments to some of the packages which gets installed (e.g. libpng-dev, libhdf5-serial-dev) and the build commands due to the changes from Ubuntu 16.04 to 16.10, and because I'm using Anaconda environments rather than virtualenv.

I'll be installing OpenCV 3.1, and will be using the Lubuntu 16.10 virtual machine which I used in my earlier post. But the steps and commands will be exactly the same for any flavor of Ubuntu 16.10.

First, as a habit, get and install the latest updates for Ubuntu,

 sudo apt-get update   
 sudo apt-get upgrade   

Then (if you have not done already) install the necessary build tools,

 sudo apt-get install build-essential cmake git unzip pkg-config  

Then, we install the following packages which allows OpenCV to interact with various image and video formats,

 sudo apt-get install libjpeg8-dev libtiff5-dev libjasper-dev libpng-dev  
 sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev  
 sudo apt-get install libxvidcore-dev libx264-dev  

Note: on Ubuntu 16.04, the package name for libpng was libpng12-dev. But on 16.10, it should be libpng-dev.

Getting the LeNet model working with Face Recognition

In my last post, I talked about how the LeNet Convolutional Neural Network model is capable of handling much more complex data than the intended MNIST dataset. We saw how it got ~99% accuracy when it learned to identify 10 faces from the raw pixel intensities.

So, let’s see the code I used to get it working.

First of all, I needed a training dataset. For that, I created a set of face images of 10 subjects with around 500 images each.

The training dataset (yep, that's my face)

I use a file naming convention as <subject_label>-<subject_name>-<unique_number>.jpg (e.g. 0-Thimira-1475137898.65.jpg) for the training images to make it easier to read in and get the metadata of the images in one go. (I will do a separate post on how to easily create training datasets of face images like this).

We'll mainly be using Keras to build the model, and scikit-learn for some utility functions. We’ll need to import the following packages,

 from sklearn.cross_validation import train_test_split  
 from keras.optimizers import SGD  
 from keras.utils import np_utils  
 import numpy as np  
 import argparse  
 import cv2  
 import os  
 import sys  
 from PIL import Image  

Getting Dlib Face Landmark Detection working with OpenCV

Dlib has excellent Face Detection and Face Landmark Detection algorithms built-in. Its face detection is based on Histogram of Oriented Gradients (HOG) feature combined with a linear classifier, on a sliding window detection scheme (Ref. http://dlib.net/) and it provides pre-trained models for face landmark detection. It also provides handy utility functions like dlib.get_frontal_face_detector() to make our lives easier.

Dlib Face Landmark Detection in action

Note: Image used for testing is in the Public Domain - https://en.wikipedia.org/wiki/File:Arnold_Schwarzenegger_edit%28ws%29.jpg

To check out Dlib with it's native functions, you can try out the Dlib example from the official site: http://dlib.net/face_landmark_detection.py.html.It works well, but we can do better.

Although Dlib offers all the simplicity in implementing face landmark detection, it's still no match for the flexibility of OpenCV. (Simply put, Dlib is a library for Machine Learning, while OpenCV is for Computer Vision and Image Processing)

So, can we use Dlib face landmark detection functionality in an OpenCV context? Yes, here's how.