+// ImageFile::comparativeStatistics Calculate comparative stats
+//
+// OUTPUT
+// d Normalized root mean squared distance measure
+// r Normalized mean absolute distance measure
+// e Worst case distance measure
+//
+// REFERENCES
+// G.T. Herman, Image Reconstruction From Projections, 1980
+
+bool
+ImageFile::comparativeStatistics (const ImageFile& imComp, double& d, double& r, double& e) const
+{
+ if (imComp.nx() != m_nx && imComp.ny() != m_ny) {
+ sys_error (ERR_WARNING, "Image sizes differ [ImageFile::comparativeStatistics]");
+ return false;
+ }
+ ImageFileArrayConst v = getArray();
+ ImageFileArrayConst vComp = imComp.getArray();
+
+ double myMean = 0.;
+ for (int ix = 0; ix < m_nx; ix++) {
+ for (int iy = 0; iy < m_ny; iy++) {
+ myMean += v[ix][iy];
+ }
+ }
+ myMean /= (m_nx * m_ny);
+
+ double sqErrorSum = 0.;
+ double absErrorSum = 0.;
+ double sqDiffFromMeanSum = 0.;
+ double absValueSum = 0.;
+ for (int ix = 0; ix < m_nx; ix++) {
+ for (int iy = 0; iy < m_ny; iy++) {
+ double diff = v[ix][iy] - vComp[ix][iy];
+ sqErrorSum += diff * diff;
+ absErrorSum += fabs(diff);
+ double diffFromMean = v[ix][iy] - myMean;
+ sqDiffFromMeanSum += diffFromMean * diffFromMean;
+ absValueSum += fabs(v[ix][iy]);
+ }
+ }
+
+ d = sqrt (sqErrorSum / sqDiffFromMeanSum);
+ r = absErrorSum / absValueSum;
+
+ int hx = m_nx / 2;
+ int hy = m_ny / 2;
+ double eMax = -1;
+ for (int ix = 0; ix < hx; ix++) {
+ for (int iy = 0; iy < hy; iy++) {
+ double avgPixel = 0.25 * (v[2*ix][2*iy] + v[2*ix+1][2*iy] + v[2*ix][2*iy+1] + v[2*ix+1][2*iy+1]);
+ double avgPixelComp = 0.25 * (vComp[2*ix][2*iy] + vComp[2*ix+1][2*iy] + vComp[2*ix][2*iy+1] + vComp[2*ix+1][2*iy+1]);
+ double error = fabs (avgPixel - avgPixelComp);
+ if (error > eMax)
+ eMax = error;
+ }
+ }
+
+ e = eMax;
+
+ return true;
+}
+
+
+bool
+ImageFile::printComparativeStatistics (const ImageFile& imComp, ostream& os) const
+{
+ double d, r, e;
+
+ if (comparativeStatistics (imComp, d, r, e)) {
+ os << " Normalized root mean squared distance (d): " << d << endl;
+ os << " Normalized mean absolute distance (r): " << r << endl;
+ os << "Worst case distance (2x2 pixel average) (e): " << e << endl;
+ }
+}
+
+
+void
+ImageFile::printStatistics (ostream& os) const
+{
+ double min, max, mean, mode, median, stddev;
+
+ statistics (min, max, mean, mode, median, stddev);
+
+ os << " min: " << min << endl;
+ os << " max: " << max << endl;
+ os << " mean: " << mean << endl;
+ os << " mode: " << mode << endl;
+ os << "median: " << median << endl;
+ os << "stddev: " << stddev << endl;
+}
+
+
+void
+ImageFile::statistics (double& min, double& max, double& mean, double& mode, double& median, double& stddev) const
+{
+ int nx = m_nx;
+ int ny = m_ny;
+ ImageFileArrayConst v = getArray();
+
+ mean = 0;
+ min = v[0][0];
+ max = v[0][0];
+ for (int ix = 0; ix < nx; ix++) {
+ for (int iy = 0; iy < ny; iy++) {
+ if (v[ix][iy] > max)
+ max = v[ix][iy];
+ if (v[ix][iy] < min)
+ min = v[ix][iy];
+ mean += v[ix][iy];
+ }
+ }
+ mean /= (nx * ny);
+
+ static const int nbin = 256;
+ int hist[ nbin ] = {0};
+ double spread = max - min;
+ mode = 0;
+ stddev = 0;
+ for (int ix = 0; ix < nx; ix++) {
+ for (int iy = 0; iy < ny; iy++) {
+ int b = static_cast<int>((((v[ix][iy] - min) / spread) * (nbin - 1)) + 0.5);
+ hist[b]++;
+ double diff = (v[ix][iy] - mean);
+ stddev += diff * diff;
+ }
+ }
+ stddev = sqrt(stddev / (nx * ny));
+
+ int max_binindex = 0;
+ int max_bin = -1;
+ for (int ibin = 0; ibin < nbin; ibin++) {
+ if (hist[ibin] > max_bin) {
+ max_bin = hist[ibin];
+ max_binindex = ibin;
+ }
+ }
+
+ mode = (max_binindex * spread / (nbin - 1)) + min;
+
+ median = 0.;
+}
+