Is it possible to alter the focal point of a foveated image in OpenCV?

I have written some fairly basic code to create a foveated image.

int w = source_image.cols; // Getting the width of the source_image.
int h = source_image.rows; // Getting the height of the source_image.
int ro0 = 1; // Radius of blind spot.
int R = 120; // Number of rings.

Point2i point(x, y); // Point around which to foveate.

// Function that uses a bilinear polar transform and gives maximum resolution at the 'point' of interest.
LogPolar_Interp bilinear(w, h, point, R, ro0, INTER_LINEAR);

Mat cortical, retinal;

// Converting the source_image to a cortical one, using the bilinear transform.
cortical = bilinear.to_cortical(source_image);

// Converting the cortical image to a retinal image, using the bilinear transform.
retinal = bilinear.to_cartesian(cortical);

imshow("Cortical", cortical);
imshow("Retinal", retinal);

My question is:

Is there any way I can alter the size of the focal point of this image?

I have tried to alter the openCV source code, but cannot seem to get it to do what I want.

Any help is appreciated.