Implement MinimumInterval property

Change-Id: I26cb0129a8e131f77dad45f1d02440e79c1c2880

appinventor/components/src/edu/mit/appinventor/ai/personalimageclassifier/PersonalImageClassifier.java

@@ -106,6 +106,7 @@ public final class PersonalImageClassifier extends AndroidNonvisibleComponent
   private List<String> labels = Collections.emptyList();
   private String modelPath = null;
   private boolean running = false;
+  private int minClassTime = 0;
 
   public PersonalImageClassifier(final Form form) {
     super(form);
@@ -286,6 +287,21 @@ public boolean Running() {
     return running;
   }
 
+  @DesignerProperty(editorType = PropertyTypeConstants.PROPERTY_TYPE_NON_NEGATIVE_INTEGER,
+      defaultValue = "0")
+  @SimpleProperty(category = PropertyCategory.BEHAVIOR)
+  public void MinimumInterval(int interval) {
+    minClassTime = interval;
+    if (webview != null) {
+      webview.evaluateJavascript("minClassTime = " + interval + ";", null);
+    }
+  }
+
+  @SimpleProperty
+  public int MinimumInterval() {
+    return minClassTime;
+  }
+
   @SimpleFunction(description = "Performs classification on the image at the given path and triggers the GotClassification event when classification is finished successfully.")
   public void ClassifyImageData(final String image) {
     assertWebView("ClassifyImageData");
@@ -348,6 +364,7 @@ public void StopContinuousClassification() {
   @SimpleEvent(description = "Event indicating that the classifier is ready.")
   public void ClassifierReady() {
     InputMode(inputMode);
+    MinimumInterval(minClassTime);
     EventDispatcher.dispatchEvent(this, "ClassifierReady");
   }
 

appinventor/components/src/edu/mit/appinventor/ai/personalimageclassifier/assets/personal_image_classifier.js

@@ -41,6 +41,8 @@ img.style.display = "block";
 let frontFacing = false;
 let isVideoMode = false;
 let isRunning = false;
+let minClassTime = 0;
+let lastClassification = new Date();
 let webcamHolder = document.getElementById('webcam-box');
 let video = /** @type {HTMLVideoElement} */ (document.getElementById('webcam'));
 webcamHolder.style.display = 'none';
@@ -260,7 +262,13 @@ function cvcHandler() {
   if (!isRunning || !isVideoMode) {
     return;
   }
-  predict(video, true).then(() => setTimeout(cvcHandler, 16));
+  let now = new Date();
+  if (now.getTime() - lastClassification.getTime() > minClassTime) {
+    lastClassification = now;
+    predict(video, true).then(() => requestAnimationFrame(cvcHandler));
+  } else {
+    requestAnimationFrame(cvcHandler);
+  }
 }
 
 // Called from PersonalImageClassifier.java