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  #               N  O  T  E  S    &    T  O  D  O  S              #
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  #                      Nevma (info@nevma.gr)                     #
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    Features
    ========

    ****************************************************************

     - ADD SPECIAL URL PARAMETER TO THE IMAGES VIA JAVASCRIPT 
       SO THAT THE CDN MAY BE ABLE TO CACHE DIFFERENT VERSIONS OF IT

     - MY JPEG COVERSIONS ARE ALMOST AS GOOD AS THE TINYJPG ONES
       FOR INSTANCE 175KB ~ 162KB

    ****************************************************************

      ADAPTIVE IMAGES CRUNCH

      - NOT A SERVICE
      - NO API KEY
      - LOSSY JPG
      - LOSSLESS PNG
      - PNG2JPG

      Kraken, 
      EWWW, 
      Smushit, 
      TinyJPG,
      TinyPNG,
      ShortPixel, 
      Prizm       => require API key
      EWWW        => requires API key for JPEGs
      Imsanity    => has no support for true batch compression
      CW          => has no support for lossy JPEG compression

      <img sizes="(min-width: 300px) 1024px, (min-width: 150x) 300px, 150px"
           srcset="thumbnail.jpg 150w,
           medium.jpg 300w,
           large.jpg 1024w"
           alt="Image description">

      <picture>
          <source srcset="full-size.jpg" media="(min-width: 1024px)">
          <source srcset="large.jpg" media="(min-width: 300px)">
          <source srcset="medium.jpg" media="(min-width: 150px)">
          <img srcset="thumbnail.jpg" alt="Image description">
      </picture>

    ****************************************************************

    - Functions prefix "ai_".

    - Test with NextGEN.

    - Testing

      Set up functions in a way that the image generation can be tested.

    - Settings

      - Allow debug
      - Types of images to handle
      - Transform PNGs to PNG8 or not
      - Exceptions for certain images
      - PNG colour depth to keep

    - WP Multisite
    - WP content outside of installation
    - W3 Total Cache compatibility
    - WP Super Cache compatibility

    - WordPress 3.0 and down allow the "+"" character in filenames.
    - Delete old Adaptive Images files
    - In "?debug=true" mode, after the "image requested" part, show "image to be send" info
    - Use PHP::exec for cache purge and cache size calculation
    - Does this plugin work for you? Then say so!
    - Resize (crunch) even the original images!
    - Upscale images (smoothly)?
    
    - Responsive image art direction

      Default anchors and zoom levels

        1. zoom level 1, 2, 3...
        2. anchor in image

          ---------------- 
          | tl   tc   tr |
          |              |
          | ml   mc   mr |
          |              |
          | bl   bc   br |
          ----------------

        3. different aspect ratio/dimensions

          - by breakpoint
          - by orientation

          https://usecases.responsiveimages.org/#art-direction/
          http://davidwalsh.name/responsive-images/
          https://developers.google.com/web/fundamentals/media/images/images-in-markup/
          https://css-tricks.com/which-responsive-images-solution-should-you-use/
          http://www.smashingmagazine.com/2013/07/08/choosing-a-responsive-image-solution/



    Benchmarks
    ==========

    - Image generation
    - Cache calculation
    - Cache purge



    Compatibility
    =============

    - W3 Total Cache
    - WP Super Cache
    - NginX

        location assets {
        }
          
        location ai-cache { ==> *** THE CACHE DIR ***
        }
          
        location / {
          rewrite \.(?:jpe?g|gif|png)$ /adaptive-images.php; ==> *** THE PHP SCRIPT ***
        }

    - Varnish
      Pressidium for configuration
    - SSL (Jonas Tietgen)
      The problem seemed to be wrong settings for my SSL certificate. I installed the plugin WordPress HTTPS and now 
      everything works fine. I guess the problem was that the file was loaded via http instead of https...



    Unit tests for image generation
    ===============================

    - PNG
    - PNG8
    - PNG256
    - PNG with alpha
    - PNG with trasparency
    - GIF
    - GIF with trasparency
    - JPEG

    (Compare with services like TinyPNG, etc.)



    Documentation
    =============

    - What-could-go-wrong section for usual problems.
    - A website!



    Also
    ====

    - https://wordpress.org/plugins/ricg-responsive-images/
    - https://wordpress.org/plugins/responsify-wp/
    - WURFL
    - https://usecases.responsiveimages.org/#art-direction/
    - http://davidwalsh.name/responsive-images/
    - https://developers.google.com/web/fundamentals/media/images/images-in-markup/
    - https://css-tricks.com/which-responsive-images-solution-should-you-use/
    - http://www.smashingmagazine.com/2013/07/08/choosing-a-responsive-image-solution/



  Future ideas
  ============

  - Put the stylings in separate CSS files.
  - Ask users to rate plugin after x-images have been cached. 
  - Ajax calculate image cache size.
  - Ajax cleanup image cache size.
  - Report all folders and files in cache.
  - Per image cache purge.
  - Purge image cache beyond a size.
  - Per breakpoint cache purge.
  - Notify about cache size in WP cron, in WP admin, perhaps an email to the admin.
  - What if a user actually wants to see the full version of an image, even in a mobile network? 
  - When an image is deleted in the media gallery then its resized versions should be deleted, too.
  - When breakpoints are changed delete the cache directories of the unused breakpoints to clean up.
  - Original adaptive images PHP script error log is output inside the plugin files.
  - Send original images to search engine bots to preserve their metadata.



  Plugin needs 3 settings in order to function properly
  =====================================================

  1. database options set
  2. htacess file bit inserted
  3. user settings php file created



  Test cases to check with each version
  =====================================

  - Clean install
  - Deactivate then activate
  - Version 0.2.08 upgrade
  - Older version upgrade
  - Print debug info 
  - Images correctly sent for each breakpoint
  - Uninstall cleanup

  - Images

    - JPG
    - GIF
    - GIF with transparency
    - PNG
    - PNG with transparency