Dolphin 8: Images Transcoder

AlexT posted 19th of September 2011 in News. 0 comments.

The new high level API in Dolphin 8 - Automatic Images Transcoder. No need to write code for images resizing and storing. The new API will do it for you automatically.

The advantages of the new system:

  • Less code to write - so you can concentrate on the main functionality
  • Less space usage - only usable data is transcoded and unused data can be automatically deleted
  • Flexibility - you can change image filters (for example, new image dimentions) and all images will be transcoded automatically, upon first access
  • Security - the transcoded image can have the same security setting as original

So the tech part goes below...

Images Transcoder is working together with Storage Engine to store transcoded data. So, for example, you can store transcoded data on Amazon S3 with reduced redundancy option to save some money.

Adding new images transcode object

To add image transcoder object add record to sys_objects_transcoder_images table:

  • object - name of the transcoder object, in the format: vendor prefix, underscore, module prefix, underscore, image size name; for example: bx_images_thumb.
  • storage_object - name of the storage object to store transcoded data, the specified storage object need to be created too, @see BxDolStorage.
  • source_type - type of the source, where is source image is taken from, available options Storage and Folder for now.
  • source_params - source_type params, each source_type can have own set of params, please read futher for more info about particular source_types, serialized array of params is stored here.
  • private - how to store transcoded data:
    • no - store transcoded data publicly.
    • yes - store transcoded data privately.
    • auto - detect automatically, not supported for Folder source type.
  • atime_tracking - track last access time to the transcoded data, allowed values 0 - disables or 1 - enabled.
  • atime_pruning - prune transcoded images by last access time, if last access time of the image is older than atime_pruning seconds - it is deleted, it works when atime_tracking is enabled
  • ts - unix timestamp of the last change of transcoder parameters, if transcoded image is older than this value - image is deleted and transcoded again.

Then you need to add image filters to sys_transcoder_images_filters table:

  • transcoder_object - name of the transcoded object to apply filter to.
  • filter - filter name, please read futher for available filters.
  • filter_params - serialized array of filter params, please read futher for particular filters params.
  • order - if there are several filters for one object, they will be applied in this order.

Source types

  • Folder - this source type is some folder with original images for the transcoding, the identifier of the image (handler) is file name.
    The params are the following:
    • path - path to the folder with original images
    This source type has some limitation:
    • automatic detection of private files is not supported
    • transcoded file is not automaticlaly deleted/renewed if original file is changed
  • Storage - the source of original files is Storage engine, the identifier of the image (handler) is file id.
    The params are the following:
    • object - name of the Storage object


  • Resize - this filter resizes original image, the parameters are the following:
    • w - width of resulted image.
    • h - height of resulted image.
    • square_resize - make resulted image square, even of original image is not square, w and h parameters must be the same.
    • force_type - always change type of the image to the specified type: png, jpg or gif.
  • Grayscale - make image grayscale, there is no parameters for this filter

Automatic deletetion

Automatic deletetion of associated data is supported - in the case if original or transcoded file is deleted. All you need is to register alert handlers, just call registerHandlers () function to register handler (for example, during module installation) and call unregisterHandlers () function to unregister handlers (for example, during module uninstallation).

Example of usage

$oTranscoder = BxDolImageTranscoder::getObjectInstance('bx_images_thumb'); // change images transcode object name to your own
$oTranscoder->registerHandlers(); // make sure to call it only once! before the first usage, no need to call it every time
$sTranscodedImageUrl = $oTranscoder->getImageUrl('my_dog.jpg'); // the name of file, in the case of 'Folder' storage type this is filename
echo 'My dog : <img src="' . $sUrl . '" />'; // transcoded(resized and/or grayscaled) image will be shown, according to the specified filters

Images Transcoder Wiki

- 2011-11-22: 'force_jpeg' parameter was changed to 'force_type'
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