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Contents
#! /usr/local/bin/ruby -w
require 'RMagick'
# Demonstrate the Image#stegano method.
# Create a small watermark from the Snake image by
# shrinking it and converting it to B&W.
begin
watermark = Magick::Image.read('images/Snake.wmf').first
watermark.scale!(64.0/watermark.rows)
watermark = watermark.quantize(256, Magick::GRAYColorspace)
wmrows = watermark.rows
wmcols = watermark.columns
# Read the image in which we'll hide the watermark.
img = Magick::Image.read('images/Flower_Hat.jpg').first
img.scale!(250.0/img.rows)
# Embed the watermark starting at offset 91.
puts 'Embedding watermark...'
stegano = img.stegano(watermark, 91)
puts 'Watermark embedded'
# Write the watermarked image in MIFF format. Note that
# the format must be lossless - Image#stegano doesn't work
# with lossy formats like JPEG.
stegano.write('img.miff')
# Read the image and retrieve the watermark. The size
# attribute describes the size and offset of the watermark.
# This can take some time. Keep track of how far along we are.
# We have to be careful, though. Recent versions of ImageMagick support the
# Info#monitor= method and deprecate Magick.set_monitor, so don't use
# Magick.set_monitor if Info#monitor= is supported.
monitor = Proc.new do |text, quantum, span|
printf("Extracting watermark...%3.0f%% complete\n", ((1.0-(quantum/span.to_f))*100.0))
true
end
stegano = Magick::Image.read('stegano:img.miff') do
self.size = Magick::Geometry.new(wmcols, wmrows, 91)
begin
self.monitor = monitor
rescue NotImplementedError
Magick.set_monitor(monitor)
end
end
begin
stegano[0].monitor = nil
rescue NotImplementedError
Magick.set_monitor(nil)
end
# We don't need this any more.
File.delete('img.miff')
stegano[0].write('stegano.gif')
rescue Magick::ImageMagickError
puts "#{$0}: ImageMagickError - #{$!}"
end
exit
Version data entries
26 entries across 26 versions & 1 rubygems