Adds an operation to threshold the moving parts of an image

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

@@ -88,7 +88,8 @@ public class Operations {
                 NormalizeOperation::new,
                 WatershedOperation::new,
                 SwitchOperation::new,
-                ValveOperation::new
+                ValveOperation::new,
+                ThresholdMoving::new
         );
     }
 

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

@@ -0,0 +1,70 @@
+package edu.wpi.grip.core.operations.composite;
+
+import com.google.common.eventbus.EventBus;
+import edu.wpi.grip.core.Operation;
+import edu.wpi.grip.core.sockets.InputSocket;
+import edu.wpi.grip.core.sockets.OutputSocket;
+import edu.wpi.grip.core.sockets.SocketHints;
+import org.bytedeco.javacpp.opencv_core;
+import org.bytedeco.javacpp.opencv_core.Mat;
+import org.bytedeco.javacpp.opencv_core.Size;
+
+import java.util.Optional;
+
+import static edu.wpi.grip.core.Operation.Category.IMAGE_PROCESSING;
+
+/**
+ * Finds the absolute difference between the current image and the previous image.
+ */
+public class ThresholdMoving implements Operation {
+
+
+    @Override
+    public String getName() {
+        return "Threshold Moving";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Thresholds off parts of the image that have moved or changed between the previous and next image.";
+    }
+
+    @Override
+    public InputSocket<?>[] createInputSockets(EventBus eventBus) {
+        return new InputSocket<?>[]{
+                new InputSocket<>(eventBus, SocketHints.Inputs.createMatSocketHint("image", false))
+        };
+    }
+
+    @Override
+    public OutputSocket<?>[] createOutputSockets(EventBus eventBus) {
+        return new OutputSocket<?>[]{
+                new OutputSocket<>(eventBus, SocketHints.Outputs.createMatSocketHint("moved"))
+        };
+    }
+
+    @Override
+    public Category getCategory() {
+        return IMAGE_PROCESSING;
+    }
+
+    @Override
+    public Optional<?> createData() {
+        return Optional.of(new Mat());
+    }
+
+    @Override
+    public void perform(InputSocket<?>[] inputs, OutputSocket<?>[] outputs, Optional<?> data) {
+        final Mat input = ((InputSocket<Mat>) inputs[0]).getValue().get();
+        final OutputSocket<Mat> outputSocket = (OutputSocket<Mat>) outputs[0];
+        final Mat lastImage = (Mat) data.get();
+
+        final Size lastSize = lastImage.size();
+        final Size inputSize = input.size();
+        if (!lastImage.empty() && lastSize.height() == inputSize.height() && lastSize.width() == inputSize.width()) {
+            opencv_core.absdiff(input, lastImage, outputSocket.getValue().get());
+        }
+        input.copyTo(lastImage);
+        outputSocket.setValue(outputSocket.getValue().get());
+    }
+}