numpy "bug" - reproduced when running examples/basic/ptext.py (if versions the same I suppose)

Originally reported by: Steve Clement (Bitbucket: SteveClement, GitHub: SteveClement)

Dear all,

When you run ptext.py example you get this error:

TypeError: Cannot cast ufunc multiply output from dtype('float64') to dtype('uint8') with casting rule 'same_kind'

Not sure how safe my fix is, but it works. Should I do a pull request?
Also not sure there are other locations where you need to do unsafe casts…

It can be fixed as follows

#!patch

--- /usr/local/lib/python3.5/site-packages/pgzero/ptext.py.orig	2016-12-02 16:05:29.000000000 +0100
+++ /usr/local/lib/python3.5/site-packages/pgzero/ptext.py	2016-12-02 16:04:50.000000000 +0100
@@ -201,7 +201,8 @@
 			lineheight=lineheight, cache=cache)
 		surf = surf0.copy()
 		array = pygame.surfarray.pixels_alpha(surf)
-		array *= alpha
+		import numpy
+		numpy.multiply(array, alpha, out=array, casting="unsafe")
 	elif spx is not None:
 		surf0 = getsurf(text, fontname, fontsize, width, widthem, color=color,
 			background=(0,0,0,0), antialias=antialias, gcolor=gcolor, align=align,
@@ -255,8 +256,8 @@
 			for lsurf in lsurfs:
 				array = pygame.surfarray.pixels3d(lsurf)
 				for j in (0, 1, 2):
-					array[:,:,j] *= 1.0 - m
-					array[:,:,j] += m * gcolor[j]
+					numpy.multiply(array[:,:,j], 1.0 - m, out=array[:,:,j], casting="unsafe")
+					numpy.multiply(array[:,:,j], m * gcolor[j], out=array[:,:,j], casting="unsafe")
 				del array

 		if len(lsurfs) == 1 and gcolor is None:

My versions

• numpy==1.11.2
• pgzero==1.1
• pygame==1.9.2b8
• Python 3.5.2
• Darwin Steves-iMac.local 16.1.0 Darwin Kernel Version 16.1.0: Thu Oct 13 21:26:57 PDT 2016; root:xnu-3789.21.3~60/RELEASE_X86_64 x86_64 (MacOS Sierra)

Run output

#!bash

~/Desktop/code/pgzeroBB/examples/basic  ☿ 179@default  pgzrun ptext.py
Traceback (most recent call last):
  File "/usr/local/bin/pgzrun", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.5/site-packages/pgzero/runner.py", line 89, in main
    PGZeroGame(mod).run()
  File "/usr/local/lib/python3.5/site-packages/pgzero/game.py", line 219, in run
    draw()
  File "ptext.py", line 115, in draw
    gcolor="#442200"
  File "/usr/local/lib/python3.5/site-packages/pgzero/screen.py", line 61, in text
    ptext.draw(*args, surf=self._surf, **kwargs)
  File "/usr/local/lib/python3.5/site-packages/pgzero/ptext.py", line 320, in draw
    ocolor, owidth, scolor, shadow, gcolor, alpha, align, lineheight, angle, cache)
  File "/usr/local/lib/python3.5/site-packages/pgzero/ptext.py", line 229, in getsurf
    lineheight=lineheight, cache=cache)
  File "/usr/local/lib/python3.5/site-packages/pgzero/ptext.py", line 258, in getsurf
    array[:,:,j] *= 1.0 - m
TypeError: Cannot cast ufunc multiply output from dtype('float64') to dtype('uint8') with casting rule 'same_kind'

• Bitbucket: https://bitbucket.org/lordmauve/pgzero/issue/48

Run examples/basic/ptext.py with the reported Python, NumPy, pgzero, and pygame versions, then inspect the getsurf operations in pgzero/ptext.py around the failing lines 229-258. Confirm the example no longer raises the NumPy casting error and that the affected text rendering still works.