add alpha blending sample (examples/alpha_blend.rb)

examples/alpha_blend.rb

@@ -0,0 +1,21 @@
+#!/usr/bin/env ruby
+# -*- mode: ruby; coding: utf-8-unix -*-
+
+# Alpha blending sample with GUI
+
+require 'opencv'
+include OpenCV
+
+img1 = IplImage.load('lenna.jpg', CV_LOAD_IMAGE_ANYCOLOR | CV_LOAD_IMAGE_ANYDEPTH)
+img2 = IplImage.load('tiffany.jpg', CV_LOAD_IMAGE_ANYCOLOR | CV_LOAD_IMAGE_ANYDEPTH)
+
+window = GUI::Window.new('Alpha blend')
+max = 100.0
+val = max / 2.0
+window.set_trackbar("Alpha", max, val) { |v|
+  a = v.to_f / max
+  window.show CvMat.add_weighted(img1, a, img2, 1.0 - a, 0)
+}
+window.show CvMat.add_weighted(img1, val / max, img2, 1.0 - val / max, 0)
+GUI::wait_key
+