QImage creates incorrect Images from TIFF-Files

When reading TIFF-Files QImage can create slightly incorrect images (RGB-Value #ffc4c4c4 instead of #ffc3c3c3).

When you load the attached TIF-File 'ORG.TIF' into Qt and write a TIF-File with QImage-Writer, the results are different between Qt4 and Qt5 ('OUT_QT5.9.5' vs. 'OUT_QT4.5.2').
As we matched our images in unit-tests with Qt4 which don't succeed with Qt5, we assume an error in Qt5.

Step by Step:

1. Export ORG.TIF with QImageWriter on Qt4: OUT_QT4.5.2.TIF
2. Compare ORG.TIF with OUT_QT4.5.2.TIF on Qt4: equal
3. Export ORG.TIF with QImageWriter on Qt5: OUT_QT5.9.5.TIF
4. Compare ORG.TIF with OUT_QT5.9.5.TIF on Qt5: equal
5. Compare ORG.TIF with OUT_QT4.5.2.TIF on Qt5: different

Code (for Qt4 and Qt5):

#include <qcoreapplication.h>
#include <qimage.h>
#include <qimagewriter.h>
#include <stdio.h>

bool imageWrite(QString const& fn_in, QString const fn_out) {
  QImage img(fn_in);
  QImageWriter iw(fn_out, "TIFF");
  return iw.write(img);
}

QString imageCompare(QString const& fn_lhs, QString const& fn_rhs) {
  QImage lhs(fn_lhs);
  QImage rhs(fn_rhs);
  int w = lhs.width();
  int h = lhs.height();
  if (w != rhs.width()) return "width different";
  if (h != rhs.height()) return "height different";
  for (int yy = 0; yy < h; ++yy) {
    for (int xx = 0; xx < w; ++xx) {
      QRgb rl = lhs.pixel(xx, yy);
      QRgb rr = rhs.pixel(xx, yy);
      if ((rl & RGB_MASK) != (rr & RGB_MASK)) {
        return QString("Pixel x=%1, y=%2: #%3 different from #%4")
          .arg(xx).arg(yy)
          .arg(rl,8,16,QLatin1Char('0'))
          .arg(rr,8,16,QLatin1Char('0'));
             }
        }
    }
  return QString();
}

int main(int argc, char* argv[]) {
  QCoreApplication app(argc, argv);
  QString fn_lhs = argc > 1
    ? argv[1]
    : "ORG.TIF";
  QString fn_rhs = argc > 2
    ? argv[2]
    : QString("OUT_QT%1.TIF").arg(QT_VERSION_STR);
  if (argc <= 2) {
    if (!imageWrite(fn_lhs, fn_rhs)) return 1;
    }
  QString res = imageCompare(fn_lhs, fn_rhs);
  QString msg = res.isEmpty()
    ? QString("'%1' equals '%2'").arg(fn_lhs, fn_rhs)
    : QString("'%1' != '%2': %3").arg(fn_lhs, fn_rhs, res);
  fputs(msg.toLatin1(), stderr);
  return 0;
}