util.py

# Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except
# in compliance with the License. A copy of the License is located at
#
# https://aws.amazon.com/apache-2-0/
#
# or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
# specific language governing permissions and limitations under the License.
"""Shared utility helper functions"""
import os
from io import BytesIO
from PIL import Image, ExifTags

EXIF_ORIENTATION = 274  # Magic numbers from http://www.exiv2.org/tags.html

def random_hex_bytes(n_bytes):
    """Create a hex encoded string of random bytes"""
    return os.urandom(n_bytes).hex()

def resize_image(file_p, size):
    """Resize an image to fit within the size, and save to the path directory"""
    dest_ratio = size[0] / float(size[1])
    try:
        image = Image.open(file_p)
    except IOError:
        print("Error: Unable to open image")
        return None

    try:
        exif = dict(image._getexif().items())
        if exif[EXIF_ORIENTATION] == 3:
            image = image.rotate(180, expand=True)
        elif exif[EXIF_ORIENTATION] == 6:
            image = image.rotate(270, expand=True)
        elif exif[EXIF_ORIENTATION] == 8:
            image = image.rotate(90, expand=True)
    except:
        print("No exif data")

    source_ratio = image.size[0] / float(image.size[1])

    # the image is smaller than the destination on both axis
    # don't scale it
    if image.size < size:
        new_width, new_height = image.size
    elif dest_ratio > source_ratio:
        new_width = int(image.size[0] * size[1]/float(image.size[1]))
        new_height = size[1]
    else:
        new_width = size[0]
        new_height = int(image.size[1] * size[0]/float(image.size[0]))
    image = image.resize((new_width, new_height), resample=Image.LANCZOS)

    final_image = Image.new("RGBA", size)
    topleft = (int((size[0]-new_width) / float(2)),
               int((size[1]-new_height) / float(2)))
    final_image.paste(image, topleft)
    bytes_stream = BytesIO()
    final_image.save(bytes_stream, 'PNG')
    return bytes_stream.getvalue()