Is there any OpenCV or IPP equivalent for this function?

Question

I have this interpolate function taken from this code which I want to optimize:

bool interpolate(const Mat &im, float ofsx, float ofsy, float a11, float a12, float a21, float a22, Mat &res)
{         
   bool ret = false;
   // input size (-1 for the safe bilinear interpolation)
   const int width = im.cols-1;
   const int height = im.rows-1;
   // output size
   const int halfWidth  = res.cols >> 1;
   const int halfHeight = res.rows >> 1;
   int dim = res.rows * res.cols;
   float *out = res.ptr<float>(0);
   for (int j=-halfHeight; j<=halfHeight; ++j)
   {
      const float rx = ofsx + j * a12;
      const float ry = ofsy + j * a22;
      #pragma omp simd
      for(int i=-halfWidth; i<=halfWidth; ++i)
      {
         float wx = rx + i * a11;
         float wy = ry + i * a21;
         const int x = (int) floor(wx);
         const int y = (int) floor(wy);
         if (x >= 0 && y >= 0 && x < width && y < height)
         {
            // compute weights
            wx -= x; wy -= y;
            // bilinear interpolation
            *out++ = 
               (1.0f - wy) * ((1.0f - wx) * im.at<float>(y,x)   + wx * im.at<float>(y,x+1)) +
               (       wy) * ((1.0f - wx) * im.at<float>(y+1,x) + wx * im.at<float>(y+1,x+1));
         } else {
            *out++ = 0;
            ret =  true; // touching boundary of the input            
         }
      }
   }
   return ret;
}

I'm not the image processing guy and I'm really struggling to perform the equivalent using the opencv implementation. This is crucial for my project since the function above is incredibly time consuming.

Please help.

To help you, these are examples in different parts of the code where interpolate is used:

  // warp input according to current shape matrix
  interpolate(wrapper.prevBlur, lx, ly, u11*ratio, u12*ratio, u21*ratio, u22*ratio, img);

  Mat smoothed(patchImageSize, patchImageSize, CV_32FC1, (void *)&workspace.front());
  // interpolate with det == 1
  if (!interpolate(img, x, y, a11, a12, a21, a22, smoothed))
  {

  // subsample with corresponding scale
  interpolate(smoothed, (float)(patchImageSize>>1), (float)(patchImageSize>>1), imageToPatchScale, 0, 0, imageToPatchScale, patch);


  // ok, do the interpolation
  interpolate(img, x, y, a11, a12, a21, a22, patch);