Book Image

OpenCV 3.0 Computer Vision with Java

By : Daniel Lelis Baggio
Book Image

OpenCV 3.0 Computer Vision with Java

By: Daniel Lelis Baggio

Overview of this book

Table of Contents (15 chapters)
OpenCV 3.0 Computer Vision with Java
About the Author
About the Reviewers

Histogram equalization

The human visual system is very sensitive to contrast in images, which is the difference in the color and brightness of different objects. Besides, the human eye is a miraculous system that can feel intensities at the 1016 light levels [4]. No wonder some sensors could mess up the image data.

When analyzing images, it is very useful to draw their histograms. They simply show you the lightness distribution of a digital image. In order to do that, you need to count the number of pixels with the exact lightness and plot that as a distribution graph. This gives us a great insight into the dynamic range of an image.

When a camera picture has been captured with a very narrow light range, it gets difficult to see the details in the shadowed areas or other areas with poor local contrast. Fortunately, there's a technique to spread frequencies for uniform intensity distribution, which is called histogram equalization. The following image shows the same picture with their respective...