Indicate that optimize and progressive kwords are JPEG specific.

dabana · dabana · commit e9e34e9d391f · 2018-09-06T16:00:56.000-04:00
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2018,12 +2018,14 @@ def savefig(self, fname, *, frameon=None, transparent=None, **kwargs):
             JPEG quantization stage.
 
         optimize : bool
-            If *True*, indicates that the encoder should make an extra pass
+            If *True*, indicates that the JPEG encoder should make an extra pass
             over the image in order to select optimal encoder settings.
+            Applicable only if *format* is jpg or jpeg, ignored otherwise.
 
         progressive : bool
             If *True*, indicates that this image should be stored as a
-            progressive JPEG file.
+            progressive JPEG file. Applicable only if *format* is jpg or
+            jpeg, ignored otherwise.
 
         facecolor : color spec or None, optional
             The facecolor of the figure; if *None*, defaults to
