Bilinear interpolation Grid

Hi there, I have a question regarding Bilinear Interpolation. According to Wikipedia, a Bilinear Interpolation depends on the pixel(x,y).


I am wondering If is any way to know what is the value of x0, x1, y1 and y2. Normally I use the following call:
new_color = F.grid_sample(color, pixels, padding_mode=“border”)

For further research, I am calculating analytically the derivative of the function posted above but I need the constants x0, x1, y1 and y2.
Any suggestion?