A callback which can be used to cancel the scan. May be
null.
Notes
Analysing populates the following properties.
ColorProfiles
VectorImageCount
PathPaintCount
PathClipCount
TextObjectCount
HasVectorAlpha
HasRasterAlpha
HasRasterMatte
TilingPatternCount
ShadingPatternCount
RasterImageCount
You can optionally pass in a function which will get called
immediately after each property gets updated. If you return true
from this callback the analysis will be cancelled. This can be used
to limit the amount of processing if you are only interested in
limited information.