PyCS/pycs/frontend/endpoints/data/GetResizedFile.py

import cv2
import os
import re

from PIL import Image
from eventlet import tpool
from flask import abort
from flask import send_from_directory
from flask.views import View

from pycs.database.File import File
from pycs.database.Project import Project


class GetResizedFile(View):
    """
    returns binary file after resizing
    """
    # pylint: disable=arguments-differ
    methods = ['GET']

    def dispatch_request(self, file_id: int, resolution: str):
        # get file from database
        file = File.query.get(file_id)
        if file is None:
            return abort(404, "file object not found")

        if not os.path.exists(file.path):
            return abort(404, "image not found!")

        project = file.project

        # extract desired resolution
        resolution = re.split(r'[^0-9]', resolution)
        max_width = int(resolution[0])
        max_height = int(resolution[1]) if len(resolution) > 1 else 2 ** 24

        # send data
        file_directory, file_name = tpool.execute(resize_file,
                                                  project.id, file.id, max_width, max_height)
        return send_from_directory(file_directory, file_name)

def resize_file(project_id, file_id, max_width, max_height):
    """
    If file type equals video this function extracts a thumbnail first. It calls resize_image
    to resize and returns the resized files directory and name.

    :param project: associated project
    :param file: file object
    :param max_width: maximum image or thumbnail width
    :param max_height: maximum image or thumbnail height
    :return: resized file directory, resized file name
    """
    file = File.query.get(file_id)
    project = Project.query.get(project_id)

    # get absolute path
    if os.path.isabs(file.path):
        abs_file_path = file.path
    else:
        abs_file_path = os.path.join(getcwd(), file.path)

    # extract video thumbnail
    if file.type == 'video':
        abs_target_path = os.path.join(os.getcwd(), project.root_folder, 'temp', f'{file.uuid}.jpg')
        create_thumbnail(abs_file_path, abs_target_path)

        abs_file_path = abs_target_path

    # resize image file
    abs_target_path = os.path.join(os.getcwd(), project.root_folder,
                                'temp', f'{file.uuid}_{max_width}_{max_height}.jpg')
    result = resize_image(abs_file_path, abs_target_path, max_width, max_height)

    # return path
    if result is not None:
        return os.path.split(abs_target_path)

    return os.path.split(abs_file_path)

def resize_image(file_path, target_path, max_width, max_height):
    """
    resize an image so width < max_width and height < max_height

    :param file_path: path to source file
    :param target_path: path to target file
    :param max_width: maximum image width
    :param max_height: maximum image height
    :return:
    """
    # return if file exists
    if os.path.exists(target_path):
        return True

    # load full size image
    image = Image.open(file_path)
    img_width, img_height = image.size

    # abort if file is smaller than desired
    if img_width < max_width and img_height < max_height:
        return None

    # calculate target size
    target_width = int(max_width)
    target_height = int(max_width * img_height / img_width)

    if target_height > max_height:
        target_height = int(max_height)
        target_width = int(max_height * img_width / img_height)

    # resize image
    resized_image = image.resize((target_width, target_height))

    # save to file
    resized_image.save(target_path, quality=80)
    return True

def create_thumbnail(file_path, target_path):
    """
    extract a thumbnail from a video

    :param file_path: path to source file
    :param target_path: path to target file
    :return:
    """
    # return if file exists
    if os.path.exists(target_path):
        return

    # load video
    video = cv2.VideoCapture(file_path)

    # create thumbnail
    _, image = video.read()
    cv2.imwrite(target_path, image)

    # close video file
    video.release()