beets/beets/util/artresizer.py

# This file is part of beets.
# Copyright 2016, Fabrice Laporte
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

"""Abstraction layer to resize images using PIL, ImageMagick, or a
public resizing proxy if neither is available.
"""

from itertools import chain
import subprocess
import os
import os.path
import platform
import re
from tempfile import NamedTemporaryFile
from urllib.parse import urlencode
from beets import logging
from beets import util
from beets.util import bytestring_path, displayable_path, py3_path, syspath

PROXY_URL = 'https://images.weserv.nl/'

log = logging.getLogger('beets')


def resize_url(url, maxwidth, quality=0):
    """Return a proxied image URL that resizes the original image to
    maxwidth (preserving aspect ratio).
    """
    params = {
        'url': url.replace('http://', ''),
        'w': maxwidth,
    }

    if quality > 0:
        params['q'] = quality

    return '{}?{}'.format(PROXY_URL, urlencode(params))


def temp_file_for(path):
    """Return an unused filename with the same extension as the
    specified path.
    """
    ext = os.path.splitext(path)[1]
    with NamedTemporaryFile(suffix=py3_path(ext), delete=False) as f:
        return bytestring_path(f.name)


class LocalBackendNotAvailableError(Exception):
    pass


_NOT_AVAILABLE = object()


class LocalBackend:
    @classmethod
    def available(cls):
        try:
            cls.version()
            return True
        except LocalBackendNotAvailableError:
            return False


class IMBackend(LocalBackend):
    NAME = "ImageMagick"

    # These fields are used as a cache for `version()`. `_legacy` indicates
    # whether the modern `magick` binary is available or whether to fall back
    # to the old-style `convert`, `identify`, etc. commands.
    _version = None
    _legacy = None

    @classmethod
    def version(cls):
        """Obtain and cache ImageMagick version.

        Raises `LocalBackendNotAvailableError` if not available.
        """
        if cls._version is None:
            for cmd_name, legacy in (('magick', False), ('convert', True)):
                try:
                    out = util.command_output([cmd_name, "--version"]).stdout
                except (subprocess.CalledProcessError, OSError) as exc:
                    log.debug('ImageMagick version check failed: {}', exc)
                    cls._version = _NOT_AVAILABLE
                else:
                    if b'imagemagick' in out.lower():
                        pattern = br".+ (\d+)\.(\d+)\.(\d+).*"
                        match = re.search(pattern, out)
                        if match:
                            cls._version = (int(match.group(1)),
                                            int(match.group(2)),
                                            int(match.group(3)))
                            cls._legacy = legacy

        if cls._version is _NOT_AVAILABLE:
            raise LocalBackendNotAvailableError()
        else:
            return cls._version

    def __init__(self):
        """Initialize a wrapper around ImageMagick for local image operations.

        Stores the ImageMagick version and legacy flag. If ImageMagick is not
        available, raise an Exception.
        """
        self.version()

        # Use ImageMagick's magick binary when it's available.
        # If it's not, fall back to the older, separate convert
        # and identify commands.
        if self._legacy:
            self.convert_cmd = ['convert']
            self.identify_cmd = ['identify']
            self.compare_cmd = ['compare']
        else:
            self.convert_cmd = ['magick']
            self.identify_cmd = ['magick', 'identify']
            self.compare_cmd = ['magick', 'compare']

    def resize(self, maxwidth, path_in, path_out=None, quality=0,
               max_filesize=0):
        """Resize using ImageMagick.

        Use the ``magick`` program or ``convert`` on older versions. Return
        the output path of resized image.
        """
        path_out = path_out or temp_file_for(path_in)
        log.debug('artresizer: ImageMagick resizing {0} to {1}',
                  displayable_path(path_in), displayable_path(path_out))

        # "-resize WIDTHx>" shrinks images with the width larger
        # than the given width while maintaining the aspect ratio
        # with regards to the height.
        # ImageMagick already seems to default to no interlace, but we include
        # it here for the sake of explicitness.
        cmd = self.convert_cmd + [
            syspath(path_in, prefix=False),
            '-resize', f'{maxwidth}x>',
            '-interlace', 'none',
        ]

        if quality > 0:
            cmd += ['-quality', f'{quality}']

        # "-define jpeg:extent=SIZEb" sets the target filesize for imagemagick
        # to SIZE in bytes.
        if max_filesize > 0:
            cmd += ['-define', f'jpeg:extent={max_filesize}b']

        cmd.append(syspath(path_out, prefix=False))

        try:
            util.command_output(cmd)
        except subprocess.CalledProcessError:
            log.warning('artresizer: IM convert failed for {0}',
                        displayable_path(path_in))
            return path_in

        return path_out

    def get_size(self, path_in):
        cmd = self.identify_cmd + [
            '-format', '%w %h', syspath(path_in, prefix=False)
        ]

        try:
            out = util.command_output(cmd).stdout
        except subprocess.CalledProcessError as exc:
            log.warning('ImageMagick size query failed')
            log.debug(
                '`convert` exited with (status {}) when '
                'getting size with command {}:\n{}',
                exc.returncode, cmd, exc.output.strip()
            )
            return None
        try:
            return tuple(map(int, out.split(b' ')))
        except IndexError:
            log.warning('Could not understand IM output: {0!r}', out)
            return None

    def deinterlace(self, path_in, path_out=None):
        path_out = path_out or temp_file_for(path_in)

        cmd = self.convert_cmd + [
            syspath(path_in, prefix=False),
            '-interlace', 'none',
            syspath(path_out, prefix=False),
        ]

        try:
            util.command_output(cmd)
            return path_out
        except subprocess.CalledProcessError:
            # FIXME: Should probably issue a warning?
            return path_in

    def get_format(self, filepath):
        cmd = self.identify_cmd + [
            '-format', '%[magick]',
            syspath(filepath)
        ]

        try:
            return util.command_output(cmd).stdout
        except subprocess.CalledProcessError:
            # FIXME: Should probably issue a warning?
            return None

    def convert_format(self, source, target, deinterlaced):
        cmd = self.convert_cmd + [
            syspath(source),
            *(["-interlace", "none"] if deinterlaced else []),
            syspath(target),
        ]

        try:
            subprocess.check_call(
                cmd,
                stderr=subprocess.DEVNULL,
                stdout=subprocess.DEVNULL
            )
            return target
        except subprocess.CalledProcessError:
            # FIXME: Should probably issue a warning?
            return source

    @property
    def can_compare(self):
        return self.version() > (6, 8, 7)

    def compare(self, im1, im2, compare_threshold):
        is_windows = platform.system() == "Windows"

        # Converting images to grayscale tends to minimize the weight
        # of colors in the diff score. So we first convert both images
        # to grayscale and then pipe them into the `compare` command.
        # On Windows, ImageMagick doesn't support the magic \\?\ prefix
        # on paths, so we pass `prefix=False` to `syspath`.
        convert_cmd = self.convert_cmd + [
            syspath(im2, prefix=False), syspath(im1, prefix=False),
            '-colorspace', 'gray', 'MIFF:-'
        ]
        compare_cmd = self.compare_cmd + [
            '-define', 'phash:colorspaces=sRGB,HCLp',
            '-metric', 'PHASH', '-', 'null:',
        ]
        log.debug('comparing images with pipeline {} | {}',
                  convert_cmd, compare_cmd)
        convert_proc = subprocess.Popen(
            convert_cmd,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            close_fds=not is_windows,
        )
        compare_proc = subprocess.Popen(
            compare_cmd,
            stdin=convert_proc.stdout,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            close_fds=not is_windows,
        )

        # Check the convert output. We're not interested in the
        # standard output; that gets piped to the next stage.
        convert_proc.stdout.close()
        convert_stderr = convert_proc.stderr.read()
        convert_proc.stderr.close()
        convert_proc.wait()
        if convert_proc.returncode:
            log.debug(
                'ImageMagick convert failed with status {}: {!r}',
                convert_proc.returncode,
                convert_stderr,
            )
            return None

        # Check the compare output.
        stdout, stderr = compare_proc.communicate()
        if compare_proc.returncode:
            if compare_proc.returncode != 1:
                log.debug('ImageMagick compare failed: {0}, {1}',
                          displayable_path(im2), displayable_path(im1))
                return None
            out_str = stderr
        else:
            out_str = stdout

        try:
            phash_diff = float(out_str)
        except ValueError:
            log.debug('IM output is not a number: {0!r}', out_str)
            return None

        log.debug('ImageMagick compare score: {0}', phash_diff)
        return phash_diff <= compare_threshold

    @property
    def can_write_metadata(self):
        return True

    def write_metadata(self, file, metadata):
        assignments = list(chain.from_iterable(
            ('-set', k, v) for k, v in metadata.items()
        ))
        command = self.convert_cmd + [file, *assignments, file]

        util.command_output(command)


class PILBackend(LocalBackend):
    NAME = "PIL"

    @classmethod
    def version(cls):
        try:
            __import__('PIL', fromlist=['Image'])
        except ImportError:
            raise LocalBackendNotAvailableError()

    def __init__(self):
        """Initialize a wrapper around PIL for local image operations.

        If PIL is not available, raise an Exception.
        """
        self.version()

    def resize(self, maxwidth, path_in, path_out=None, quality=0,
               max_filesize=0):
        """Resize using Python Imaging Library (PIL).  Return the output path
        of resized image.
        """
        path_out = path_out or temp_file_for(path_in)
        from PIL import Image

        log.debug('artresizer: PIL resizing {0} to {1}',
                  displayable_path(path_in), displayable_path(path_out))

        try:
            im = Image.open(syspath(path_in))
            size = maxwidth, maxwidth
            im.thumbnail(size, Image.ANTIALIAS)

            if quality == 0:
                # Use PIL's default quality.
                quality = -1

            # progressive=False only affects JPEGs and is the default,
            # but we include it here for explicitness.
            im.save(py3_path(path_out), quality=quality, progressive=False)

            if max_filesize > 0:
                # If maximum filesize is set, we attempt to lower the quality
                # of jpeg conversion by a proportional amount, up to 3 attempts
                # First, set the maximum quality to either provided, or 95
                if quality > 0:
                    lower_qual = quality
                else:
                    lower_qual = 95
                for i in range(5):
                    # 5 attempts is an arbitrary choice
                    filesize = os.stat(syspath(path_out)).st_size
                    log.debug("PIL Pass {0} : Output size: {1}B", i, filesize)
                    if filesize <= max_filesize:
                        return path_out
                    # The relationship between filesize & quality will be
                    # image dependent.
                    lower_qual -= 10
                    # Restrict quality dropping below 10
                    if lower_qual < 10:
                        lower_qual = 10
                    # Use optimize flag to improve filesize decrease
                    im.save(py3_path(path_out), quality=lower_qual,
                            optimize=True, progressive=False)
                log.warning("PIL Failed to resize file to below {0}B",
                            max_filesize)
                return path_out

            else:
                return path_out
        except OSError:
            log.error("PIL cannot create thumbnail for '{0}'",
                      displayable_path(path_in))
            return path_in

    def get_size(self, path_in):
        from PIL import Image

        try:
            im = Image.open(syspath(path_in))
            return im.size
        except OSError as exc:
            log.error("PIL could not read file {}: {}",
                      displayable_path(path_in), exc)
            return None

    def deinterlace(self, path_in, path_out=None):
        path_out = path_out or temp_file_for(path_in)
        from PIL import Image

        try:
            im = Image.open(syspath(path_in))
            im.save(py3_path(path_out), progressive=False)
            return path_out
        except IOError:
            # FIXME: Should probably issue a warning?
            return path_in

    def get_format(self, filepath):
        from PIL import Image, UnidentifiedImageError

        try:
            with Image.open(syspath(filepath)) as im:
                return im.format
        except (ValueError, TypeError, UnidentifiedImageError,
                FileNotFoundError):
            log.exception("failed to detect image format for {}", filepath)
            return None

    def convert_format(self, source, target, deinterlaced):
        from PIL import Image, UnidentifiedImageError

        try:
            with Image.open(syspath(source)) as im:
                im.save(py3_path(target), progressive=not deinterlaced)
                return target
        except (ValueError, TypeError, UnidentifiedImageError,
                FileNotFoundError, OSError):
            log.exception("failed to convert image {} -> {}", source, target)
            return source

    @property
    def can_compare(self):
        return False

    def compare(self, im1, im2, compare_threshold):
        # It is an error to call this when ArtResizer.can_compare is not True.
        raise NotImplementedError()

    @property
    def can_write_metadata(self):
        return True

    def write_metadata(self, file, metadata):
        from PIL import Image, PngImagePlugin

        # FIXME: Detect and handle other file types (currently, the only user
        # is the thumbnails plugin, which generates PNG images).
        im = Image.open(syspath(file))
        meta = PngImagePlugin.PngInfo()
        for k, v in metadata.items():
            meta.add_text(k, v, 0)
        im.save(py3_path(file), "PNG", pnginfo=meta)


class Shareable(type):
    """A pseudo-singleton metaclass that allows both shared and
    non-shared instances. The ``MyClass.shared`` property holds a
    lazily-created shared instance of ``MyClass`` while calling
    ``MyClass()`` to construct a new object works as usual.
    """

    def __init__(cls, name, bases, dict):
        super().__init__(name, bases, dict)
        cls._instance = None

    @property
    def shared(cls):
        if cls._instance is None:
            cls._instance = cls()
        return cls._instance


BACKEND_CLASSES = [
    IMBackend,
    PILBackend,
]


class ArtResizer(metaclass=Shareable):
    """A singleton class that performs image resizes.
    """

    def __init__(self):
        """Create a resizer object with an inferred method.
        """
        # Check if a local backend is available, and store an instance of the
        # backend class. Otherwise, fallback to the web proxy.
        for backend_cls in BACKEND_CLASSES:
            try:
                self.local_method = backend_cls()
                log.debug(f"artresizer: method is {self.local_method.NAME}")
                break
            except LocalBackendNotAvailableError:
                continue
        else:
            log.debug("artresizer: method is WEBPROXY")
            self.local_method = None

    @property
    def method(self):
        if self.local:
            return self.local_method.NAME
        else:
            return "WEBPROXY"

    def resize(
        self, maxwidth, path_in, path_out=None, quality=0, max_filesize=0
    ):
        """Manipulate an image file according to the method, returning a
        new path. For PIL or IMAGEMAGIC methods, resizes the image to a
        temporary file and encodes with the specified quality level.
        For WEBPROXY, returns `path_in` unmodified.
        """
        if self.local:
            return self.local_method.resize(
                maxwidth, path_in, path_out,
                quality=quality, max_filesize=max_filesize
            )
        else:
            # Handled by `proxy_url` already.
            return path_in

    def deinterlace(self, path_in, path_out=None):
        """Deinterlace an image.

        Only available locally.
        """
        if self.local:
            return self.local_method.deinterlace(path_in, path_out)
        else:
            # FIXME: Should probably issue a warning?
            return path_in

    def proxy_url(self, maxwidth, url, quality=0):
        """Modifies an image URL according the method, returning a new
        URL. For WEBPROXY, a URL on the proxy server is returned.
        Otherwise, the URL is returned unmodified.
        """
        if self.local:
            # Going to be handled by `resize()`.
            return url
        else:
            return resize_url(url, maxwidth, quality)

    @property
    def local(self):
        """A boolean indicating whether the resizing method is performed
        locally (i.e., PIL or ImageMagick).
        """
        return self.local_method is not None

    def get_size(self, path_in):
        """Return the size of an image file as an int couple (width, height)
        in pixels.

        Only available locally.
        """
        if self.local:
            return self.local_method.get_size(path_in)
        else:
            # FIXME: Should probably issue a warning?
            return path_in

    def get_format(self, path_in):
        """Returns the format of the image as a string.

        Only available locally.
        """
        if self.local:
            return self.local_method.get_format(path_in)
        else:
            # FIXME: Should probably issue a warning?
            return None

    def reformat(self, path_in, new_format, deinterlaced=True):
        """Converts image to desired format, updating its extension, but
        keeping the same filename.

        Only available locally.
        """
        if not self.local:
            # FIXME: Should probably issue a warning?
            return path_in

        new_format = new_format.lower()
        # A nonexhaustive map of image "types" to extensions overrides
        new_format = {
            'jpeg': 'jpg',
        }.get(new_format, new_format)

        fname, ext = os.path.splitext(path_in)
        path_new = fname + b'.' + new_format.encode('utf8')

        # allows the exception to propagate, while still making sure a changed
        # file path was removed
        result_path = path_in
        try:
            result_path = self.local_method.convert_format(
                path_in, path_new, deinterlaced
            )
        finally:
            if result_path != path_in:
                os.unlink(path_in)
        return result_path

    @property
    def can_compare(self):
        """A boolean indicating whether image comparison is available"""

        if self.local:
            return self.local_method.can_compare
        else:
            return False

    def compare(self, im1, im2, compare_threshold):
        """Return a boolean indicating whether two images are similar.

        Only available locally.
        """
        if self.local:
            return self.local_method.compare(im1, im2, compare_threshold)
        else:
            # FIXME: Should probably issue a warning?
            return None

    @property
    def can_write_metadata(self):
        """A boolean indicating whether writing image metadata is supported."""

        if self.local:
            return self.local_method.can_write_metadata
        else:
            return False

    def write_metadata(self, file, metadata):
        """Write key-value metadata to the image file.

        Only available locally. Currently, expects the image to be a PNG file.
        """
        if self.local:
            self.local_method.write_metadata(file, metadata)
        else:
            # FIXME: Should probably issue a warning?
            pass