Implemented difference of gaussian algorithm.

SIFT/ComputeDifferenceOfGaussian.asv

@@ -0,0 +1,14 @@
+% This function computes the difference in gaussian and outputs a new pyramid
+function gaussianPyramid = ComputeDifferenceOfGaussian(pyramid)
+    if isempty(pyramid)
+        return
+    end
+
+    gaussianPyramid = {};    % Initialize difference of gaussian cell array
+
+    for i=1:size(pyramid,2)     % Iterate through the octaves
+        for j=1:size(pyramid{1},2)-1  % Iterate through the scales
+            gaussianPyramid{i}{j} = pyramid{i}{j} - pyramid{i;
+        end
+    end 
+end

SIFT/ComputeDifferenceOfGaussian.m

@@ -0,0 +1,14 @@
+% This function computes the difference in gaussian and outputs a new pyramid
+function gaussianPyramid = ComputeDifferenceOfGaussian(pyramid)
+    if isempty(pyramid)
+        return
+    end
+
+    gaussianPyramid = {};    % Initialize difference of gaussian cell array
+
+    for i=1:size(pyramid,2)     % Iterate through the octaves
+        for j=1:size(pyramid{1},2)-1  % Iterate through the scales
+            gaussianPyramid{i}{j} = pyramid{i}{j+1} - pyramid{i}{j};
+        end
+    end 
+end

SIFT/SIFT.m

@@ -1,7 +1,7 @@
 % Perform edge detection with interpolation during non maximum suppression
 function CannyEdgeDetector()
     close all;  % Close figures
-    OCTAVES = 4;
+    OCTAVES = 3;
 
     % Change the current folder to the folder of this m-file.
     % Courtesy of Brett Shoelson
@@ -15,4 +15,8 @@ function CannyEdgeDetector()
 
     pyramid = MakePyramid(im,OCTAVES);
     ShowPyramid(pyramid);
+
+    pyramid = ComputeDifferenceOfGaussian(pyramid);
+    ShowPyramid(pyramid);
+
 end

SIFT/ShowPyramid.m

@@ -15,8 +15,9 @@ function ShowPyramid(pyramid)
         end
     end 
 
+    figure;
     for i=1:length(pyramidImage)
-        figure;
+        subplot(length(pyramidImage),1,i);
         imshow(pyramidImage{i});
     end
 end