# sketch.rb

    #!/usr/local/bin/ruby18 -w

    require 'RMagick'

    img = Magick::Image.read('images/Flower_Hat.jpg').first

    # Convert to grayscale
    sketch = img.quantize(256, Magick::GRAYColorspace)

    # Apply histogram equalization
    sketch = sketch.equalize

    # Sketch, then dissolve 25% of the original back in
    sketch = sketch.sketch(0, 10, 135)
    img = img.dissolve(sketch, 0.75, 0.25)

    img.write('sketch.jpg')

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