Add HTML template placeholders for filename

src/wireviz/svgembed.py

@@ -8,6 +8,20 @@
 mime_subtype_replacements = {"jpg": "jpeg", "tif": "tiff"}
 
 
+# TODO: Share cache and code between data_URI_base64() and embed_svg_images()
+def data_URI_base64(file: Union[str, Path], media: str = "image") -> str:
+    """Return Base64-encoded data URI of input file."""
+    file = Path(file)
+    b64 = base64.b64encode(file.read_bytes()).decode("utf-8")
+    uri = f"data:{media}/{get_mime_subtype(file)};base64, {b64}"
+    # print(f"data_URI_base64('{file}', '{media}') -> {len(uri)}-character URI")
+    if len(uri) > 65535:
+        print(
+            "data_URI_base64(): Warning: Browsers might have different URI length limitations"
+        )
+    return uri
+
+
 def embed_svg_images(svg_in: str, base_path: Union[str, Path] = Path.cwd()) -> str:
     images_b64 = {}  # cache of base64-encoded images
 

src/wireviz/wv_html.py

@@ -2,10 +2,11 @@
 
 import re
 from pathlib import Path
-from typing import Dict, List, Union
+from typing import Callable, Dict, List, Union
 
 from wireviz import APP_NAME, APP_URL, __version__, wv_colors
 from wireviz.DataClasses import Metadata, Options
+from wireviz.svgembed import data_URI_base64
 from wireviz.wv_gv_html import html_line_breaks
 from wireviz.wv_helper import (
     flatten2d,
@@ -36,12 +37,12 @@ def generate_html_output(
 
     html = open_file_read(templatefile).read()
 
-    # embed SVG diagram
-    with open_file_read(f"{filename}.tmp.svg") as file:
-        svgdata = re.sub(
+    # embed SVG diagram (only if used)
+    def svgdata() -> str:
+        return re.sub(
             "^<[?]xml [^?>]*[?]>[^<]*<!DOCTYPE [^>]*>",
             "<!-- XML and DOCTYPE declarations from SVG file removed -->",
-            file.read(),
+            open_file_read(f"{filename}.tmp.svg").read(),
             1,
         )
 
@@ -80,13 +81,24 @@ def generate_html_output(
         "<!-- %generator% -->": f"{APP_NAME} {__version__} - {APP_URL}",
         "<!-- %fontname% -->": options.fontname,
         "<!-- %bgcolor% -->": wv_colors.translate_color(options.bgcolor, "hex"),
-        "<!-- %diagram% -->": svgdata,
+        "<!-- %filename% -->": str(filename),
+        "<!-- %filename_stem% -->": Path(filename).stem,
         "<!-- %bom% -->": bom_html,
         "<!-- %bom_reversed% -->": bom_html_reversed,
         "<!-- %sheet_current% -->": "1",  # TODO: handle multi-page documents
         "<!-- %sheet_total% -->": "1",  # TODO: handle multi-page documents
     }
 
+    def replacement_if_used(key: str, func: Callable[[], str]) -> None:
+        """Append replacement only if used in html."""
+        if key in html:
+            replacements[key] = func()
+
+    replacement_if_used("<!-- %diagram% -->", svgdata)
+    replacement_if_used(
+        "<!-- %diagram_png_base64% -->", lambda: data_URI_base64(f"{filename}.png")
+    )
+
     # prepare metadata replacements
     if metadata:
         for item, contents in metadata.items():