Added watershed operation

Author: SamCarlberg

core/src/main/java/edu/wpi/grip/core/operations/Operations.java

@@ -43,5 +43,6 @@ public static void addOperations(EventBus eventBus) {
         eventBus.post(new OperationAddedEvent(new NTPublishOperation<>(BlobsReport.class)));
         eventBus.post(new OperationAddedEvent(new NTPublishOperation<>(LinesReport.class)));
         eventBus.post(new OperationAddedEvent(new PublishVideoOperation()));
+        eventBus.post(new OperationAddedEvent(new WatershedOperation()));
     }
 }

core/src/main/java/edu/wpi/grip/core/operations/composite/WatershedOperation.java

@@ -0,0 +1,87 @@
+
+package edu.wpi.grip.core.operations.composite;
+
+import com.google.common.eventbus.EventBus;
+
+import edu.wpi.grip.core.InputSocket;
+import edu.wpi.grip.core.Operation;
+import edu.wpi.grip.core.OutputSocket;
+import edu.wpi.grip.core.SocketHint;
+import edu.wpi.grip.core.SocketHints;
+
+import static org.bytedeco.javacpp.opencv_core.*;
+import static org.bytedeco.javacpp.opencv_imgproc.*;
+
+/**
+ * GRIP {@link Operation} for
+ * {@link org.bytedeco.javacpp.opencv_imgproc#watershed}.
+ */
+public class WatershedOperation implements Operation {
+
+    private final SocketHint<Mat> srcHint = SocketHints.Inputs.createMatSocketHint("Input", false);
+    private final SocketHint<ContoursReport> contoursHint = new SocketHint.Builder<>(ContoursReport.class)
+            .identifier("Contours")
+            .initialValueSupplier(ContoursReport::new)
+            .build();
+
+    private final SocketHint<Mat> outputHint = SocketHints.Inputs.createMatSocketHint("Output", true);
+
+    @Override
+    public String getName() {
+        return "Watershed";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Isolates overlapping objects from the background and each other";
+    }
+
+    @Override
+    public InputSocket<?>[] createInputSockets(EventBus eventBus) {
+        return new InputSocket<?>[]{
+            new InputSocket<>(eventBus, srcHint),
+            new InputSocket<>(eventBus, contoursHint)
+        };
+    }
+
+    @Override
+    public OutputSocket<?>[] createOutputSockets(EventBus eventBus) {
+        return new OutputSocket<?>[]{
+            new OutputSocket<>(eventBus, outputHint)
+        };
+    }
+
+    @Override
+    public void perform(InputSocket<?>[] inputs, OutputSocket<?>[] outputs) {
+        final Mat input = (Mat) inputs[0].getValue().get();
+        if (input.type() != CV_8UC3) {
+            throw new IllegalArgumentException("Watershed only works on 8-bit, 3-channel images");
+        }
+
+        final ContoursReport contourReport = (ContoursReport) inputs[1].getValue().get();
+        final MatVector contours = contourReport.getContours();
+
+        final OutputSocket<Mat> outputSocket = (OutputSocket<Mat>) outputs[0];
+        final Mat markers = new Mat(input.size(), CV_32SC1, new Scalar(0.0));
+        final Mat output = new Mat(markers.size(), CV_8UC1, new Scalar(0.0));
+
+        // draw foreground markers (these have to be different colors)
+        for (int i = 0; i < contours.size(); i++) {
+            drawContours(markers, contours, i, Scalar.all((i + 1) * (255 / contours.size())), CV_FILLED, LINE_8, null, 2, null);
+        }
+
+        // draw background marker a different color from the foreground markers
+        // TODO maybe make this configurable? There may be something in the corner
+        circle(markers, new Point(5, 5), 3, Scalar.WHITE, -1, LINE_8, 0);
+
+        watershed(input, markers);
+        markers.convertTo(output, CV_8UC1);
+        bitwise_not(output, output); // watershed inverts colors; invert them back
+
+        outputSocket.setValue(output);
+
+        // make sure that the working mat is freed to avoid a memory leak
+        markers.release();
+    }
+
+}