Save memory

weasyprint/__init__.py

@@ -138,7 +138,11 @@ def render(self, stylesheets=None, presentational_hints=False,
         :param font_config: A font configuration handling ``@font-face`` rules.
         :type counter_style: :class:`css.counters.CounterStyle`
         :param counter_style: A dictionary storing ``@counter-style`` rules.
-        :param dict image_cache: A dictionary used to cache images.
+        :param image_cache:
+            A dictionary used to cache images, or a folder path where images
+            are temporarily stored.
+        :type image_cache:
+            :obj:`dict`, :obj:`str` or :class:`document.DiskCache`
         :param bool forms: Whether PDF forms have to be included.
         :returns: A :class:`document.Document` object.
 
@@ -186,7 +190,11 @@ def write_pdf(self, target=None, stylesheets=None, zoom=1,
         :param font_config: A font configuration handling ``@font-face`` rules.
         :type counter_style: :class:`css.counters.CounterStyle`
         :param counter_style: A dictionary storing ``@counter-style`` rules.
-        :param dict image_cache: A dictionary used to cache images.
+        :param image_cache:
+            A dictionary used to cache images, or a folder path where images
+            are temporarily stored.
+        :type image_cache:
+            :obj:`dict`, :obj:`str` or :class:`document.DiskCache`
         :param bytes identifier: A bytestring used as PDF file identifier.
         :param str variant: A PDF variant name.
         :param str version: A PDF version number.

weasyprint/__main__.py

@@ -94,6 +94,11 @@ def main(argv=None, stdout=None, stdin=None):
         multiple times, ``all`` adds all allowed values, ``none`` removes all
         previously set values.
 
+    .. option:: -c <folder>, --cache-folder <folder>
+
+        Store cache on disk instead of memory. The ``folder`` is created if
+        needed and cleaned after the PDF is generated.
+
     .. option:: -v, --verbose
 
         Show warnings and information messages.
@@ -156,6 +161,10 @@ def main(argv=None, stdout=None, stdin=None):
         '-O', '--optimize-size', action='append',
         help='optimize output size for specified features',
         choices=('images', 'fonts', 'all', 'none'), default=['fonts'])
+    parser.add_argument(
+        '-c', '--cache-folder',
+        help='Store cache on disk instead of memory. The ``folder`` is '
+        'created if needed and cleaned after the PDF is generated.')
     parser.add_argument(
         '-v', '--verbose', action='store_true',
         help='show warnings and information messages')
@@ -203,6 +212,7 @@ def main(argv=None, stdout=None, stdin=None):
         'version': args.pdf_version,
         'forms': args.pdf_forms,
         'custom_metadata': args.custom_metadata,
+        'image_cache': args.cache_folder,
     }
 
     # Default to logging to stderr.

weasyprint/document.py

@@ -2,7 +2,8 @@
 
 import functools
 import io
-import shutil
+from hashlib import md5
+from pathlib import Path
 
 from . import CSS
 from .anchors import gather_anchors, make_page_bookmark_tree
@@ -159,6 +160,52 @@ def __init__(self, title=None, authors=None, description=None,
         self.custom = custom or {}
 
 
+class DiskCache:
+    """Dict-like storing images content on disk.
+
+    Bytestrings values are stored on disk. Other Python objects (i.e.
+    RasterImage instances) are still stored in memory, but are much more
+    lightweight.
+
+    """
+    def __init__(self, folder):
+        self._path = Path(folder)
+        self._path.mkdir(parents=True, exist_ok=True)
+        self._memory_cache = {}
+        self._disk_paths = set()
+
+    def _path_from_key(self, key):
+        return self._path / md5(key.encode()).hexdigest()
+
+    def __getitem__(self, key):
+        if key in self._memory_cache:
+            return self._memory_cache[key]
+        else:
+            return self._path_from_key(key).read_bytes()
+
+    def __setitem__(self, key, value):
+        if isinstance(value, bytes):
+            path = self._path_from_key(key)
+            self._disk_paths.add(path)
+            path.write_bytes(value)
+        else:
+            self._memory_cache[key] = value
+
+    def __contains__(self, key):
+        return (
+            key in self._memory_cache or
+            self._path_from_key(key).exists())
+
+    def __del__(self):
+        try:
+            for path in self._disk_paths:
+                path.unlink(missing_ok=True)
+            self._path.rmdir()
+        except Exception:
+            # Silently ignore errors while clearing cache
+            pass
+
+
 class Document:
     """A rendered document ready to be painted in a pydyf stream.
 
@@ -181,7 +228,10 @@ def _build_layout_context(cls, html, stylesheets, presentational_hints,
         target_collector = TargetCollector()
         page_rules = []
         user_stylesheets = []
-        image_cache = {} if image_cache is None else image_cache
+        if image_cache is None:
+            image_cache = {}
+        elif not isinstance(image_cache, DiskCache):
+            image_cache = DiskCache(image_cache)
         for css in stylesheets or []:
             if not hasattr(css, 'matcher'):
                 css = CSS(
@@ -364,15 +414,13 @@ def write_pdf(self, target=None, zoom=1, attachments=None, finisher=None,
         if finisher:
             finisher(self, pdf)
 
-        output = io.BytesIO()
-        pdf.write(output, version=pdf.version, identifier=identifier)
-
         if target is None:
+            output = io.BytesIO()
+            pdf.write(output, version=pdf.version, identifier=identifier)
             return output.getvalue()
+
+        if hasattr(target, 'write'):
+            pdf.write(target, version=pdf.version, identifier=identifier)
         else:
-            output.seek(0)
-            if hasattr(target, 'write'):
-                shutil.copyfileobj(output, target)
-            else:
-                with open(target, 'wb') as fd:
-                    shutil.copyfileobj(output, fd)
+            with open(target, 'wb') as fd:
+                pdf.write(fd, version=pdf.version, identifier=identifier)

weasyprint/draw.py

@@ -1199,7 +1199,7 @@ def draw_first_line(stream, textbox, text_overflow, block_ellipsis, x, y,
                     pillow_image = Image.open(BytesIO(png_data))
                     image_id = f'{font.hash}{glyph}'
                     image = RasterImage(
-                        pillow_image, image_id, optimize_size=())
+                        pillow_image, image_id, optimize_size=(), cache={})
                     d = font.widths[glyph] / 1000
                     a = pillow_image.width / pillow_image.height * d
                     pango.pango_font_get_glyph_extents(