How do I generate website thumbnails without 3rd party tools?

问题

Are there any gems out there for Rails 3.2.1 that generate website thumbnails? I see a lot of 3rd party solutions but I don't like the fact that they aren't hosted on my server. It's really important the app I'm building is as stable as possible and I think this is not a good solution in the long run.

My ruby knowledge is fairly good, I think enough to use a gem and implement it, but definitely not good enough to write something like this from scratch if no gems exist.

Thanks!

回答1:

You could try dragonfly or carrierwave

回答2:

Well, here's the first thing that came up on Rubygems: thumbnailer. It uses Amazon and costs a small fee per image it generates, so you probably don't want this...

~~But there's also thumbnailer-ruby which looks like it works completely on the local machine. Haven't tested it out, though.~~ It appears that this doesn't actually do what you want. Nevermind.

Now another gem called snapurl looks pretty fancy. Once again, I haven't tried it out yet. I'll do that now.

EDIT: Won't run for me; keeps failing with an error.

回答3:

https://url2png.com/ has worked great so far

回答4:

aBrowshot has a gem available.

回答5:

There's no need to use a third party service for this. You can do something like this in your model:

class MySexyModel < ActiveRecord::Base

  ... stuff

  # Generate the thumbnail on validate so we can return errors on failure
  validate :generate_thumbnail_from_url

  # Cleanup temp files when we are done
  after_save :cleanup_temp_thumbnail

  # Generate a thumbnail from the remote URL
  def generate_thumbnail_from_url

    # Skip thumbnail generation if:
    # a) there are already other validation errors
    # b) an image was manually specified
    # c) an image is already stored and the URL hasn't changed
    skip_generate = self.errors.any? || (self.image_changed? ||
        (self.image_stored? && !self.url_changed?))
    # p "*** generating thumbnail: #{!skip_generate}"
    return if skip_generate

    # Generate and assign an image or set a validation error
    begin
      tempfile = temp_thumbnail_path
      cmd = "wkhtmltoimage --quality 95 \"#{self.url}\" \"#{tempfile}\""
      # p "*** grabbing thumbnail: #{cmd}"
      system(cmd) # sometimes returns false even if image was saved
      self.image = File.new(tempfile) # will throw if not saved
    rescue => e
      # p "*** thumbnail error: #{e}"
      self.errors.add(:base, "Cannot generate thumbnail. Is your URL valid?")
    ensure
    end
  end

  # Return the absolute path to the temporary thumbnail file
  def temp_thumbnail_path
    File.expand_path("#{self.url.parameterize.slice(0, 20)}.jpg", Dragonfly.app.datastore.root_path)
  end

  # Cleanup the temporary thumbnail image
  def cleanup_temp_thumbnail
    File.delete(temp_thumbnail_path) rescue 0
  end
end

The original post is on this blog: http://sourcey.com

来源：https://stackoverflow.com/questions/9449065/how-do-i-generate-website-thumbnails-without-3rd-party-tools

标签

ruby-on-rails

ruby

ruby-on-rails-3

thumbnails