vtkImageSSIM: Fix an issue with mode logic

Rework vtkImageSSIM mode logic to separate an explicit automatic mode (default)
from a new MODE_INPUT_RANGE. MODE_NONE has been removed.

Imaging/Core/vtkImageSSIM.cxx

@@ -261,6 +261,17 @@ vtkImageSSIM::vtkImageSSIM()
   this->SetNumberOfOutputPorts(1);
 }
 
+//------------------------------------------------------------------------------
+void vtkImageSSIM::SetInputToAdditiveChar(unsigned int size)
+{
+  this->C.resize(size);
+  for (unsigned int i = 0; i < size; ++i)
+  {
+    this->C[i][0] = 6.5025;
+    this->C[i][1] = 58.5225;
+  }
+}
+
 //------------------------------------------------------------------------------
 void vtkImageSSIM::GrowExtent(int* uExt, int* wholeExtent)
 {
@@ -327,18 +338,23 @@ void vtkImageSSIM::SetInputToLab()
   }
 }
 
+//------------------------------------------------------------------------------
+void vtkImageSSIM::SetInputToRGBA()
+{
+  if (this->Mode != MODE_RGBA)
+  {
+    this->SetInputToAdditiveChar(4);
+    this->Mode = MODE_RGBA;
+    this->Modified();
+  }
+}
+
 //------------------------------------------------------------------------------
 void vtkImageSSIM::SetInputToRGB()
 {
   if (this->Mode != MODE_RGB)
   {
-    this->C.resize(3);
-    for (int i = 0; i < 3; ++i)
-    {
-      this->C[i][0] = 6.5025;
-      this->C[i][1] = 58.5225;
-    }
-
+    this->SetInputToAdditiveChar(3);
     this->Mode = MODE_RGB;
     this->Modified();
   }
@@ -349,19 +365,26 @@ void vtkImageSSIM::SetInputToGrayscale()
 {
   if (this->Mode != MODE_GRAYSCALE)
   {
-    this->C.resize(1);
-    this->C[0][0] = 6.5025;
-    this->C[0][1] = 58.5225;
-
+    this->SetInputToAdditiveChar(1);
     this->Mode = MODE_GRAYSCALE;
     this->Modified();
   }
 }
 
+//------------------------------------------------------------------------------
+void vtkImageSSIM::SetInputToAuto()
+{
+  if (this->Mode != MODE_AUTO)
+  {
+    this->Mode = MODE_AUTO;
+    this->Modified();
+  }
+}
+
 //------------------------------------------------------------------------------
 void vtkImageSSIM::SetInputRange(std::vector<int>& range)
 {
-  if (this->Mode != MODE_NONE)
+  if (this->Mode != MODE_INPUT_RANGE)
   {
     this->C.resize(range.size());
     for (std::size_t i = 0; i < range.size(); ++i)
@@ -370,8 +393,8 @@ void vtkImageSSIM::SetInputRange(std::vector<int>& range)
       this->C[i][1] = 0.0009 * range[i] * range[i];
     }
 
+    this->Mode = MODE_INPUT_RANGE;
     this->Modified();
-    this->Mode = MODE_NONE;
   }
 }
 
@@ -402,8 +425,7 @@ int vtkImageSSIM::RequestData(
     return 0;
   }
 
-  // The user hasn't put the right input range
-  if (C.size() != static_cast<std::size_t>(nComp))
+  if (this->Mode == MODE_AUTO)
   {
     C.resize(nComp);
     double r[2];
@@ -416,6 +438,15 @@ int vtkImageSSIM::RequestData(
       C[i][1] = 9 * C[i][1];
     }
   }
+  else if (C.size() < static_cast<std::size_t>(nComp))
+  {
+    vtkLog(ERROR, "Input range is too small for provided input, aborting");
+    return 0;
+  }
+  else if (C.size() > static_cast<std::size_t>(nComp))
+  {
+    vtkLog(TRACE, "Input range is bigger than provided input");
+  }
 
   return this->Superclass::RequestData(request, inputVector, outputVector);
 }

Imaging/Core/vtkImageSSIM.h

@@ -65,12 +65,24 @@ public:
    */
   void SetInputToRGB();
 
+  /**
+   * Assume the input is in RGBA format, using integers from 0 to 255.
+   * This will set appropriate constants c1 and c2 for each input channel
+   */
+  void SetInputToRGBA();
+
   /**
    * Assume the input is in grayscale, using integers from 0 to 255.
    * This will set appropriate constants c1 and c2
    */
   void SetInputToGrayscale();
 
+  /**
+   * The c1 and c2 constant will be computed automatically based on the range of each individual
+   * components Please note the resulting SSIM can be NaN in specific cases.
+   */
+  void SetInputToAuto();
+
   /**
    * Setup the range of each components of the input scalars. If the range has not been set, or if
    * the number of components in the input does not match the number of provided ranges,
@@ -125,7 +137,9 @@ protected:
     vtkInformationVector* outputVector) override;
 
 private:
+  void SetInputToAdditiveChar(unsigned int size);
   void GrowExtent(int* uExt, int* wholeExtent);
+
   int PatchRadius = 6;
   bool ClampNegativeValues = false;
 
@@ -133,10 +147,12 @@ private:
   {
     MODE_LAB,
     MODE_RGB,
+    MODE_RGBA,
     MODE_GRAYSCALE,
-    MODE_NONE
+    MODE_AUTO,
+    MODE_INPUT_RANGE
   };
-  int Mode = MODE_NONE;
+  int Mode = MODE_AUTO;
 
   /**
    * Regularization constants. They are set depending on the range of the input data.