=== Adaptive Images for WordPress === Contributors: nevma Donate link: http://www.nevma.gr/ Tags: adaptive images, responsive images, mobile images, resize images, optimize images, adaptive, responsive, mobile, resize, optimize, images Requires at least: 4.0 Tested up to: 4.2.2 Stable tag: 0.5.0 License: GPLv2 or later License URI: http://www.gnu.org/licenses/gpl-2.0.html Adaptive images plugin transparently resizes your images, per device screen size, in order to reduce download times in mobile environments. == Description == = Adaptive Images = Resizes and optimizes images delivered to mobile devices, in a transparent and unobtrusive way, so that the total download time is dramatically reduced. It works as a filter between the device and your WordPress website. It actually works for all types of deveice screen sizes, although it is targeted mostly at mobile environments. = Fundamental goals = 1. Reduce the total download time in mobile devices dramatically. 2. Work transparantly and unobtrusively by being independant of your code. 4. Be agnostic of the yet-not-finalized `picture` element or `srcset` attribute. = Supported formats = - JPEG (adjustable quality) - PNG (is transformed to PNG8) - GIF (not animated) HiDPI (high device pixel density/retina) screens are supported. = Default breakpoints = - 1024px wide screens - 640px wide screens - 480px wide screens Since version 0.5.0 and upwards it is configurable whether the plugin should take into account the landscape or the portrait orientation of each device. = How to test = 1. Test with Chrome's device emulation mode https://developer.chrome.com/devtools/docs/device-mode in Developer Tools. Unfortunately, Firefox's Responsive Design Mode does not emulate a mobile screen size! 2. Test with a tool like Webpagetest http://www.webpagetest.org/. Make sure you set the "Emulate Mobile Browser" setting in the "Advanced Settings" > "Chrome" tab. 3. Test with a tool like GTmetrix http://gtmetrix.com/. Make sure you enable mobile device testing. The plugin will have no effect on desktop sized devices. 4. Test with an actual mobile device, a smartphone or tablet. Watch your website load in a snap. 5. Check in the `/wp-contents/cache` directory to see the `/adaptive-images` directory and its contents. This is where the resized images are kept and cached by default. 6. View an image straight from a browser and add a "?debug=true" at the end of the url like this "http://www.website.com/wp-content/uploads/2015/01/image.jpg?debug=true". This should print useful debug information about the plugin functions in your installation. If you keep seeing your image, then the plugin is not working and the cause is probably the failure to update the .htaccess file properly. You may test with a normal desktop browser but only of the computer screen size falls under at least on of the specified breakpoints! = Stuff to keep in mind = - The plugin needs to add a little bit of code to your `.htaccess` file in order to function properly. It removes this code once disabled. If you are not cool with that, then… tough luck! - It cannot work out of the box with a CDN (or Varnish server, for that matter), because the CDN or Varnish server are unaware of the device size cookie and they cannot know in a definitive way which image they should serve or cache for each device. - The plugin does not care whether the device is actually mobile or not. It checks the device screen resolution. If you have set your breakpoints big enough then it should work just as good for desktop devices as well. However it targets mostly the mobile ones. - The resized versions of the pictures are kept in a special directory in the `/wp-content/cache` directory. = Credits = - The plugin was originally based on the WP-Resolutions plugin https://github.com/JorgenHookham/WP-Resolutions/, but right, now it is a complete rewrite! - Both plugins, WP-Resolutions and this one, take ideas from the Adaptive Images http://adaptive-images.com/ adapted specifically for WordPress. Thank you for using the plugin and, please, do let us know how it works (or doesn't work) for you. We love comments and creative feedback! == Installation == = Usual process = 1. Install the plugin via "Plugins > Add New". 2. Activate the plugin. 3. Go to its settings and save them! The plugin should simply work! De-activate the plugin to disable it. Activate the plugin to enable it. Delete it and it's gone. So simple. = Debugging = 1. See the "How to test" paragraph in the "Description" tab. 2. Hit the "Print debug info" button in the plugin settings page and check the output. 3. Hit the "Print diagnostics" button in the plugin settings page and check the output. = Incompatibilities = 1. Does not support WordPress Multisite (^μ or MU) yet. 2. Supports Nginx but it must be manually configured first. 3. Cannot work with installations where the `/wp-content` directory is not in its default position, which is inside the root directory of the WordPress installation, along with `/wp-admin` and `/wp-includes`. == Frequently Asked Questions == = What's the story? = First came the Adaptive Images solution http://adaptive-images.com/ which is still there and works on its own. Then came the WP-Resolutions plugin https://github.com/JorgenHookham/WP-Resolutions. But it is not in the WordPress plugin repository anymore and the Github version is not compatible with the latest WordPress versions. So we are updating and maintaining it. Many under the hood changes have taken place, but the overall functionality is the same. Since version 0.5.0 the plugin has been completely rewritten, in order to not rely on the Adaptive Images solution, which was released under a CC-BY license that is not compatible with the GPL. This problem has now been overcome and the part that used to rely on the Adaptive Images is brand new! = Is this plugin heavy? = Well, not much really. The image resizing process is not computationally negligible, but the images are only resized when they are first requested and then they are cached. However, it must be noted that the images in the watched directories, the ones the plugin is responsible for resizing and delivering, are ultimately delivered by a PHP script and not a generic server process! So actually one has to decide on a balance between creating and storing too many image sizes in contrast to burderning their server resources. = Can it work with a CDN/Varnish? = Not out of the box! The reason is that the service responsible for delivering the images (in this case the CDN or Varnish) must be aware of the resizing process and the client cookie it is based on. If one has access to their CDN or Varnish configuration, then they could probably extend it to take that cookie into account and act accordingly. = Does the plugin help with art direction? = No! Simple as that. Art direction https://usecases.responsiveimages.org/#art-direction in responsive images is an entirely different, yet important, problem. This plugin does not tackle with it. But it works in a supplementary way without interfereing with other solutions that do. This means that you can combine it with any art direction solution. This plugin will continue to work and serve resized versions of your responsive images even after you have done art direction on them. == Screenshots == 1. Plugin settings page in the admin area. 2. Resized versions of your images are cached by default in `/wp-content/cache/adaptive-images`. 3. Total web page load time is reduced dramatically on a mobile device (tested in http://webpagetest.org/). 4. Each device is served an image resized its real dimensions, therefore a lot smaller in total size. == Upgrade Notice == = 0.5.0 = It is recommended, but not absolutely necessary, to save ones settings anew, due to the big change in the image resizing script, which was completely re-written, renamed and relocated inside the plugin's directories since this version. = 0.3.0 = Upgrading to version 0.3.0 you may need to: - Save settings anew. If you do not then the plugin will operate with its current default settings without problems as it is expected. - Manually delete the old image cache directory `/wp-content/cache-ai`. The new default image cache directory is `/wp-content/cache/adaptive-images`. Apologies for the inconvenience! We are still in early versions. What is important is that the plugin actually works as intended. We try to minimize the hassle between these versions. This is not expected to happen pretty often. == Changelog == = 0.5.0 = - New option in settings to define whether the plugin should use the bigger dimension of a device as its with or take into account the current orientation. Up to now the plugin used the width of the landscape orientation, which is the biggest of each device's dimensions. - New option in settings to define whether the plugin should use take special care for HiDPI (retina, high pixel density screens and serve these devices better quality images according to their pixel density. - Better PNG compression via PNG8. This converts true color PNG images to palette image, which reduces colours and the alpha channel Kudos http://stackoverflow.com/questions/5752514/how-to-convert-png-to-8-bit-png-using-php-gd-library/. - Fixed some edge cases of not being able to serve a resized image by reverting to original image. - More analytical settings page debugging and diagnostics. - Added debugging methods in the image cache generation script. - Plugin can be configured to respect your default expires headers. - Some documentation stuff (as always). - Completely rewritten the script that generates and caches the resized versions of images in order to avoid the GPL vs CC-BY-3.0 licensing incompatibility of the original Adaptive Images script (http://adaptive-images.com/). Plugin is now totally independant and free of any licensing issues. - Due to the above, the image resizing script is no longer the same, it has been transformed to a new script, named `adaptive-images-script.php` which is in the root folder of the plugin. However the old script is still left inside the plugin folders for compatibility purposes (old versions and users not having saved their settings anew). = 0.3.52 = - Documentation stuff. = 0.3.51 = - Minor bug in settings page url parameters. - Documentation stuff. = 0.3.5 = - Allow for default browser cache settings. - More thorough debugging information. - Added diagnostics debugging in the settings page. - Nicer admin area user messages with icons. - Minor fixes here (and there). - Documentation enhancements. = 0.3.04 = - Documentation enhancements (yeah). - Added "noptimize" tag in HEAD Javascript to exclude it from optimizers. = 0.3.03 = - Added Last-modified HTTP header for resized images, as the best practices do suggest. = 0.3.02 = - When no device size/resolution is detected then show the original image. Helps avoid misunderstandings and sends search engines the actual images instead of the resized ones. = 0.3.01 = - Documentation enhancements. = 0.3.0 = - Almost a complete rewrite of the code. - Completely updated the settings page to be user friendly. - Added action in the settings page for cache cleanup. - Added action in the settings page for debug info. - Added action in the settings page for cache size calculation. - Added watched directories field in the settings page anew. - Divided the plugin files into logical parts. - Default resolutions changed to 1024, 640 and 480 because the cookie is set based on the max value between screen width and height and most screens have a height between 480 and 640px. Tablets are between 640 and 1024px wide/tall. The iPad is 1024px tall. A screen with a width higher than 1024px is probably not a mobile screen. - Changed default image cache directory in order to place it inside the expected WordPress `/wp-content/cache` directory, so now by default it is `/wp-content/cache/adaptive-images`. - Added check for the plugin options. - Added check for the PHP GD library. - Added check for the .htaccess file. - Added upgrade from older versions functions. - Added upgrade from 0.2.08 to 0.3.0 versions functions. - Added unistall script `uninstall.php`. - Documentation enhancements (as usual). = 0.2.08 = - Added cache size calculation. - Added cache clean up methods. - Added nonces to admin actions. - Documentation enhancements. = 0.2.06 = - Settings are now separate in an ai-user-settings.php file. = 0.2.05 = - If the original requested image width and the device screen size are bigger than maximum available breakpoint, then serve the the original image. = 0.2.04 = - Refactoring code. = 0.2.03 = - Set the default screen size breakpoints to 1024, 600, 320. = 0.2.02 = - Refactoring code to separate Adaptive Images files from the other plugin files. = 0.2.01 = - The first stable version after the initial fork. - Corrected basic PHP errors. - Corrected basic WordPress errors. - Now compatible with version 4.1.1. - New document root takes into account installations in subdirectories. = 0.1 = - The version forked from the WP Resolutions plugin https://github.com/JorgenHookham/WP-Resolutions. - This version does not work with WordPress anymore (at least version 4.1.1 and upwards).