server/posts: auto convert GIFs to WEBMs/MP4s

- Default setting is false for both conversions, as this will require
  additional resources of the server, but is bandwidth friendly for
  viewers
- WEBM conversion is slow, but better quality than MP4 conversion with
  a typically smaller file size
- Tags are copied over from the original upload
- Snapshots are generated for the new auto posts

4 files changed, 132 insertions, 6 deletions

diff --git a/server/szurubooru/api/post_api.py b/server/szurubooru/api/post_api.py
index 27f10c1..aaa7437 100644
--- a/server/szurubooru/api/post_api.py
+++ b/server/szurubooru/api/post_api.py
@@ -1,4 +1,4 @@
-from typing import Optional, Dict
+from typing import Optional, Dict, List
 from datetime import datetime
 from szurubooru import db, model, errors, rest, search
 from szurubooru.func import (
@@ -69,13 +69,26 @@ def create_post(
         posts.update_post_thumbnail(post, ctx.get_file('thumbnail'))
     ctx.session.add(post)
     ctx.session.flush()
-    snapshots.create(post, None if anonymous else ctx.user)
-    for tag in new_tags:
-        snapshots.create(tag, None if anonymous else ctx.user)
+    create_snapshots_for_post(post, new_tags, None if anonymous else ctx.user)
+    alternate_format_posts = posts.generate_alternate_formats(post, content)
+    for alternate_post, alternate_post_new_tags in alternate_format_posts:
+        create_snapshots_for_post(
+            alternate_post,
+            alternate_post_new_tags,
+            None if anonymous else ctx.user)
     ctx.session.commit()
     return _serialize_post(ctx, post)
 
 
+def create_snapshots_for_post(
+        post: model.Post,
+        new_tags: List[model.Tag],
+        user: Optional[model.User]):
+    snapshots.create(post, user)
+    for tag in new_tags:
+        snapshots.create(tag, user)
+
+
 @rest.routes.get('/post/(?P<post_id>[^/]+)/?')
 def get_post(ctx: rest.Context, params: Dict[str, str]) -> rest.Response:
     auth.verify_privilege(ctx.user, 'posts:view')
diff --git a/server/szurubooru/func/images.py b/server/szurubooru/func/images.py
index 9e62aef..b3df55e 100644
--- a/server/szurubooru/func/images.py
+++ b/server/szurubooru/func/images.py
@@ -79,6 +79,68 @@ class Image:
             '-',
         ])
 
+    def to_webm(self) -> bytes:
+        with util.create_temp_file_path(suffix='.log') as phase_log_path:
+            # Pass 1
+            self._execute([
+                '-i', '{path}',
+                '-pass', '1',
+                '-passlogfile', phase_log_path,
+                '-vcodec', 'libvpx-vp9',
+                '-crf', '4',
+                '-b:v', '2500K',
+                '-acodec', 'libvorbis',
+                '-f', 'webm',
+                '-y', '/dev/null'
+            ])
+
+            # Pass 2
+            return self._execute([
+                '-i', '{path}',
+                '-pass', '2',
+                '-passlogfile', phase_log_path,
+                '-vcodec', 'libvpx-vp9',
+                '-crf', '4',
+                '-b:v', '2500K',
+                '-acodec', 'libvorbis',
+                '-f', 'webm',
+                '-'
+            ])
+
+    def to_mp4(self) -> bytes:
+        with util.create_temp_file_path(suffix='.dat') as mp4_temp_path:
+            width = self.width
+            height = self.height
+            altered_dimensions = False
+
+            if self.width % 2 != 0:
+                width = self.width - 1
+                altered_dimensions = True
+
+            if self.height % 2 != 0:
+                height = self.height - 1
+                altered_dimensions = True
+
+            args = [
+                '-i', '{path}',
+                '-vcodec', 'libx264',
+                '-preset', 'slow',
+                '-crf', '22',
+                '-b:v', '200K',
+                '-profile:v', 'main',
+                '-pix_fmt', 'yuv420p',
+                '-acodec', 'aac',
+                '-f', 'mp4'
+            ]
+
+            if altered_dimensions:
+                args += ['-filter:v', 'scale=\'%d:%d\'' % (width, height)]
+
+            self._execute(args + ['-y', mp4_temp_path])
+
+            with open(mp4_temp_path, 'rb') as mp4_temp:
+                return mp4_temp.read()
+
     def _execute(
             self,
             cli: List[str],
diff --git a/server/szurubooru/func/posts.py b/server/szurubooru/func/posts.py
index 406f6e1..219c832 100644
--- a/server/szurubooru/func/posts.py
+++ b/server/szurubooru/func/posts.py
@@ -5,7 +5,7 @@ import sqlalchemy as sa
 from szurubooru import config, db, model, errors, rest
 from szurubooru.func import (
     users, scores, comments, tags, util,
-    mime, images, files, image_hash, serialization)
+    mime, images, files, image_hash, serialization, snapshots)
 
 
 EMPTY_PIXEL = (
@@ -364,7 +364,7 @@ def create_post(
 
     update_post_content(post, content)
     new_tags = update_post_tags(post, tag_names)
-    return (post, new_tags)
+    return post, new_tags
 
 
 def update_post_safety(post: model.Post, safety: str) -> None:
@@ -429,6 +429,47 @@ def _sync_post_content(post: model.Post) -> None:
         generate_post_thumbnail(post)
 
 
+def generate_alternate_formats(post: model.Post, content: bytes) \
+        -> List[Tuple[model.Post, List[model.Tag]]]:
+    assert post
+    assert content
+    new_posts = []
+    if mime.is_animated_gif(content):
+        tag_names = [
+            tag_name.name
+            for tag_name in [tag.names for tag in post.tags]]
+
+        if config.config['convert']['gif']['to_mp4']:
+            mp4_post, new_tags = create_post(
+                images.Image(content).to_mp4(),
+                tag_names,
+                post.user)
+            update_post_flags(mp4_post, ['loop'])
+            update_post_safety(mp4_post, post.safety)
+            update_post_source(mp4_post, post.source)
+            new_posts += [(mp4_post, new_tags)]
+
+        if config.config['convert']['gif']['to_webm']:
+            webm_post, new_tags = create_post(
+                images.Image(content).to_webm(),
+                tag_names,
+                post.user)
+            update_post_flags(webm_post, ['loop'])
+            update_post_safety(webm_post, post.safety)
+            update_post_source(webm_post, post.source)
+            new_posts += [(webm_post, new_tags)]
+
+        db.session.flush()
+
+        new_posts = [p for p in new_posts if p[0] is not None]
+
+        new_relations = [p[0].post_id for p in new_posts]
+        if len(new_relations) > 0:
+            update_post_relations(post, new_relations)
+
+    return new_posts
+
+
 def update_post_content(post: model.Post, content: Optional[bytes]) -> None:
     assert post
     if not content:
diff --git a/server/szurubooru/func/util.py b/server/szurubooru/func/util.py
index 61e975b..ba2d4dc 100644
--- a/server/szurubooru/func/util.py
+++ b/server/szurubooru/func/util.py
@@ -41,6 +41,16 @@ def create_temp_file(**kwargs: Any) -> Generator:
         os.remove(path)
 
 
+@contextmanager
+def create_temp_file_path(**kwargs: Any) -> Generator:
+    (descriptor, path) = tempfile.mkstemp(**kwargs)
+    os.close(descriptor)
+    try:
+        yield path
+    finally:
+        os.remove(path)
+
+
 def unalias_dict(source: List[Tuple[List[str], T]]) -> Dict[str, T]:
     output_dict = {}  # type: Dict[str, T]
     for aliases, value in source: