Merge pull request matplotlib#21274 from kinshukdua/master

ENH: Add support to save images in WebP format

Author: QuLogic

lib/matplotlib/backend_bases.py

@@ -69,6 +69,7 @@
     'svgz': 'Scalable Vector Graphics',
     'tif': 'Tagged Image File Format',
     'tiff': 'Tagged Image File Format',
+    'webp': 'WebP Image Format',
 }
 _default_backends = {
     'eps': 'matplotlib.backends.backend_ps',
@@ -84,6 +85,7 @@
     'svgz': 'matplotlib.backends.backend_svg',
     'tif': 'matplotlib.backends.backend_agg',
     'tiff': 'matplotlib.backends.backend_agg',
+    'webp': 'matplotlib.backends.backend_agg',
 }
 
 

lib/matplotlib/backends/backend_agg.py

@@ -596,6 +596,28 @@ def print_tif(self, filename_or_obj, *, pil_kwargs=None):
 
     print_tiff = print_tif
 
+    @_check_savefig_extra_args
+    def print_webp(self, filename_or_obj, *, pil_kwargs=None):
+        """
+        Write the figure to a WebP file.
+
+        Parameters
+        ----------
+        filename_or_obj : str or path-like or file-like
+            The file to write to.
+
+        Other Parameters
+        ----------------
+        pil_kwargs : dict, optional
+            Additional keyword arguments that are passed to
+            `PIL.Image.Image.save` when saving the figure.
+        """
+        FigureCanvasAgg.draw(self)
+        if pil_kwargs is None:
+            pil_kwargs = {}
+        return (Image.fromarray(np.asarray(self.buffer_rgba()))
+                .save(filename_or_obj, format='webp', **pil_kwargs))
+
 
 @_Backend.export
 class _BackendAgg(_Backend):

lib/matplotlib/tests/test_agg.py

@@ -249,6 +249,25 @@ def test_pil_kwargs_tiff():
     assert tags["ImageDescription"] == "test image"
 
 
+def test_pil_kwargs_webp():
+    plt.plot([0, 1, 2], [0, 1, 0])
+    buf_small = io.BytesIO()
+    pil_kwargs_low = {"quality": 1}
+    plt.savefig(buf_small, format="webp", pil_kwargs=pil_kwargs_low)
+    buf_large = io.BytesIO()
+    pil_kwargs_high = {"quality": 100}
+    plt.savefig(buf_large, format="webp", pil_kwargs=pil_kwargs_high)
+    assert buf_large.getbuffer().nbytes > buf_small.getbuffer().nbytes
+
+
+def test_webp_alpha():
+    plt.plot([0, 1, 2], [0, 1, 0])
+    buf = io.BytesIO()
+    plt.savefig(buf, format="webp", transparent=True)
+    im = Image.open(buf)
+    assert im.mode == "RGBA"
+
+
 def test_draw_path_collection_error_handling():
     fig, ax = plt.subplots()
     ax.scatter([1], [1]).set_paths(path.Path([(0, 1), (2, 3)]))