A package to convert every image stored and uploaded to a Plone site to PNG format.

If you are concerned about images format patent issues this package is for you.

Portable Network Graphics (PNG) is a bitmapped image format that employs lossless data compression. PNG was created to improve upon and replace GIF (Graphics Interchange Format) as an image-file format not requiring a patent license.

Even as the JPEG compression used in various image file formats has been subject to a number of patent issues by well-known patent trolls of the industry for many years, there is currently no patent-free alternative for these formats (WebP has been available for some time, but is currently only supported by Google Chrome and Opera web browsers).

• Go to 'Site Setup'.
• Select 'Image WatchDog'.
• Select the files formats that should be converted to PNG.
• You can choose to optimize the PNG file checking the 'Optimize PNG' checkbox.
• 'Migration delay (milliseconds)' and 'Transaction threshold' are only used for migration.
• Activate the on-fly convertion checking the 'Enabled' checkbox.

• First Configure.

• Now in the 'Image WatchDog' control panel you can set:

  • 'Migration delay (milliseconds)', this parameter indicates a delay between every processed image. 0 means no delay, more fast, but CPU intensive, bigger values are nicer with the CPU but will slow down the process.
  • 'Transaction threshold', this parameter is the number of images processed in a single transaction. 0 means one single transaction, more fast, but RAM intensive, small values are nicer with the RAM but will slow down the process.

• Click on 'Save & Migrate' button to start the migration process.
• Get your prefered caffeinated beverage because this could take some time, you could check your logs to see the progress of migration process.

The package includes a handy method to migrate images, sometimes prefered for running long processes.

• From your command line run: instance run <path_to_openmultimedia.imagewatchdog_package>/openmultimedia/imagewatchdog/script/install_and_migrate.py <plone_site_name>
• This will install de product in the Plone site and migrate the images to PNG.
• Get your prefered caffeinated beverage because this could take some time, you will see the progress of migration process in your console.

Here is a small resume including just the downsides of PNG against GIF and JPEG; you can find the complete comparison in the Wikipedia:

• On small images, GIF can achieve greater compression than PNG.
• GIF intrinsically supports animated images. PNG supports animation only via unofficial extensions.

• JPEG formats can produce smaller files than PNG for photographic (and photo-like) images, since JPEG uses a lossy encoding method specifically designed for photographic image data.

Have an idea? Found a bug? Let us know by opening a support ticket.