Openimaj: SuzukiContourProcessor does not return all holes or even crashes

Question

I am new to openimaj and i cannot find any tutorials with detailed informations about it. I only found the tutorial-pdf from openimaj.org. So i tried myself starting with contours. But the SuzukiContourProcessor does not work for me. Here's my code:

try {
        File f = new File("contours_i.bmp");
        System.out.println(f.getAbsolutePath());
        FImage image = ImageUtilities.readF(f);

        BufferedImage bi = ImageUtilities.createBufferedImage(image);
        jPanel1.getGraphics().drawImage(bi, 0, 0, null);

        Border contours = SuzukiContourProcessor.findContours(image);

        final MBFImage imgC = new MBFImage(640, 480, ColourSpace.RGB);
        ContourRenderer.drawContours(imgC, contours);
        DisplayUtilities.display(imgC);

    } catch (IOException ex) {
        Logger.getLogger(ContoursTest.class.getName()).log(Level.SEVERE, null, ex);
    }

here are the used images: the lower 'hole' is not recognised: https://i.stack.imgur.com/4NUGQ.png

crashes with NullPointerException in SuzukiContourProcessor: https://i.stack.imgur.com/IEM15.png

Here is the stacktrace with the second image used:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at org.openimaj.image.contour.SuzukiContourProcessor.findContours(SuzukiContourProcessor.java:223)
at org.openimaj.image.contour.SuzukiContourProcessor.findContours(SuzukiContourProcessor.java:185)
at sudoku.ContoursTest.jButton1ActionPerformed(ContoursTest.java:86)
at sudoku.ContoursTest.access$000(ContoursTest.java:18)
at sudoku.ContoursTest$1.actionPerformed(ContoursTest.java:47)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

The problem seems to be that

borderMap.get(lnbd[0])

returns null and

switch (borderPrime.type) {...

throws the NullPointerException. Maybe i am doing something wrong.

Thx for any help.

chris.

Answer 1

As you have noted the contour detection works as expected when the image is thresholded. That being said it definitely should not crash when given a grey scale image! I'll discuss with the other developers and see what a more appropriate behaviour should be :)