here is another video, technically more useful
https://youtu.be/6Qi0UBBXZVw

ok i got it. numpy.save cannot decode tuples by itself...
surprising that there is no simple way to save a structured array, and that i must flatten the structure to save it. Extra work and risk of errors... Anyway...

still in trouble.
I am trying to save my numpy structured array with np.save, here is the code for details

# differents tests avec Luv

from labColor import *
import numpy as np
from console import clear
# compute all colors

def getAllColors(step):
  dtype = [('L', float), ('u', float), ('v', float), ('c', tuple), ('d', float)]
  data = []
  for r in np.arange(0, 256, step):
    print(r)
    for g in np.arange(0, 256, step):
      for b in np.arange(0, 256, step):
        L, u, v = rgb_to_sLuv(r, g, b)
        data.append((L, u, v, (r/255,g/255,b/255), 0.0))
  ar = np.array(data,dtype=dtype)
  return ar

clear()
ar = getAllColors(50)
print(len(ar))
print(ar.dtype)
np.save('rgb.npy',ar)
a = np.load('rgb.npy')
print(len(a))
print(a.dtype)

but i get this error

Traceback (most recent call last):
  File "/private/var/mobile/Containers/Shared/AppGroup/..../Pythonista3/Documents/couleurs/labColor6.py", line 24, in <module>
    np.save('rgb.npy',ar)
  File "/var/containers/Bundle/Application/..../Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/numpy/lib/npyio.py", line 451, in save
    format.write_array(fid, arr)
  File "/var/containers/Bundle/Application/.../Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/numpy/lib/format.py", line 407, in write_array
    pickle.dump(array, fp, protocol=2)
_pickle.PicklingError: Can't pickle <built-in function _reconstruct>: import of module 'multiarray' failed

what am i doing wrong?
thanks

@mikael actually
1/ i have not computed enough intermediate frames (each take 30s on my ipad air)
2/ i use the video to view it frame by frame from the ipad photo roll, to turn around as i wish, so it is enough for my usage
3/ i have tried 0.5s once but it skipped 1 frame in the middle, so i thought i would remain at 1 Hz.
thanks.

here is the code

import ui
from console import clear
from PIL import Image
import io as io
def pil2ui(pil_img):
    with io.BytesIO() as buffer:
        pil_img.save(buffer, format='PNG')
        return ui.Image.from_data(buffer.getvalue())

class MyView (ui.View):
  def __init__(self):
    # global view settings
    self.name = 'Viewing where colors lie in the CIE L*u*v* color space'                                    
    self.background_color = 'gray'     
    # trying to update 1 per second
    self.update_interval = 1
    
    # image settings
    img = ui.Button(name='image')
    img.width = 1476/1.5
    img.height = 1024/1.5
    img.enable = False
    img.hidden = False
    self.add_subview(img)
    self.img = img
    
    # add a copyright
    txt = ui.Label()
    txt.text = 'copyright JMV38 2019'
    txt.text_color = (0.5, 0.5, 0.5, 0.2)
    txt.width = 600
    txt.height = 100
    txt.alignment = ui.ALIGN_CENTER
    fontName, fontSize = txt.font
    txt.font = (fontName,30)
    self.add_subview(txt)
    self.txt = txt
    
  def update(self):
    self.img.center = (self.width * 0.5, self.height * 0.5)
    self.txt.center = (self.width * 0.5, self.height * 0.5)
    try:
      self.azim -= 10
    except:
      self.azim = 180
    file = 'CieLuv_'+str(self.azim)+'.png'
    try:
      print(file)
      im = Image.open(file)
      ui_image = pil2ui(im)
      self.img.background_image = ui_image
    except:
      exit()
    
if __name__ == '__main__':
  clear()
  view = MyView()      
  view.present('full_screen')  
  

thanks for your advices. I chose to go for the ui.view. It worked nicely https://youtu.be/Li5gV2tUj5M
(make sure to set 1080p when you watch the video, otherwise the quality is bad)

btw, for anyone interested, here is the kind of video i want to make
https://youtu.be/eXBGYHKKytI
this one i made by assembling the images manually with Splice, i am trying to make it more automatic.

with scene + update, how can i trigger something once per second? When i try to use globals to keep track of a global state t, i keep getting some ‘local variable t used before being assigned’ , although it is global and assigned in the main... I pbly dont get fully how python namespaces work or in which order things are called, so i am stuck.

also searching in the forum with keywords really leads me nowhere. The search engine does not seem very smart, cause i am fairly sure i saw that kind of problems disucussed in the past, but i dont get any usefull link...

@cvp thanks, i’ll have a look.
The problem is that with Scene or ui.View some fair amount a background is needed to get it work smoothly. I wish i could just tweek a couple lines in an example and get what i need. The built in example are a bit too complex for that.
Thanks anyway. And happy new year!