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--- contrib:externalviewers [2019/06/26 12:11] – transparency knockout explanation sluka
+++ contrib:externalviewers [2019/07/13 09:41] (current) – typo What it means "transparency knockout" sluka
@@ Line 59: / Line 59: @@
 Objects with //–place top// render the same as objects with default placement over areas with default placement in both viewers.
-The Foxit behaviour is preferable I think, although, with some symbol sets, you can never get a rock that looks like it is definitively ‘high and dry above the water’, unless you say, draw two rocks, one directly above the other.\\ (Note: Anyway, Foxit ignores official definition of PDF - [[https://www.pdfa.org/what-does-%C2%93support-pdf%C2%94-really-mean/?highlight=knockout|official definition of PDF]], Sluka)
+The Foxit behaviour is preferable I think, although, with some symbol sets, you can never get a rock that looks like it is definitively ‘high and dry above the water’, unless you say, draw two rocks, one directly above the other.\\ (Note: Anyway, Foxit ignores [[https://www.pdfa.org/what-does-%C2%93support-pdf%C2%94-really-mean/?highlight=knockout|official definition of PDF]], Sluka)
 Some further information here [[:tips#drawing_order_how_to_draw_symbols_over_or_under_an_area]]
-What it means "transparency knockout":\\
+**What it means "transparency knockout"**\\
-Transparency knockout is part of PDF definition which uses Adobe applications as Illustrator, InDesign, Photoshop, etc. for example. It means, that there is possibility to switch off transparency for a particular group of objects (sublayer) when transparency of superior layer is on. The explanation you may find [[https://helpx.adobe.com/illustrator/using/transparency-blending-modes.html|here]].\\
+Transparency knockout is part of PDF definition which Adobe applications as Illustrator, InDesign, Photoshop, etc. use. It means, that there is possibility to switch off transparency for a particular group of objects (sublayer) when transparency of superior layer is on. The explanation you may find [[https://helpx.adobe.com/illustrator/using/transparency-blending-modes.html|here]].\\
 In case of Therion it means that you didn't want rocks to be transparent, but rocks in position above another passage should be partially transparent to show details from underlaying passage.
-See attached examples of preview in program using PDFToolkit (correct) and PDFKit (transparency knockout ignored).\\
+See attached examples of preview in program using PDFToolkit (transparency knockout rendered) and PDFKit (transparency knockout ignored).\\
 {{:contrib:pdftoolkit.png|300px|}}{{:contrib:pdfkit.png|300px|}}
 =====Examples of Rendering Differences Between PDF Viewers=====
@@ Line 96: / Line 96: @@
 **xpdf** \\
-Correct rendering of overlap objects. On MacOSX it is possible to install it by homebrew installer. xpdf should antialias vectors, but not in this case, so rendering is quite coarse.
+Correct rendering of overlap objects. On MacOSX it is possible to install it by homebrew installer. xpdf should antialias vectors, but not in this case, so rendering is quite coarse. The reason is when transparency knockout is used, the antialiasing in layers is not rendered. It should be corrected in next version of xpdf - current version is 4.
 {{:contrib:xpdf.png|}}