ExampleImageDiff.cpp

Example for difference calculation of images: Takes two RGB input images and calculates the difference between them. Should be used for images that were taken from the same viewpoint with different aperture/exposure to visualize the difference in the two images. If the images are bigger than 1024x256 the difference for each channel will be visualized in a diagram as well.NOTE THAT the first image should be the brighter one! If you don't stick to this, the diff image might be black due to (prevented) underflows!

Author

rwulff

/*
This file is part of the BIAS library (Basic ImageAlgorithmS).

Copyright (C) 2003-2009    (see file CONTACT for details)
  Multimediale Systeme der Informationsverarbeitung
  Institut fuer Informatik
  Christian-Albrechts-Universitaet Kiel


BIAS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

BIAS is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with BIAS; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/


/**
 * @example ExampleImageDiff.cpp
   @relates Image
   @brief Example for difference calculation of images:
   Takes two RGB input images and calculates the difference between them.
   Should be used for images that were taken from the same viewpoint with
   different aperture/exposure to visualize the difference in the two
   images.
   If the images are bigger than 1024x256 the difference for each channel
   will be visualized in a diagram as well.
  
   NOTE THAT the first image should be the brighter one! If you don't stick
   to this, the diff image might be black due to (prevented) underflows!
   
   @ingroup g_examples
   @author  rwulff
*/

#include <Base/Image/Image.hh>
#include <Base/Image/ImageIO.hh>
#include <Base/ImageUtils/ImageDraw.hh>


using namespace BIAS;
using namespace std;

int main(int argc, char *argv[]) {

  // check params
  if (argc < 3) {
    cout << "wrong parameter count!!" << endl << endl;
    cout << "usage:" << endl;
    cout << argv[0] << " " << "<brighter_image> <darker_image>" << endl;
    return -1;
  }

  // load images (suppose that first image is the brighter one)
  Image<unsigned char> im1;
  Image<unsigned char> im2;
  if (ImageIO::Load(argv[1], im1) != 0) {
    cout << "image 1 could not be loaded!" << endl;
    return -1;
  }
  else {
    cout << "image 1 loaded!" << endl;
  }
  if (ImageIO::Load(argv[2], im2) != 0) {
    cout << "image 2 could not be loaded!" << endl;
    return -1;
  }
  else {
    cout << "image 2 loaded!" << endl;
  }

  cout << "images loaded" << endl;

  // ensure that input images have same size and RGB color model and init diffImage
  BIASASSERT(im1.GetWidth() == im2.GetWidth() && im1.GetHeight() == im2.GetHeight());
  BIASASSERT(im1.GetColorModel() == ImageBase::CM_RGB && im2.GetColorModel() == ImageBase::CM_RGB);
  Image<unsigned char> imDiff(im1);

  // draw per-channel differences only if pictures are at least 1024x256
  bool drawChannelDiffs = im1.GetWidth() >= 1024 && im1.GetHeight() >= 256;

  // get image data
  unsigned char *im1Data = im1.GetImageData();
  unsigned char *im2Data = im2.GetImageData();
  unsigned char *imDiffData = imDiff.GetImageData();
  unsigned int offset = 0;
  int diff = 0;
  unsigned int gammaX, gammaY;

  cout << "starting iteration..." << endl;

  // iterate over pixels and draw difference image
  for (unsigned int y = 0; y < im1.GetHeight(); y++) {
    for (unsigned int x = 0; x < im1.GetWidth(); x++) {
      offset = y*im1.GetWidth()*im1.GetChannelCount() + x*im1.GetChannelCount();

      // produce difference image in gray-scale
      diff = (int)im1Data[offset] - (int)im2Data[offset]
        + (int)im1Data[offset+1] - (int)im2Data[offset+1]
        + (int)im1Data[offset+2] - (int)im2Data[offset+2];
      diff /= 3;

      diff = diff < 0 ? 0 : diff;
      diff = diff > 255 ? 255 : diff;
      imDiffData[offset] = (unsigned char)diff;
      imDiffData[offset+1] = (unsigned char)diff;
      imDiffData[offset+2] = (unsigned char)diff;

      // draw per-channel difference visualiziation
      if (drawChannelDiffs) {
        // red
        gammaX = (unsigned int)im1Data[offset];
        gammaY = 256 - (unsigned int)im2Data[offset];
        imDiffData[gammaY*im1.GetWidth()*im1.GetChannelCount() + gammaX*im1.GetChannelCount()]
          = 255;

        // green
        gammaX = (unsigned int)im1Data[offset+1] + 256;
        gammaY = 256 - (unsigned int)im2Data[offset+1];
        imDiffData[gammaY*im1.GetWidth()*im1.GetChannelCount() + gammaX*im1.GetChannelCount() + 1]
          = 255;

        // blue
        gammaX = (unsigned int)im1Data[offset+2] + 512;
        gammaY = 256 - (unsigned int)im2Data[offset+2];
        imDiffData[gammaY*im1.GetWidth()*im1.GetChannelCount() + gammaX*im1.GetChannelCount() + 2]
          = 255;

        // arithmetic mean
        gammaX = (unsigned int)im1Data[offset] + (unsigned int)im1Data[offset+1] + (unsigned int)im1Data[offset+2];
        gammaX /= 3;
        gammaX += 768;
        gammaY = (unsigned int)im2Data[offset] + (unsigned int)im2Data[offset+1] + (unsigned int)im2Data[offset+2];
        gammaY /= 3;
        gammaY = 256 - gammaY;
        offset = gammaY*im1.GetWidth()*im1.GetChannelCount() + gammaX*im1.GetChannelCount();
        imDiffData[offset] = 255;
        imDiffData[offset + 1] = 255;
        imDiffData[offset + 2] = 255;
      }
    }
  }

  ImageIO::Save("diff.mip", imDiff);

  cout << "done!" << endl;

  return 0;
}