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Hi Zdenek,<br class="">
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<div class="">On 26 May 2020, at 9:31 am, Zdenek Wagner <<a href="mailto:zdenek.wagner@gmail.com" class="">zdenek.wagner@gmail.com</a>> wrote:</div>
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<div dir="ltr" class="gmail_attr">út 26. 5. 2020 v 0:59 odesílatel Ross Moore <<a href="mailto:ross.moore@mq.edu.au" class="">ross.moore@mq.edu.au</a>> napsal:<br class="">
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<div bgcolor="#FFFFFF" class="">and at the time, that appeared to solve my problem. However, it would appear that since then "xdvipdfmx" has been enhanced to support transparency, as a result of which Khaled's suggested FFFFFF00 no longer works (the text is
invisible, see attached). Could anyone tell me how, short of using \specials, I can achieve 100% white with 100% opacity (= 0% ink) in XeTeX ?<br class="">
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<div class="">I’m sorry, but this just doesn’t make any sense to me — but see further below.</div>
<div class="">Surely 100% opacity means that the blend between background and foreground is 100% background, 0% foreground.</div>
<div class="">Thus your text will be invisible, whatever colour has been specified; that this is white becomes irrelevant.</div>
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<div class="">The only way to get 100% white, over a coloured background, would be with 100% ink, so 0% opacity.</div>
<div class="">Any other opacity level will allow some of the background colour to be mixed in.</div>
<div class="">At least that is how I understand what colour mixing is all about.</div>
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<div class="">Sorry, correct me if my English is wrong but I would expect 100% ink = 100% opacity = 0% transparency<br class="">
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<div>You’re absolutely correct, my mistake.</div>
<div>Certainly I meant 0% *transparency*, the opposite of what Phil was trying to do.</div>
<div>It was he who said 100% opacity (= 0% ink) which is where the error lies.</div>
<div>Surely 100% ink = 100% opacity = 0% transparency, as you say.</div>
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<div class="">However, there is another PDF parameter called “knockout”.</div>
<div class="">See this link for an brief description of the issue:</div>
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<div class=""> <a href="https://protect-au.mimecast.com/s/tuWYCBNqgBCvBNrAuzR3NV?domain=enfocus.com" target="_blank" class="">https://www.enfocus.com/en/products/pitstop-pro/pdf-editing/knockout-white-text-in-a-pdf</a></div>
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<div class="">This is another topic. This addresses "black overprint" in printing.
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<div>Sure, but it is about knocking out the colour in the background.</div>
<div>Using black text is probably its most common usage.</div>
<div>But if you want the natural paper to come through, then surely this is the only way to do it conveniently. </div>
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<div>Otherwise you would have to manually define regions outlining the letters, and make these</div>
<div>boundary curves for your background. Totally impractical. </div>
<div>PDF does this for you, if you have used the correct way to ask for it.</div>
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<div class="">The idea is that process colours are printed in the following order: cyan-magenta-yellow-black. If you want to print a yellow text on a cyan background, RIP must erase the cyan plate to white where the characters will later appear on the yellow
plate, otherwise the text would not be yellow. If the offset films are not precisely adjusted, you will see colour artifacts at the boarders of the characters. If you want to type a dark text (usually black) to a light background, it can just be overprinted.
In order to make it work, both colours must be defined in CMYK (not RGB, not grayscale). Professional Acrobat since version 9 contains a prepress checking function which can verify whether overprint was really used. Black overprint is implemented in my zwpagelayout
package. It was tested in xelatex, pdflatex, and latex + dvips. The package does not my test files. If you like, I can send them.<br class="">
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Sure; I’d love to see these.</div>
<div>I’m sure that this would most closely approach what Phil seems to want to do.<br class="">
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<div class="">How to achieve knockout using TeX+gs or pdfTeX or XeTeX? </div>
<div class="">I’m not at all sure. It must have a graphics state parameter.</div>
<div class="">The next image shows what I think is the relevant portion of the PDF specs.</div>
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<div class=""><span id="cid:1724e1de929780f054c1"><Screen Shot 2020-05-26 at 8.38.02 am.png></span></div>
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<div class="">There’s a whole section on “Transparency Groups”, but mostly it is about how different transparent objects</div>
<div class="">must combine to produce the final colour where objects overlap.</div>
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<div class="">Transparency should not be used for prepress. It works fine on office printers but often come out as black on phototypesetters and CTP.</div>
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Phil hasn’t said what is his application.</div>
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<div class="">After a cursory look, I think you need to use a Form X Object, which can be done in pdftex using the \pdfxform primitive,</div>
<div class="">with appropriate attributes specified.</div>
<div class="">For XeTeX you would need to be using \special commands. </div>
<div class="">Someone here must have some experience with this.</div>
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<div dir="ltr" class="gmail_signature">Zdeněk Wagner<br class="">
<a href="https://protect-au.mimecast.com/s/TZFICD1vRkCX0ZzMs5cgKz?domain=ttsm.icpf.cas.cz" target="_blank" class="">http://ttsm.icpf.cas.cz/team/wagner.shtml</a><br class="">
<a href="https://protect-au.mimecast.com/s/4H07CE8wlRCBMj2nhptby5?domain=icebearsoft.euweb.cz" target="_blank" class="">http://icebearsoft.euweb.cz</a></div>
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<div bgcolor="#FFFFFF" class="">Philip Taylor<br class="">
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<span id="gmail-m_-623522321642928064cid:19ACD8EB-D18B-4386-BFFD-666B7C908C5F@telstra.com.au" class=""><Demo.pdf></span><span id="gmail-m_-623522321642928064cid:636E46BE-0887-4C87-8837-418D1A26B567@telstra.com.au" class=""><Demo.tex></span><span id="gmail-m_-623522321642928064cid:CD809896-CACA-41F2-B6FD-CEC19309E898@telstra.com.au" class=""><Lighter
ground.pdf></span></div>
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<div>Sorry for my error adding to confusion.</div>
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<div>Cheers.</div>
<div>Stay safe.</div>
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<div><span class="Apple-tab-span" style="white-space:pre"></span>Ross</div>
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Dr Ross Moore<br class="">
Department of Mathematics and Statistics
<div class="">12 Wally’s Walk, Level 7, Room 734<br class="">
Macquarie University, NSW 2109, Australia<br class="">
T: +61 2 9850 8955 | F: +61 2 9850 8114<br class="">
M:+61 407 288 255 | E: <a href="mailto:ross.moore@mq.edu.au" class="">ross.moore@mq.edu.au</a><br class="">
<a href="http://www.maths.mq.edu.au" class="">http://www.maths.mq.edu.au</a><span style="font-size: 12px; line-height: normal;"><a href="http://mq.edu.au/" target="_blank" style="font-size: 12px; line-height: normal;" class=""><span><br class="Apple-interchange-newline" style="caret-color: rgb(0, 105, 217); color: rgb(0, 105, 217); font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-family: Arial, sans-serif; orphans: 2; widows: 2;">
<span style="caret-color: rgb(0, 105, 217); color: rgb(0, 105, 217); font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-family: Arial, sans-serif; orphans: 2; widows: 2;"><span><span><span><span><img apple-inline="yes" id="1B165294-8BE0-4C51-BAD3-59B87E85EE14" src="cid:image001.png@01D030BE.D37A46F0" class=""></span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">CRICOS
Provider Number 00002J. Think before you</span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class=""> </span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">print. </span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">Please
consider the environment before printing this</span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class=""> </span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">email.</span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">This
message is intended for the addressee named</span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class=""> </span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">and
may </span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">contain
confidential information. If you are not the</span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class=""> </span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">intended </span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">recipient,
please delete it and notify the sender. Views</span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class=""> </span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">expressed </span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">in
this message are those of the individual sender, and</span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class=""> </span><span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">are
not </span><br style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none;" class="">
<span style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; text-decoration: none; float: none; display: inline !important;" class="">necessarily
the views of Macquarie University.</span> </span></span></span></span></span></a></span></div>
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