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Articles by Maruthi Krishna
Page 40 of 50
How to compare two images using Java OpenCV library?
To compare two images −Read Both of them using the Image.IO.read() method.Get the height and width of both of them to make sure they are equal.Get the pixel values and, get the RGB values of both of the images.Get the sum of the differences between the RGB values of these two images.Calculate the percentage of the difference using the following formula −Average = difference/weight*height*3; Percentage = (Average/255)*100;Exampleimport java.awt.Color; import java.awt.image.BufferedImage; import javax.imageio.ImageIO; import java.io.File; public class ComparingImages { public static void main(String[] args) throws Exception { BufferedImage img1 = ImageIO.read(new File("D:\Images\test1.jpg")); BufferedImage img2 ...
Read MoreHow to flip an image using Java OpenCV library?
The flip() method of the Core class of OpenCV flips an image along the x/y axis. This method accepts −A source matrix congaing the data of the original image.An empty destination matrix to hold the data of the resultant image.A flip code to specify the direction of the image (0 –x axis, +ve – y axis, – ve both the axes).To flip an image −Load the OpenCV core native library, using the loadLibrary() method.Read the contents of the image file to a matrix using the imread() method.Create an empty matric to hold the result.Invoke the flip() method by passing the ...
Read MoreHow to create a mirror image using Java OpenCV library?
To create a mirror imageRead the required image using ImageIO.read() method.Get the height and width of the image.Create an empty buffered image to store the resultUsing nested for loops traverse through each pixel in the image.Iterate the width of the image from right to left.Get the pixel value using the getRGB() method.Set the pixel values to the result image object using the setRGB() method, by replacing the new width values.Exampleimport java.io.File; import java.io.IOException; import java.awt.image.BufferedImage; import javax.imageio.ImageIO; public class MirrorImage { public static void main(String args[])throws IOException { //Reading the image File file= ...
Read MoreHow to convert a colored image to Sepia image using Java OpenCV library?
Algorithm to convert a colored image to sepia −Get the red green blue values of each pixelGet the average of these 3 colors.Define the depth and intensity values (ideally 20, and 30).Modify the values as −red = red + (depth*2).Green = green +depth.blue = blue-intensity.Make sure that the modified values are between 0 to 255.Create a new pixel value from the modified colors and set the new value to the pixel.Implementation in JavaRead the required image using ImageIO.read() method.Get the height and width of the image.Using nested for loops traverse through each pixel in the image.Get the pixel value using ...
Read MoreHow to convert a colored image to blue/green/red image using Java OpenCV library?
The cvtColor() method of the Imgproc class changes/converts the color of the image from one to another. This method accepts three parameters −src − A Matrix object representing source.dst − A Matrix object representing the destination.code − An integer value representing the color of the destination image.To convert a colored image to grayscale you need to pass Imgproc.COLOR_RGB2BGR as the third parameter to this method.Exampleimport org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; public class ColorToGrayscale { public static void main(String args[]) throws Exception { //Loading the OpenCV core library System.loadLibrary( Core.NATIVE_LIBRARY_NAME ); ...
Read MoreHow to write an image using Java OpenCV library?
Using the OpenCV library you can perform image processing operations such as image filtering, geometrical image transformations, color space conversion, histograms, etc.Writing an imageWhenever you read the contents of an image using the imread() method of the Imgcodecs class the result is read into the Matrix object.You can write/save an image using the imwrite() method. This accepts two parameters namely −File − A string value representing the file path to which the result should be stored.Img − A matrix object containing the data of the image to be saved.ExampleThe following Java example reads the contents of the image cat.jpg as a ...
Read MoreAccepting date strings (MM-dd-yyyy format) using Java regex?
The following is the regular expression to match the date in the dd-MM-yyyy format.^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$To match a date in a string in that format.Compile the above expression of the compile() method of the Pattern class.Get the Matcher object bypassing the required input string as a parameter to the matcher() method of the Pattern class.The matches() method of the Matcher class returns true if a match occurs else it returns false. Therefore, invoke this method to validate the data.Example 1import java.util.regex.Matcher; import java.util.regex.Pattern; public class MatchingDate { public static void main(String[] args) { String date = "01/12/2019"; ...
Read MoreHow to match bold fields in a HTML script using a regular expression in Java?
The regular expression "\S" matches a non-whitespace character and the following regular expression matches one or more non space characters between the bold tags."(\S+)"Therefore to match the bold fields in a HTML script you need to −Compile the above regular expression using the compile() method.Retrieve the matcher from the obtained pattern using the matcher() method.Print the matched parts of the input string using the group() method.Exampleimport java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { String str = "This is an example>/b> HTML script."; //Regular expression to match contents of ...
Read MoreHow to remove non-ASCII characters from strings
The Posix character class \p{ASCII} matches the ASCII characters and the meta character ^ acts as negation.i.e. The following expression matches all the non-ASCII characters."[^\p{ASCII}]"The replaceAll() method of the String class accepts a regular expression and a replacement-string and, replaces the characters of the current string (matching the given pattern) with the specified replacement-string.Therefore, You can remove the matched characters by replacing them with the empty string “, using the replaceAll() method.Example 1import java.util.Scanner; public class Exp { public static void main( String args[] ) { Scanner sc = new Scanner(System.in); String regex = ...
Read MoreHow to match the regex meta characters in java as literal characters.
The compile method of the patter class accepts two parameters −A string value representing the regular expression.An integer value a field of the Pattern class.The filed LITERAL of the enables literal parsing of the pattern. i.e. all the regular expression metacharacters and escape sequences don’t have any special meaning they are treated as literal characters. Therefore, If you need to match the regular expression metacharacters as normal characters you need to pass this as a flag value to the compile() method along with the regular expression.Exampleimport java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] ...
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