diff --git a/INSTALL b/INSTALL
index 3642a5c..d15b5d5 100644
--- a/INSTALL
+++ b/INSTALL
@@ -5,21 +5,21 @@ Dependencies
 - CUDA (>= 4.0) (Not required for the CPU-only feature extractor).
 
 - HDF5 (>= 1.8.11)
-  Download the source code http://www.hdfgroup.org/ftp/HDF5/prev-releases/hdf5-1.8.12/src/hdf5-1.8.12.tar.gz
+  Download the source code http://www.hdfgroup.org/ftp/HDF5/releases/hdf5-1.8.16/src/hdf5-1.8.16.tar.gz
   To install locally -
   $ ./configure --prefix=~/local/ --enable-threadsafe --with-pthread=/usr/include
-  $ make
+  $ make -j7
   $ make install
 
 - Protocol Buffers (>= 2.5.0)
-  Download the source code https://protobuf.googlecode.com/files/protobuf-2.5.0.tar.gz
+  Download the source code https://github.com/google/protobuf/releases/download/v2.6.1/protobuf-2.6.1.tar.gz
   To install locally -
   $ ./configure --prefix=~/local/
-  $ make
+  $ make -j7
   $ make install
 
 - OpenCV
-  Download the source code https://github.com/Itseez/opencv/archive/3.0.0-alpha.zip
+  Download the source code https://github.com/Itseez/opencv/archive/3.1.0.tar.gz
   To quick install -
   $ cmake-gui, set CMAKE_BUILD_TYPE to Release
   $ cd build directory
@@ -29,6 +29,7 @@ Dependencies
 - libjpeg
   This is often present on standard operating systems since it is used by a lot of programs.
   It can be downloaded from http://libjpeg.sourceforge.net/
+  For Ubuntu: sudo apt-get install libjpeg-dev
 
 - This code uses C++11. Some features require gcc >= 4.6.
 
diff --git a/src/image_iterators.cc b/src/image_iterators.cc
index 79115f4..0ff3ba9 100644
--- a/src/image_iterators.cc
+++ b/src/image_iterators.cc
@@ -63,13 +63,11 @@ void getData(Mat &image, T* data_ptr) {
   int num_pixels = image.cols * image.rows;
   if (num_image_colors >= 3) {  // Image has 3 channels.
     // Convert from opencv Mat to format: "rr..gg..bb".
-    unsigned int base1 =     num_pixels;
-    unsigned int base2 = 2 * num_pixels;
     for (int j=0, posr=0; j < image.rows; ++j, posr+=image.cols) {
-      unsigned int offset0 =         posr;
-      unsigned int offset1 = base1 + posr;
-      unsigned int offset2 = base2 + posr;
-      char *imgr = image.ptr<char>(j);
+      unsigned int offset0 = posr;
+      unsigned int offset1 = posr + num_pixels;
+      unsigned int offset2 = posr + 2 * num_pixels;
+      unsigned char *imgr = image.ptr<unsigned char>(j);
       for (int k=0, posc=0; k < image.cols; ++k, posc+=3) {
         data_ptr[offset0 + k] = imgr[posc+2];
         data_ptr[offset1 + k] = imgr[posc+1];
@@ -77,8 +75,17 @@ void getData(Mat &image, T* data_ptr) {
       }
     }
   } else if (num_image_colors == 1) { // Image has 1 channel.
-    for (int i=0; i < 3; ++i) {
-      memcpy(data_ptr + i * num_pixels, image.data, num_pixels * sizeof(T));
+    // Convert from opencv Mat to format: "rr..gg..bb".
+    for (int j=0, posr=0; j < image.rows; ++j, posr+=image.cols) {
+      unsigned int offset0 = posr;
+      unsigned int offset1 = posr + num_pixels;
+      unsigned int offset2 = posr + 2 * num_pixels;
+      unsigned char *imgr = image.ptr<unsigned char>(j);
+      for (int k=0; k < image.cols; ++k) {
+        data_ptr[offset0 + k] = imgr[k];
+        data_ptr[offset1 + k] = imgr[k];
+        data_ptr[offset2 + k] = imgr[k];
+      }
     }
   } else {
     cerr << "Image has " << num_image_colors << "colors." << endl;