get_pixels.rb in rmagick-3.2.0

- old
+ new

@@ -36,10 +36,10 @@
   pixels.each_with_index { |p, x| p.opacity = opacity_steps[x] }
   grayrocks.store_pixels(0, y, cols, 1, pixels)
 end
 
 # Composite the mono version of the image over the color version.
-grayrocks.matte = true
+grayrocks.alpha(Magick::ActivateAlphaChannel)
 combine = rocks.composite(grayrocks, Magick::CenterGravity, Magick::OverCompositeOp)
 # combine.display
 combine.write 'get_pixels.jpg'
 exit