New Local Thresholding Algorithm

.vscode/c_cpp_properties.json

@@ -0,0 +1,17 @@
+{
+    "configurations": [
+        {
+            "name": "Linux",
+            "includePath": [
+                "${workspaceFolder}/**"
+            ],
+            "defines": [],
+            "compilerPath": "/usr/bin/gcc",
+            "cStandard": "gnu17",
+            "cppStandard": "gnu++14",
+            "intelliSenseMode": "linux-gcc-x64",
+            "configurationProvider": "ms-vscode.makefile-tools"
+        }
+    ],
+    "version": 4
+}

.vscode/settings.json

@@ -47,6 +47,21 @@
         "streambuf": "cpp",
         "cinttypes": "cpp",
         "typeinfo": "cpp",
-        "files.eol": "\n"
+        "files.eol": "\n",
+        "regex": "cpp",
+        "bitset": "cpp",
+        "chrono": "cpp",
+        "complex": "cpp",
+        "condition_variable": "cpp",
+        "cstring": "cpp",
+        "ctime": "cpp",
+        "set": "cpp",
+        "ratio": "cpp",
+        "future": "cpp",
+        "iomanip": "cpp",
+        "mutex": "cpp",
+        "shared_mutex": "cpp",
+        "thread": "cpp",
+        "variant": "cpp"
     }
 }

src/centroiders.cpp

@@ -11,11 +11,11 @@
 
 #include <unordered_set>
 #include <string.h>
+#include <cassert>
 
 namespace lost {
 
-// DUMMY
-
+// DUMMYS
 std::vector<Star> DummyCentroidAlgorithm::Go(unsigned char *image, int imageWidth, int imageHeight) const {
     std::vector<Star> result;
 
@@ -26,7 +26,7 @@ std::vector<Star> DummyCentroidAlgorithm::Go(unsigned char *image, int imageWidt
     return result;
 }
 
-// a poorly designed thresholding algorithm
+// UNUSED: a poorly designed thresholding algorithm
 int BadThreshold(unsigned char *image, int imageWidth, int imageHeight) {
     //loop through entire array, find sum of magnitudes
     long totalMag = 0;
@@ -36,7 +36,7 @@ int BadThreshold(unsigned char *image, int imageWidth, int imageHeight) {
     return (((totalMag/(imageHeight * imageWidth)) + 1) * 15) / 10;
 }
 
-// a more sophisticated thresholding algorithm, not tailored to star images
+// UNUSED: a more sophisticated thresholding algorithm, not tailored to star images
 int OtsusThreshold(unsigned char *image, int imageWidth, int imageHeight) {
     // code here, duh
     long total = imageWidth * imageHeight;
@@ -76,7 +76,7 @@ int OtsusThreshold(unsigned char *image, int imageWidth, int imageHeight) {
     return level;
 }
 
-// a simple, but well tested thresholding algorithm that works well with star images
+// UNUSED: a simple, but well tested thresholding algorithm that works well with star images.
 int BasicThreshold(unsigned char *image, int imageWidth, int imageHeight) {
     unsigned long totalMag = 0;
     float std = 0;
@@ -92,7 +92,9 @@ int BasicThreshold(unsigned char *image, int imageWidth, int imageHeight) {
     return mean + (std * 5);
 }
 
-// basic thresholding, but do it faster (trade off of some accuracy?)
+// UNUSED: Accepts an array of brightnesses and image dimensions, and returns the 
+// threshold brightness for the entire image, which is defined as 5 standard deviations
+// above the mean.
 int BasicThresholdOnePass(unsigned char *image, int imageWidth, int imageHeight) {
     unsigned long totalMag = 0;
     float std = 0;
@@ -105,9 +107,98 @@ int BasicThresholdOnePass(unsigned char *image, int imageWidth, int imageHeight)
     float mean = totalMag / totalPixels;
     float variance = (sq_totalMag / totalPixels) - (mean * mean);
     std = std::sqrt(variance);
-    return mean + (std * 5);
+    return std::round(mean + (std * 5));
+}
+
+//                          *****START OF COG ALGORITHM*****
+
+// This algorithm takes an image and finds all "centroids" or potential stars in it. It divides
+// the image into a square grid, calculates the threshold brightness of each subsection, or "box",
+// and uses that information to find the centroids. A threshold is defined as 5 standard deviations
+// above the mean brightness of pixels.
+
+// Commonly used terms:
+    // box: A subsection in the subdivision scheme
+    // subdivision scheme: The square grid that contains the boxes the image is divided into. Each
+        // box can be assigned an index in this scheme, which follows row-major order.
+    // subdivisions: The number of slices the image is sliced into on each side. The square of
+        // this quantity indicates the number of boxes.
+    // leftover: When doing this division, we often cannot give each box the same number of
+        // rows/columns to each box. This quantity tell us how many rows/columns in the subdivision
+        // scheme will have 1 extra row/column, and these always start with the first rows/columns.
+    // div: The minimum rows/columns each box will have.
+    // For leftover and div, "horizontal" refers to rows and "vertical" refers to columns
+
+// By default, this algorithm ensures that regardless of the subdivisions entered, the number of
+// pixels in each subdivision is imageWidth*imageHeight <= size <= 100 to ensure that enough
+// pixles will be sampled in each subdivision
+
+// Accepts an index in the subdivision scheme, and a horizontal/vertical leftover and div
+// This method uses these quantities to find the first row/column index in the actual image
+// that "i" references.
+int StartOfSubdivision(int i, int leftover, int div) {
+    if(i < leftover) {
+        return i * (div + 1);
+    } else {
+        return leftover * (div + 1) + (i - leftover) * div;
+    }
+}
+
+// Refer to definition for details
+long FindSubdivision(long i, int imageWidth, int imageHeight, int subdivisions);
+
+
+// Accepts a subdivsion, or "box" number, the image's brightness array and associated dimensions, 
+// and the subdivisions.
+// Returns the threshold for the corresponding box.
+int LocalBasicThreshold(int box, unsigned char *image, int imageWidth, int imageHeight, 
+        int subdivisions) {
+
+    int horizontalDiv = imageHeight / subdivisions;
+    int verticalDiv = imageWidth / subdivisions;
+    int horizontalLeftover = imageHeight % subdivisions;
+    int verticalLeftover = imageWidth % subdivisions;
+    int row = box / subdivisions; // Finds the current row in the subdivision scheme
+    int col = box % subdivisions; // Finds the current column in the subdivision scheme
+    double average = 0;
+    double squareSum = 0;
+    long count = 0;
+
+    // Runs through "box" in row-major order
+    for(long i = StartOfSubdivision(row, horizontalLeftover, horizontalDiv); 
+            i < StartOfSubdivision(row + 1, horizontalLeftover, horizontalDiv); i++) {
+        for(long j = StartOfSubdivision(col, verticalLeftover, verticalDiv); 
+                j < StartOfSubdivision(col + 1, verticalLeftover, verticalDiv); j++) {
+            average += image[i * imageWidth + j];
+            squareSum += image[i * imageWidth + j] * image[i * imageWidth + j];
+            count++;
+
+            // Checks for Error
+            assert(FindSubdivision(i*imageWidth+j, imageWidth, imageHeight, subdivisions) == box);
+        }
+    }
+
+    average /= count;
+    return std::round(average + (5 * std::sqrt((squareSum - count * average * average) / (count - 1))));
+}
+
+// Accepts the image's brightness array and dimensions, and the subdivisions, and returns
+// a vector with the threshold for each "box" in row-major order
+std::vector<int> LocalThresholding(unsigned char *image, int imageWidth, int imageHeight, 
+        int subdivisions) {
+
+    std::vector<int> thresholds;
+    for(int i = 0; i < subdivisions * subdivisions; i++) {
+        thresholds.push_back(LocalBasicThreshold(i, image, imageWidth, imageHeight, 
+                subdivisions));
+    }
+
+    return thresholds;
 }
 
+// Used in function CenterOfGravityAlgorithm:Go, and is useful for keeping track of
+// star dimensions and characteristics, as well as the database of thresholds among
+// other quantities relating to the image
 struct CentroidParams {
     float yCoordMagSum; 
     float xCoordMagSum;
@@ -116,17 +207,47 @@ struct CentroidParams {
     int xMax;
     int yMin;
     int yMax;
-    int cutoff;
+    std::vector<int> localCutoff;
     bool isValid;
     std::unordered_set<int> checkedIndices;
 };
 
-//recursive helper here
-void CogHelper(CentroidParams &p, long i, unsigned char *image, int imageWidth, int imageHeight) {
+// Accepts the row/column of an index on the image, the imageWidth/imageHeight, the subdivisions
+// and the horizontal/vertical div and leftover
+// Returns the index of the row/column in the subdivision scheme for the corresponding "i".
+// NOTE: This function is the inverse of the StartOfSubdivision function in a way that
+// RowOrColumn(StartOfSubdivision(x)) = x for any given row/column index "x" in the subdivision 
+// scheme, but StartOfSubdivision(RowOrColumn(x)) only equals x if x = StartOfSubdivision(y),
+// for any given row/column index "y" in the subdivision scheme 
+long RowOrColumn(long i, int leftover, int div) {
+    if(i < (div + 1) * leftover) {
+        return i / (div + 1);
+    } else {
+        return leftover + (i - (div + 1) * leftover) / (div);
+    }
+}
+
+// Accepts an index in the image, its dimensions and the subdivisions, and returns the 
+// corresponding "box" number that the index "i" is in
+long FindSubdivision(long i, int imageWidth, int imageHeight, int subdivisions) {
+    long row = RowOrColumn(i / imageWidth, imageHeight % subdivisions, imageHeight / subdivisions);
+    long col = RowOrColumn(i % imageWidth, imageWidth % subdivisions, imageWidth / subdivisions);
+    return  row * subdivisions + col;
+}
+
+// Accepts a CentroidParams struct, the current index, image's array of brightnesses and dimensions, 
+// and the subdivisions. This is a recursive helper method that is used with 
+// CenterOfGravityAlgorithm:Go and finds the dimensions of an individual star in the context of the
+// image
+void CogHelper(CentroidParams &p, long i, unsigned char *image, int imageWidth, int imageHeight, 
+        int subdivisions) {
 
-    if (i >= 0 && i < imageWidth * imageHeight && image[i] >= p.cutoff && p.checkedIndices.count(i) == 0) {
+    if (i >= 0 && i < imageWidth * imageHeight && 
+            image[i] >= p.localCutoff.at(FindSubdivision(i, imageWidth, imageHeight, subdivisions)) 
+                    && p.checkedIndices.count(i) == 0) {
         //check if pixel is on the edge of the image, if it is, we dont want to centroid this star
-        if (i % imageWidth == 0 || i % imageWidth == imageWidth - 1 || i / imageWidth == 0 || i / imageWidth == imageHeight - 1) {
+        if (i % imageWidth == 0 || i % imageWidth == imageWidth - 1 || i / imageWidth == 0 || 
+                i / imageWidth == imageHeight - 1) {
             p.isValid = false;
         }
         p.checkedIndices.insert(i);
@@ -144,25 +265,36 @@ void CogHelper(CentroidParams &p, long i, unsigned char *image, int imageWidth,
         p.xCoordMagSum += ((i % imageWidth)) * image[i];
         p.yCoordMagSum += ((i / imageWidth)) * image[i];
         if(i % imageWidth != imageWidth - 1) {
-            CogHelper(p, i + 1, image, imageWidth, imageHeight);
+            CogHelper(p, i + 1, image, imageWidth, imageHeight, subdivisions);
         }
         if (i % imageWidth != 0) {
-            CogHelper(p, i - 1, image, imageWidth, imageHeight);
+            CogHelper(p, i - 1, image, imageWidth, imageHeight, subdivisions);
         }
-        CogHelper(p, i + imageWidth, image, imageWidth, imageHeight);
-        CogHelper(p, i - imageWidth, image, imageWidth, imageHeight);
+        CogHelper(p, i + imageWidth, image, imageWidth, imageHeight, subdivisions);
+        CogHelper(p, i - imageWidth, image, imageWidth, imageHeight, subdivisions);
     }
 }
 
+// Accepts an array of the image's brightnesses, and the image's dimensions, and finds all
+// stars in the image and returns the stars as an array
 std::vector<Star> CenterOfGravityAlgorithm::Go(unsigned char *image, int imageWidth, int imageHeight) const {
     CentroidParams p;
-
+    // Program will use divisions to represent the subdivisions
+    int divisions = subdivisions;
+    int min = 0;
+    if(imageWidth > imageHeight) {
+        min = imageWidth;
+    } else {
+        min = imageHeight;
+    }
+    if(min / subdivisions < 10) {
+        divisions = min / 10;
+    }
     std::vector<Star> result;
-
-    p.cutoff = BasicThreshold(image, imageWidth, imageHeight);
+    p.localCutoff = LocalThresholding(image, imageWidth, imageHeight, divisions);
     for (long i = 0; i < imageHeight * imageWidth; i++) {
-        if (image[i] >= p.cutoff && p.checkedIndices.count(i) == 0) {
-
+        if (image[i] >= p.localCutoff.at(FindSubdivision(i, imageWidth, imageHeight, divisions)) 
+                && p.checkedIndices.count(i) == 0) {
             //iterate over pixels that are part of the star
             int xDiameter = 0; //radius of current star
             int yDiameter = 0;
@@ -178,7 +310,7 @@ std::vector<Star> CenterOfGravityAlgorithm::Go(unsigned char *image, int imageWi
 
             int sizeBefore = p.checkedIndices.size();
 
-            CogHelper(p, i, image, imageWidth, imageHeight);
+            CogHelper(p, i, image, imageWidth, imageHeight, divisions);
             xDiameter = (p.xMax - p.xMin) + 1;
             yDiameter = (p.yMax - p.yMin) + 1;
 
@@ -187,13 +319,16 @@ std::vector<Star> CenterOfGravityAlgorithm::Go(unsigned char *image, int imageWi
             float yCoord = (p.yCoordMagSum / (p.magSum * 1.0));
 
             if (p.isValid) {
-                result.push_back(Star(xCoord + 0.5f, yCoord + 0.5f, ((float)(xDiameter))/2.0f, ((float)(yDiameter))/2.0f, p.checkedIndices.size() - sizeBefore));
+                result.push_back(Star(xCoord + 0.5f, yCoord + 0.5f, ((float)(xDiameter))/2.0f, 
+                        ((float)(yDiameter))/2.0f, p.checkedIndices.size() - sizeBefore));
             }
         }
     }
     return result;
 }
 
+//                          *****END OF COG ALGORITHM*****
+
 //Determines how accurate and how much iteration is done by the IWCoG algorithm,
 //smaller means more accurate and more iterations.
 float iWCoGMinChange = 0.0002;
@@ -203,17 +338,19 @@ struct IWCoGParams {
     int xMax;
     int yMin;
     int yMax;
-    int cutoff;
+    std::vector<int> localCutoff;
     int maxIntensity;
     int guess;
     bool isValid;
     std::unordered_set<int> checkedIndices;
 };
 
-void IWCoGHelper(IWCoGParams &p, long i, unsigned char *image, int imageWidth, int imageHeight, std::vector<int> &starIndices) {
-    if (i >= 0 && i < imageWidth * imageHeight && image[i] >= p.cutoff && p.checkedIndices.count(i) == 0) {
+void IWCoGHelper(IWCoGParams &p, long i, unsigned char *image, int imageWidth, int imageHeight, int subdivisions, std::vector<int> &starIndices) {
+    if (i >= 0 && i < imageWidth * imageHeight && image[i] >= p.localCutoff.at(FindSubdivision(i, imageWidth, imageHeight, subdivisions))
+        && p.checkedIndices.count(i) == 0) {
         //check if pixel is on the edge of the image, if it is, we dont want to centroid this star
-        if (i % imageWidth == 0 || i % imageWidth == imageWidth - 1 || i / imageWidth == 0 || i / imageWidth == imageHeight - 1) {
+        if (i % imageWidth == 0 || i % imageWidth == imageWidth - 1 || i / imageWidth == 0 
+                || i / imageWidth == imageHeight - 1) {
             p.isValid = false;
         }
         p.checkedIndices.insert(i);
@@ -233,23 +370,34 @@ void IWCoGHelper(IWCoGParams &p, long i, unsigned char *image, int imageWidth, i
             p.yMin = i / imageWidth;
         }
         if(i % imageWidth != imageWidth - 1) {
-            IWCoGHelper(p, i + 1, image, imageWidth, imageHeight, starIndices);
+            IWCoGHelper(p, i + 1, image, imageWidth, imageHeight, subdivisions, starIndices);
         }
         if (i % imageWidth != 0) {
-            IWCoGHelper(p, i - 1, image, imageWidth, imageHeight, starIndices);
+            IWCoGHelper(p, i - 1, image, imageWidth, imageHeight, subdivisions, starIndices);
         }
-        IWCoGHelper(p, i + imageWidth, image, imageWidth, imageHeight, starIndices);
-        IWCoGHelper(p, i - imageWidth, image, imageWidth, imageHeight, starIndices);
+        IWCoGHelper(p, i + imageWidth, image, imageWidth, imageHeight, subdivisions, starIndices);
+        IWCoGHelper(p, i - imageWidth, image, imageWidth, imageHeight, subdivisions, starIndices);
     }
 }
 
 Stars IterativeWeightedCenterOfGravityAlgorithm::Go(unsigned char *image, int imageWidth, int imageHeight) const {
     IWCoGParams p;
+    int divisions = subdivisions;
+    int min = 0;
+    if(imageWidth > imageHeight) {
+        min = imageWidth;
+    } else {
+        min = imageHeight;
+    }
+    if(min / subdivisions < 10) {
+        divisions = min / 10;
+    }
     std::vector<Star> result;
-    p.cutoff = BasicThreshold(image, imageWidth, imageHeight);
+    p.localCutoff = LocalThresholding(image, imageWidth, imageHeight, divisions);
     for (long i = 0; i < imageHeight * imageWidth; i++) {
         //check if pixel is part of a "star" and has not been iterated over
-        if (image[i] >= p.cutoff && p.checkedIndices.count(i) == 0) {
+        if (image[i] >= p.localCutoff.at(FindSubdivision(i, imageWidth, imageHeight, subdivisions))
+             && p.checkedIndices.count(i) == 0) {
             // TODO: store longs --Mark
             std::vector<int> starIndices; //indices of the current star
             p.maxIntensity = 0;
@@ -269,7 +417,7 @@ Stars IterativeWeightedCenterOfGravityAlgorithm::Go(unsigned char *image, int im
             p.isValid = true;
 
 
-            IWCoGHelper(p, i, image, imageWidth, imageHeight, starIndices);
+            IWCoGHelper(p, i, image, imageWidth, imageHeight, divisions, starIndices);
 
             xDiameter = (p.xMax - p.xMin) + 1;
             yDiameter = (p.yMax - p.yMin) + 1;