Implement radial blur with OpenCV

Question

We would like to correct for field curvature introduced by a lens in a digital camera. We plan to use a digital unsharp mask Instead of applying a Gaussian blur we would like to try a radial blur, so the sharpening has more impact toward the edges of the image.

What is simplest way to create a radial blur using OpenCV ?

Answer 1

The answer above is close but missing a few key elements that took me a bit to figure out. I've changed the maps so that they are correctly calculating the zoom and shrink and added/subtracted them from the x and y at each position (otherwise you will just end up remapping your image to a tiny square. Also I changed the /blur to *blur otherwise your maps will contain very large numbers and just not come out right (extremely large multiples of each position).

float center_x = width/2; //or whatever
float center_y = height/2;
float blur = 0.002; //blur radius per pixels from center. 2px blur at 1000px from center
int iterations = 5;

Mat growMapx, growMapy;
Mat shrinkMapx, shrinkMapy;
for(int x = 0; x < width; x++) {
  for(int y = 0; y < height; y++) {
    growMapx[x,y] = x+((x - center_x)*blur);
    growMapy[x,y] = y+((y - center_y)*blur);
    shrinkMapx[x,y] = x-((x - center_x)*blur);
    shrinkMapy[x,y] = y-((y - center_y)*blur);
  }
}

Mat tmp1, tmp2;
for(int i = 0; i < iterations; i++)  {
  remap(src, tmp1, growMapx, growMapy, CV_INTER_LINEAR); // enlarge
  remap(src, tmp2, shrinkMapx, shrinkMapy, CV_INTER_LINEAR); // shrink
  addWeighted(tmp1, 0.5, tmp2, 0.5, 0, src); // blend back to src
}