Data commit

Task/Bitmap-Histogram/Ruby/bitmap-histogram.rb

@@ -0,0 +1,41 @@
+class Pixmap
+  def histogram
+    histogram = Hash.new(0)
+    @height.times do |y|
+      @width.times do |x|
+        histogram[self[x,y].luminosity] += 1
+      end
+    end
+    histogram
+  end
+
+  def to_blackandwhite
+    hist = histogram
+
+    # find the median luminosity
+    median = nil
+    sum = 0
+    hist.keys.sort.each do |lum|
+      sum += hist[lum]
+      if sum > @height * @width / 2
+        median = lum
+        break
+      end
+    end
+
+    # create the black and white image
+    bw = self.class.new(@width, @height)
+    @height.times do |y|
+      @width.times do |x|
+        bw[x,y] = self[x,y].luminosity < median ? RGBColour::BLACK : RGBColour::WHITE
+      end
+    end
+    bw
+  end
+
+  def save_as_blackandwhite(filename)
+    to_blackandwhite.save(filename)
+  end
+end
+
+Pixmap.open('file.ppm').save_as_blackandwhite('file_bw.ppm')