The convertTo() method of the org.opencv.core.Mat class performs the required calculations on the given matrix to alter the contrast and brightness of an image. This method accepts 4 parameters −mat − Empty matrix to hold the result with the same size and type as the source matrix.rtype − integer value specifying the type of the output matrix. If this value is negative, the type will be the same as the source.alpha − Gain value, which must be greater than 0 (default value 1).beta − Bias value (default value 0).Altering the brightness of an image using OpenCV Java libraryAs mentioned the ... Read More

The increasing/decreasing of brightness and contrast of an image are the operations that can be achieved by transforming the pixels of the image. this can be expressed in the form of an equation as −g(i, j) = α . f(i, j)+ βWhere, (i, j) are the positions of the pixels.α (gain) and β (bias) are the parameters of the transformation.At times the gain parameter controls the contrast of an image and the bias parameter controls the brightness of an image.The convertTo() method of the org.opencv.core.Mat class performs the required calculations on the given matrix to alter the contrast and brightness ... Read More

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 More

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 More

Following Java example draws a watermark (“Hello”) on the given image and saves it back.Exampleimport java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import javax.imageio.ImageIO; public class WaterMarkExample {    public static void main(String[] args) throws IOException {       //Reading the contents of an image       File file = new File("D:\Images\test1.jpg");       BufferedImage img = ImageIO.read(file);       //Creating an empty image for output       int height = img.getHeight();       int width = img.getWidth();       BufferedImage res = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);     ... Read More

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 More

To convert the colored image to grayscale.Get the red green blue values of each pixelGet the average of these 3 colors.Replace the RGB values with the average.Create a new pixel value from the modified colors.Set the new value to the pixel.Exampleimport java.io.File; import java.io.IOException; import java.awt.Color; import java.awt.image.BufferedImage; import javax.imageio.ImageIO; public class Color2Grey {    public static void main(String args[])throws IOException {       //Reading the image       File file= new File("D:\Images\car.jpg");       BufferedImage img = ImageIO.read(file);       for (int y = 0; y < img.getHeight(); y++) {          for ... Read More

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 More

To convert a negative image to positive −Read 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 the getRGB() method.To retrieve each value from a pixel you need to right shift to the beginning position of each color i.e. 24 for alpha 16 for red etc. and perform bitwise and operation with 0Xff. This masks the variable leaving the last 8 bits and ignoring all the rest of the bits.Calculate the new red, green and blue values by subtracting them from 255.Reconstruct ... Read More

Algorithm to convert an image to negativeGet the red green blue values of each pixelSubtract each color value from 255 and save them as new color values.Create a new pixel value from the modified colors.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 the getRGB() method.Create a Color object bypassing the above-retrieved pixel value as parameter.Get the red, green, blue values from the color object using the getRed(), getGreen() and getBlue() methods respectively.Calculate ... Read More