Delving into Histogram and Filters

In the last chapter, we learned the basics of user interfaces in OpenCV, using Qt libraries or native ones; we also learned how to use advanced OpenGL user interfaces. We learned about basic color conversions, and filters that allow us to create our first application. This chapter will introduce you to the following concepts:

• Histogram and histogram equalization
• Look-up tables
• Blur and median blur
• Canny filter
• Image-color equalization
• Understanding the conversion between image types

After we learn the basics of OpenCV and user interfaces, we are going to create our first complete application in this chapter, a basic photo tool, and cover the following topics:

• Generating a CMake script file
• Creating the graphical user interface
• Calculating and drawing a histogram
• Histogram equalization
• The lomography camera effect
• The cartoonize effect

This application will help us to understand how to create an entire project from scratch and understand the histogram concept. We will see how to equalize the histogram of the color image and create two effects, using a combination of filters and the use of look-up tables.