![]() ![]() Line 10 defines our order_points_old function. Otherwise, if you do have imutils installed, you should upgrade to the latest version (which has the updated order_points implementation): $ pip install -upgrade imutils ![]() We’ll be using the imutils package later in this blog post, so if you don’t already have it installed, be sure to install it via pip : $ pip install imutils Lines 2-8 handle importing our required Python packages for this example. # whereas the bottom-left will have the largest difference # top-right point will have the smallest difference, # now, compute the difference between the points, the # the bottom-right point will have the largest sum # the top-left point will have the smallest sum, whereas # bottom-right, and the fourth is the bottom-left # the second entry is the top-right, the third is the # such that the first entry in the list is the top-left, # initialize a list of coordinates that will be ordered To get started, open up a new file and name it order_coordinates.py : # import the necessary packages I have renamed the (flawed) order_points method to order_points_old so we can compare our original and updated methods. The original (flawed) methodīefore we can learn how to arrange a set of bounding box coordinates in (1) clockwise order and more specifically, (2) a top-left, top-right, bottom-right, and bottom-left order, we should first review the order_points method detailed in the original 4 point getPerspectiveTransform blog post. ![]() By resolving this bug, our order_points function will no longer be susceptible to a debilitating bug.Īll that said, let’s get this blog post started by reviewing the original, flawed method at ordering our bounding box coordinates in clockwise order. The secondary purpose is to address a subtle, hard-to-find bug in the order_points method of the imutils package.Organizing bounding box coordinates in such an order is a prerequisite to performing operations such as perspective transforms or matching corners of objects (such as when we compute the distance between objects). The primary purpose is to learn how to arrange the (x, y)-coordinates associated with a rotated bounding box in top-left, top-right, bottom-right, and bottom-left order.Looking for the source code to this post? Jump Right To The Downloads Section Ordering coordinates clockwise with Python and OpenCV To learn more about this bug, and how to squash it, keep reading. You see, there are cases where the pre-processing step of arranging our four points in top-left, top-right, bottom-right, and bottom-left order can return incorrect results! Our perspective transform has a deadly flaw that makes it unsuitable for use in production environments. ![]() Even though this tutorial is over a year old, its still one of the most popular blog posts on PyImageSearch.īuilding our mobile document scanner was predicated on our ability to apply a 4 point cv2.getPerspectiveTransform with OpenCV, enabling us to obtain a top-down, birds-eye-view of our document. However, before we start learning how to measure the size (and not to mention, the distance between) objects in images, we first need to talk about something…Ī little over a year ago, I wrote one my favorite tutorials on the PyImageSearch blog: How to build a kick-ass mobile document scanner in just 5 minutes. I’m super excited to get them underway - and I’m sure you are too. These tutorials have been some of the most heavily requested lessons on the PyImageSearch blog. Today we are going to kick-off a three part series on calculating the size of objects in images along with measuring the distances between them. Click here to download the source code to this post ![]()
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