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Articles by Maruthi Krishna
Page 28 of 50
Is there any alternative for OpenCV imshow() method in Java?
The HighGui class of the org.opencv.highgui package allows you to create and manipulate windows and display them. You can display an image in a window using the imshow() method of this class. This method accepts two parameters−A string variable representing the name of the window.A Mat object representing the contents of an image.It is recommended to invoke the waitKey() method after imshow().ExampleThe following example reads an image, converts it into a grayscale image, detects the edges in it and displays all the three images (original, gray-scale and, edges) in windows using HighGui.import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.highgui.HighGui; import org.opencv.imgcodecs.Imgcodecs; import ...
Read MoreWhat is morphological gradient in image processing?
Erosion and dilation are the two basic morphological operations. As the name implies, morphological operations are the set of operations that process images according to their shapes.During dilation operation additional pixels are added to an image boundary and, during erosion operation, additional pixels are removed from image boundaries, The total number of pixels added during the dilation process depends on the dimensions of the structuring element used.Morphological Gradient is the operation that is equal to the difference between dilation and erosion of an image. Each pixel value in the resulting image indicates the contrast intensity in the nearby pixels. This ...
Read MoreExplain Morphological Opening in OpenCV using Java.
Morphological operations are the set of operations that process images according to the given shapes. Erosion and dilation are the two basic morphological operations.During dilation, additional pixels are added to the image boundaries.During erosion, additional pixels are removed from the image boundaries.The total number of pixels added/removed depends on the dimensions of the structuring element used. You can perform erosion and dilation operations using the erode() and dilate() methods respectively.In addition to dilation, OpenCV provides more morphological transformations such as Opening, Closing, Morphological Gradient, Top Hat, Black Hat.Morphological openingThis is an operation that is equivalent to applying erosion on an ...
Read MoreHow to perform Bitwise Not operation on images using Java OpenCV?
You can compute the bitwise conjunction between two images using the bitwise_not() method of the org.opencv.core.Core class.This method accepts two Mat objects representing the source and destination matrices, calculates the inverse of each element in the source matrix and stores the result in the destination matrix.Exampleimport org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.highgui.HighGui; import org.opencv.imgcodecs.Imgcodecs; public class BitwiseNOTExample { public static void main(String args[]) throws Exception { //Loading the OpenCV core library System.loadLibrary( Core.NATIVE_LIBRARY_NAME ); //Reading the Image String file ="D://images//elephant.jpg"; Mat src = Imgcodecs.imread(file); ...
Read MoreHow to get pixels (RGB values) of an image using Java OpenCV library?
A digital image is stored as a 2D array of pixels and a pixel is the smallest element of a digital image.Each pixel contains the values of alpha, red, green, blue values and the value of each color lies between 0 to 255 which consumes 8 bits (2^8).The ARGB values are stored in 4 bytes of memory in the same order (right to left) with blue value at 0-7 bits, Green value at 8-15 bits, Red value at 16-23 bits and, alpha at 24-31 bits.Retrieving the pixel contents (ARGB values) of an image −To get the pixel values from an ...
Read MoreHow to draw markers on an image using Java OpenCV library?
You can draw makers on an image using the drawMarker() method of the org.opencv.imgproc.Imgproc class. This method accepts the following parameters −img − A Mat object representing the input image.position − An object of the class Point to specify the position of the marker.color − An object of the class Scalar to specify the color of the marker.markerType − An integer constant specifying the type of the marker.size − An integer value specifying the size of the marker.thickness − An integer value specifying the thickness of the marker.Exampleimport org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.core.Point; import org.opencv.core.Scalar; import org.opencv.highgui.HighGui; import org.opencv.imgcodecs.Imgcodecs; import ...
Read MoreHow to Detect the key points of an image using OpenCV Java library?
The detect() method of the org.opencv.features2d.Feature2D (abstract) class detects the key points of the given image. To this method, you need to pass a Mat the object representing the source image and an empty MatOfKeyPoint object to hold the read key points.You can draw the draw key points on the image using the drawKeypoints() method of the org.opencv.features2d.Features2d class.NoteSince Feature2D is an abstract class you need to instantiate one of its subclasses to invoke the detect() method. Here we have used the FastFeatureDetector class.Features2D and Features2d are two different classes of the package features2d don’t get confused...Exampleimport org.opencv.core.Core; import org.opencv.core.Mat; ...
Read MoreHow to find the area of an image contour Java OpenCV library?
Contours are nothing but the line joining all the points along the boundary of a particular shape. Using this you can −Find the shape of an object.Calculate the area of an object.Detect an object.Recognize an object.You can find the contours of various shapes, objects in an image using the findContours() method. In the same way you can drawYou can also find the area of the shapes in the given input images. To do so you need to invoke the contourArea() method of the Imgproc class. This method accepts the contour of a particular shape, finds and returns its area.ExampleFollowing java ...
Read MoreHow to find Image Contours using Java OpenCV library?
Contours are nothing but the line joining all the points along the boundary of a particular shape. Using this you can −Find the shape of an object.Calculate the area of an object.Detect an object.Recognize an object.You can find the contours of various shapes, objects in an image using the findContours() method. This method accepts the following parameters −A binary image.An empty list object of type MatOfPoint to store the contours.An empty Mat object to store the image topology.Two integer variables to specify the mode and method to find the contours of the given image.Exampleimport java.util.ArrayList; import java.util.Iterator; import java.util.List; import ...
Read MoreHow to perform Bitwise And operation on two images using Java OpenCV?
You can compute bitwise conjunction between two images using the bitwise_and() method of the org.opencv.core.Core class.This method accepts three Mat objects representing the source, destination and result matrices, calculates the bitwise conjunction of each every element in the source matrices and stores the result in the destination matrix.ExampleIn the following Java example we are converting an image into binary and gray scale and calculating the bitwise conjunction of the results.import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.highgui.HighGui; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; public class BitwiseAndExample { public static void main(String args[]) throws Exception { //Loading the OpenCV core library ...
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