This section tells about transforming user-selected images before upload. HTML5/Flash Uploader can resize, recompress, and rotate images on a client side. These transformations may be combined, for example, an image can be resized and rotated at the same time. You can create three or less transformed versions of one image, for instance, the first one is a considerably downsized version and the second one is recompressed. An image you get after applying any set of transformations is called thumbnail.
To configure a thumbnail you should add a Converter to the ImageUploaderFlash.Converters collection and set its Mode property to Thumbnail. For more information about converters, please, see the Configuring Files to be Uploaded in HTML5/Flash Uploader topic.
Each thumbnail is a file, so on the server you can save uploaded thumbnails using any approach examined in the saving uploaded files topic.
HTML5/Flash Uploader allows to use up to three converters. Thus, if you already set, for example, a source file converter, you can specify one or two thumbnails only.
Now, when you have an idea about what thumbnail means in terms of HTML5/Flash Uploader, how to configure converters, and how to save uploaded files, let us briefly describe each topic of this section:
HTML5/Flash Uploader can load a lot of image formats and display previews for them, however, it can save the image only into the single format - JPEG. So, all thumbnails created by HTML5/Flash Uploader are JPEG images.