--- a/cagou/plugins/plugin_wid_chat.kv	Wed Mar 18 20:26:21 2020 +0100
+++ b/cagou/plugins/plugin_wid_chat.kv	Sun Mar 22 14:10:59 2020 +0100
@@ -172,11 +172,18 @@
 
 <AttachmentsToSend>:
     attachments: attachments_layout.attachments
+    reduce_checkbox: reduce_checkbox
     orientation: "vertical"
     size_hint: 1, None
     height: self.minimum_height if self.attachments.children else 0
     opacity: 1 if self.attachments.children else 0
     padding: [app.MARGIN_LEFT, dp(5), app.MARGIN_RIGHT, dp(5)]
+    canvas.before:
+        Color:
+            rgba: app.c_prim
+        Rectangle:
+            pos: self.pos
+            size: self.size
     Label:
         size_hint: 1, None
         size: self.texture_size
@@ -184,13 +191,26 @@
         bold: True
     AttachmentsLayout:
         id: attachments_layout
-        canvas.before:
-            Color:
-                rgba: app.c_prim
-            Rectangle:
-                pos: self.pos
-                size: self.size
-
+    BoxLayout:
+        id: resize_box
+        size_hint: 1, None
+        opacity: 1 if root.show_resize else 0
+        height: dp(25) if root.show_resize else 0
+        Widget:
+        CheckBox:
+            id: reduce_checkbox
+            size_hint: None, 1
+            width: dp(20)
+            active: True
+        Label:
+            size_hint: None, 1
+            text: _("reduce images size")
+            text_size: None, None
+            size: self.texture_size
+            valign: "middle"
+            padding_x: dp(10)
+            font_size: sp(15)
+        Widget:
 
 <Chat>:
     attachments_to_send: attachments_to_send

--- a/cagou/plugins/plugin_wid_chat.py	Wed Mar 18 20:26:21 2020 +0100
+++ b/cagou/plugins/plugin_wid_chat.py	Sun Mar 22 14:10:59 2020 +0100
@@ -21,6 +21,7 @@
 from pathlib import Path
 import sys
 import uuid
+import mimetypes
 from urllib.parse import urlparse
 from kivy.uix.boxlayout import BoxLayout
 from kivy.uix.gridlayout import GridLayout
@@ -95,6 +96,15 @@
 class AttachmentsToSend(BoxLayout):
     """Layout for attachments to be sent with current message"""
     attachments = properties.ObjectProperty()
+    reduce_checkbox = properties.ObjectProperty()
+    show_resize = properties.BooleanProperty(False)
+
+    def on_kv_post(self, __):
+        self.attachments.bind(children=self.onAttachment)
+
+    def onAttachment(self, __, attachments):
+        if len(attachments) == 0:
+            self.show_resize = False
 
 
 class BaseAttachmentItem(BoxLayout):
@@ -974,6 +984,13 @@
                 "path": str(item.data["path"]),
                 "progress_id": progress_id,
             }
+            if 'media_type' in item.data:
+                attachment[C.MESS_KEY_ATTACHMENTS_MEDIA_TYPE] = item.data['media_type']
+
+            if ((self.attachments_to_send.reduce_checkbox.active
+                 and attachment.get('media_type', '').split('/')[0] == 'image')):
+                attachment[C.MESS_KEY_ATTACHMENTS_RESIZE] = True
+
             attachments.append(attachment)
 
             Clock.schedule_once(
@@ -999,12 +1016,41 @@
             )
         input_widget.text = ''
 
-    def addAttachment(self, file_path):
+    def _imageCheckCb(self, report_raw):
+        report = data_format.deserialise(report_raw)
+        if report['too_large']:
+            self.attachments_to_send.show_resize=True
+            self.attachments_to_send.reduce_checkbox.active=True
+
+    def addAttachment(self, file_path, media_type=None):
         file_path = Path(file_path)
+        if media_type is None:
+            media_type = mimetypes.guess_type(file_path, strict=False)[0]
+        if not self.attachments_to_send.show_resize and media_type is not None:
+            # we check if the attachment is an image and if it's too large.
+            # If too large, the reduce size check box will be displayed, and checked by
+            # default.
+            main_type = media_type.split('/')[0]
+            if main_type == "image":
+                G.host.bridge.imageCheck(
+                    str(file_path),
+                    callback=self._imageCheckCb,
+                    errback=partial(
+                        G.host.errback,
+                        title=_("Can't check image size"),
+                        message=_("Can't check image at {path}: {{msg}}").format(
+                            path=file_path),
+                    )
+                )
+
         data = {
             "path": file_path,
             "name": file_path.name,
         }
+
+        if media_type is not None:
+            data['media_type'] = media_type
+
         self.attachments_to_send.attachments.add_widget(
             AttachmentToSendItem(data=data)
         )