Addition of partial support for form (xobject) smask support. To enable this feature org.icepdf.core.disableXObjectSMask=false system property must be set.

I've flushed out most of what is needed to apply a basic image smask. There as still a some issue around a pattern based smask. So as a result I've dissabled this features by default until I can work out the pattern issue as well as few corner cases.

The new system property is org.icepdf.core.disableXObjectSMask and defaults to true out of the box.

I believe this file may be affected by the same issue. Hopefully, this will be useful, please disregard if not relevant.

The type 4 example has been update/fixed some time ago but this PDF sill has an unimplemented feature with respect to graphics states smask reference. Moving to 5.1 with the intent we add support.

Quite a few improvement have been make in the rendering quality of the PDF in question. Still more work is needed to fix the transparency group issues. And the gradient background on the second page is not quite right colour wise.

I've implemented a type 4 function handling but the PDF in question still has some problems. The blue gradient is showing up correctly now that the type 4 function is being used however there appears to be other cmyk colour and masking issue with the file in question.

This pdf also has numerous examples of blending between transparency groups which would be a nice to have

Scheduling for 4.2, hopefully taking a closer look at the alternative colour space or implementing type 4 functions will do the trick.

test case.