In this tutorial, you will learn how to compute image histograms using OpenCV and the cv2.calcHist function. Histograms are prevalent in nearly every aspect of computer vision. We use grayscale histograms for thresholding. We use histograms for white balancing. We…

In this tutorial, you will learn how to perform automatic color correction with OpenCV using a color matching/balancing card. Last week we discovered how to perform histogram matching. Using histogram matching, we can take the color distribution of one image…

In this tutorial, you will learn how to perform histogram matching using OpenCV and scikit-image. Last week we discussed histogram equalization, a basic image processing technique that can improve the contrast of an input image. But what if you wanted…

In this tutorial, you will learn to perform both histogram equalization and adaptive histogram equalization with OpenCV. Histogram equalization is a basic image processing technique that adjusts the global contrast of an image by updating the image histogram’s pixel intensity…

This is a guest post by Michael Herman from Real Python – learn Python programming and web development through hands-on, interesting examples that are useful and fun! In this tutorial, we’ll take the command line image search engine from the…

Let’s face it. Trying to search for images based on text and tags sucks. Whether you are tagging and categorizing your personal images, searching for stock photos for your company website, or simply trying to find the right image for…

Take a second to look at the Jurassic Park movie poster above. What are the dominant colors? (i.e. the colors that are represented most in the image) Well, we see that the background is largely black. There is some red…

If you haven’t noticed, the term “feature vector” is used quite often in this blog. And while we’ve seen it a lot, I wanted to dedicate an entire post to defining what exactly a feature vector is. What is an…

It’s…it’s a histogram. – Dr. Grant Okay. So maybe that isn’t the exact quote. But I think Dr. Grant would have been equally thrilled had he known the power of color histograms. And more importantly, when the power goes out,…