Yep, that's it! Here's the same thing in R...

  library(imager)
  download.file("https://upload.wikimedia.org/wikipedia/en/2/24/Lenna.png",'lena.png', mode = 'wb')
  
  lena <- load.image("./lena.png")
  plot(lena)
  
  lena_fft <- FFT(lena)
  lena_pwr <- sqrt( lena_fft$real^2 + lena_fft$imag^2)
  lena_ph  <- atan2(lena_fft$imag, lena_fft$real)
  
  lena_ph[1:512,1:512,1,] <-  matrix(runif(512*512,-pi,pi),ncol=512) 
 
  lena_mess <- FFT(lena_pwr*cos(lena_ph),lena_pwr*sin(lena_ph),inverse = TRUE)
  
  plot(sqrt(lena_mess$real^2 + lena_mess$imag^2))