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Topic: Transparency images in PDF
Conf: (P-PDF) Developers, Msg: 95051
From: nextstepguy
Date: 8/23/2003 05:21 AM

I've implemented a simple (I think) way to deal with transparent gif images in PDF. I use Java AWT to do the main work, then use the /Mask entry to specify the range of included values for specifying the transparent colors (chroma key.) See sect. 4.8.5. This works fine with Acrobat reader 4/5/6 on Windows when displaying the document on screen. Unfortunatly, a problem arises when I try to print the image. The transparency color is replaced with white.

On Solaris, it's even worse. AcroRead 5 will show the transparent color as it is encoded even on the screen.

I believe that this is a bug in the implementation of mask on both systems because at least for windows it works on the screen. If my code was bogus, result on the screen would render the same problem on a display and on the printer.
The fact that it doesn't even work on Solaris at all is little surprise to me as I am sure that Adobe didn't go in too many efforts on that platform anyway.

Should I use the /Mask in the other way (generating an image mask with the transparent color) and will this work fine on Windows printing and Solaris too? I'd like to make sure this will work before going through the task of reimplementing this functionality.

Thanks for the help in advance.

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