anchor.diff:      offset = cmplx(x_center - 0.5*pixel_size*width, &
       y_center + 0.5*pixel_size*height)
   
  -    do x = 1, width
  -      do y = 1, height
  +    !$omp parallel do private(y, x, coord)
  +    do y = 1, height
  +      do x = 1, width
           coord = offset + cmplx(x*pixel_size, -y*pixel_size)
  -        image(:,x,y) = to_rgb(pixel_value(coord, 256))
  +        image(:,x,y) = to_rgb(pixel_value(coord, 255))
         end do
       end do
  +    !$omp end parallel do
   
     end function image
   
  
positive.code: contains
  
    ! calculate loop count for a (complex) pixel
    pure integer function pixel_value (z, n_max)
      implicit none
  
      complex, intent( in ) :: z
  
negative.code: 
      ! header
      write(99,111) "P3"
      write(99,222) width, height, 255
  
      ! pixel data
      write (99, *) image
      !do x = 1, width
      !  do y = 1, height
      !    write (99,333) image(y,x,:)
      !  end do
      !end do
  
      ! close ppm file
      close (99)
  