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crop_with_gravity.rb.html
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<!DOCTYPE public PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<title>RMagick example: crop_with_gravity.rb</title>
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<h1>crop_with_gravity.rb</h1>
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<pre class="language-ruby">
# frozen_string_literal: true
#=======================================================#
# Thanks to Robert Wagner for the idea of allowing a #
# GravityType instead of the x- and y-offset arguments! #
#=======================================================#
# Demo the use of the GravityType argument to Image#crop.
require 'rmagick'
shorts = Magick::Image.read('images/Shorts.jpg').first
regwidth = shorts.columns / 2
regheight = shorts.rows / 2
mask = Magick::Image.new(regwidth, regheight) { |info| info.background_color = 'white' }
mask.alpha(Magick::ActivateAlphaChannel)
mask.quantum_operator(Magick::SetQuantumOperator, 0.50 * Magick::QuantumRange, Magick::AlphaChannel)
black = Magick::Image.new(shorts.columns, shorts.rows) { |info| info.background_color = 'black' }
pairs = Magick::ImageList.new
[
Magick::NorthWestGravity, Magick::NorthGravity, Magick::NorthEastGravity,
Magick::WestGravity, Magick::CenterGravity, Magick::EastGravity,
Magick::SouthWestGravity, Magick::SouthGravity, Magick::SouthEastGravity
].each do |gravity|
pattern = shorts.composite(mask, gravity, Magick::OverCompositeOp)
cropped = shorts.crop(gravity, regwidth, regheight)
result = black.composite(cropped, gravity, Magick::OverCompositeOp)
result.border_color = 'white'
pairs << pattern
pairs << result
end
# Montage into a single image
montage = pairs.montage do |options|
options.geometry = "#{pairs.columns}x#{pairs.rows}+0+0"
options.tile = '6x3'
options.border_width = 1
end
montage.write('crop_with_gravity.png')
# montage.display
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