Add contour angle to contours report

Angle is from minAreaRect, and is in the range [-90, 0)
Rework contours operations to be a bit more functional
Make filter contours a bit more optimized

Author: SamCarlberg

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

@@ -4,17 +4,21 @@
 import edu.wpi.grip.core.operations.network.Publishable;
 import edu.wpi.grip.core.sockets.NoSocketTypeLabel;
 import edu.wpi.grip.core.sockets.Socket;
+import edu.wpi.grip.core.util.LazyInit;
+import edu.wpi.grip.core.util.PointerStream;
 
 import com.google.auto.value.AutoValue;
 
+import org.bytedeco.javacpp.opencv_core.RotatedRect;
+import org.bytedeco.javacpp.opencv_imgproc;
+
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Optional;
+import java.util.stream.Stream;
 
 import static org.bytedeco.javacpp.opencv_core.Mat;
 import static org.bytedeco.javacpp.opencv_core.MatVector;
 import static org.bytedeco.javacpp.opencv_core.Rect;
-import static org.bytedeco.javacpp.opencv_imgproc.boundingRect;
 import static org.bytedeco.javacpp.opencv_imgproc.contourArea;
 import static org.bytedeco.javacpp.opencv_imgproc.convexHull;
 
@@ -29,7 +33,9 @@ public final class ContoursReport implements Publishable {
   private final int rows;
   private final int cols;
   private final MatVector contours;
-  private Optional<Rect[]> boundingBoxes = Optional.empty();
+  private final LazyInit<Rect[]> boundingBoxes = new LazyInit<>(this::computeBoundingBoxes);
+  private final LazyInit<RotatedRect[]> rotatedBoundingBoxes =
+      new LazyInit<>(this::computeMinAreaBoundingBoxes);
 
   /**
    * Construct an empty report.  This is used as a default value for {@link Socket}s containing
@@ -68,9 +74,10 @@ public List<Contour> getProcessedContours() {
     double[] width = getWidth();
     double[] height = getHeights();
     double[] solidity = getSolidity();
+    double[] angles = getAngles();
     for (int i = 0; i < contours.size(); i++) {
       processedContours.add(Contour.create(area[i], centerX[i], centerY[i], width[i], height[i],
-          solidity[i]));
+          solidity[i], angles[i]));
     }
     return processedContours;
   }
@@ -80,66 +87,51 @@ public List<Contour> getProcessedContours() {
    * boxes are used to compute several different properties, so it's probably not a good idea to
    * compute them over and over again.
    */
-  private synchronized Rect[] computeBoundingBoxes() {
-    if (!boundingBoxes.isPresent()) {
-      Rect[] bb = new Rect[(int) contours.size()];
-      for (int i = 0; i < contours.size(); i++) {
-        bb[i] = boundingRect(contours.get(i));
-      }
-
-      boundingBoxes = Optional.of(bb);
-    }
+  private Rect[] computeBoundingBoxes() {
+    return PointerStream.ofMatVector(contours)
+        .map(opencv_imgproc::boundingRect)
+        .toArray(Rect[]::new);
+  }
 
-    return boundingBoxes.get();
+  private RotatedRect[] computeMinAreaBoundingBoxes() {
+    return PointerStream.ofMatVector(contours)
+        .map(opencv_imgproc::minAreaRect)
+        .toArray(RotatedRect[]::new);
   }
 
   @PublishValue(key = "area", weight = 0)
   public double[] getArea() {
-    final double[] areas = new double[(int) contours.size()];
-    for (int i = 0; i < contours.size(); i++) {
-      areas[i] = contourArea(contours.get(i));
-    }
-    return areas;
+    return PointerStream.ofMatVector(contours)
+        .mapToDouble(opencv_imgproc::contourArea)
+        .toArray();
   }
 
   @PublishValue(key = "centerX", weight = 1)
   public double[] getCenterX() {
-    final double[] centers = new double[(int) contours.size()];
-    final Rect[] boundingBoxes = computeBoundingBoxes();
-    for (int i = 0; i < contours.size(); i++) {
-      centers[i] = boundingBoxes[i].x() + boundingBoxes[i].width() / 2;
-    }
-    return centers;
+    return Stream.of(boundingBoxes.get())
+        .mapToDouble(r -> r.x() + r.width() / 2)
+        .toArray();
   }
 
   @PublishValue(key = "centerY", weight = 2)
   public double[] getCenterY() {
-    final double[] centers = new double[(int) contours.size()];
-    final Rect[] boundingBoxes = computeBoundingBoxes();
-    for (int i = 0; i < contours.size(); i++) {
-      centers[i] = boundingBoxes[i].y() + boundingBoxes[i].height() / 2;
-    }
-    return centers;
+    return Stream.of(boundingBoxes.get())
+        .mapToDouble(r -> r.y() + r.height() / 2)
+        .toArray();
   }
 
   @PublishValue(key = "width", weight = 3)
   public synchronized double[] getWidth() {
-    final double[] widths = new double[(int) contours.size()];
-    final Rect[] boundingBoxes = computeBoundingBoxes();
-    for (int i = 0; i < contours.size(); i++) {
-      widths[i] = boundingBoxes[i].width();
-    }
-    return widths;
+    return Stream.of(boundingBoxes.get())
+        .mapToDouble(Rect::width)
+        .toArray();
   }
 
   @PublishValue(key = "height", weight = 4)
   public synchronized double[] getHeights() {
-    final double[] heights = new double[(int) contours.size()];
-    final Rect[] boundingBoxes = computeBoundingBoxes();
-    for (int i = 0; i < contours.size(); i++) {
-      heights[i] = boundingBoxes[i].height();
-    }
-    return heights;
+    return Stream.of(boundingBoxes.get())
+        .mapToDouble(Rect::height)
+        .toArray();
   }
 
   @PublishValue(key = "solidity", weight = 5)
@@ -154,11 +146,19 @@ public synchronized double[] getSolidity() {
     return solidities;
   }
 
+  @PublishValue(key = "angle", weight = 6)
+  public synchronized double[] getAngles() {
+    return Stream.of(rotatedBoundingBoxes.get())
+        .mapToDouble(RotatedRect::angle)
+        .toArray();
+  }
+
   @AutoValue
   public abstract static class Contour {
     static Contour create(double area, double centerX, double centerY, double width, double
-        height, double solidity) {
-      return new AutoValue_ContoursReport_Contour(area, centerX, centerY, width, height, solidity);
+        height, double solidity, double angle) {
+      return new AutoValue_ContoursReport_Contour(area, centerX, centerY, width, height, solidity,
+          angle);
     }
 
     public abstract double area();
@@ -172,5 +172,7 @@ static Contour create(double area, double centerX, double centerY, double width,
     public abstract double height();
 
     public abstract double solidity();
+
+    public abstract double angle();
   }
 }

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

@@ -15,9 +15,7 @@
 
 import static org.bytedeco.javacpp.opencv_core.Mat;
 import static org.bytedeco.javacpp.opencv_core.MatVector;
-import static org.bytedeco.javacpp.opencv_core.Rect;
 import static org.bytedeco.javacpp.opencv_imgproc.arcLength;
-import static org.bytedeco.javacpp.opencv_imgproc.boundingRect;
 import static org.bytedeco.javacpp.opencv_imgproc.contourArea;
 import static org.bytedeco.javacpp.opencv_imgproc.convexHull;
 
@@ -73,6 +71,8 @@ public class FilterContoursOperation implements Operation {
   private final SocketHint<Number> maxRatioHint =
       SocketHints.Inputs.createNumberSpinnerSocketHint("Max Ratio", 1000, 0, Integer.MAX_VALUE);
 
+  private final SocketHint<List<Number>> angleHint =
+      SocketHints.Inputs.createNumberListRangeSocketHint("Angle", -90, 0);
 
   private final InputSocket<ContoursReport> contoursSocket;
   private final InputSocket<Number> minAreaSocket;
@@ -86,6 +86,7 @@ public class FilterContoursOperation implements Operation {
   private final InputSocket<Number> maxVertexSocket;
   private final InputSocket<Number> minRatioSocket;
   private final InputSocket<Number> maxRatioSocket;
+  private final InputSocket<List<Number>> angleSocket;
 
   private final OutputSocket<ContoursReport> outputSocket;
 
@@ -105,6 +106,7 @@ public FilterContoursOperation(InputSocket.Factory inputSocketFactory, OutputSoc
     this.maxVertexSocket = inputSocketFactory.create(maxVertexHint);
     this.minRatioSocket = inputSocketFactory.create(minRatioHint);
     this.maxRatioSocket = inputSocketFactory.create(maxRatioHint);
+    this.angleSocket = inputSocketFactory.create(angleHint);
 
     this.outputSocket = outputSocketFactory.create(contoursHint);
   }
@@ -123,7 +125,8 @@ public List<InputSocket> getInputSockets() {
         maxVertexSocket,
         minVertexSocket,
         minRatioSocket,
-        maxRatioSocket
+        maxRatioSocket,
+        angleSocket
     );
   }
 
@@ -138,6 +141,7 @@ public List<OutputSocket> getOutputSockets() {
   @SuppressWarnings("unchecked")
   public void perform() {
     final InputSocket<ContoursReport> inputSocket = contoursSocket;
+    final ContoursReport report = inputSocket.getValue().get();
     final double minArea = minAreaSocket.getValue().get().doubleValue();
     final double minPerimeter = minPerimeterSocket.getValue().get().doubleValue();
     final double minWidth = minWidthSocket.getValue().get().doubleValue();
@@ -150,9 +154,10 @@ public void perform() {
     final double maxVertexCount = maxVertexSocket.getValue().get().doubleValue();
     final double minRatio = minRatioSocket.getValue().get().doubleValue();
     final double maxRatio = maxRatioSocket.getValue().get().doubleValue();
+    final double minAngle = angleSocket.getValue().get().get(0).doubleValue();
+    final double maxAngle = angleSocket.getValue().get().get(1).doubleValue();
 
-
-    final MatVector inputContours = inputSocket.getValue().get().getContours();
+    final MatVector inputContours = report.getContours();
     final MatVector outputContours = new MatVector(inputContours.size());
     final Mat hull = new Mat();
 
@@ -163,15 +168,14 @@ public void perform() {
     for (int i = 0; i < inputContours.size(); i++) {
       final Mat contour = inputContours.get(i);
 
-      final Rect bb = boundingRect(contour);
-      if (bb.width() < minWidth || bb.width() > maxWidth) {
+      if (report.getWidth()[i] < minWidth || report.getWidth()[i] > maxWidth) {
         continue;
       }
-      if (bb.height() < minHeight || bb.height() > maxHeight) {
+      if (report.getHeights()[i] < minHeight || report.getHeights()[i] > maxHeight) {
         continue;
       }
 
-      final double area = contourArea(contour);
+      final double area = report.getArea()[i];
       if (area < minArea) {
         continue;
       }
@@ -190,11 +194,16 @@ public void perform() {
         continue;
       }
 
-      final double ratio = (double) bb.width() / (double) bb.height();
+      final double ratio = report.getWidth()[i] / report.getHeights()[i];
       if (ratio < minRatio || ratio > maxRatio) {
         continue;
       }
 
+      final double angle = report.getAngles()[i];
+      if (angle < minAngle || angle > maxAngle) {
+        continue;
+      }
+
       outputContours.put(filteredContourCount++, contour);
     }
 

core/src/main/java/edu/wpi/grip/core/util/LazyInit.java

@@ -0,0 +1,44 @@
+package edu.wpi.grip.core.util;
+
+import java.util.Objects;
+import java.util.function.Supplier;
+
+/**
+ * A holder for data that gets lazily initialized.
+ *
+ * @param <T> the type of held data
+ */
+public class LazyInit<T> {
+
+  private T value = null;
+  private final Supplier<? extends T> factory;
+
+  /**
+   * Creates a new lazily initialized data holder.
+   *
+   * @param factory the factory to use to create the held value
+   */
+  public LazyInit(Supplier<? extends T> factory) {
+    this.factory = Objects.requireNonNull(factory, "factory");
+  }
+
+  /**
+   * Gets the value, initializing it if it has not yet been created.
+   *
+   * @return the held value
+   */
+  public T get() {
+    if (value == null) {
+      value = factory.get();
+    }
+    return value;
+  }
+
+  /**
+   * Clears the held value. The next call to {@link #get()} will re-instantiate the held value.
+   */
+  public void clear() {
+    value = null;
+  }
+
+}

core/src/main/java/edu/wpi/grip/core/util/PointerStream.java

@@ -0,0 +1,26 @@
+package edu.wpi.grip.core.util;
+
+import java.util.stream.LongStream;
+import java.util.stream.Stream;
+
+import static org.bytedeco.javacpp.opencv_core.Mat;
+import static org.bytedeco.javacpp.opencv_core.MatVector;
+
+/**
+ * Utility class for streaming native vector wrappers like {@code MatVector}
+ * ({@code std::vector<T>}) with the Java {@link Stream} API.
+ */
+public final class PointerStream {
+
+  /**
+   * Creates a stream of {@code Mat} objects in a {@code MatVector}.
+   *
+   * @param vector the vector of {@code Mats} to stream
+   *
+   * @return a new stream object for the contents of the vector
+   */
+  public static Stream<Mat> ofMatVector(MatVector vector) {
+    return LongStream.range(0, vector.size())
+        .mapToObj(vector::get);
+  }
+}

core/src/test/java/edu/wpi/grip/core/util/LazyInitTest.java

@@ -0,0 +1,45 @@
+package edu.wpi.grip.core.util;
+
+import org.junit.Test;
+
+import java.util.function.Supplier;
+
+import static org.junit.Assert.assertEquals;
+
+public class LazyInitTest {
+
+  @Test
+  public void testFactoryIsOnlyCalledOnce() {
+    final String output = "foo";
+    final int[] count = {0};
+    final Supplier<String> factory = () -> {
+      count[0]++;
+      return output;
+    };
+
+    LazyInit<String> lazyInit = new LazyInit<>(factory);
+    lazyInit.get();
+    assertEquals(1, count[0]);
+
+    lazyInit.get();
+    assertEquals("Calling get() more than once should only call the factory once", 1, count[0]);
+  }
+
+  @Test
+  public void testClear() {
+    final String output = "foo";
+    final int[] count = {0};
+    final Supplier<String> factory = () -> {
+      count[0]++;
+      return output;
+    };
+    LazyInit<String> lazyInit = new LazyInit<>(factory);
+    lazyInit.get();
+    assertEquals(1, count[0]);
+
+    lazyInit.clear();
+    lazyInit.get();
+    assertEquals(2, count[0]);
+  }
+
+}