# bounding_box.rb

    #!/usr/bin/ruby1.9.1 -w
    require 'RMagick'

    img = Magick::Image.new(200,200) { self.background_color = "#ffffcc" }

    # Draw a blue circle.
    gc = Magick::Draw.new
    gc.stroke_width(5)
    gc.stroke("blue")
    gc.fill_opacity(0)
    gc.circle(100,100, 100,150)
    gc.draw(img)

    # Get the bounding box. Use the values to draw
    # a gray square surrounding the circle. Highlight
    # the corners with tiny red circles.

    bb = img.bounding_box
    gc = Magick::Draw.new
    gc.stroke("gray50")
    gc.fill_opacity(0)
    gc.rectangle(bb.x, bb.y, bb.x+bb.width, bb.y+bb.height)
    gc.stroke("red")
    gc.circle(bb.x, bb.y, bb.x+2, bb.y+2)
    gc.circle(bb.x+bb.width, bb.y, bb.x+bb.width+2, bb.y+2)
    gc.circle(bb.x, bb.y+bb.height, bb.x+2, bb.y+bb.height+2)
    gc.circle(bb.x+bb.width, bb.y+bb.height, bb.x+bb.width+2, bb.y+bb.height+2)

    gc.fill("black")
    gc.stroke("transparent")
    gc.font_weight(Magick::NormalWeight)
    gc.font_style(Magick::NormalStyle)
    gc.pointsize(9)
    gc.text(bb.x-15, bb.y-5, "\'#{bb.x},#{bb.y}\'")
    gc.text(bb.x+bb.width-15, bb.y-5, "\'#{bb.x+bb.width},#{bb.y}\'")
    gc.text(bb.x-15, bb.y+bb.height+15, "\'#{bb.x},#{bb.y+bb.height}\'")
    gc.text(bb.x+bb.width-15, bb.y+bb.height+15, "\'#{bb.x+bb.width},#{bb.y+bb.height}\'")

    gc.draw(img)

    img.write("bounding_box.gif")
    exit

Close window