Add PIL image regression feature

CHANGELOG.rst

@@ -1,3 +1,10 @@
+2.9.0
+-----
+
+*UNRELEASED*
+
+* `#218 <https://github.com/ESSS/pytest-regressions/pull/218>`__: ``ImageRegression.check`` now supports receiving an ``PIL.Image`` object directly.
+
 2.8.3
 -----
 

src/pytest_regressions/image_regression.py

@@ -5,6 +5,7 @@
 from typing import Any
 from typing import Optional
 from typing import TYPE_CHECKING
+from typing import Union
 
 import pytest
 
@@ -13,6 +14,7 @@
 
 if TYPE_CHECKING:
     from pytest_datadir import LazyDataDir
+    from PIL import Image
 
 
 class ImageRegressionFixture:
@@ -140,7 +142,7 @@ def check_result(equal: bool, manhattan_distance: Optional[float]) -> None:
 
     def check(
         self,
-        image_data: bytes,
+        image_data: Union[bytes, "Image.Image"],
         diff_threshold: float = 0.1,
         expect_equal: bool = True,
         basename: Optional[str] = None,
@@ -149,7 +151,7 @@ def check(
         """
         Checks that the given image contents are comparable with the ones stored in the data directory.
 
-        :param image_data: image data
+        :param image_data: image data bytes which can be read with PIL, or directly a PIL image object.
         :param basename: basename to store the information in the data directory. If none, use the name
             of the test function.
         :param expect_equal: if the image should considered equal below of the given threshold. If False, the
@@ -170,7 +172,11 @@ def check(
             raise ModuleNotFoundError(import_error_message("Pillow"))
 
         def dump_fn(target: Path) -> None:
-            image = Image.open(io.BytesIO(image_data))
+            if isinstance(image_data, Image.Image):
+                image = image_data
+            else:
+                image = Image.open(io.BytesIO(image_data))
+
             image.save(str(target), "PNG")
 
         perform_regression_check(

tests/test_image_regression.py

@@ -1,10 +1,14 @@
 import io
 from functools import partial
 
+import pytest
+from PIL import Image
+
 from pytest_regressions.testing import check_regression_fixture_workflow
 
 
-def test_image_regression(image_regression, lazy_datadir):
+@pytest.mark.parametrize("image_type", ["pil", "bytes"])
+def test_image_regression(image_regression, lazy_datadir, image_type):
     import matplotlib
 
     # this ensures matplot lib does not use a GUI backend (such as Tk)
@@ -29,19 +33,27 @@ def test_image_regression(image_regression, lazy_datadir):
     image_filename = lazy_datadir / "test.png"
     fig.savefig(str(image_filename))
 
-    image_regression.check(image_filename.read_bytes(), diff_threshold=1.0)
+    if image_type == "bytes":
+        image_data = image_filename.read_bytes()
+    else:
+        image_data = Image.open(image_filename)
+    image_regression.check(image_data, diff_threshold=1.0)
 
 
-def test_image_regression_workflow(pytester, monkeypatch):
+@pytest.mark.parametrize("image_type", ["pil", "bytes"])
+def test_image_regression_workflow(pytester, monkeypatch, image_type):
     import sys
 
     from PIL import Image
 
     def get_image(color):
-        f = io.BytesIO()
         img = Image.new("RGB", (100, 100), color)
-        img.save(f, "PNG")
-        return f.getvalue()
+        if image_type == "pil":
+            return img
+        else:
+            f = io.BytesIO()
+            img.save(f, "PNG")
+            return f.getvalue()
 
     monkeypatch.setattr(sys, "get_image", partial(get_image, "white"), raising=False)
     source = """
@@ -54,7 +66,11 @@ def test_1(image_regression):
     def get_file_contents():
         fn = pytester.path / "test_file" / "test_1.png"
         assert fn.is_file()
-        return fn.read_bytes()
+        if image_type == "pil":
+            # Copy is necessary because Image.open returns a ImageFile class
+            return Image.open(fn).copy()
+        else:
+            return fn.read_bytes()
 
     check_regression_fixture_workflow(
         pytester,