In examples, prefer buffer_rgba to print_to_buffer.

anntzer · anntzer · commit 86fbce741040 · 2019-07-30T11:22:56.000+02:00
buffer_rgba avoids a copy and returns an object (a memoryview) that
knows its shape and can readily be converted to a numpy array, rather
than separately a string and a shape.
diff --git a/examples/misc/agg_buffer.py b/examples/misc/agg_buffer.py
@@ -3,8 +3,8 @@
 Agg Buffer
 ==========
 
-Use backend agg to access the figure canvas as an RGB string and then
-convert it to an array and pass it to Pillow for rendering.
+Use backend agg to access the figure canvas as an RGBA buffer, convert it to an
+array, and pass it to Pillow for rendering.
 """
 
 import numpy as np
@@ -18,14 +18,11 @@
 
 agg = canvas.switch_backends(FigureCanvasAgg)
 agg.draw()
-s, (width, height) = agg.print_to_buffer()
-
-# Convert to a NumPy array.
-X = np.frombuffer(s, np.uint8).reshape((height, width, 4))
+X = np.asarray(agg.buffer_rgba())
 
 # Pass off to PIL.
 from PIL import Image
-im = Image.frombytes("RGBA", (width, height), s)
+im = Image.fromarray(X)
 
 # Uncomment this line to display the image using ImageMagick's `display` tool.
 # im.show()
diff --git a/examples/user_interfaces/canvasagg.py b/examples/user_interfaces/canvasagg.py
@@ -37,16 +37,14 @@
 # etc.).
 fig.savefig("test.png")
 
-# Option 2: Save the figure to a string.
+# Option 2: Retrieve a view on the renderer buffer...
 canvas.draw()
-s, (width, height) = canvas.print_to_buffer()
-
-# Option 2a: Convert to a NumPy array.
-X = np.frombuffer(s, np.uint8).reshape((height, width, 4))
-
-# Option 2b: Pass off to PIL.
+buf = canvas.buffer_rgba()
+# ... convert to a NumPy array ...
+X = np.asarray(buf)
+# ... and pass it to PIL.
 from PIL import Image
-im = Image.frombytes("RGBA", (width, height), s)
+im = Image.fromarray(X)
 
 # Uncomment this line to display the image using ImageMagick's `display` tool.
 # im.show()
