from PIL import Image
import numpy as np
import cv2
import os
os.environ["CUDA_VISIBLE_DEVICES"]="0"

def write_video(file_path, frames, fps, reversed = True):
  """
  Writes frames to an mp4 video file
  :param file_path: Path to output video, must end with .mp4
  :param frames: List of PIL.Image objects
  :param fps: Desired frame rate
  :param reversed: if order of images to be reversed (default = True)
  """
  if reversed == True:
    frames.reverse()

  w, h = frames[0].size
  fourcc = cv2.VideoWriter_fourcc('m', 'p', '4', 'v')
  #fourcc = cv2.VideoWriter_fourcc(*'avc1')
  writer = cv2.VideoWriter(file_path, fourcc, fps, (w, h))

  for frame in frames:
      np_frame = np.array(frame.convert('RGB'))
      cv_frame = cv2.cvtColor(np_frame, cv2.COLOR_RGB2BGR)
      writer.write(cv_frame)

  writer.release() 

def image_grid(imgs, rows, cols):
  assert len(imgs) == rows*cols

  w, h = imgs[0].size
  grid = Image.new('RGB', size=(cols*w, rows*h))
  grid_w, grid_h = grid.size

  for i, img in enumerate(imgs):
      grid.paste(img, box=(i%cols*w, i//cols*h))
  return grid

def shrink_and_paste_on_blank(current_image, mask_width):
  """
  Decreases size of current_image by mask_width pixels from each side,
  then adds a mask_width width transparent frame, 
  so that the image the function returns is the same size as the input. 
  :param current_image: input image to transform
  :param mask_width: width in pixels to shrink from each side
  """

  height = current_image.height
  width = current_image.width

  #shrink down by mask_width
  prev_image = current_image.resize((height-2*mask_width,width-2*mask_width))
  prev_image = prev_image.convert("RGBA")
  prev_image = np.array(prev_image)

  #create blank non-transparent image
  blank_image = np.array(current_image.convert("RGBA"))*0
  blank_image[:,:,3] = 1

  #paste shrinked onto blank
  blank_image[mask_width:height-mask_width,mask_width:width-mask_width,:] = prev_image
  prev_image = Image.fromarray(blank_image)

  return prev_image

def dummy(images, **kwargs):
    return images, False