log_image: Support matplotlib.figure.Figure as input. (#658)

Closes #224

src/dvclive/plots/image.py

@@ -1,5 +1,7 @@
 from pathlib import Path, PurePath
 
+from dvclive.utils import isinstance_without_import
+
 from .base import Data
 
 
@@ -17,20 +19,25 @@ def output_path(self) -> Path:
     def could_log(val: object) -> bool:
         acceptable = {
             ("numpy", "ndarray"),
+            ("matplotlib.figure", "Figure"),
             ("PIL.Image", "Image"),
         }
         for cls in type(val).mro():
-            if (cls.__module__, cls.__name__) in acceptable:
+            if any(isinstance_without_import(val, *cls) for cls in acceptable):
                 return True
         if isinstance(val, (PurePath, str)):
             return True
         return False
 
     def dump(self, val, **kwargs) -> None:  # noqa: ARG002
-        if val.__class__.__module__ == "numpy":
+        if isinstance_without_import(val, "numpy", "ndarray"):
             from PIL import Image as ImagePIL
 
-            pil_image = ImagePIL.fromarray(val)
-        else:
-            pil_image = val
-        pil_image.save(self.output_path)
+            ImagePIL.fromarray(val).save(self.output_path)
+        elif isinstance_without_import(val, "matplotlib.figure", "Figure"):
+            import matplotlib.pyplot as plt
+
+            plt.savefig(self.output_path)
+            plt.close(val)
+        elif isinstance_without_import(val, "PIL.Image", "Image"):
+            val.save(self.output_path)

src/dvclive/utils.py

@@ -148,3 +148,10 @@ def clean_and_copy_into(src: StrPath, dst: StrPath) -> str:
         shutil.copy2(src, dst_path)
 
     return str(dst_path)
+
+
+def isinstance_without_import(val, module, name):
+    for cls in type(val).mro():
+        if (cls.__module__, cls.__name__) == (module, name):
+            return True
+    return False

tests/plots/test_image.py

@@ -1,3 +1,4 @@
+import matplotlib.pyplot as plt
 import numpy as np
 import pytest
 from PIL import Image
@@ -100,3 +101,17 @@ def test_custom_class(tmp_dir):
     live.log_image("image.png", extended_img)
 
     assert (tmp_dir / live.plots_dir / LiveImage.subfolder / "image.png").exists()
+
+
+def test_matplotlib(tmp_dir):
+    live = Live()
+    fig, ax = plt.subplots()
+    ax.plot([1, 2, 3, 4])
+
+    assert plt.fignum_exists(fig.number)
+
+    live.log_image("image.png", fig)
+
+    assert not plt.fignum_exists(fig.number)
+
+    assert (tmp_dir / live.plots_dir / LiveImage.subfolder / "image.png").exists()