GDI engine and Multiply blend mode problem

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James Dustin

Jul 16, 2013, 7:20:33 PM7/16/13
I've come across a problem with a pdf that uses a multiply blend mode for two images.

Using the e_GDIPlus rasterizer this mode seems to be ignored and one of the images obscures the view of the other image.

Using the e_BuiltIn rasterizer the images are displayed with the correct transparency but it is slower at drawing the page.

Is there any way to raise an error or detect that there is a problem when using the e_GDIPlus rasterizer?

That way I could try to use e_GDIPlus first and then switch to e_BuiltIn if there is a problem.

many thanks,


Jul 22, 2013, 6:36:23 PM7/22/13
There is no error callback, however just before rendering the page you could search page.GetResources().FindObj("ExtGState").FindObj("BM" or "bm") . If ExtGState dictionary contains 'bm' or "BM" key you could switch to using built-in rasterizer, otherwise stick with e_GDIPlus.
Not sure if this is worth it in the long run, since we are putting lots of effort to further improve built-in rasterizer performance. Even with the current version, built-in rasterizer outperforms gdi+ on many files.  
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