refactor: improved image diffing

capella2polarion/elements/api_helper.py

@@ -1,16 +1,14 @@
 # Copyright DB Netz AG and contributors
 # SPDX-License-Identifier: Apache-2.0
 """Capella2Polarion specific helper functions to use the API."""
-import base64
+import base64 as b64
 import collections.abc as cabc
-import io
 import logging
-import re
 import typing as t
 
+import cairosvg
 import polarion_rest_api_client as polarion_api
 from capellambse.model import common
-from PIL import Image, ImageChops
 
 from capella2polarion.elements import serialize
 
@@ -82,38 +80,25 @@ def patch_work_item(
             logger.error("Updating work item %r failed. %s", wi, error.args[0])
 
 
-def decode_diagram(dia: str):
-    """Decode a diagram from a base64 string."""
-    encoded = dia.replace("data:image/", "").split(";base64,", 1)
-
-    decoded = base64.b64decode(encoded[1])
-
-    return encoded[0], decoded
+def split_and_decode_diagram(diagram: str) -> tuple[str, bytes]:
+    """Split the diagram into type and data and decode the data."""
+    prefix, encoded = diagram.split(";base64,")
+    return prefix.replace("data:image/", ""), b64.b64decode(encoded)
 
 
 def has_visual_changes(old: str, new: str) -> bool:
     """Return True if the images of the diagrams differ."""
-    type_old, decoded_old = decode_diagram(old)
-    type_new, decoded_new = decode_diagram(new)
+    type_old, decoded_old = split_and_decode_diagram(old)
+    type_new, decoded_new = split_and_decode_diagram(new)
 
     if type_old != type_new:
         return True
 
     if type_old == "svg+xml":
-        d_new = decoded_new.decode("utf-8").splitlines()
-        for i, d_old in enumerate(decoded_old.decode("utf-8").splitlines()):
-            if re.sub(r'id=["\'][^"\']*["\']', "", d_old) != re.sub(
-                r'id=["\'][^"\']*["\']', "", d_new[i]
-            ):
-                return True
-        return False
-
-    image_old = Image.open(io.BytesIO(decoded_old))
-    image_new = Image.open(io.BytesIO(decoded_new))
-
-    diff = ImageChops.difference(image_old, image_new)
+        decoded_old = cairosvg.svg2png(bytestring=decoded_old)
+        decoded_new = cairosvg.svg2png(bytestring=decoded_new)
 
-    return bool(diff.getbbox())
+    return decoded_old != decoded_new
 
 
 def handle_links(

pyproject.toml

@@ -33,6 +33,7 @@ dependencies = [
   "PyYAML",
   "polarion-rest-api-client @ git+https://github.com/DSD-DBS/polarion-rest-api-client.git@feat-add-attachments-workitem-relations",
   "requests",
+  "cairosvg",
 ]
 
 [project.urls]

tests/test_elements.py

@@ -80,36 +80,6 @@ class TestAPIHelper:
         pathlib.Path(__file__).parent / "data" / "svg_diff" / "example.svg"
     )
     SVG_PREFIX = "data:image/svg+xml;base64,"
-    PNG_PREFIX = "data:image/png;base64,"
-
-    def encode_png(self, img: Image.Image) -> str:
-        image_buffer = io.BytesIO()
-        img.save(image_buffer, format="PNG")
-        image_buffer.seek(0)
-        encoded = base64.b64encode(image_buffer.read()).decode()
-        image_buffer.close()
-        return f"{self.PNG_PREFIX}{encoded}"
-
-    def test_pixel_diff(self):
-        img1 = Image.new("RGB", (100, 100))
-        img2 = Image.new("RGB", (100, 100))
-        img2.putpixel((0, 0), (255, 0, 0))
-
-        assert (
-            api_helper.has_visual_changes(
-                self.encode_png(img1),
-                self.encode_png(img2),
-            )
-            is True
-        )
-
-        assert (
-            api_helper.has_visual_changes(
-                self.encode_png(img1),
-                self.encode_png(img1),
-            )
-            is False
-        )
 
     def encode_svg(self, params) -> str:
         svg = self.SVG_PATH.read_text()
@@ -146,7 +116,7 @@ def encode_svg(self, params) -> str:
             ),
         ],
     )
-    def test_svg_diff(self, changed_params, expected):
+    def test_image_diff(self, changed_params, expected):
         old_params, new_params = changed_params
 
         assert (