Whenever FxFactory gives you the option to map an input from the host to an image input port in the Quartz composition, it will also give you a chance to set up a secondary (and optional) mapping, called “Image Info”.
If a standard Image mapping simply transfers image contents from the host to your composition, the “Image Info” mapping is meant to transfer metadata about that image. The structure contains the following keys and values:

• pixelsWide and pixelsHigh contain the image dimensions (in pixels)
• pixelAspect contains the pixel aspect of the image (e.g. 0.9 for a full frame of NTSC DV footage shot at 4:3; 0.44 for a single field of NTSC DV footage shot at 4:3)
• displayAspect contains the aspect ratio at which the image is ultimately displayed to the viewer (usually 4:3, 19:9).
• fieldOrder contains a numeric value which is equal to 0 if the image source is progressive, 1 if the image source is interlaced and the upper field comes first, 2 if the image source is interlaced and the lower field comes first.
• field contains a value which is equal to 0 if the image contains progressive data, 1 if the image represents the upper field, 2 if the image represents the lower field.
• pixelFormat a value which represents the pixel format of the image: 0 for RGB + alpha images, 1 for YUV + alpha (Y'CbCr) images. (Please note that the plug-in must be YUV-capable for the pixel format to be YUV + alpha.)
• startFrame contains a value which represents the start time (in frames) of the image source.
• endFrame contains a value which represents the end time (in frame) of the image source
• duration contains a value which represents the total duration (in frames) of the image source

The startFrame, endFrame and duration properties are represented by an integer value if the image source is progressive (1, 2, 3, etc.) or by a fractional value if the image source is interlaced (0.5, 1.0, 1.5, etc.). The fractional component, if present, is usually equal to 0.5 and it represents the first field in a given frame (e.g. 2.5 represents the first field in the 3rd frame).

Although it is certainly possible to extract values from an Image Info structure using multiple “Structure Key Member” patches in Quartz Composer, it is recommended that you use the “FxFactory Image Info” patch instead. This patch has been designed to make this job easier for you, and it also provides additional outputs that will help you develop plug-ins: