Refactor blob detection outside of the Touch class

.gitignore

@@ -3,3 +3,4 @@ build/
 .vscode/
 *.user
 *code-workspace
+library.json

CMakeLists.txt

@@ -30,6 +30,7 @@ add_library(puara_gestures
   include/puara/descriptors/tilt.h
   include/puara/descriptors/touch.h
 
+  include/puara/utils/blobDetector.h
   include/puara/utils/calibration.h
   include/puara/utils/circularbuffer.h
   include/puara/utils/leakyintegrator.h

include/puara/descriptors/touch.h

@@ -1,43 +1,41 @@
 #pragma once
 
 #include <puara/utils.h>
+#include <puara/utils/blobDetector.h>
 #include <puara/utils/leakyintegrator.h>
 
 #include <cmath>
+#include<iostream>
 
 namespace puara_gestures
 {
 
 class Touch
 {
 public:
+  static constexpr int maxNumBlobs = BlobDetector::maxNumBlobs;
   float touchAll = 0.0f;    // f, 0--1
   float touchTop = 0.0f;    // f, 0--1
   float touchMiddle = 0.0f; // f, 0--1
   float touchBottom = 0.0f; // f, 0--1
   float brush = 0.0f;       // f, 0--? (~cm/s)
-  double multiBrush[4]{};   // ffff, 0--? (~cm/s)
+  double multiBrush[maxNumBlobs]{}; // ffff, 0--? (~cm/s)
   float rub{};              // f, 0--? (~cm/s)
-  double multiRub[4]{};     // ffff, 0--? (~cm/s)
+  double multiRub[maxNumBlobs]{}; // ffff, 0--? (~cm/s)
 
   // touch array
-  int touchSizeEdge
-      = 4; // amount of touch stripes for top and bottom portions (arbitrary)
-  int lastState_blobPos[4]{};
-  int maxBlobs = 4;    // max amount of blobs to be detected
-  int blobAmount{};    // amount of detected blobs
-  int blobCenter[4]{}; // shows the "center" (index) of each blob (former blobArray)
-  int blobPos[4]{};    // starting position (index) of each blob
-  float blobSize[4]{}; // "size" (amount of stripes) of each blob
-  int brushCounter[4]{};
+  int touchSizeEdge = 4; // amount of touch stripes for top and bottom portions (arbitrary)
+
+  BlobDetector blobDetector;
+  int brushCounter[maxNumBlobs]{};
 
   // Arrays of LeakyIntegrator instances
-  utils::LeakyIntegrator multiBrushIntegrator[4];
-  utils::LeakyIntegrator multiRubIntegrator[4];
+  utils::LeakyIntegrator multiBrushIntegrator[maxNumBlobs];
+  utils::LeakyIntegrator multiRubIntegrator[maxNumBlobs];
 
   Touch()
   {
-    for(int i = 0; i < 4; ++i)
+    for(int i = 0; i < maxNumBlobs; ++i)
     {
       multiBrushIntegrator[i] = utils::LeakyIntegrator(0.0f, 0.0f, 0.7f, 100, 0);
       multiRubIntegrator[i] = utils::LeakyIntegrator(0.0f, 0.0f, 0.7f, 100, 0);
@@ -67,28 +65,15 @@ class Touch
     // normalized between 0 and 1
     touchBottom = touchAverage(discrete_touch, (touchSize - touchSizeEdge), touchSize);
 
-    // Save last blob detection state before reading new data
-    for(int i = 0; i < (sizeof(blobPos) / sizeof(blobPos[0])); ++i)
-    {
-      lastState_blobPos[i] = blobPos[i];
-    }
-
-    // 1D blob detection: used for brush
-    blobDetection1D(discrete_touch, touchSize);
+     // 1D blob detection: used for brush
+    const auto movement = blobDetector.detect1D(discrete_touch, touchSize);
 
     // brush: direction and intensity of capsense brush motion
     // rub: intensity of rub motion
     // in ~cm/s (distance between stripes = ~1.5cm)
-    for(int i = 0; i < (sizeof(blobPos) / sizeof(blobPos[0])); ++i)
+    for(int i = 0; i < movement.size(); ++i)
     {
-      float movement = blobPos[i] - lastState_blobPos[i];
-      if(blobPos[i] == -1)
-      {
-        multiBrush[i] = 0;
-        multiRub[i] = 0;
-        brushCounter[i] = 0;
-      }
-      else if(movement == 0)
+      if(movement[i] == 0)
       {
         if(brushCounter[i] < 10)
         {
@@ -109,11 +94,11 @@ class Touch
           //       (std::abs(movement * 0.15)), multiRub[i], 0.7, leakyRubFreq,
           //       leakyRubTimer);
           //
-          multiBrush[i] = multiBrushIntegrator[i].integrate(movement * 0.15);
-          multiRub[i] = multiRubIntegrator[i].integrate(std::abs(movement * 0.15));
+          multiBrush[i] = multiBrushIntegrator[i].integrate(movement[i] * 0.15);
+          multiRub[i] = multiRubIntegrator[i].integrate(std::abs(movement[i] * 0.15));
         }
       }
-      else if(std::abs(movement) > 1)
+      else if(std::abs(movement[i]) > 1)
       {
         // multiBrush[i] = multiBrushIntegrator[i].integrate(
         //     0, multiBrush[i], 0.6, leakyBrushFreq, leakyBrushTimer);
@@ -128,14 +113,14 @@ class Touch
         //     (std::abs(movement * 0.15)) * 0.15, multiRub[i], 0.99, leakyRubFreq,
         //     leakyRubTimer);
 
-        multiBrush[i] = multiBrushIntegrator[i].integrate(movement * 0.15);
-        multiRub[i] = multiRubIntegrator[i].integrate((std::abs(movement * 0.15)));
+        multiBrush[i] = multiBrushIntegrator[i].integrate(movement[i] * 0.15);
+        multiRub[i] = multiRubIntegrator[i].integrate((std::abs(movement[i] * 0.15)));
 
         brushCounter[i] = 0;
       }
     }
-    brush = utils::arrayAverageZero(multiBrush, 4);
-    rub = utils::arrayAverageZero(multiRub, 4);
+    brush = utils::arrayAverageZero(multiBrush, maxNumBlobs);
+    rub = utils::arrayAverageZero(multiRub, maxNumBlobs);
   }
 
   float touchAverage(float* touchArrayStrips, int firstStrip, int lastStrip)
@@ -155,39 +140,5 @@ class Touch
 
     return ((float)sum) / (lastStrip - firstStrip);
   }
-
-  //TODO: move to utils
-  void blobDetection1D(int* discrete_touch, int touchSize)
-  {
-    blobAmount = 0;
-    int sizeCounter = 0;
-    int stripe = 0;
-    for(int i = 0; i < 4; i++)
-    {
-      blobCenter[i] = 0;
-      blobPos[i] = 0;
-      blobSize[i] = 0;
-    }
-
-    for(; stripe < touchSize; stripe++)
-    {
-      if(blobAmount < maxBlobs)
-      {
-        if(discrete_touch[stripe] == 1)
-        { // check for beggining of blob...
-          sizeCounter = 1;
-          blobPos[blobAmount] = stripe;
-          while(discrete_touch[stripe + sizeCounter] == 1)
-          { // then keep checking for end
-            sizeCounter++;
-          }
-          blobSize[blobAmount] = sizeCounter;
-          blobCenter[blobAmount] = stripe + (sizeCounter / 2);
-          stripe += sizeCounter + 1; // skip stripes already read
-          blobAmount++;
-        }
-      }
-    }
-  }
 };
 }

include/puara/utils/blobDetector.h

@@ -0,0 +1,138 @@
+#pragma once
+
+#include <boost/container/small_vector.hpp>
+
+namespace puara_gestures
+{
+
+/**
+ * @struct BlobDetector
+ * @brief A structure for detecting contiguous regions (blobs) of `1`s in binary arrays.
+ *
+ * The `BlobDetector` identifies contiguous blobs in a binary input array where elements are either
+ * `0` or `1`.
+ * For each blob, it computes:
+ * - The start position (`blobStartPos`)
+ * - The size in terms of consecutive `1`s (`blobSize`)
+ * - The center index (`blobCenter`)
+ * - Movement compared to the previous detection (`lastState_blobPos`)
+ * @warning Most of these values are reset when a detection function, e.g., detect1D(), is called,
+ * and calculated during the detection funtion calls -- so their value is only really valid right
+ * after such a call. There is no locking mechanism on any of these values so it is on the client
+ * to ensure there is no race conditions.
+ *
+ * @details
+ * The struct maintains internal arrays to store information about detected blobs, including their
+ * start positions, sizes, and centers. It also tracks blob positions from the previous invocation
+ * of the detection function to compute movement values.
+ *
+ * ## Key Functionalities:
+ * - **Blob Detection:** Detects contiguous regions of `1`s in a binary input array.
+ * - **Movement Calculation:** Computes the positional changes (movement) of blobs compared to
+ *   their last positions.
+ * - **Data Management:** Maintains internal state between function calls to facilitate movement
+ *   tracking.
+ *
+ * @note
+ * - The number of blobs processed is limited by `maxNumBlobs` (default is `4`).
+ * - If the input contains more blobs than `maxNumBlobs`, the additional blobs are ignored.
+ */
+class BlobDetector
+{
+public:
+  /** The maximum number of blobs that the algorithm should detect. */
+  static constexpr int maxNumBlobs = 4;
+
+  /** The start index of detected blobs. */
+  int blobStartPos[maxNumBlobs]{};
+
+  /** The cached start index of detected blobs, from the previous time detect1D
+    * was called.
+    */
+  int lastState_blobPos[maxNumBlobs]{};
+
+  /** size (amount of stripes) of each blob */
+  int blobSize[maxNumBlobs]{};
+
+  /** shows the "center"(index)of each blob */
+  float blobCenter[maxNumBlobs]{};
+
+  /** amount of detected blobs */
+  int blobAmount{};
+
+  /**
+    * @brief Detects contiguous regions (blobs) of `1`s in a 1D binary array and computes their movement.
+    *
+    * This function identifies blobs in the input binary array `touchArray`, calculates their start
+    * positions, sizes, and centers, and returns the movement of the blobs compared to their positions
+    * from the previous function call.
+    *
+    * @param touchArray Pointer to the 1D binary array representing touch data. Each element is expected to be 0 or 1.
+    * @param touchArraySize The size of the `touchArray`, representing the number of touch sensor in the array.
+    *        This is expected to be larger than maxNumBlobs, which by definition will be a portion of the number
+    *        of sensors, or at most equal to the number of sensors.
+    * @return A small_vector of integers representing the movement of each blob's start position since the
+    *         last invocation of `detect1D`.
+    *
+    * @note
+    * - The function updates the global variables `blobStartPos`, `blobSize`, `blobCenter`,
+    *   and `lastState_blobPos`.
+    * - The number of blobs detected is limited by `maxNumBlobs`.
+    * - If the number of blobs exceeds `maxNumBlobs`, additional blobs are ignored.
+    *
+    * @warning
+    * - Ensure that `touchArray` has at least `size` elements to avoid out-of-bounds access.
+    * - The function relies on external global variables (`blobStartPos`, `blobSize`, `blobCenter`,
+    *   `lastState_blobPos`, `maxNumBlobs`, `blobAmount`). Ensure they are initialized appropriately
+    *   before calling the function.
+    */
+  boost::container::small_vector<int, maxNumBlobs>
+  detect1D(const int* const touchArray, const int touchArraySize)
+  {
+    blobAmount = 0;
+    for(int i = 0; i < maxNumBlobs; i++)
+    {
+      //cache the last blobStartPos before clearing it
+      lastState_blobPos[i] = blobStartPos[i];
+      blobStartPos[i] = 0;
+      blobSize[i] = 0;
+      blobCenter[i] = 0;
+    }
+
+    for(int stripe = 0; stripe < touchArraySize;)
+    {
+      if(touchArray[stripe] == 1)
+      {
+        //start the blob
+        blobStartPos[blobAmount] = stripe;
+
+        //continue the blob until we no longer have 1s
+        int sizeCounter = 1;
+        while((stripe + sizeCounter) <= touchArraySize
+              && touchArray[stripe + sizeCounter] == 1)
+        {
+          sizeCounter++;
+        }
+
+        blobSize[blobAmount] = sizeCounter;
+        blobCenter[blobAmount] = stripe + (sizeCounter - 1.0) / 2.0;
+        stripe += sizeCounter;
+
+        if(++blobAmount >= maxNumBlobs)
+          break;
+      }
+      else
+      {
+        ++stripe;
+      }
+    }
+
+    //return the movement since the last time detect1D was called
+    boost::container::small_vector<int, maxNumBlobs> movement(maxNumBlobs, 0);
+    for(int i = 0; i < maxNumBlobs; ++i)
+      movement[i] = blobStartPos[i] - lastState_blobPos[i];
+
+    return movement;
+  }
+};
+}

tests/testing_touch.cpp

@@ -1,26 +1,64 @@
 #include <puara/gestures.h>
 
-#include <iostream>
-
 using namespace puara_gestures;
 
 int main()
 {
   Touch touch;
 
-  int touchSize = 16;
-  int discrete_touch[16] = {0};
+  constexpr int touchSize = 16;
+  int discrete_touch[touchSize] = {0};
+
+  // simulate a blob of size 1 starting at position 0
+  discrete_touch[0] = 1;
 
-  // simulate a touch (1) at a position 5
+  // simulate a blob of size 2 starting at position 5
   discrete_touch[5] = 1;
+  discrete_touch[6] = 1;
 
-  // Update the touch data
-  touch.updateTouchArray(discrete_touch, touchSize);
+  // simulate a blob of size 3 starting at position 8
+  discrete_touch[8] = 1;
+  discrete_touch[9] = 1;
+  discrete_touch[10] = 1;
+
+  // simulate a blob of size 1 at position 12 -- commented out to test the end of the array in the next blob
+  //discrete_touch[12] = 1;
 
-  // Output the computed values
+  // simulate a blob of size 2 starting at position 14
+  discrete_touch[14] = 1;
+  discrete_touch[15] = 1;
+
+  // Update the touch data and print the computed values
+  touch.updateTouchArray(discrete_touch, touchSize);
   std::cout << "touchAll: " << touch.touchAll << std::endl;
   std::cout << "brush: " << touch.brush << std::endl;
   std::cout << "rub: " << touch.rub << std::endl;
 
-  // multi touch
+  //reset the touch array, and next we'll repeat the above blobs but offset by 1 to simulate movement
+  for(int i = 0; i < touchSize; ++i)
+    discrete_touch[i] = 0;
+
+  // simulate a blob of size 1 starting at position 1
+  discrete_touch[1] = 1;
+
+  // simulate a blob of size 2 starting at position 6
+  discrete_touch[6] = 1;
+  discrete_touch[7] = 1;
+
+  // simulate a blob of size 3 starting at position 9
+  discrete_touch[9] = 1;
+  discrete_touch[10] = 1;
+  discrete_touch[11] = 1;
+
+  // simulate a blob of size 1 at position 13 -- commented out to test the end of the array in the next blob
+  //discrete_touch[13] = 1;
+
+  // simulate a blob of size 1 starting at position 15
+  discrete_touch[15] = 1;
+
+  // Update the touch data and print the computed values
+  touch.updateTouchArray(discrete_touch, touchSize);
+  std::cout << "touchAll: " << touch.touchAll << std::endl;
+  std::cout << "brush: " << touch.brush << std::endl;
+  std::cout << "rub: " << touch.rub << std::endl;
 }