I wish to interpolate an image by a factor of 2, both horizontally and vertically. What is the bicubic interpolation operator in Julia that is the counterpart of interp2 in Matlab?

Take a look at Interpolations.jl package which has number of options for configuring interpolation algorithm.

Thanks to the rely. I am currently using:

using GR

X = Y = 1:2:512

Xq = Yq = 1:512

yy=y1[1:2:512,1:2:512]

Zq = interp2(X, Y, yy, Xq, Yq, 3)

(here y1 is a 512-by-512 matrix)

However, the result is slightly different from Matlabâ€™s result.