qa_cli: increase to 1200dpi + use 1 pixel erosion in comparisons to golden sample

qa/tests/cli/test_sch.py

@@ -28,7 +28,7 @@ from pathlib import Path
 import pytest
 from typing import List
 import platform
-from PIL import Image, ImageChops
+from PIL import Image, ImageChops, ImageFilter
 import numpy as np
 
 def images_are_equal( image1: str, image2: str ):
@@ -45,13 +45,27 @@ def images_are_equal( image1: str, image2: str ):
     retval = True
 
     if sum != 0.0:
-        norm_sum = sum / np.sqrt( sum )
-        retval = norm_sum < 0.001
+        # images are not identical - lets allow 1 pixel error difference (for curved edges)
 
-    if not retval:
         diff = ImageChops.difference( image1, image2 )
-        diff_name = image1.filename + ".diff.png"
-        diff.save( diff_name )
+        diffgray=diff.convert("L")
+        diffThresholded=diffgray.point(lambda x: 255 if x > 1 else 0)
+        diffBinary=diffThresholded.convert("1")
+
+        # erode binary image by 1 pixel
+        diffEroded = diffBinary.filter(ImageFilter.MinFilter(3))
+        
+        erodedSum = np.sum( np.asarray ( diffEroded ).astype( np.float32 ) )
+
+        retval = erodedSum == 0
+
+        if not retval:
+            diff_name = image1.filename + ".diff1.png"
+            diff.save( diff_name )
+            diffEroded_name = image1.filename + ".diffEroded_erodedsum" + str(erodedSum)+ ".png"
+            diffEroded.convert("RGB")
+            diffEroded.save( diffEroded_name )
+
 
     return retval
 
@@ -93,7 +107,7 @@ def test_sch_export_svg( kitest,
 
     compare_file_path = kitest.get_data_file_path( compare_fn )
 
-    cairosvg.svg2png( url=str( output_svg_path ), write_to=str( png_converted_from_svg_path ), dpi=300 )
+    cairosvg.svg2png( url=str( output_svg_path ), write_to=str( png_converted_from_svg_path ), dpi=1200 )
 
     assert images_are_equal( png_converted_from_svg_path, compare_file_path  )