diff --git a/cs677/pa3/edge-detect.cc b/cs677/pa3/edge-detect.cc
index 88dbe9f..98c7706 100644
--- a/cs677/pa3/edge-detect.cc
+++ b/cs677/pa3/edge-detect.cc
@@ -5,6 +5,10 @@
 #include "BMP.h"
 using namespace std;
 
+void usage(const char * progName);
+void squashAndPadData(unsigned char * raw_data, unsigned char * padded_data,
+                      int width, int height);
+
 void usage(const char * progName)
 {
     cout << "Usage: " << progName << " [options] <input-BMP-file>" << endl;
@@ -20,9 +24,6 @@ int main(int argc, char * argv[])
     string outputFileName;
     unsigned int threshold_level = 60;
 
-    if (argc < 2)
-        usage(argv[0]);
-
     for (argi = 0; argi < argc; argi++)
     {
         if (!strcmp(argv[argi], "-l"))
@@ -40,23 +41,41 @@ int main(int argc, char * argv[])
         }
     }
 
+    if (inputFileName == "")
+        usage(argv[0]);
 
     BMP inputImage(inputFileName.c_str());
-    unsigned char * data =
-        new unsigned char[inputImage.getWidth() * inputImage.getHeight() * 3];
-    inputImage.read(data);
+    int width = inputImage.getWidth();
+    int height = inputImage.getHeight();
+    int num_pixels = width * height;
+    unsigned char * bmp_data =
+        new unsigned char[num_pixels * 3];
+    inputImage.read(bmp_data);
 
-    unsigned char * data_ptr = data;
-    for (int i = 0; i < inputImage.getWidth() * inputImage.getHeight(); i++)
-    {
-        *data_ptr++ = 0;
-        *data_ptr++ = 0;
-        data_ptr++;
-    }
+    unsigned char * padded_data =
+        new unsigned char[(width + 2) * (height + 2)];
+    squashAndPadData(bmp_data, padded_data, width, height);
+    delete[] bmp_data;
 
-    BMP edges(outputFileName.c_str(),
-              inputImage.getWidth(),
-              inputImage.getHeight(),
-              data);
-    delete[] data;
+    delete[] padded_data;
 }
+
+void squashAndPadData(unsigned char * raw_data, unsigned char * padded_data,
+                      int width, int height)
+{
+    for (int i = 0; i < width + 2; i++)
+        *padded_data++ = 0;
+    for (int i = 0; i < height; i++)
+    {
+        *padded_data++ = 0;
+        for (int j = 0; j < width; j++)
+        {
+            *padded_data++ = (raw_data[0] + raw_data[1] + raw_data[2]) / 3;
+            raw_data += 3;
+        }
+        *padded_data++ = 0;
+    }
+    for (int i = 0; i < width + 2; i++)
+        *padded_data++ = 0;
+}
+