Perform a spatially varying box blur based on an input map. Box blur only for the moment. Uses a summed area table.

iBlur.cpp

/* iBlur - Compute a box-blur based on a control image input.
    Requires a Summed Area Table input.
*/

kernel iBlur : ImageComputationKernel<eComponentWise> {
  Image<eRead, eAccessPoint, eEdgeClamped> src;
  Image<eRead, eAccessPoint, eEdgeClamped> ctr;
  Image<eRead, eAccessRandom, eEdgeClamped> sat;
  Image<eWrite> dst;

  param:
    float2 size;

  local:

  void init() {
  }
  
  // Find Summed Area Table sum given point p and radius r (box of size 2*r+1)
  float satsum(float2 p, float2 r) { 
    float d = bilinear(sat, p.x+r.x, p.y+r.y);
    float b = bilinear(sat, p.x+r.x, p.y-r.y-1);
    float c = bilinear(sat, p.x-r.x-1, p.y+r.y);
    float a = bilinear(sat, p.x-r.x-1, p.y-r.y-1);
    return d-b-c+a;
  }

  void process(int2 p) {

    // Blur size using ctr input as multiplier
    float2 s = float2(ctr()*size.x, ctr()*size.y);
    
    // Don't process if size is small
    if (s.x<1e-8&&s.y<1e-8) { dst() = src(); return; }

    // Normalization factor
    float norm = (s.x*2.0f+1)*(s.y*2.0f+1);
    
    // Get sum from SAT
    float sum = satsum(float2(p.x, p.y), s);

    // Write normalized sum to output
    dst() = sum/norm;


  }
};

SummedAreaTable.cpp

/* Create a summed area table in one direction, based on an input image. 
    In order to create a 2-dimensional summed area table, 
    you need two copies of the node, the 2nd with col=true

    Currently there are issues with precision for higher resolution images...
*/
kernel SummedAreaTable : ImageComputationKernel<eComponentWise> {
  Image<eRead, eAccessRandom, eEdgeConstant> src;
  Image<eReadWrite, eAccessRandom> dst;

  param:
    bool col;

  local:
    int n; 

  void init() {
    n = col?src.bounds.height():src.bounds.width();
  }

  void process(int2 p) {
    if (col?p.y>0:p.x>0) return;
    dst(col?p.x:0, col?0:p.y) = src(col?p.x:0, col?0:p.y);
    for (int i=1; i<n; i++)
      dst(col?p.x:i, col?i:p.y) = src(col?p.x:i, col?i:p.y) + dst(col?p.x:i-1, col?i-1:p.y);
  }
};