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OpenCV Articles
Found 107 articles
How to detect a rectangle and square in an image using OpenCV Python?
To detect a rectangle and square in an image, we first detect all the contours in the image. Then Loop over all contours. Find the approximate contour for each of the contours. If the number of vertex points in the approximate contour is 4 then we compute the aspect ratio to make a difference between the rectangle and square. If the aspect ratio is between 0.9 and 1.1 we say it is a square else a rectangle See the below pseudocode. for cnt in contours: approx = cv2.approxPolyDP(cnt) if len(approx) == 4: x, y, w, h = ...
Read MoreHow to change the contrast and brightness of an image using OpenCV in Python?
In OpenCV, to change the contrast and brightness of an image we could use cv2.convertScaleAbs(). The syntax we use for this method is as follows − cv2.convertScaleAbs(image, alpha, beta) Where image is the original input image. alpha is the contrast value. To lower the contrast, use 0 < alpha < 1. And for higher contrast use alpha > 1. beta is the brightness value. A good range for brightness value is [-127, 127] We could also apply the cv2.addWeighted() function to change the contrast and brightness of an image. We have discussed it in example 2. Steps ...
Read MoreHow to normalize an image in OpenCV Python?
We use the function cv2.normalize() to normalize an image in OpenCV. This function accepts the parameters- src, dst, alpha, beta, norm_type, dtype and mask. src and dst are input image and output of the same size as input, alpha is lower norm value for range normalization, beta is upper norm value for range normalization, norm_type is normalization type, dtype is data type of output and mask is optional operation mask. Steps To normalize an image, we could follow the steps given below − Import the required library. In all the following examples, the required Python library is OpenCV. ...
Read MoreHow to mask an image in OpenCV Python?
We can apply a mask to an image by computing the cv2.bitwise_and() between the mask and the image. To track a color, we define a mask in HSV color space using cv2.inRange() passing lower and upper limits of color values in HSV.Also Read: Color Identification in Images using Python and OpenCV To track a part of the image we can define a mask using np.zeros() and slicing the entries with white (255) for the region in the input image to examine. Follow the given steps to mask an image − The first step is to import required libraries. The ...
Read MoreAnimate image using OpenCV in Python
Introduction Animated pictures are a sequence of static images that are automatically played to display relevant material in a continuous and dynamic manner, and they have the benefit of being smaller than videos. Additionally, many online and mobile applications enable animated images in the same manner that they support static photos, although they do not always permit the upload of movies. In this situation, animated pictures can be really helpful. Clearly, there are several other reasons why animated graphics are preferable. Sometimes, combining similar or unrelated photos is simply for fun. In this article, we would learn the steps to ...
Read MoreHow to compare two images in OpenCV Python?
To compare two images, we use the Mean Square Error (MSE) of the pixel values of the two images. Similar images will have less mean square error value. Using this method, we can compare two images having the same height, width and number of channels. Steps You can use the following steps to compare two images using OpenCV − Import the required library. In all the following Python examples, the required Python library is OpenCV. Make sure you have already installed it. import cv2 Read the input images using cv2.imread() and convert it to grayscale. The height, width and ...
Read MoreMapping CSV to JavaBeans using OpenCSV
CSV files are basically plain text files that stores data in columns separated a comma. OpenCSV is the library that parses these CSV files which are quite difficult to handle otherwise. It is a quite easy to use library that supports several features like reading and writing of CSV files with headers. We will be discussing the mapping of CSV files to JavaBeans via OpenCSV in this article. Additionally. OpenCSV is a tool that aids in this process. Mapping the CSV to JavaBeans The OpenCSV library provides certain classes and mapping strategies to map the CSV files into Java Beans. ...
Read MoreHolistically-Nested Edge Detection with OpenCV and Deep Learning
Holistically-Nested Edge Detection (HED) is a deep learning-based method for detecting edges in images which can be performed using deep learning and a Python library, OpenCV. The holistically-Nested Edge detection was first introduced by Xie and Tu in 2015 and has since been widely used in computer-vision applications.Currently, it has gained a lot of popularity in recent years due to its ability to produce accurate and high-quality edge maps in an image. In this article, we will discuss the basics of HED, how it works, and how to implement it using OpenCV and deep learning, and also using Canny ...
Read MoreDraw a triangle with centroid using OpenCV
The centroid is also called the geometric center; it is defined as the center point of the object. Whereas the centroid of a triangle is defined as the point of intersection of all three medians of a triangle. Calculating the Centroid of a triangle: Let’s consider an ABC triangle, the three vertices of the triangle are A(x1, y1), B(x2, y2), and C(x3, y3). Then the centroid of a triangle can be calculated by taking the average of the x and y coordinates of all three vertices. centroid of a triangle = ((x1+x2+x3)/3 , (y1+y2+y3)/3 ) In ...
Read MoreConnect new point to the previous point on a image with a straight line in OpenCV-Python
We might have to draw lines on an image for various purposes like drawing, scribbling, tracking the movements of a point etc. so it is necessary to know how to connect 2 points in image processing. OpenCV is a library of programming functions primarily for real-time computer vision. The library is cross-platform and licensed as free and open source software under the Apache License. In this article, we will learn how we can connect a new point to the previous point on an image with a straight line using OpenCV-Python. Connecting a Points on with the Previous One ...
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