--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sat/tools/images.py	Tue Oct 29 20:38:39 2019 +0100
@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+# SAT: a jabber client
+# Copyright (C) 2009-2019 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 sat.core.constants import Const as C
+from pathlib import Path
+from twisted.internet import threads
+
+
+def checkImage(host, path, context=C.CONTEXT_CHAT):
+    """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 context(str): context in which the image is transfered
+    @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
+    """
+    # TODO: context is not used yet
+    report = {}
+    image = Image.open(path)
+    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'] = [image.width*factor, image.height*factor]
+    else:
+        report['too_large'] = False
+
+    return report
+
+
+def _resizeImageBlocking(image_path, new_size):
+    im_path = Path(image_path)
+    im = Image.open(im_path)
+    resized = im.resize(new_size, Image.LANCZOS)
+    with tempfile.NamedTemporaryFile(suffix=im_path.suffix, delete=False) as f:
+        resized.save(f, format=im.format)
+    return Path(f.name)
+
+
+def resizeImage(image_path, new_size):
+    """Resize an image to a new temporary file, and return it path
+
+    @param image_path(str, Path): path of the original image
+    @param new_size(tuple[int, int]): size to use for new image
+    @return (Path): path of the resized file. The image at this path must be deleted
+        after use
+    """
+    return threads.deferToThread(_resizeImageBlocking, image_path, new_size)