Starting implementing local extrema detection algorithm.

delete

SIFT/DetectLocalExtrema.asv

@@ -0,0 +1,28 @@
+function DetectLocalExtrema(pyramid)
+    for octaveNum=1:size(pyramid,2)     % Iterate through the octaves
+        for scaleNum=1:size(pyramid{1},2)-2  % Iterate through the scales
+            [h,w] = size(pyramid{octaveNum}{scaleNum});
+            for row=2:h-1    % Iterate through rows
+                for col=2:w-1   % Iterate through cols
+                    CompareNeighbors(pyramid, octaveNum, scaleNum);
+                end
+            end
+        end
+    end 
+end
+
+% Compares the neighbors for all the pixels
+function CompareNeighbors(pyramid, octaveNum, scaleNum)
+    % Compare the 26 neighbors
+    for i=-1:1:1
+        for j=-1:1:1
+            for k=0:2
+                if pyramid{octaveNum}{scaleNum}(row,col) < ...
+                    pyramid{octaveNum}{scaleNum+k}(row+i,col+j)
+                    return;
+                end
+            end
+        end
+    end
+
+end

SIFT/DetectLocalExtrema.m

@@ -0,0 +1,38 @@
+function [localExtrema] = DetectLocalExtrema(pyramid)
+%     THRESHOLD = 
+    localExtrema = {};
+    count = 0;
+    for octaveNum=1:size(pyramid,2)     % Iterate through the octaves
+        for scaleNum=1:size(pyramid{1},2)-2  % Iterate through the scales
+            [h,w] = size(pyramid{octaveNum}{scaleNum});
+            for row=2:h-1    % Iterate through rows
+                for col=2:w-1   % Iterate through cols
+                    count = count + 1;
+                    temp = CompareNeighbors(pyramid, octaveNum, scaleNum, row, col);
+                    if ~isempty(temp)
+                        localExtrema(end+1) = temp;
+                    end
+                end
+            end
+        end
+    end 
+    count
+end
+
+% Compares the neighbors for all the pixels
+function [localExtrema] = CompareNeighbors(pyramid, octaveNum, scaleNum, row, col)
+    % Compare the 26 neighbors
+    for i=-1:1:1
+        for j=-1:1:1
+            for k=0:2
+                if pyramid{octaveNum}{scaleNum+1}(row,col) < ...
+                    pyramid{octaveNum}{scaleNum+k}(row+i,col+j)
+                    localExtrema = {};
+                    return;
+                end
+            end
+        end
+    end
+    localExtrema = {[row,col]};
+
+end

SIFT/MakePyramid.m

@@ -3,7 +3,7 @@
 % in the template
 function[pyramid] = MakePyramid(im, octaves)
     SCALE = 1.6;
-    SCALES_PER_OCTAVE = 3;
+    SCALES_PER_OCTAVE = 4;
     K = sqrt(2);
     RATIO = 0.5;
 

SIFT/SIFT.m

@@ -18,5 +18,7 @@ function CannyEdgeDetector()
 
     pyramid = ComputeDifferenceOfGaussian(pyramid);
     ShowPyramid(pyramid);
-
+
+    localExtrema = DetectLocalExtrema(pyramid);
+    test = 5;
 end