Imaging contains VCL/LCL TGraphic descendant which uses Imaging library for loading and saving various different file formats. They actually descend from TBitmap and override only loading, saving, and assigning procedures. These classes are implemented in ImagingComponents.pas unit.

Classes are automatically registered in unit's initialization section so you only need to add ImagingComponents to uses list somewhere in your project and TPicture class will be able to load and save images using Imaging. There are packages for Delphi, and Lazarus in Source\Projects directory which you can install to your IDEs and use Imaging classes in form design stage too.

Note that TImagingGraphic and all its descendants can load images in all file formats supported by Imaging but save images only in file format they are named after (i.e. TImagingJpeg saves jpeg images). TImagingGraphic itself doesn't override saving methods so TBitmap's saving is used.