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# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License 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.
import PIL.Image as Image
from io import BytesIO
import logging
logger = logging.getLogger(__name__)
class Thumbnailer(object):
FORMATS = {
"image/jpeg": "JPEG",
"image/png": "PNG",
}
def __init__(self, input_path):
self.image = Image.open(input_path)
self.width, self.height = self.image.size
def aspect(self, max_width, max_height):
"""Calculate the largest size that preserves aspect ratio which
fits within the given rectangle::
(w_in / h_in) = (w_out / h_out)
w_out = min(w_max, h_max * (w_in / h_in))
h_out = min(h_max, w_max * (h_in / w_in))
Args:
max_width: The largest possible width.
max_height: The larget possible height.
"""
if max_width * self.height < max_height * self.width:
return (max_width, (max_width * self.height) // self.width)
else:
return ((max_height * self.width) // self.height, max_height)
def scale(self, width, height, output_type):
"""Rescales the image to the given dimensions.
Returns:
BytesIO: the bytes of the encoded image ready to be written to disk
"""
scaled = self.image.resize((width, height), Image.ANTIALIAS)
return self._encode_image(scaled, output_type)
def crop(self, width, height, output_type):
"""Rescales and crops the image to the given dimensions preserving
aspect::
(w_in / h_in) = (w_scaled / h_scaled)
w_scaled = max(w_out, h_out * (w_in / h_in))
h_scaled = max(h_out, w_out * (h_in / w_in))
Args:
max_width: The largest possible width.
max_height: The larget possible height.
Returns:
BytesIO: the bytes of the encoded image ready to be written to disk
"""
if width * self.height > height * self.width:
scaled_height = (width * self.height) // self.width
scaled_image = self.image.resize(
(width, scaled_height), Image.ANTIALIAS
)
crop_top = (scaled_height - height) // 2
crop_bottom = height + crop_top
cropped = scaled_image.crop((0, crop_top, width, crop_bottom))
else:
scaled_width = (height * self.width) // self.height
scaled_image = self.image.resize(
(scaled_width, height), Image.ANTIALIAS
)
crop_left = (scaled_width - width) // 2
crop_right = width + crop_left
cropped = scaled_image.crop((crop_left, 0, crop_right, height))
return self._encode_image(cropped, output_type)
def _encode_image(self, output_image, output_type):
output_bytes_io = BytesIO()
output_image.save(output_bytes_io, self.FORMATS[output_type], quality=80)
return output_bytes_io
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