The scaleX and scaleY parameters are defined as attributes of BitmapImage Element (and others) in the FXG 2 specification: http://sourceforge.net/adobe/flexsdk/wiki/FXG%202.0%20Specification/
When you create an area for the image to populate, in the authoring application, the original image dimensions are divided by the height and width of this specified area to generate scaleX and scaleY attributes. (They are seen as Bitmap Scale:W and Bitmap Scale:H in the Template Publishing Editor, respectively.)
The only reason to worry about it is if you have to change an image. For example, with parameterization or DOM manipulation, you still have the original scaleX and scaleY attribute values preserved. It scales the replaced image in a similar manner as the original, so images have a similar aspect ratio.
More information on related settings:
Within the exported s7FXG, there is a BitmapGraphic Object exported for every image that was initially placed in a template. Within this BitmapGraphic Object, Scene7 exports the following attributes to define how the resultant template renders this image in a template.
- x: Sets x coordinate of upper-left corner of image with respect to the upper-left corner of the template itself (measured in points).
- y: Sets y coordinate of upper-left corner of image with respect to the upper-left corner of the template itself (measured in points).
- height: The height (in pixels) of the original image before it was placed in Adobe Illustrator or InDesign.
- width: The width (in pixels) of the original image before it was placed in Adobe Illustrator or InDesign.
- scaleX: The horizontal scale factor Illustrator or InDesign used, to fit the image into the user-designated frame.
- scaleY: The horizontal scale factor Illustrator or InDesign used, to fit the image into the user-designated frame.
height * scaleY = Image frame height dimension within a Template rendering.
width * scaleY = Image frame width dimension within a Template rendering.