server/posts: fix custom thumbnails

I can see the intent, sadly this was always broken in the case where the
post already has a custom thumbnail from initial load, and we don't drag
any new files. It did not actually remove the existing thumbnail.
Before 12c4542bb2482fac89aae9a04b15984a56bb8fb0 it would actually crash,
but this now makes it behave as expected.
Also properly syncs internal state with what's displayed to the user.

client/css/core-general.styl

@@ -106,6 +106,11 @@ form .fa-question-circle-o
                     background-color: $scrollbar-bg-color
                 &::-webkit-scrollbar-thumb
                     background-color: $scrollbar-thumb-color
+                li[data-name=view]
+                    background: $button-enabled-background-color
+                    margin-right: 1em
+                    a
+                        color: $button-enabled-text-color
     >.content-wrapper:not(.transparent)
         background: $top-navigation-color
         padding: 1.8em
@@ -214,8 +219,6 @@ nav
         ul li[data-name=settings],
         ul li[data-name=help]
             float: none
-        .access-key
-            text-decoration: underline
         .thumbnail
             width: 1.5em
             height: 1.5em
@@ -244,9 +247,6 @@ nav
             #mobile-navigation-toggle
                 color: $text-color-darktheme
 
-a .access-key
-    text-decoration: underline
-
 .messages
     margin: 0 auto
     text-align: left
@@ -284,28 +284,25 @@ a .access-key
     /*background-image: attr(data-src url)*/ /* not available yet */
     vertical-align: middle
     background-repeat: no-repeat
-    background-size: cover
+    background-size: contain
     background-position: center
     display: inline-block
+    overflow: hidden
     width: 20px
     height: 20px
     &.empty
         background-image:
-            linear-gradient(45deg, $transparency-grid-square-color 25%, transparent 25%),
-            linear-gradient(-45deg, $transparency-grid-square-color 25%, transparent 25%),
-            linear-gradient(45deg, transparent 75%, $transparency-grid-square-color 75%),
-            linear-gradient(-45deg, transparent 75%, $transparency-grid-square-color 75%)
-        background-position: 0 0, 0 10px, 10px -10px, -10px 0px
-        background-repeat: repeat
-        background-size: 20px 20px
-    img
+            repeating-linear-gradient(45deg, $window-color, $window-color 10px, #e6e6e6 10px, #e6e6e6 20px)
+    img, video
         opacity: 0
-        width: auto
-        height: 100%
-    video
-        width: auto
+        object-fit: cover
+        width: 100%
         height: 100%
 
+.darktheme .thumbnail.empty
+    background-image:
+        repeating-linear-gradient(45deg, $window-color-darktheme, $window-color-darktheme 10px, #333 10px, #333 20px)
+
 .flexbox-dummy
     height: 0 !important
     padding-top: 0 !important

client/css/post-content-control.styl

@@ -1,14 +1,16 @@
 @import colors
 
 .post-container
-    .post-content.transparency-grid img
-        background-image:
-            linear-gradient(45deg, $transparency-grid-square-color 25%, transparent 25%),
-            linear-gradient(-45deg, $transparency-grid-square-color 25%, transparent 25%),
-            linear-gradient(45deg, transparent 75%, $transparency-grid-square-color 75%),
-            linear-gradient(-45deg, transparent 75%, $transparency-grid-square-color 75%)
-        background-size: 20px 20px
-        background-position: 0 0, 0 10px, 10px -10px, -10px 0px
+    .post-content
+        &.transparency-grid, &.post-error
+            background-image:
+                linear-gradient(45deg, $transparency-grid-square-color 25%, transparent 25%),
+                linear-gradient(-45deg, $transparency-grid-square-color 25%, transparent 25%),
+                linear-gradient(45deg, transparent 75%, $transparency-grid-square-color 75%),
+                linear-gradient(-45deg, transparent 75%, $transparency-grid-square-color 75%)
+            background-position: 0 0, 0 10px, 10px -10px, -10px 0px
+            background-repeat: repeat
+            background-size: 20px 20px
 
     text-align: center
     .post-content
@@ -17,6 +19,8 @@
         position: relative
 
         .resize-listener
+            background-repeat: no-repeat
+            background-size: cover
             position: absolute
             left: 0
             right: 0
@@ -27,3 +31,14 @@
 
         img
             image-orientation: from-image
+
+.darktheme .post-container .post-content
+    &.transparency-grid, &.post-error
+        background-image:
+            linear-gradient(45deg, $transparency-grid-square-color 25%, transparent 25%),
+            linear-gradient(-45deg, $transparency-grid-square-color 25%, transparent 25%),
+            linear-gradient(45deg, transparent 75%, $transparency-grid-square-color 75%),
+            linear-gradient(-45deg, transparent 75%, $transparency-grid-square-color 75%)
+        background-position: 0 0, 0 10px, 10px -10px, -10px 0px
+        background-repeat: repeat
+        background-size: 20px 20px

client/css/post-upload.styl

@@ -62,22 +62,22 @@ $cancel-button-color = tomato
             margin: 0 0 1.2em 0
             padding-left: 13em
 
-            img
-                width: 100%
-                height: 100%
-            
-            video
-                width: 100%
-                height: 100%
-
             &>.thumbnail-wrapper
                 float: left
                 width: 12em
                 height: 8em
                 margin: 0 0 0 -13em
+                a
+                    display: block
+                    height: 100%
+                    width: 100%
                 .thumbnail
                     width: 100%
                     height: 100%
+                    video
+                        opacity: 1
+                    img, video
+                        object-fit: contain
 
             .uploadable
                 border: 1px solid $upload-border-color

client/html/post_content.tpl

@@ -1,13 +1,14 @@
 <div class='post-content post-type-<%- ctx.post.type %>'>
     <% if (['image', 'animation'].includes(ctx.post.type)) { %>
 
-        <img class='resize-listener' alt='' src='<%- ctx.post.contentUrl %>'/>
+        <img class='resize-listener' alt='' src='<%- ctx.post.contentUrl %>' draggable='false' fetchPriority='high'/>
 
     <% } else if (ctx.post.type === 'flash') { %>
 
         <object class='resize-listener' width='<%- ctx.post.canvasWidth %>' height='<%- ctx.post.canvasHeight %>' data='<%- ctx.post.contentUrl %>'>
-            <param name='wmode' value='opaque'/>
+            <param name='wmode' value='transparent'/>
             <param name='movie' value='<%- ctx.post.contentUrl %>'/>
+            <div class='messages'><div class='message-wrapper'><div class='message error'>Your browser does not support Flash.</div></div></div>
         </object>
 
     <% } else if (ctx.post.type === 'video') { %>
@@ -19,6 +20,8 @@
                 loop: (ctx.post.flags || []).includes('loop'),
                 playsinline: true,
                 autoplay: ctx.autoplay,
+                preload: 'auto',
+                poster: ctx.post.originalThumbnailUrl,
             },
             ctx.makeElement('source', {
                 type: ctx.post.mimeType,

client/html/post_upload_row.tpl

@@ -10,7 +10,7 @@
 
             <div class='thumbnail'>
                 <a href='<%= ctx.uploadable.previewUrl %>'>
-                    <video id='video' nocontrols muted>
+                    <video nocontrols muted>
                         <source type='<%- ctx.uploadable.mimeType %>' src='<%- ctx.uploadable.previewUrl %>'/>
                     </video>
                 </a>

client/js/api.js

@@ -294,11 +294,16 @@ class Api extends events.EventTarget {
         // transform the request: upload each file, then make the request use
         // its tokens.
         data = Object.assign({}, data);
+        let fileData = {};
         let abortFunction = () => {};
         let promise = Promise.resolve();
         if (files) {
             for (let key of Object.keys(files)) {
                 const file = files[key];
+                if (file === null) {
+                    fileData[key] = null;
+                    continue;
+                }
                 const fileId = this._getFileId(file);
                 if (fileTokens[fileId]) {
                     data[key + "Token"] = fileTokens[fileId];
@@ -324,7 +329,7 @@ class Api extends events.EventTarget {
                     url,
                     requestFactory,
                     data,
-                    {},
+                    fileData,
                     options
                 );
                 abortFunction = () => requestPromise.abort();
@@ -388,7 +393,7 @@ class Api extends events.EventTarget {
             if (files) {
                 for (let key of Object.keys(files)) {
                     const value = files[key];
-                    if (value.constructor === String) {
+                    if (value !== null && value.constructor === String) {
                         data[key + "Url"] = value;
                     } else {
                         req.attach(key, value || new Blob());

client/js/controllers/comments_controller.js

@@ -8,7 +8,7 @@ const PageController = require("../controllers/page_controller.js");
 const CommentsPageView = require("../views/comments_page_view.js");
 const EmptyView = require("../views/empty_view.js");
 
-const fields = ["id", "comments", "commentCount", "thumbnailUrl"];
+const fields = ["id", "comments", "commentCount", "thumbnailUrl", "customThumbnailUrl"];
 
 class CommentsController {
     constructor(ctx) {

client/js/controllers/post_list_controller.js

@@ -14,6 +14,7 @@ const EmptyView = require("../views/empty_view.js");
 const fields = [
     "id",
     "thumbnailUrl",
+    "customThumbnailUrl",
     "type",
     "safety",
     "score",

client/js/controllers/post_main_controller.js

@@ -178,15 +178,11 @@ class PostMainController extends BasePostController {
         if (e.detail.relations !== undefined) {
             post.relations = e.detail.relations;
         }
-        if (e.detail.content !== undefined) {
-            post.newContent = e.detail.content;
-        }
-        if (e.detail.thumbnail !== undefined) {
-            post.newThumbnail = e.detail.thumbnail;
-        }
         if (e.detail.source !== undefined) {
             post.source = e.detail.source;
         }
+        post.newContent = e.detail.content;
+        post.newThumbnail = e.detail.thumbnail;
         post.save().then(
             () => {
                 this._view.sidebarControl.showSuccess("Post saved.");

client/js/controls/post_content_control.js

@@ -119,9 +119,28 @@ class PostContentControl {
             post: this._post,
             autoplay: settings.get().autoplayVideos,
         });
-        if (settings.get().transparencyGrid) {
+        function load(argument) {
+            if (settings.get().transparencyGrid) {
+                newNode.classList.add("transparency-grid");
+            }
+            newNode.firstElementChild.style.backgroundImage = "";
+        }
+        if (["image", "flash"].includes(this._post.type)) {
+            newNode.firstElementChild.style.backgroundImage = "url("+this._post.originalThumbnailUrl+")";
+        }
+        if (this._post.type == "image") {
+            newNode.firstElementChild.addEventListener("load", load);
+        } else if (settings.get().transparencyGrid) {
             newNode.classList.add("transparency-grid");
         }
+        newNode.firstElementChild.addEventListener("error", (e) => {
+            newNode.classList.add("post-error");
+            if (["image", "animation"].includes(this._post.type)) {
+                newNode.firstElementChild.removeEventListener("load", load);
+                newNode.firstElementChild.style.backgroundImage = "url("+this._post.originalThumbnailUrl+")";
+                newNode.firstElementChild.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7";
+            }
+        });
         if (this._postContentNode) {
             this._hostNode.replaceChild(newNode, this._postContentNode);
         } else {

client/js/controls/post_edit_sidebar_control.js

@@ -138,10 +138,7 @@ class PostEditSidebarControl extends events.EventTarget {
             this._thumbnailRemovalLinkNode.addEventListener("click", (e) =>
                 this._evtRemoveThumbnailClick(e)
             );
-            this._thumbnailRemovalLinkNode.style.display = this._post
-                .hasCustomThumbnail
-                ? "block"
-                : "none";
+            this._thumbnailRemovalLinkUpdate(this._post);
         }
 
         if (this._addNoteLinkNode) {
@@ -249,12 +246,25 @@ class PostEditSidebarControl extends events.EventTarget {
         this._poolsExpander.title = `Pools (${this._post.pools.length})`;
     }
 
+    _thumbnailRemovalLinkUpdate(post) {
+        if (this._thumbnailRemovalLinkNode) {
+            this._thumbnailRemovalLinkNode.style.display = post
+                .customThumbnailUrl
+                ? "block"
+                : "none";
+        }
+    }
+
     _evtPostContentChange(e) {
         this._contentFileDropper.reset();
+        this._thumbnailRemovalLinkUpdate(e.detail.post);
+        this._newPostContent = null;
     }
 
     _evtPostThumbnailChange(e) {
         this._thumbnailFileDropper.reset();
+        this._thumbnailRemovalLinkUpdate(e.detail.post);
+        this._newPostThumbnail = undefined;
     }
 
     _evtRemoveThumbnailClick(e) {
@@ -427,9 +437,7 @@ class PostEditSidebarControl extends events.EventTarget {
                         : undefined,
 
                     thumbnail:
-                        this._newPostThumbnail !== undefined
-                            ? this._newPostThumbnail
-                            : undefined,
+                        this._newPostThumbnail,
 
                     source: this._sourceInputNode
                         ? this._sourceInputNode.value

client/js/models/post.js

@@ -70,6 +70,14 @@ class Post extends events.EventTarget {
         return this._thumbnailUrl;
     }
 
+    get customThumbnailUrl() {
+        return this._customThumbnailUrl;
+    }
+
+    get originalThumbnailUrl() {
+        return this._originalThumbnailUrl;
+    }
+
     get source() {
         return this._source;
     }
@@ -146,10 +154,6 @@ class Post extends events.EventTarget {
         return this._ownScore;
     }
 
-    get hasCustomThumbnail() {
-        return this._hasCustomThumbnail;
-    }
-
     set flags(value) {
         this._flags = value;
     }
@@ -477,7 +481,9 @@ class Post extends events.EventTarget {
                 response.contentUrl,
                 document.getElementsByTagName("base")[0].href
             ).href,
-            _thumbnailUrl: response.thumbnailUrl,
+            _thumbnailUrl: response.customThumbnailUrl ? response.customThumbnailUrl : response.thumbnailUrl,
+            _customThumbnailUrl: response.customThumbnailUrl,
+            _originalThumbnailUrl: response.thumbnailUrl,
             _source: response.source,
             _canvasWidth: response.canvasWidth,
             _canvasHeight: response.canvasHeight,
@@ -491,7 +497,6 @@ class Post extends events.EventTarget {
             _favoriteCount: response.favoriteCount,
             _ownScore: response.ownScore,
             _ownFavorite: response.ownFavorite,
-            _hasCustomThumbnail: response.hasCustomThumbnail,
         });
 
         for (let obj of [this, this._orig]) {

client/js/util/views.js

@@ -49,7 +49,7 @@ function makeThumbnail(url) {
                   style: `background-image: url(\'${url}\')`,
               }
             : { class: "thumbnail empty" },
-        makeElement("img", { alt: "thumbnail", src: url })
+        makeElement("img", { alt: "thumbnail", src: url, draggable: "false" })
     );
 }
 

client/js/views/post_upload_view.js

@@ -401,6 +401,14 @@ class PostUploadView extends events.EventTarget {
             .addEventListener("click", (e) =>
                 this._evtMoveClick(e, uploadable, 1)
             );
+        if (uploadable.type == "video") {
+            const video = rowNode.querySelector("video");
+            if (video) {
+                video.addEventListener("loadedmetadata", (e) => {
+                    if (!isNaN(video.duration)) video.currentTime = Math.floor(video.duration * 0.3)
+                });
+            }
+        }
     }
 
     _updateThumbnailNode(uploadable) {

server/szurubooru/func/files.py

@@ -1,4 +1,5 @@
 import os
+import glob
 from typing import Any, List, Optional
 
 from szurubooru import config
@@ -24,6 +25,10 @@ def scan(path: str) -> List[Any]:
     return []
 
 
+def find(path: str, pattern: str, recursive: bool = False) -> List[Any]:
+    return glob.glob(glob.escape(_get_full_path(path) + "/") + pattern, recursive=recursive)
+
+
 def move(source_path: str, target_path: str) -> None:
     os.rename(_get_full_path(source_path), _get_full_path(target_path))
 

server/szurubooru/func/images.py

@@ -24,10 +24,18 @@ def convert_heif_to_png(content: bytes) -> bytes:
     return img_byte_arr.getvalue()
 
 
+def check_for_loop(content: bytes) -> bytes:
+    img = PILImage.open(BytesIO(content))
+    return "loop" in img.info
+
+
 class Image:
     def __init__(self, content: bytes) -> None:
         self.content = content
         self._reload_info()
+        if self.info["format"]["format_name"] == "swf":
+            self.content = self.swf_to_png()
+            self._reload_info()
 
     @property
     def width(self) -> int:
@@ -41,7 +49,7 @@ class Image:
     def frames(self) -> int:
         return self.info["streams"][0]["nb_read_frames"]
 
-    def resize_fill(self, width: int, height: int) -> None:
+    def resize_fill(self, width: int, height: int, keep_transparency: bool = True, seek=True) -> None:
         width_greater = self.width > self.height
         width, height = (-1, height) if width_greater else (width, -1)
 
@@ -50,8 +58,12 @@ class Image:
             "{path}",
             "-f",
             "image2",
-            "-filter:v",
-            "scale='{width}:{height}'".format(width=width, height=height),
+            "-filter_complex",
+            (
+                "format=rgb32,scale={width}:{height}:flags=bicubic"
+                if keep_transparency else
+                "[0:v]format=rgb32,scale={width}:{height}:flags=bicubic[a];color=white[b];[b][a]scale2ref[b][a];[b][a]overlay"
+            ).format(width=width, height=height),
             "-map",
             "0:v:0",
             "-vframes",
@@ -60,10 +72,7 @@ class Image:
             "png",
             "-",
         ]
-        if (
-            "duration" in self.info["format"]
-            and self.info["format"]["format_name"] != "swf"
-        ):
+        if seek and "duration" in self.info["format"]:
             duration = float(self.info["format"]["duration"])
             if duration > 3:
                 cli = [
@@ -76,6 +85,19 @@ class Image:
         self.content = content
         self._reload_info()
 
+    def swf_to_png(self) -> bytes:
+        return self._execute(
+            [
+                "--silent",
+                "-g",
+                "gl",
+                "--",
+                "{path}",
+                "-",
+            ],
+            program="exporter",
+        )
+
     def to_png(self) -> bytes:
         return self._execute(
             [
@@ -96,24 +118,13 @@ class Image:
     def to_jpeg(self) -> bytes:
         return self._execute(
             [
-                "-f",
-                "lavfi",
-                "-i",
-                "color=white:s=%dx%d" % (self.width, self.height),
-                "-i",
+                "-quality",
+                "85",
+                "-sample",
+                "1x1",
                 "{path}",
-                "-f",
-                "image2",
-                "-filter_complex",
-                "overlay",
-                "-map",
-                "0:v:0",
-                "-vframes",
-                "1",
-                "-vcodec",
-                "mjpeg",
-                "-",
-            ]
+            ],
+            program="cjpeg",
         )
 
     def to_webm(self) -> bytes:
@@ -274,7 +285,10 @@ class Image:
         with util.create_temp_file(suffix="." + extension) as handle:
             handle.write(self.content)
             handle.flush()
-            cli = [program, "-loglevel", "32" if get_logs else "24"] + cli
+            if program in ["ffmpeg", "ffprobe"]:
+                cli = [program, "-loglevel", "32" if get_logs else "24"] + cli
+            else:
+                cli = [program] + cli
             cli = [part.format(path=handle.name) for part in cli]
             proc = subprocess.Popen(
                 cli,
@@ -285,7 +299,7 @@ class Image:
             out, err = proc.communicate()
             if proc.returncode != 0:
                 logger.warning(
-                    "Failed to execute ffmpeg command (cli=%r, err=%r)",
+                    "Failed to execute {program} command (cli=%r, err=%r)".format(program=program),
                     " ".join(shlex.quote(arg) for arg in cli),
                     err,
                 )
@@ -315,7 +329,7 @@ class Image:
         )
         assert "format" in self.info
         assert "streams" in self.info
-        if len(self.info["streams"]) < 1:
+        if len(self.info["streams"]) < 1 and self.info["format"]["format_name"] != "swf":
             logger.warning("The video contains no video streams.")
             raise errors.ProcessingError(
                 "The video contains no video streams."

server/szurubooru/func/posts.py

@@ -124,6 +124,15 @@ def get_post_thumbnail_url(post: model.Post) -> str:
     )
 
 
+def get_post_custom_thumbnail_url(post: model.Post) -> str:
+    assert post
+    return "%s/generated-thumbnails/custom-thumbnails/sample_%d_%s.jpg" % (
+        config.config["data_url"].rstrip("/"),
+        post.post_id,
+        get_post_security_hash(post.post_id),
+    )
+
+
 def get_post_content_path(post: model.Post) -> str:
     assert post
     assert post.post_id
@@ -134,6 +143,15 @@ def get_post_content_path(post: model.Post) -> str:
     )
 
 
+def get_post_custom_content_path(post: model.Post) -> str:
+    assert post
+    assert post.post_id
+    return "posts/custom-thumbnails/%d_%s.dat" % (
+        post.post_id,
+        get_post_security_hash(post.post_id),
+    )
+
+
 def get_post_thumbnail_path(post: model.Post) -> str:
     assert post
     return "generated-thumbnails/%d_%s.jpg" % (
@@ -142,9 +160,9 @@ def get_post_thumbnail_path(post: model.Post) -> str:
     )
 
 
-def get_post_thumbnail_backup_path(post: model.Post) -> str:
+def get_post_custom_thumbnail_path(post: model.Post) -> str:
     assert post
-    return "posts/custom-thumbnails/%d_%s.dat" % (
+    return "generated-thumbnails/custom-thumbnails/sample_%d_%s.jpg" % (
         post.post_id,
         get_post_security_hash(post.post_id),
     )
@@ -180,6 +198,7 @@ class PostSerializer(serialization.BaseSerializer):
             "canvasHeight": self.serialize_canvas_height,
             "contentUrl": self.serialize_content_url,
             "thumbnailUrl": self.serialize_thumbnail_url,
+            "customThumbnailUrl": self.serialize_custom_thumbnail_url,
             "flags": self.serialize_flags,
             "tags": self.serialize_tags,
             "relations": self.serialize_relations,
@@ -195,7 +214,6 @@ class PostSerializer(serialization.BaseSerializer):
             "featureCount": self.serialize_feature_count,
             "lastFeatureTime": self.serialize_last_feature_time,
             "favoritedBy": self.serialize_favorited_by,
-            "hasCustomThumbnail": self.serialize_has_custom_thumbnail,
             "notes": self.serialize_notes,
             "comments": self.serialize_comments,
             "pools": self.serialize_pools,
@@ -319,8 +337,9 @@ class PostSerializer(serialization.BaseSerializer):
             for rel in self.post.favorited_by
         ]
 
-    def serialize_has_custom_thumbnail(self) -> Any:
-        return files.has(get_post_thumbnail_backup_path(self.post))
+    def serialize_custom_thumbnail_url(self) -> Any:
+        if files.has(get_post_custom_thumbnail_path(self.post)):
+            return get_post_custom_thumbnail_url(self.post)
 
     def serialize_notes(self) -> Any:
         return sorted(
@@ -357,7 +376,7 @@ def serialize_micro_post(
     post: model.Post, auth_user: model.User
 ) -> Optional[rest.Response]:
     return serialize_post(
-        post, auth_user=auth_user, options=["id", "thumbnailUrl"]
+        post, auth_user=auth_user, options=["id", "thumbnailUrl", "customThumbnailUrl"]
     )
 
 
@@ -462,32 +481,28 @@ def _before_post_delete(
 ) -> None:
     if post.post_id:
         if config.config["delete_source_files"]:
-            files.delete(get_post_content_path(post))
-            files.delete(get_post_thumbnail_path(post))
+            pattern = f"{post.post_id}_*"
+            for file in files.find("posts", "**/" + pattern, recursive=True) + files.find("generated-thumbnails", "**/sample_" + pattern, recursive=True):
+                files.delete(file)
 
 
 def _sync_post_content(post: model.Post) -> None:
-    regenerate_thumb = False
-
     if hasattr(post, "__content"):
         content = getattr(post, "__content")
         files.save(get_post_content_path(post), content)
+        generate_post_thumbnail(get_post_thumbnail_path(post), content, seek=False)
+        if mime.is_video(post.mime_type):
+            generate_post_thumbnail(get_post_custom_thumbnail_path(post), content, seek=True)
         delattr(post, "__content")
-        regenerate_thumb = True
 
     if hasattr(post, "__thumbnail"):
         if getattr(post, "__thumbnail"):
-            files.save(
-                get_post_thumbnail_backup_path(post),
-                getattr(post, "__thumbnail"),
-            )
+            thumbnail = getattr(post, "__thumbnail")
+            files.save(get_post_custom_content_path(post), thumbnail)
+            generate_post_thumbnail(get_post_custom_thumbnail_path(post), thumbnail, seek=True)
         else:
-            files.delete(get_post_thumbnail_backup_path(post))
+            files.delete(get_post_custom_thumbnail_path(post))
         delattr(post, "__thumbnail")
-        regenerate_thumb = True
-
-    if regenerate_thumb:
-        generate_post_thumbnail(post)
 
 
 def generate_alternate_formats(
@@ -677,22 +692,19 @@ def update_post_thumbnail(
     setattr(post, "__thumbnail", content)
 
 
-def generate_post_thumbnail(post: model.Post) -> None:
-    assert post
-    if files.has(get_post_thumbnail_backup_path(post)):
-        content = files.get(get_post_thumbnail_backup_path(post))
-    else:
-        content = files.get(get_post_content_path(post))
+def generate_post_thumbnail(path: str, content: bytes, seek=True) -> None:
     try:
         assert content
         image = images.Image(content)
         image.resize_fill(
             int(config.config["thumbnails"]["post_width"]),
             int(config.config["thumbnails"]["post_height"]),
+            keep_transparency=False,
+            seek=seek,
         )
-        files.save(get_post_thumbnail_path(post), image.to_jpeg())
+        files.save(path, image.to_jpeg())
     except errors.ProcessingError:
-        files.save(get_post_thumbnail_path(post), EMPTY_PIXEL)
+        files.save(path, EMPTY_PIXEL)
 
 
 def update_post_tags(

server/szurubooru/rest/context.py

@@ -51,7 +51,7 @@ class Context:
         use_video_downloader: bool = False,
         allow_tokens: bool = True,
     ) -> bytes:
-        if name in self._files and self._files[name]:
+        if name in self._files:
             return self._files[name]
 
         if name + "Url" in self._params:

server/szurubooru/tests/func/test_posts.py

@@ -72,12 +72,12 @@ def test_get_post_thumbnail_path(input_mime_type):
 
 
 @pytest.mark.parametrize("input_mime_type", ["image/jpeg", "image/gif"])
-def test_get_post_thumbnail_backup_path(input_mime_type):
+def test_get_post_custom_thumbnail_path(input_mime_type):
     post = model.Post()
     post.post_id = 1
     post.mime_type = input_mime_type
     assert (
-        posts.get_post_thumbnail_backup_path(post)
+        posts.get_post_custom_thumbnail_path(post)
         == "posts/custom-thumbnails/1_244c8840887984c4.dat"
     )