1 files changed, 90 insertions, 0 deletions
diff --git a/hw2/bin/image_compare.cpp b/hw2/bin/image_compare.cpp
new file mode 100644
index 0000000..4f1a798
--- /dev/null
+++ b/hw2/bin/image_compare.cpp
@@ -0,0 +1,90 @@
+#include <string>
+#include <iostream>
+
+#include "util.h"
+#include "image.h"
+#include "imageIO.h"
+#include "constants.h"
+#include "errorMessage.h"
+
+int main(int argc, char** argv)
+{
+  // parse command line
+  if(argc != 3)
+  {
+    std::cout << "Usage: " << argv[0] << " <image A> <image B>" << std::endl;
+    return -1;
+  }
+
+  std::string nameA(argv[1]);
+  std::string nameB(argv[2]);
+
+  // get image extensions
+  std::string extA = getExtension(nameA);
+  std::string extB = getExtension(nameB);
+
+  // check if both images have the same extension
+  if(extA != extB) errorMessage(" => different image types (PPM vs PFM).");
+
+  // load images
+  image imgA, imgB;
+  importImage(nameA, imgA);
+  importImage(nameB, imgB);
+
+  // check if both have the same dimension
+  if(imgA.width() != imgB.width() || imgA.height() != imgB.height())
+    errorMessage(" => different images sizes (%dx%d) vs (%dx%d).", imgA.width(), imgA.height(), imgB.width(), imgB.height());
+
+  // compute the difference image
+  image diff(imgA.width(), imgA.height());
+  color avgDiff, maxDiff;
+  unsigned long diffCount = 0;
+
+  for(image::size_type y=0; y < diff.height(); y++)
+    for(image::size_type x=0; x < diff.width(); x++)
+    {
+      // per pixel difference 
+      color diffColor = imgA(x,y) - imgB(x,y);
+      diff(x,y) = (extA == "ppm") ? abs(diffColor) : diffColor;
+
+      // if different => update average and max (abs value)
+      diffColor.abs();
+      if(diffColor.r > EPSILON || diffColor.g > EPSILON || diffColor.b > EPSILON)
+      {
+	diffCount++;
+	avgDiff += diffColor;
+	maxDiff = color(std::max(maxDiff.r, diffColor.r), std::max(maxDiff.g, diffColor.g), std::max(maxDiff.b, diffColor.b));
+      }
+    }
+
+  // output results if different
+  if(extA == "ppm" && diffCount != 0)
+  {
+    avgDiff /= diffCount;
+    std::cout << " => There are " << diffCount << " pixels that differ." << std::endl;
+    std::cout << "    Average difference: " << avgDiff << " [base 256: " << (avgDiff * 256.0f) << "]" << std::endl;
+    std::cout << "    Maximum difference: " << maxDiff << " [base 256: " << (maxDiff * 256.0f) << "]" << std::endl;
+
+    // write out difference image
+    exportImage("diff.ppm", diff);
+  }
+
+  else if(extA == "pfm" && diffCount != 0)
+  {
+    avgDiff /= diffCount;
+    std::cout << " => There are " << diffCount << " pixels that differ." << std::endl;
+    std::cout << "    Average difference: " << avgDiff << std::endl;
+    std::cout << "    Maximum difference: " << maxDiff << std::endl;
+
+    // write out difference image
+    exportImage("diff.pfm", diff);
+  }
+
+  // if equal, let the user know
+  else {
+    std::cout << " => Both images are equal.\r\n";
+  }
+
+  // Done.
+  return 0;
+}