app.py

import streamlit as st

color_step = st.slider('color_step', value=10, min_value=1, max_value=179, step=1)

#duration of each frame of the gif in milliseconds 
duration_parameter = st.slider('duration_parameter aka duration of each frame of the gif in milliseconds', value=10, min_value=1, max_value=2000, step=10)

#Loop parameter = number of times gif loops. 0 = loops infinitely. 
loop_parameter = st.slider('Loop parameter aka number of times gif loops', value=0, min_value=0, max_value=10, step=1)


if color_step == 0:
  my_hue_list = [0]
else:
  my_hue_list = list( range(0, 180, color_step) ) #Color step basically gives step range of this list, ie if color_step = 2 then it is [0,2,4,6,....,178]

import cv2
import numpy as np

user_image_name = st.file_uploader(label, type=['png', 'jpg'], accept_multiple_files=False)

if user_image_name is not None:
  st.image(user_image_name )

# load image with alpha channel
img = cv2.imread( user_image_name , cv2.IMREAD_UNCHANGED)

# extract alpha channel  
#alpha = img[:,:,3]

# extract bgr channels
bgr = img[:,:,0:3]

# convert to HSV
hsv = cv2.cvtColor(bgr, cv2.COLOR_BGR2HSV)
#h = hsv[:,:,0]
#s = hsv[:,:,1]
#v = hsv[:,:,2]
h,s,v = cv2.split(hsv)


if color_step == 0:
  my_hue_list = [0]
else:
  my_hue_list = list( range(0, 180, color_step) ) #Color step basically gives step range of this list, ie if color_step = 2 then it is [0,2,4,6,....,178]
#180 at end means highest it can go is 179 (same as hue param )
#including 0 makes original image part of the outputs/gif 
print(my_hue_list)

#H,S,V = Hue , Saturation, Value (ie color value) parameters
#Hue has range [0,179] , Saturation [0,255] , Value [0,255]

for i in my_hue_list:
  # modify hue channel by adding difference and modulo 180 (modulo because hue parameter only goes up to index 180, shouldn't exceed that )
  hnew = np.mod(h + i, 180).astype(np.uint8)   #<<<<<<<<<<<<<<<< where the iter comes in 

  # recombine channels
  hsv_new = cv2.merge([hnew,s,v])

  # convert back to bgr
  bgr_new = cv2.cvtColor(hsv_new, cv2.COLOR_HSV2BGR)

  # put alpha back into bgr_new
  #bgra = cv2.cvtColor(bgr_new, cv2.COLOR_BGR2BGRA)
  #bgra[:,:,3] = alpha

  # save output AS FILE LABELED BY ITERABLE 
  output_filename = 'output_bgr_new_' + str(i) +'.png'        #<<<<<<<<<<<<<<<< where the iter comes in 
  cv2.imwrite(output_filename, bgr_new)


'''for this demo prob need to retain image objects bgr_new in an img_array by appending them to that then build them into a gif from the array'''


for i in my_hue_list:
  output_filename = 'output_bgr_new_' + str(i) +'.png'        #<<<<<<<<<<<<<<<< where the iter comes in 
  Image(filename='/main_outputs/' + output_filename) 

# filepaths
fp_in = "/main_outputs/*.png"
fp_out = "/" + original_filename + "_HueShiftGIF_color_step_" + str(color_step) + "_duration_" + str(duration_parameter) + "_loop_" + str(loop_parameter) + ".gif"

# https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html#gif
img, *imgs = [Image.open(f) for f in sorted(glob.glob(fp_in))]
img.save(fp=fp_out, format='GIF', append_images=imgs,
         save_all=True, duration=duration_parameter, loop=loop_parameter)



st.image(fp_out)