Data commit

Task/Image-convolution/Ruby/image-convolution.rb

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+class Pixmap
+  # Apply a convolution kernel to a whole image
+  def convolute(kernel)
+    newimg = Pixmap.new(@width, @height)
+    pb = ProgressBar.new(@width) if $DEBUG
+    @width.times do |x|
+      @height.times do |y|
+        apply_kernel(x, y, kernel, newimg)
+      end
+      pb.update(x) if $DEBUG
+    end
+    pb.close if $DEBUG
+    newimg
+  end
+
+  # Applies a convolution kernel to produce a single pixel in the destination
+  def apply_kernel(x, y, kernel, newimg)
+    x0 = x==0 ? 0 : x-1
+    y0 = y==0 ? 0 : y-1
+    x1 = x
+    y1 = y
+    x2 = x+1==@width  ? x : x+1
+    y2 = y+1==@height ? y : y+1
+
+    r = g = b = 0.0
+    [x0, x1, x2].zip(kernel).each do |xx, kcol|
+      [y0, y1, y2].zip(kcol).each do |yy, k|
+        r += k * self[xx,yy].r
+        g += k * self[xx,yy].g
+        b += k * self[xx,yy].b
+      end
+    end
+    newimg[x,y] = RGBColour.new(luma(r), luma(g), luma(b))
+  end
+
+  # Function for clamping values to those that we can use with colors
+  def luma(value)
+    if value < 0
+      0
+    elsif value > 255
+      255
+    else
+      value
+    end
+  end
+end
+
+
+# Demonstration code using the teapot image from Tk's widget demo
+teapot = Pixmap.open('teapot.ppm')
+[ ['Emboss',  [[-2.0, -1.0, 0.0],  [-1.0, 1.0, 1.0],  [0.0, 1.0, 2.0]]],
+  ['Sharpen', [[-1.0, -1.0, -1.0], [-1.0, 9.0, -1.0], [-1.0, -1.0, -1.0]]],
+  ['Blur',    [[0.1111,0.1111,0.1111],[0.1111,0.1111,0.1111],[0.1111,0.1111,0.1111]]],
+].each do |label, kernel|
+  savefile = 'teapot_' + label.downcase + '.ppm'
+  teapot.convolute(kernel).save(savefile)
+end