matte_replace.rb in rmagick-3.2.0

- old
+ new

@@ -4,10 +4,10 @@
 
 img = Magick::Image.new(200, 200)
 img.compression = Magick::LZWCompression
 
 bg = Magick::Image.read('plasma:fractal') { self.size = '200x200' }
-bg[0].matte = false
+bg[0].alpha(Magick::DeactivateAlphaChannel)
 
 gc = Magick::Draw.new
 gc.stroke_width(2)
 gc.stroke('black')
 gc.fill('white')