Refs #11104. Add intensity/setIntensity methods to IPeakFunction

Code/Mantid/Framework/API/inc/MantidAPI/IPeakFunction.h

@@ -49,6 +49,12 @@ class MANTID_API_DLL IPeakFunction : public IFunctionWithLocation {
   /// Sets the parameters such that FWHM = w
   virtual void setFwhm(const double w) = 0;
 
+  /// Returns the integral intensity of the peak
+  virtual double intensity() const;
+
+  /// Sets the integral intensity of the peak
+  virtual void setIntensity(const double intensity);
+
   /// General implementation of the method for all peaks.
   void function1D(double *out, const double *xValues, const size_t nData) const;
   /// General implementation of the method for all peaks.

Code/Mantid/Framework/API/src/IPeakFunction.cpp

@@ -3,6 +3,7 @@
 //----------------------------------------------------------------------
 #include "MantidAPI/IPeakFunction.h"
 #include "MantidAPI/Jacobian.h"
+#include "MantidAPI/PeakFunctionIntegrator.h"
 #include "MantidKernel/Exception.h"
 #include "MantidKernel/ConfigService.h"
 
@@ -130,5 +131,31 @@ void IPeakFunction::setPeakRadius(const int &r) {
   }
 }
 
+double IPeakFunction::intensity() const {
+  double x0 = centre();
+  double dx = fabs(s_peakRadius * fwhm());
+
+  PeakFunctionIntegrator integrator;
+  IntegrationResult result = integrator.integrate(*this, x0 - dx, x0 + dx);
+
+  if(!result.success) {
+      return 0.0;
+  }
+
+  return result.result;
+}
+
+void IPeakFunction::setIntensity(const double newIntensity)
+{
+    double currentHeight = height();
+    double currentIntensity = intensity();
+
+    if(currentIntensity == 0.0) {
+        setHeight(0.0);
+    } else {
+        setHeight(newIntensity / currentIntensity * currentHeight);
+    }
+}
+
 } // namespace API
 } // namespace Mantid