SkAR Java: smooth finger painting, planes draw with outlines

Bug: skia:
Change-Id: I0e6f3c00f030f7a03c3829cd4ff22ac7459dc132
Reviewed-on: https://skia-review.googlesource.com/142685
Reviewed-by: Mike Reed <reed@google.com>

4 files changed, 104 insertions, 24 deletions

diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java
index 9732cb1647..98f36fbe1f 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java
@@ -46,7 +46,7 @@ public class DrawManager {
     private ColorFilter lightFilter;
     private BitmapShader planeShader;
     public ArrayList<float[]> modelMatrices = new ArrayList<>();
-    public SkARFingerPainting fingerPainting = new SkARFingerPainting();
+    public SkARFingerPainting fingerPainting = new SkARFingerPainting(false);
 
     public void updateViewport(float width, float height) {
         viewportWidth = width;
@@ -65,10 +65,6 @@ public class DrawManager {
         lightFilter = SkARUtil.createLightCorrectionColorFilter(colorCorr);
     }
 
-    public void updateFingerPainting(PointF p) {
-        fingerPainting.addPoint(p);
-    }
-
     // Sample function for drawing a circle
     public void drawCircle(Canvas canvas) {
         if (modelMatrices.isEmpty()) {
@@ -143,6 +139,10 @@ public class DrawManager {
     }
 
     public void drawFingerPainting(Canvas canvas) {
+        // Build the path before rendering
+        fingerPainting.buildPath();
+
+        // If path empty, return
         if (fingerPainting.path.isEmpty()) {
             return;
         }
@@ -166,7 +166,12 @@ public class DrawManager {
 
         // Set up paint
         Paint p = new Paint();
-        p.setColor(Color.GREEN);
+        if (fingerPainting.getSmoothness()) {
+            p.setColor(Color.CYAN);
+        } else {
+            p.setColor(Color.GREEN);
+        }
+
         p.setStyle(Paint.Style.STROKE);
         p.setStrokeWidth(30f);
         p.setAlpha(120);
@@ -269,19 +274,24 @@ public class DrawManager {
 
         // Set up paint
         Paint p = new Paint();
-        p.setShader(planeShader);
-        p.setColorFilter(new PorterDuffColorFilter(Color.argb(0.4f, 1, 0, 0),
+
+        if (false) {
+            //p.setShader(planeShader);
+            p.setColorFilter(new PorterDuffColorFilter(Color.argb(0.4f, 1, 0, 0),
                              PorterDuff.Mode.SRC_ATOP));
+        }
 
         p.setColor(Color.RED);
         p.setAlpha(100);
+        p.setStrokeWidth(0.01f);
+        p.setStyle(Paint.Style.STROKE);
+
 
         if (true) {
             // Shader local matrix
             android.graphics.Matrix lm = new android.graphics.Matrix();
             lm.setScale(0.00005f, 0.00005f);
             planeShader.setLocalMatrix(lm);
-
             // Draw dest path
             canvas.save();
             canvas.setMatrix(mvpv);
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/HelloSkARActivity.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/HelloSkARActivity.java
index d8161c7979..56b46017e7 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/HelloSkARActivity.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/HelloSkARActivity.java
@@ -104,6 +104,7 @@ public class HelloSkARActivity extends AppCompatActivity implements GLSurfaceVie
     // 2D Renderer
     private DrawManager drawManager = new DrawManager();
     private DrawingType currentDrawabletype = DrawingType.circle;
+    private boolean drawSmoothPainting = false;
 
     // Temporary matrix allocated here to reduce number of allocations for each frame.
     private final float[] anchorMatrix = new float[16];
@@ -384,6 +385,10 @@ public class HelloSkARActivity extends AppCompatActivity implements GLSurfaceVie
                             PointF distance = new PointF(point[0] - previousEvent.x,
                                                          point[2] - previousEvent.y);
 
+                            if (distance.length() < 0.05f) {
+                                continue;
+                            }
+
                             // New point is distance + old point
                             PointF p = new PointF(distance.x * localDistanceScale
                                                    + drawManager.fingerPainting.previousPoint.x,
@@ -466,24 +471,25 @@ public class HelloSkARActivity extends AppCompatActivity implements GLSurfaceVie
             switch (currentDrawabletype) {
                 case circle:
                     drawManager.drawCircle(canvas);
-                    return;
+                    break;
                 case rect:
                     drawManager.drawRect(canvas);
-                    return;
+                    break;
                 case animation:
                     drawManager.drawAnimatedRoundRect(canvas, radius);
-                    return;
+                    break;
                 case text:
                     drawManager.drawText(canvas, "Android");
-                    return;
+                    break;
                 default:
                     drawManager.drawCircle(canvas);
-                    return;
+                    break;
             }
         }
     }
 
     private void drawFingerPainting(Canvas canvas) {
+        drawManager.fingerPainting.setSmoothness(drawSmoothPainting);
         drawManager.drawFingerPainting(canvas);
     }
 
@@ -499,6 +505,12 @@ public class HelloSkARActivity extends AppCompatActivity implements GLSurfaceVie
             case R.id.reset_paint:
                 drawManager.fingerPainting.reset();
                 return true;
+            case R.id.smooth_paint:
+                drawSmoothPainting = true;
+                return true;
+            case R.id.rough_paint:
+                drawSmoothPainting = false;
+                return true;
             case R.id.draw_circle:
                 currentDrawabletype = DrawingType.circle;
                 return true;
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/SkARFingerPainting.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/SkARFingerPainting.java
index 5fc31e7ff8..c93a900f58 100644
--- a/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/SkARFingerPainting.java
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/skar/SkARFingerPainting.java
@@ -3,33 +3,80 @@ package com.google.skar;
 import android.graphics.Path;
 import android.graphics.PointF;
 
+import java.util.ArrayList;
+
 public class SkARFingerPainting {
+    // Points obtained by touching the screen. The first point is always brough to (0,0).
+    // All subsequent points are translated by the same amount.
+    public ArrayList<PointF> points = new ArrayList<>();
+
     public Path path = new Path();
 
     // Previous point added to the path. This points belongs to the path in local space.
     public PointF previousPoint;
 
-    private int numberOfPoints = 0;
-
     // Holds the model matrix of the first point added to such that the path can be drawn at the
     // model location (i.e on the Plane)
     private float[] modelMatrix;
 
-    public SkARFingerPainting() {}
+    private boolean isSmooth;
+
+    public SkARFingerPainting(boolean smooth) {
+        this.isSmooth = smooth;
+    }
+
+    public boolean getSmoothness() {
+        return isSmooth;
+    }
+
+    public void setSmoothness(boolean smooth) {
+        isSmooth = smooth;
+    }
 
     // Adds another point to the path in Local space
     public void addPoint(PointF p) {
-        if (numberOfPoints == 0) {
-            path.moveTo(p.x, p.y);
+        points.add(p);
+        previousPoint = p;
+    }
+
+    // Used to build a path before rendering it
+    public void buildPath() {
+        if (points.size() < 1) {
+            return;
+        }
+
+        path = new Path();
+        if (isSmooth) {
+            // If less than 3 points, than draw a line between the two points
+            if (points.size() <= 2 && points.size() > 0) {
+                path.moveTo(points.get(0).x, points.get(0).y);
+                path.lineTo(points.get(1).x, points.get(1).y);
+            } else if (points.size() >= 3){
+                // Else, essentially run deCasteljau
+                path.moveTo(points.get(0).x, points.get(0).y);
+                PointF mid = new PointF((points.get(0).x + points.get(1).x) / 2,
+                                        (points.get(0).y + points.get(1).y) / 2);
+                path.lineTo(mid.x, mid.y);
+
+                for (int i = 1; i < points.size() - 1; i++) {
+                    PointF p1 = points.get(i);
+                    PointF p2 = points.get(i + 1);
+                    PointF midP = new PointF((p1.x + p2.x) / 2,(p1.y + p2.y) / 2);
+                    path.quadTo(p1.x, p1.y, midP.x, midP.y);
+                }
+
+                path.lineTo(points.get(points.size() - 1).x, points.get(points.size() - 1).y);
+            }
         } else {
-            path.lineTo(p.x, p.y);
+            path.moveTo(points.get(0).x, points.get(0).y);
+            for (int i = 1; i < points.size(); i++) {
+                path.lineTo(points.get(i).x, points.get(i).y);
+            }
         }
-        previousPoint = p;
-        numberOfPoints++;
     }
 
     public boolean isEmpty() {
-        return numberOfPoints == 0;
+        return path.isEmpty();
     }
 
     public float[] getModelMatrix() {
@@ -41,7 +88,7 @@ public class SkARFingerPainting {
     }
 
     public void reset() {
+        points = new ArrayList<>();
         path = new Path();
-        numberOfPoints = 0;
     }
 }
diff --git a/platform_tools/android/apps/skar_java/src/main/res/menu/main_menu.xml b/platform_tools/android/apps/skar_java/src/main/res/menu/main_menu.xml
index f70e272aa5..d4383f99f1 100644
--- a/platform_tools/android/apps/skar_java/src/main/res/menu/main_menu.xml
+++ b/platform_tools/android/apps/skar_java/src/main/res/menu/main_menu.xml
@@ -6,6 +6,17 @@
             android:id="@+id/reset_paint"
             android:title="Reset Finger Painting"/>
     </group>
+    <group
+        android:id="@+id/menu_middle"
+        android:checkableBehavior="single">
+        <item
+            android:id="@+id/smooth_paint"
+            android:title="Smooth Painting" />
+        <item
+            android:id="@+id/rough_paint"
+            android:title="Rough Painting" />
+    </group>
+
 
     <group
         android:id="@+id/menu_bottom"