Configuration/Core/controller/extjs/media/default/preview/allowedtypes

Summary
A list of image mime types that are allowed for preview image files

controller/extjs/media/default/preview/allowedtypes = Array (   [0] => image/jpeg    [1] => image/png    [2] => image/gif )


 * Default: Array
 * Type: array - List of image mime types
 * Since: 2014.03

Description
The list of allowed image types must be explicitly configured for the preview image files. Trying to create a preview image whose mime type is not available in the list of allowed mime types will result in an exception.