MMThumb

Description

MMThumb is a sane and simple but flexible approach to automating the common tasks of processing images for use in webpages. If your image workflow includes applying:

Pre-Processing ...sharpen 2x2, normalize levels
Generating a couple of different outputs ...thumbnail, preview, full-view
Post-Processing ...watermark, vignette

Then this gem will serve you right.

This gem has been written with the intent that you should write minimal code to do what you want, but it should not limit you - configuration options are chained, so you can have sane defaults and still easily handle corner cases.

It has also been written with the intent to be usable both as an offline batch processor or as an engine for a long-running service process - therefore the approach to exception handling may be slightly different than usual.

Current version uses the mini_magick gem and therefore you will need either ImageMagick or GraphicsMagick. This, in my humble opinion, gives you by default the best trade-off between performance and functionality.

Performance note:

Due to how mini_magick works the preprocess and postprocess blocks will be called for each output block, contrary to the intuition that they should run once each (before and after outputs, respectively). In other words right now they are mostly a visual convenience to separate things.

Install

Dependencies:

Install:

$ gem install mmthumb

Examples

First my personal most-common-ever use-case, as a simple CLI batch converter:

#!/usr/bin/env ruby
# encoding: utf-8
#

require 'mmthumb'

conv = MMThumb::Converter.new
conv.preprocess do |img, opts|
  if opts[:photo]
    img.normalize
    img.sharpen '2x2'
  end
end
conv.add_output(:thumb) {|img| img.resize('320x240>') }
conv.add_output(:full)  {|img| img.resize('1024x768>') }

ARGV.each do |path|
  puts path

  ext = File.extname(path).slice(1, 4).downcase
  ext = 'jpg' if ext == 'jpeg'
  opts = {
    :format => ext,
    :photo => ext == 'jpg',
  }

  begin
    res = conv.convert(path, opts)
  rescue MMThumb::Error => e
    STDERR.puts "ERROR: #{e}"
  else
    res.each do |key, info|
      if info[:done]
        puts info[:path]
      else
        STDERR.puts "ERROR: (#{key}) #{info[:error]}"
      end
    end

    File.delete(path) if res.values.all? {|e| e[:done] }
  end
end

You can use everything mini_magick has to offer:

# Configure
conv = MMThumb::Converter.new
conv.preprocess do |img|
  img.normalize
  img.sharpen '2x2'
end
conv.add_output(:thumb) do |img|
  img.resize '160x160>'
  img.vignette '2x3+2+2'
end
conv.add_output(:preview) do |img|
  img.resize '320x256>'
end
conv.add_output(:full) do |img|
  img.resize '1920x1080>'
  img.draw 'text 10, 10 "(C) Website"'
end

Options are both chained and available for you inside the blocks:

@conv = MMThumb::Converter.new(:path => '/static/assets')
@conv.preprocess do |img, opts|
  img.sharpen '2x2' if opts[:photo]
end
@conv.add_output(:full) do |img, opts|
  img.resize '1920x1080>'
  img.draw "text 10,10 '(C) #{opts[:user]}'"
end

batch.each do |path, user|
  ext = File.extname(path).slice(1, 4).downcase
  ext = 'jpg' if ext == 'jpeg'

  opts = {
    :format => ext,
    :photo => ext == 'jpg',
    :user => user.fullname,
    :prefix => user.id,
  }

  res = @conv.convert(path, opts)
  if res.values.all? {|e| e[:done] }
    File.delete(path)
  else
    log :error, "Processing #{path} for #{user}"
    res.values.select {|e| e[:done] }.each {|e| File.delete(e[:path]) }
  end
end

Testing

I've included a rather large (2.3 MB) JPEG file for tests.

When you run rake spec a number of test images will be generated and left in the spec folder, so that you can visually inspect that everything works as advertised. These images are deleted before tests are run, but if you want to clean them afterwards there is the rake clean task.

I believe the test don't cover everything, but they are helpful nonetheless.

Trivia: The box of floppy disks is about 140 MB (or 172 MB if you use an Amiga). It weights a couple kg.

Possible TODO

Add support for other converters (speed vs. functionality)
Make pre and post blocks run only once per image

Copyright

See LICENSE for details.