Fixed Pillow AttributeError and fixed generated base64 images (#36)

* Fixed AttributeError with newer Pillow versions

Image.ANTIALIAS constant was removed in PIL 10.0.0.
This commit ensures that the new Image.LANCZOS is used for newer PIL
versions.

See:
https://pillow.readthedocs.io/en/stable/releasenotes/10.0.0.html#constants

* Fixed dimensions / cropping of base64 images

Previously, generated images where cropped to the right but not to the
left, resulting in right centered images.

This commit makes generated images cropped from center.

* Updated test case

* Fixed version comparison

Author: izimobil

jsignature/utils.py

@@ -4,7 +4,7 @@
 """
 import json
 from itertools import chain
-from PIL import Image, ImageDraw, ImageOps
+from PIL import Image, ImageDraw, ImageOps, __version__ as PIL_VERSION
 
 AA = 5  # super sampling gor antialiasing
 
@@ -29,24 +29,37 @@ def _remove_empty_pts(pt):
         raise ValueError
 
     # Compute box
-    width = int(round(max(chain(*[d['x'] for d in drawing])))) + 10
-    height = int(round(max(chain(*[d['y'] for d in drawing])))) + 10
+    min_width = int(round(min(chain(*[d['x'] for d in drawing])))) - 10
+    max_width = int(round(max(chain(*[d['x'] for d in drawing])))) + 10
+    width = max_width - min_width
+    min_height = int(round(min(chain(*[d['y'] for d in drawing])))) - 10
+    max_height = int(round(max(chain(*[d['y'] for d in drawing])))) + 10
+    height = max_height - min_height
 
     # Draw image
     im = Image.new("RGBA", (width * AA, height * AA))
     draw = ImageDraw.Draw(im)
     for line in drawing:
         len_line = len(line['x'])
-        points = [(line['x'][i] * AA, line['y'][i] * AA)
-                  for i in range(0, len_line)]
+        points = [
+            (
+                (line['x'][i] - min_width) * AA,
+                (line['y'][i] - min_height) * AA
+            )
+            for i in range(0, len_line)
+        ]
         draw.line(points, fill="#000", width=2 * AA)
     im = ImageOps.expand(im)
     # Smart crop
     bbox = im.getbbox()
     if bbox:
         im.crop(bbox)
 
-    im.thumbnail((width, height), Image.ANTIALIAS)
+    old_pil_version = int(PIL_VERSION.split('.')[0]) < 10
+    im.thumbnail(
+        (width, height),
+        Image.ANTIALIAS if old_pil_version  else Image.LANCZOS
+    )
 
     if as_file:
         ret = im._dump(format='PNG')

tests/test_filter.py

@@ -16,4 +16,4 @@ def test_inputs_bad_type_value(self):
 
     def test_outputs_as_base64(self):
         output = signature_base64(DUMMY_STR_VALUE)
-        self.assertEqual(output, "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAANwAAABNCAYAAADNYApnAAABIklEQVR4nO3ZP0odURjG4d/ce5dgE3EHgXTp07iD6B7cga3YpUoh7iFrCti4BkGw0OLMoEVIEW4yxPs81ZxzGPial+/8KQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAPh3ttW0dhFwCN4GbbNaFXAAlrCdVh/m791KtcC7tmkE7mP1XP2sPs1rQgd7NjVCd1TdNkL3UJ2tWRQciovqqRG8q0aXc6aDPZsat5RVX6q7Rui+zXPbX/wD/KFla7mc306qH9XneazLwZ4s3eu8eqwuV6wF3rXllvK4um9sI7/Oc7s8hMNeLVf/3xthu5nHzmzwF0y9drjrxvPAMgcA/7/lWUBnAwAAAAAAfucFwt4TZmdXW+AAAAAASUVORK5CYII=")
+        self.assertEqual(output, "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABkAAAAcCAYAAACUJBTQAAAAuElEQVR4nO3TMQ4BQRSH8d8uR9AQN5Do9Bo3wB3cQCs6lULcwZkkGmeQSBQU+yZEVIxC7FfNvGTnm7fvP9TU/A0NFN8UPB5eflMwQjvWzZyCMiQ9XLFHP7eoCFEL2xCdMMkleMUMl5AtVN1km1GhShcMcQjRKmqNF9+8JSnd59HFDoPYf9xNuuUUZ8w/PfCZlK4OjqpfNI5aU6bHmWK6DsEm9llmkCjcO1mqopxqv0mK8O92UFPzPjdRMBNmBFDqcwAAAABJRU5ErkJggg==")