Implement function to embed images within SVG file

src/wireviz/svgembed.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import re
+import base64
+from pathlib import Path
+
+def embed_svg_images(fn):
+    fn = Path(fn).resolve()
+    images_b64 = {}  # cache base-64 encoded images
+    num_images = 0   # just for debugging
+    re_xlink=re.compile(r"xlink:href=\"(?P<URL>.*?)\"")
+    with open(fn) as file_in, open(f'{fn.with_suffix("")}.b64.svg','w') as file_out:
+        for line in file_in:
+            for xlink in re_xlink.finditer(line):
+                num_images = num_images + 1
+                imgurl = xlink.group(1)
+                print(' Found URL in SVG:', imgurl)
+                if not imgurl in images_b64:
+                    print('  ✅This URL is new')
+                    with open(imgurl, 'rb') as img:
+                        data_bin = img.read()
+                        data_b64 = base64.b64encode(data_bin)
+                        data_str = data_b64.decode('utf-8')
+                    images_b64[imgurl] = data_str
+                else:  # only cache every image once
+                    print('  ❌This URL is not new')
+                line = line.replace(imgurl, f'data:image/png;base64, {images_b64[imgurl]}')
+            file_out.write(line)
+
+    print(f'Embedded {num_images} instances of {len(images_b64)} different images.')
+    print()
+
+# for debugging, run:
+# python -m svgembed.py path/to/file.svg
+if __name__ == '__main__':
+    import sys
+    embed_svg_images(sys.argv[1])