Python responsive images

responsive_images.py

# -*- coding: utf-8 -*-
# Create multiple responsive images to generate a srcset
#
# Usage example:
# b64_image = base64.b64decode(b64_image.split(",")[1]) # from base64-encoded image
# file_name = "lorem.ipsum.jpeg"
# srcset_results = []
# for img in create_srcset_images(BytesIO(b64_image), widths):
#     srcset_name = f'{".".join(file_name.split(".")[:-1])}-{img["width"]}w.{img["format"]}'
#     result = upload_file_to_external_service(img["image"], srcset_name) # <--- it must return a URL
#     srcset_results.append(f'{result} {img["width"]}w')
# srcset = ", ".join(srcset_results)
#
# Code adapted from https://github.com/mccarthysean/make-responsive-images/

from io import BytesIO
from PIL import Image


def get_srcset_sizes(widths: list, img_width: int, img_height: int) -> list:
    """
    Get srcset proporcional sizes and filter out duplicates sizes
    and larger than original

    :param widths: list of widths to to create the srcset
    :param img_width: image original width
    :param img_height: image original height
    :return: list of proportinal sizes like [(400, 267), (800, 533), (1200, 800)]
    """
    sizes_set = set()
    for width in widths:
        width = min(width, img_width)
        ratio = width / float(img_width)
        width = int(img_width * ratio + 0.5)
        height = int(img_height * ratio + 0.5)
        sizes_set.add((width, height))
    return sorted(sizes_set)


def create_srcset_images(
    file: BytesIO,
    widths: list = [1200, 800, 600, 400],
    output_format: str = "webp",
    output_quality: int = 100,
    resize_method: int = Image.NEAREST,
) -> list:
    """
    Resize the image to the widths specified

    :param file: file to resize
    :param output_format: output files format. Can be jpg or webp
    :param output_quality: compression files output_quality
    :param resize_method: resize method. Can be Image.NEAREST or Image.ANTIALIAS
    :return: list of dicts that contain images with their sizes
    """
    output_format = output_format.lower()
    if output_format not in ("jpg", "webp", "png"):
        raise TypeError('output_format must be either "jpg", "webp" or "png"')

    if output_quality > 100 or output_quality < 0:
        raise TypeError("output_quality must be between 0 and 100")

    image = Image.open(file).convert("RGB")  # Convert to RGB so we can save as .webp
    sizes = get_srcset_sizes(widths, image.width, image.height)

    result = []
    for (width, height) in sizes:
        if (width, height) == (image.width, image.height):
            new_image = image
        else:
            new_image = image.resize((width, height), resize_method)
            in_mem_file = BytesIO()
            new_image.save(in_mem_file, quality=output_quality, format=output_format)
            in_mem_file.seek(0)
            result.append(
                {
                    "image": in_mem_file,
                    "width": width,
                    "height": height,
                    "format": output_format,
                }
            )

    return result