Screencast: Bildbearbeitung mit RMagick

Downloads in verschiedenen Formaten:

mp4 m4v webm ogg

Resourcen:

• ImageMagick
• ImageMagick Usage Guide
• RMagick
• Image Sorcery
• Mini Magick
• Episode 253: CarrierWave File Uploads

terminal

[bash] brew install imagemagick convert -version convert octocat.png -resize ‘70x70^’ -gravity center -crop ‘70x70+0+0’ -quantize GRAY -colors 256 -contrast source.png composite stamp_overlay.png source.png source.png convert -size 70x70 canvas:red ( octocat.png -resize ‘70x70^’ -gravity center -crop ‘70x70+0+0’ -quantize GRAY -colors 256 -contrast stamp_overlay.png -composite -negate ) -compose copy-opacity -composite stamp.png gem install rmagick mate stamp.rb ruby stamp.rb [/bash]

stamp.rb

[ruby]

require “rmagick”

source = Magick::Image.read(“octocat.png”).first source = source.resize_to_fill(70, 70).quantize(256, Magick::GRAYColorspace).contrast(true) overlay = Magick::Image.read(“stamp_overlay.png”).first source.composite!(overlay, 0, 0, Magick::OverCompositeOp) colored = Magick::Image.new(70, 70) { self.background_color = “red” } colored.composite!(source.negate, 0, 0, Magick::CopyOpacityCompositeOp) colored.write(“stamp.png”)

# Or through the command line: # system <<-COMMAND # convert -size 70x70 canvas:red \( octocat.png # -resize ‘70x70^’ -gravity center -crop ‘70x70+0+0’ # -quantize GRAY -colors 256 -contrast stamp_overlay.png # -composite -negate # \) -compose copy-opacity -composite stamp.png # COMMAND [/ruby]

Gemfile

[ruby] gem ‘rmagick’ gem ‘carrierwave’ [/ruby]

models/stamp.rb

[ruby]

mount_uploader :image, StampUploader [/ruby]

app/uploaders/stamp_uploader.rb

[ruby]

class StampUploader < CarrierWave::Uploader::Base include CarrierWave::RMagick

# Include the Sprockets helpers for Rails 3.1+ asset pipeline compatibility: include Sprockets::Helpers::RailsHelper include Sprockets::Helpers::IsolatedHelper

# Choose what kind of storage to use for this uploader: storage :file

# Override the directory where uploaded files will be stored. # This is a sensible default for uploaders that are meant to be mounted: def store_dir “uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}” end

# Add a white list of extensions which are allowed to be uploaded. # For images you might use something like this: def extension_white_list %w(jpg jpeg gif png) end

%w[red green blue purple black].each do |color| version(color) { process stamp: color } end

def stamp(color) manipulate! format: “png” do |source| overlay_path = Rails.root.join(“app/assets/images/stamp_overlay.png”) overlay = Magick::Image.read(overlay_path).first source = source.resize_to_fill(70, 70).quantize(256, Magick::GRAYColorspace).contrast(true) source.composite!(overlay, 0, 0, Magick::OverCompositeOp) colored = Magick::Image.new(70, 70) { self.background_color = color } colored.composite(source.negate, 0, 0, Magick::CopyOpacityCompositeOp) end end end [/ruby]

stamps/index.html

[html] <%= image_tag stamp.image_url(:blue) %> [/html]