imshow equivalence in Java

java
imshow

asked 2013-05-02 07:43:34 -0600

phamnamlong
29 ●1 ●1 ●6

updated 2013-05-02 07:44:32 -0600

How do you do imshow in the Java binding of OpenCv ? I cannot find any reference of it in Highgui. The example below shows the use of imshow as in C++. I would like to ask for the equivalence in Java.

#include <cv.h>
#include <highgui.h>

using namespace cv;

int main( int argc, char** argv){
 char* imageName = argv[1];
 Mat image;
 image = imread( imageName, 1 );

 if( argc != 2 || !image.data ) {
   printf( " No image data \n " );
   return -1;
 }
 namedWindow( imageName, CV_WINDOW_AUTOSIZE );
 imshow( imageName, image );
 waitKey(0);
 return 0;
}

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2 answers

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answered 2013-09-23 05:08:18 -0600

Arne

34 ●1 ●5

updated 2013-09-23 05:08:47 -0600

It seems that there isn't a function like imshow in the Java HighGUI package. But after a small search i found out that its possible to encode the image to a "BufferedImage" and then just load it into your GUI. So just load it like this:

Mat image_tmp = your image
MatOfByte matOfByte = new MatOfByte();

Highgui.imencode(".jpg", image_tmp, matOfByte); 

byte[] byteArray = matOfByte.toArray();
BufferedImage bufImage = null;

try {

    InputStream in = new ByteArrayInputStream(byteArray);
    bufImage = ImageIO.read(in);
} catch (Exception e) {
    e.printStackTrace();
}

and then draw it like that:

g.drawImage(bufImage , 0, 0, null);

g in this examples is an instance of the class Graphics

Hopefully this is what you were searching for.

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Comments

Is it required to compress the image to jpg for uploading it into the component? Couldn't we just use Mat.get and copy the uncompressed byte array?

Jose Gómez ( 2013-11-09 12:13:37 -0600 )edit

You don't need to compress it to .jpg. You can do it like this:

public Image toBufferedImage(Mat m){
    int type = BufferedImage.TYPE_BYTE_GRAY;
    if ( m.channels() &gt; 1 ) {
        Mat m2 = new Mat();
        Imgproc.cvtColor(m,m2,Imgproc.COLOR_BGR2RGB);
        type = BufferedImage.TYPE_3BYTE_BGR;
        m = m2;
    }
    byte [] b = new byte[m.channels()*m.cols()*m.rows()];
    m.get(0,0,b); // get all the pixels
    BufferedImage image = new BufferedImage(m.cols(),m.rows(), type);
    image.getRaster().setDataElements(0, 0, m.cols(),m.rows(), b);
    return image;

}

Best regards,