Hi,
I need to implement Soft Mask image support for a PDF generator (specifically we need to be able to embed PNG images with transparency), read the relevant sections in the PDF specs (sections 8.9.5, 8.9.6 and 11.6.5.3), however I have several doubts:
1) Are Soft Mask images the solution for this scenario or is there another solution (we are emitting PDF 1.4 files).
2) What's exactly a subsidiary image XObject?
3) Do I need to write an image XObject in another entry in the Image Dictionary or writing in the SMask entry of the parent image enough?
4) Writing the subsidiary image XObject as a regular stream in the SMask entry would be enough?
5) Do I need to update the Graphics state when emitting the parent image with the soft mask?
Also, are there any examples of this feature that I can look upon to be able to see more clearly how are soft mask images implemented?