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-rw-r--r--src/documentation/content/xdocs/faq.xml40
-rw-r--r--src/documentation/resources/images/acrobat-anti-aliasing-artifacts.pngbin0 -> 8128 bytes
-rw-r--r--src/documentation/resources/images/anti-aliasing-artifacts-demo.fo57
3 files changed, 97 insertions, 0 deletions
diff --git a/src/documentation/content/xdocs/faq.xml b/src/documentation/content/xdocs/faq.xml
index c2f6cb7ca..2fd6e16ca 100644
--- a/src/documentation/content/xdocs/faq.xml
+++ b/src/documentation/content/xdocs/faq.xml
@@ -1016,6 +1016,46 @@ Can I control this?</question>
</p>
</answer>
</faq>
+ <faq id="acrobat-anti-aliasing">
+ <question>How can I get rid of strange single-pixel lines inside table borders or between table cells in Adobe Acrobat?</question>
+ <answer>
+ <p>
+ Since Apache FOP supports the collapsed border model, every border segment consists
+ of two separate shapes. This is due to the fact that each side of the border
+ segment can have a different color. Now, Adobe Acrobat may display thin (1 pixel wide)
+ lines inside the border segment or sometimes even between to adjacent
+ colored rectangles making up the background of a block or table cell.
+ This effect is due to the way Adobe Acrobat does anti-aliasing. Adobe's algorithm
+ seems to cause these artifacts. Other PDF viewers don't have that problem. Or at least
+ we haven't had any reports in that direction.
+ </p>
+ <p>
+ First of all, these artifacts do not appear in print since no anti-aliasing is done
+ by Adobe Acrobat in this case (except maybe if you tell Acrobat to print the page
+ as a bitmap in which case Adobe fully composes the page itself). So, if the artifacts appear
+ on screen, it doesn't mean they have to appear in print, too.
+ </p>
+ <p>
+ To get rid of the artifacts, you can call up the "Preferences" dialog of
+ Adobe Acrobat and select the tab "Page display". Enabling "Enhance thin lines"
+ may help in some situations. Otherwise, you can disable "Smooth line art".
+ You may have to disable "Use 2D graphics acceleration", too, so you can disable
+ "Smooth line art" in the first place.
+ </p>
+ <p>
+ Here an example of how the effect can look like (left: anti-aliasing on, right: anti-aliasing off):
+ </p>
+ <figure src="images/acrobat-anti-aliasing-artifacts.png" alt="Left: anti-aliasing on, Right: off"/>
+ <p>
+ Unfortunately, it is not possible to control the above settings from within the PDF file.
+ The user has to change these settings himself. Improving FOP to avoid this kind of problem
+ would be possible although rather hard to achieve because we'd need to add a considerable
+ amount of code to combine the various line segments. Something like that has been tried already
+ years ago showing that this is a tricky task. Also, the improvement may not justify the amount
+ of effort required.
+ </p>
+ </answer>
+ </faq>
</part>
<part id="part-iex">
<title>IEx specific stuff</title>
diff --git a/src/documentation/resources/images/acrobat-anti-aliasing-artifacts.png b/src/documentation/resources/images/acrobat-anti-aliasing-artifacts.png
new file mode 100644
index 000000000..db9c23a2a
--- /dev/null
+++ b/src/documentation/resources/images/acrobat-anti-aliasing-artifacts.png
Binary files differ
diff --git a/src/documentation/resources/images/anti-aliasing-artifacts-demo.fo b/src/documentation/resources/images/anti-aliasing-artifacts-demo.fo
new file mode 100644
index 000000000..5917e80e0
--- /dev/null
+++ b/src/documentation/resources/images/anti-aliasing-artifacts-demo.fo
@@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
+ <fo:layout-master-set>
+ <fo:simple-page-master master-name="page" page-height="3.1cm" page-width="6cm" margin="2mm">
+ <fo:region-body/>
+ </fo:simple-page-master>
+ </fo:layout-master-set>
+ <fo:page-sequence master-reference="page">
+ <fo:flow flow-name="xsl-region-body">
+ <fo:table table-layout="fixed" inline-progression-dimension="100%">
+ <fo:table-column column-width="50%"/>
+ <fo:table-column column-width="50%"/>
+ <fo:table-body>
+ <fo:table-row>
+ <fo:table-cell border="solid 2mm darkblue">
+ <fo:block>Cell 1/1</fo:block>
+ </fo:table-cell>
+ <fo:table-cell border="solid 2mm darkblue">
+ <fo:block>Cell 2/1</fo:block>
+ </fo:table-cell>
+ </fo:table-row>
+ <fo:table-row>
+ <fo:table-cell border="solid 2mm darkblue">
+ <fo:block>Cell 1/2</fo:block>
+ </fo:table-cell>
+ <fo:table-cell border="solid 2mm darkblue">
+ <fo:block>Cell 2/2</fo:block>
+ </fo:table-cell>
+ </fo:table-row>
+ </fo:table-body>
+ </fo:table>
+
+ <fo:table table-layout="fixed" inline-progression-dimension="100%" space-before="2mm">
+ <fo:table-column column-width="50%"/>
+ <fo:table-column column-width="50%"/>
+ <fo:table-body color="white">
+ <fo:table-row>
+ <fo:table-cell background-color="darkgreen">
+ <fo:block>Cell 1/1</fo:block>
+ </fo:table-cell>
+ <fo:table-cell background-color="darkgreen">
+ <fo:block>Cell 2/1</fo:block>
+ </fo:table-cell>
+ </fo:table-row>
+ <fo:table-row>
+ <fo:table-cell background-color="darkgreen">
+ <fo:block>Cell 1/2</fo:block>
+ </fo:table-cell>
+ <fo:table-cell background-color="darkgreen">
+ <fo:block>Cell 2/2</fo:block>
+ </fo:table-cell>
+ </fo:table-row>
+ </fo:table-body>
+ </fo:table>
+ </fo:flow>
+ </fo:page-sequence>
+</fo:root>