--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sat/tools/image.py	Sun Mar 22 12:52:43 2020 +0100
@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+
+# SàT: an XMPP client
+# Copyright (C) 2009-2020 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Methods to manipulate images"""
+
+import tempfile
+from PIL import Image
+from pathlib import Path
+from twisted.internet import threads
+
+
+def check(host, path, max_size=None):
+    """Analyze image and return a report
+
+    report will indicate if image is too large, and the recommended new size if this is
+    the case
+    @param host: SàT instance
+    @param path(str, pathlib.Path): image to open
+    @param max_size(tuple[int, int]): maximum accepted size of image
+        None to use value set in config
+    @return dict: report on image, with following keys:
+        - too_large: true if image is oversized
+        - recommended_size: if too_large is True, recommended size to use
+    """
+    report = {}
+    image = Image.open(path)
+    if max_size is None:
+        max_size = tuple(host.memory.getConfig(None, "image_max", (1200, 720)))
+    if image.size > max_size:
+        report['too_large'] = True
+        if image.size[0] > max_size[0]:
+            factor = max_size[0] / image.size[0]
+            if image.size[1] * factor > max_size[1]:
+                factor = max_size[1] / image.size[1]
+        else:
+            factor = max_size[1] / image.size[1]
+        report['recommended_size'] = [int(image.width*factor), int(image.height*factor)]
+    else:
+        report['too_large'] = False
+
+    return report
+
+
+def _resizeBlocking(image_path, new_size, dest=None):
+    im_path = Path(image_path)
+    im = Image.open(im_path)
+    resized = im.resize(new_size, Image.LANCZOS)
+
+    if dest is None:
+        dest = tempfile.NamedTemporaryFile(suffix=im_path.suffix, delete=False)
+    elif isinstance(dest, Path):
+        dest = dest.open('wb')
+
+    with dest as f:
+        resized.save(f, format=im.format)
+
+    return Path(f.name)
+
+
+def resize(image_path, new_size, dest=None):
+    """Resize an image to a new file, and return its path
+
+    @param image_path(str, Path): path of the original image
+    @param new_size(tuple[int, int]): size to use for new image
+    @param dest(None, Path, file): where the resized image must be stored, can be:
+        - None: use a temporary file
+        - Path: path to the file to create/overwrite
+        - file: a file object which must be opened for writing in binary mode
+    @return (Path): path of the resized file.
+        The image at this path should be deleted after use
+    """
+    return threads.deferToThread(_resizeBlocking, image_path, new_size, dest)