Image generation no longer generates double-precision rgba; patch by C. Gohlke

efiring · efiring · commit 358855c4ccd3 · 2011-02-04T19:18:57.000Z
Image generation via color mapping was using doubles for rgba,
after which the _image module was converting rgba to uint8;
this patch saves time and memory by using the existing ability
of the colormap to generate uint8 directly.


svn path=/trunk/matplotlib/; revision=8945
diff --git a/CHANGELOG b/CHANGELOG
@@ -1,3 +1,7 @@
+2011-02-04 Changed imshow to use rgba as uint8 from start to
+           finish, instead of going through an intermediate
+           step as double precision; thanks to Christoph Gohlke. - EF
+
 2011-01-13 Added zdir and offset arguments to contourf3d to
            bring contourf3d in feature parity with contour3d. - BVR
 
@@ -8,7 +12,7 @@
 2011-01-03 Turn off tick labeling on interior subplots for
            pyplots.subplots when sharex/sharey is True. - JDH
 
-2010-12-29 Implment axes_divider.HBox and VBox. -JJL
+2010-12-29 Implement axes_divider.HBox and VBox. -JJL
 
 
 2010-11-22 Fixed error with Hammer projection. - BVR
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -138,7 +138,7 @@ def make_image(self, magnification=1.0):
     def _get_unsampled_image(self, A, image_extents, viewlim):
         """
         convert numpy array A with given extents ([x1, x2, y1, y2] in
-        data coordinate) into the Image, given the vielim (should be a
+        data coordinate) into the Image, given the viewlim (should be a
         bbox instance).  Image will be clipped if the extents is
         significantly larger than the viewlim.
         """
@@ -193,17 +193,17 @@ def _get_unsampled_image(self, A, image_extents, viewlim):
             self._oldyslice = yslice
 
         if self._imcache is None:
-            if self._A.dtype == np.uint8 and len(self._A.shape) == 3:
+            if self._A.dtype == np.uint8 and self._A.ndim == 3:
                 im = _image.frombyte(self._A[yslice,xslice,:], 0)
                 im.is_grayscale = False
             else:
                 if self._rgbacache is None:
-                    x = self.to_rgba(self._A, self._alpha)
+                    x = self.to_rgba(self._A, self._alpha, bytes=True)
                     self._rgbacache = x
                 else:
                     x = self._rgbacache
-                im = _image.fromarray(x[yslice,xslice], 0)
-                if len(self._A.shape) == 2:
+                im = _image.frombyte(x[yslice,xslice,:], 0)
+                if self._A.ndim == 2:
                     im.is_grayscale = self.cmap.is_gray()
                 else:
                     im.is_grayscale = False
