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How to convert OpenCV Mat object to BufferedImage object using Java?
If you try to read an image using the OpenCV imread() method it returns a Mat object. If you want to display the contents of the resultant Mat object using an AWT/Swings window You need to convert the Mat object to an object of the class java.awt.image.BufferedImage. To do so, you need to follow the steps given below −
-
Encode the Mat to MatOfByte − First of all, you need to convert the matrix to the matrix of a byte. You can do it using the method imencode() of the class Imgcodecs.
This method accepts a String parameter(specifying the image format), a Mat object (representing the image), a MatOfByte object.
Convert the MatOfByte object to byte array − Convert the MatOfByte object into a byte array using the method toArray().
Instantiate ByteArrayInputStream − Instantiate the ByteArrayInputStream class by passing the byte array created in the previous step to one of its constructors.
Creating BufferedImage object − Pass the Input Stream object created in the previous step to the read() method of the ImageIO class. This will return a BufferedImage object.
Example
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.imageio.ImageIO;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfByte;
import org.opencv.imgcodecs.Imgcodecs;
public class Mat2BufferedImage {
public static BufferedImage Mat2BufferedImage(Mat mat) throws IOException{
//Encoding the image
MatOfByte matOfByte = new MatOfByte();
Imgcodecs.imencode(".jpg", mat, matOfByte);
//Storing the encoded Mat in a byte array
byte[] byteArray = matOfByte.toArray();
//Preparing the Buffered Image
InputStream in = new ByteArrayInputStream(byteArray);
BufferedImage bufImage = ImageIO.read(in);
return bufImage;
}
public static void main(String args[]) throws Exception {
//Loading the OpenCV core library
System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
//Reading the Image from the file
String file = "C:/EXAMPLES/OpenCV/sample.jpg";
Mat image = Imgcodecs.imread(file);
BufferedImage obj = Mat2BufferedImage(image);
System.out.println(obj);
}
}
Output
BufferedImage@579bb367: type = 5 ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace@1de0aca6 transparency = 1 has alpha = false isAlphaPre = false ByteInterleavedRaster: width = 500 height = 360 #numDataElements 3 dataOff[0] = 2
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