How to get the image pixel at real locations in opencv?

Question

I want to retrieve the rgb of a pixel in the image. But the location is not integer location but real values (x,y). I want a bilinear interpolated value. How could

Answer 1

bilinear interpolation just means weighting the value based on the 4 nearest pixels to the one you are examining. The weights can be calculated as follows.

cv::Point2f current_pos; //assuming current_pos is where you are in the image

//bilinear interpolation
float dx = current_pos.x-(int)current_pos.x;
float dy = current_pos.y-(int)current_pos.y;

float weight_tl = (1.0 - dx) * (1.0 - dy);
float weight_tr = (dx)       * (1.0 - dy);
float weight_bl = (1.0 - dx) * (dy);
float weight_br = (dx)       * (dy);

Your final value is calculated as the sum of the products of each pixel with its respective weight