diff --git a/plugins/ImageEncoder/ImageEncoder.php b/plugins/ImageEncoder/ImageEncoder.php
index f84263992a..798a9ec5db 100644
--- a/plugins/ImageEncoder/ImageEncoder.php
+++ b/plugins/ImageEncoder/ImageEncoder.php
@@ -19,13 +19,17 @@
 
 namespace Plugin\ImageEncoder;
 
+use App\Core\Cache;
+use App\Core\DB\DB;
 use App\Core\Event;
+use App\Core\GSFile;
 use function App\Core\I18n\_m;
 use App\Core\Log;
 use App\Core\Modules\Plugin;
 use App\Entity\Attachment;
 use App\Entity\AttachmentThumbnail;
 use App\Util\Common;
+use App\Util\TemporaryFile;
 use Exception;
 use Jcupitt\Vips;
 
@@ -47,11 +51,80 @@ class ImageEncoder extends Plugin
      *
      * @return bool
      */
-    public function onAttachmentValidation(\SplFileInfo &$file, ?string &$mimetype = null): bool
+    public function onAttachmentValidation(\SplFileInfo &$file, ?string &$mimetype, ?string &$title): bool
     {
         $original_mimetype = $mimetype;
-        // TODO: Encode in place
-        //$mimetype = self::preferredType();
+        if (GSFile::mimetypeMajor($original_mimetype) != 'image') {
+            // Nothing concerning us
+            return Event::next;
+        }
+
+        $type      = self::preferredType();
+        $extension = image_type_to_extension($type, include_dot: true);
+        $temp      = new TemporaryFile(prefix: null, suffix: $extension); // This handles deleting the file if some error occurs
+        $mimetype  = image_type_to_mime_type($type);
+        if ($mimetype != $original_mimetype) {
+            // If title seems to be a filename with an extension
+            if (preg_match('/\.[a-z0-9]/i', $title) === 1) {
+                $title = substr($title, 0, strrpos($title, '.') - 1) . $extension;
+            }
+        }
+
+        $image  = Vips\Image::newFromFile($file->getRealPath(), ['access' => 'sequential']);
+        $width  = Common::clamp($image->width, 0, Common::config('attachments', 'max_width'));
+        $height = Common::clamp($image->height, 0, Common::config('attachments', 'max_height'));
+        $image  = $image->crop(0, 0, $width, $height);
+        $image->writeToFile($temp->getRealPath());
+
+        $filesize = $temp->getSize();
+        $filepath = $file->getRealPath();
+        @unlink($filepath);
+
+        $file_quota = Common::config('attachments', 'file_quota');
+        if ($filesize > $file_quota) {
+            // TRANS: Message given if an upload is larger than the configured maximum.
+            throw new ClientException(_m('No file may be larger than {quota} bytes and the file you sent was {size} bytes. ' .
+                                         'Try to upload a smaller version.', ['quota' => $file_quota, 'size' => $filesize]));
+        }
+
+        $user  = Common::user();
+        $query = <<<END
+select sum(at.size) as total
+    from attachment at
+        join attachment_to_note an with at.id = an.attachment_id
+        join note n with an.note_id = n.id
+    where n.gsactor_id = :actor_id and at.size is not null
+END;
+
+        $user_quota = Common::config('attachments', 'user_quota');
+        if ($user_quota != false) {
+            $cache_key_user_total = 'user-' . $user->getId() . 'file-quota';
+            $user_total           = Cache::get($cache_key_user_total, fn () => DB::dql($query, ['actor_id' => $user->getId()])[0]['total']);
+            Cache::set($cache_key_user_total, $user_total + $filesize);
+
+            if ($user_total + $filesize > $user_quota) {
+                // TRANS: Message given if an upload would exceed user quota.
+                throw new ClientException(_m('A file this large would exceed your user quota of {quota} bytes.', ['quota' => $user_quota]));
+            }
+        }
+
+        $query .= ' AND MONTH(at.modified) = MONTH(CURRENT_DATE())'
+                . ' AND YEAR(at.modified)  = YEAR(CURRENT_DATE())';
+
+        $monthly_quota = Common::config('attachments', 'monthly_quota');
+        if ($monthly_quota != false) {
+            $cache_key_user_monthly = 'user-' . $user->getId() . 'monthly-file-quota';
+            $monthly_total          = Cache::get($cache_key_user_monthly, fn () => DB::dql($query, ['actor_id' => $user->getId()])[0]['total']);
+            Cache::set($cache_key_user_monthly, $monthly_total + $filesize);
+
+            if ($monthly_total + $filesize > $monthly_quota) {
+                // TRANS: Message given if an upload would exceed user quota.
+                throw new ClientException(_m('A file this large would exceed your monthly quota of {quota} bytes.', ['quota' => $monthly_quota]));
+            }
+        }
+
+        $temp->commit($filepath);
+
         return Event::stop;
     }
 
@@ -86,8 +159,6 @@ class ImageEncoder extends Plugin
         $old_limit = ini_set('memory_limit', Common::config('attachments', 'memory_limit'));
         try {
             try {
-                // -1 means load all pages, 'sequential' access means decode pixels on demand
-                // $image = Vips\Image::newFromFile(self::getPath($attachment), ['n' => -1, 'access' => 'sequential']);
                 $image = Vips\Image::thumbnail($source, $width, ['height' => $height]);
             } catch (Exception $e) {
                 Log::error(__METHOD__ . ' encountered exception: ' . print_r($e, true));