ENH: anti-alias down-sampled images

jklymak · jklymak · commit 5553dac75094 · 2019-03-20T21:18:41.000-07:00
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -5435,7 +5435,8 @@ def get_interp_point(ind):
     def imshow(self, X, cmap=None, norm=None, aspect=None,
                interpolation=None, alpha=None, vmin=None, vmax=None,
                origin=None, extent=None, shape=None, filternorm=1,
-               filterrad=4.0, imlim=None, resample=None, url=None, **kwargs):
+               filterrad=4.0, imlim=None, resample=None,
+               antialiased=True, url=None, **kwargs):
         """
         Display an image, i.e. data on a 2D regular raster.
 
@@ -5604,7 +5605,8 @@ def imshow(self, X, cmap=None, norm=None, aspect=None,
         self.set_aspect(aspect)
         im = mimage.AxesImage(self, cmap, norm, interpolation, origin, extent,
                               filternorm=filternorm, filterrad=filterrad,
-                              resample=resample, **kwargs)
+                              resample=resample, antialiased=antialiased,
+                              **kwargs)
 
         im.set_data(X)
         im.set_alpha(alpha)
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -188,6 +188,7 @@ def __init__(self, ax,
                  filternorm=True,
                  filterrad=4.0,
                  resample=False,
+                 antialiased=True,
                  **kwargs
                  ):
         """
@@ -214,6 +215,7 @@ def __init__(self, ax,
         self.set_interpolation(interpolation)
         self.set_resample(resample)
         self.axes = ax
+        self._antialiased = antialiased
 
         self._imcache = None
 
@@ -232,6 +234,22 @@ def get_size(self):
 
         return self._A.shape[:2]
 
+    def get_antialiased(self):
+        """
+        Get whether down-sampled images are low-pass filtered before
+        down-sampling (i.e. when there is more data than pixels).
+        """
+        return self._antialiased
+
+    def set_antialiased(self, antialiased):
+        """
+        Set if an anti-aliasing (low-pass) filter is applied to the data
+        if the image will down-sample the data (i.e. if the there is
+        more data than pixels).  If *True*, and the data is down-sampled,
+        any user supplied filters are ignored, and a Lanczos filter is
+        applied with radius `2 * M_data / M_image`.
+        """
+
     def set_alpha(self, alpha):
         """
         Set the alpha value used for blending - not supported on all backends.
@@ -422,6 +440,10 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
                 A_scaled += 0.1
                 A_resampled = np.zeros((out_height, out_width),
                                        dtype=A_scaled.dtype)
+                if self.get_antialiased() and A.shape[0] > out_height:
+                    self.set_interpolation('lanczos')
+                    self.set_filterrad(2.0 * A.shape[0] / out_height )
+
                 # resample the input data to the correct resolution and shape
                 _image.resample(A_scaled, A_resampled,
                                 t,
@@ -819,6 +841,7 @@ def __init__(self, ax,
                  filternorm=1,
                  filterrad=4.0,
                  resample=False,
+                 antialiased=True,
                  **kwargs
                  ):
 
@@ -847,6 +870,7 @@ def __init__(self, ax,
             filternorm=filternorm,
             filterrad=filterrad,
             resample=resample,
+            antialiased=antialiased,
             **kwargs
         )
 
@@ -1266,6 +1290,7 @@ def __init__(self, bbox,
                  filternorm=1,
                  filterrad=4.0,
                  resample=False,
+                 antialiased=True,
                  interp_at_native=True,
                  **kwargs
                  ):
@@ -1293,6 +1318,7 @@ def __init__(self, bbox,
             filternorm=filternorm,
             filterrad=filterrad,
             resample=resample,
+            antialiased=antialiased,
             **kwargs
         )
 
diff --git a/lib/matplotlib/offsetbox.py b/lib/matplotlib/offsetbox.py
@@ -1260,6 +1260,7 @@ def __init__(self, arr,
                  filternorm=1,
                  filterrad=4.0,
                  resample=False,
+                 antialiased=True,
                  dpi_cor=True,
                  **kwargs
                  ):
@@ -1275,6 +1276,7 @@ def __init__(self, arr,
                                filternorm=filternorm,
                                filterrad=filterrad,
                                resample=resample,
+                               antialiased=antialiased,
                                **kwargs
                                )
 
