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POPort ImageMagick commands to RMagick
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copied!<p>I'm doing image processing with ImageMagick commands and I would like to port them to RMagick. The goal of this task is to take a picture and to pixelate given areas (one or more) for privacy purpose.</p> <p>Here is my bash script (<code>script.sh</code>), which works very well using the <code>convert</code> command:</p> <pre class="lang-sh prettyprint-override"><code>convert invoice.png -scale 10% -scale 1000% pixelated.png convert invoice.png -gamma 0 -fill white -draw "rectangle 35, 110, 215, 250" mask.png convert invoice.png pixelated.png mask.png -composite result.png </code></pre> <p>Now I want to create the Ruby version of this script using ImageMagick. Here is what I have now:</p> <pre><code>require 'rmagick' # pixelate_areas('invoice.png', [ [ x1, y1, width, height ] ]) def pixelate_areas(image_path, areas) image = Magick::Image::read(image_path).first pixelated = image.scale(0.1).scale(10) mask = Magick::Image.new(image.columns, image.rows) { self.background_color = '#000' } areas.each do |coordinates| area = Magick::Image.new(coordinates[2], coordinates[3]) { self.background_color = '#fff' } mask.composite!(area, coordinates[0], coordinates[1], Magick::OverCompositeOp) end # Now, how can I merge my 3 images? # I need to extract the part of pixelated that overlap with the white part of the mask (everything else must be transparent). # Then I have to superpose the resulting image to the original (it's the easy part). end </code></pre> <p>As you can see, I'm stuck at the last step. What operation do I need to do with <a href="http://i.imgur.com/IWtBF.png" rel="nofollow">my original picture</a>, <a href="http://i.imgur.com/ZJIgt.png" rel="nofollow">my pixelated picture</a> and <a href="http://i.imgur.com/Mup1j.png" rel="nofollow">my mask</a> in order to have <a href="http://i.imgur.com/e0qzA.png" rel="nofollow">this result</a>?</p> <p>How can I build an image with just the overlapping of the white part of the mask and the pixelated picture. Just like <a href="http://i.imgur.com/KVC8a.png" rel="nofollow">this one</a> but with transparency instead of black?</p>

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