Bug ID: JDK-8212071 Need to set the FreeType LCD Filter to reduce fringing.

Type: Bug
Component: client-libs
Sub-Component: 2d
Affected Version: 11,12

Priority: P3
Status: Resolved
Resolution: Fixed

Submitted: 2018-10-11
Updated: 2019-11-11
Resolved: 2018-10-16

JDK 11	JDK 12	Other
11.0.6-oracleFixed	12 b17Fixed	openjdk8u242Fixed

A fix for JavaFX was just pushed :
  JDK-8188810: Fonts are blurry on Ubuntu 16.04 and Debian 9
  https://bugs.openjdk.java.net/browse/JDK-8188810
which reduces the color fringing of text on Linux distros
which enable cleartype font rendering in their bundled
freetype libraries.
The same fix is needed in OpenJDK/Java 2D

See these discussions :
http://mail.openjdk.java.net/pipermail/openjfx-dev/2018-October/022602.html
http://mail.openjdk.java.net/pipermail/2d-dev/2018-October/009522.html

Fix Request for 8u-dev: the patch from 11u-dev applies without changes (other than the path of course): https://mail.openjdk.java.net/pipermail/jdk8u-dev/2019-October/010530.html
30-10-2019
Fix request 11u (on behalf of Mario Torre): Request backport of this fix for Oracle 11.0.6 parity. Patch needed manual help, RFR: https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2019-October/002054.html
30-10-2019
I have attached the images John referenced in his email : -------- Forwarded Message -------- Subject: Re: [OpenJDK 2D-Dev] Setting the FreeType LCD filter Date: Thu, 11 Oct 2018 12:08:07 -0700 From: John Neffenger <john@status6.com> To: Java 2D List <2d-dev@openjdk.java.net> On 10/11/2018 11:41 AM, Laurent Bourg��s wrote: > Maybe just send text and your diff only and keep images as link on github. Right again. Here's just the text, no attachments, formatted in plain text as best I can. Thank you again for your help, Laurent. The symptoms of the problem are the same as in the link below, but they appear in AWT and Swing applications instead of JavaFX applications. JDK-8188810: Fonts are blurry on Ubuntu 16.04 and Debian 9 https://bugs.openjdk.java.net/browse/JDK-8188810 The description of the problem on the Java side follows. Synopsis: Reduce color fringes in FreeType subpixel rendering The text in Java applications often has severe color fringes when using OpenJDK on Ubuntu and other Debian-based distributions because the JDK fails to set the LCD filter. Adding two lines of code to the file freetypeScaler.c fixed the problem in my tests, without any regression errors for other Linux distributions. The patch is included at the very end of this message. There are some alternatives to setting the filter: �� Bundle the FreeType library by default and always use the new Harmony subpixel rendering technique. This option removes the uncertainty in the library at the expense of an additional 4.6 megabytes to the installed size �� an increase of less than one percent. OpenJDK 12 even includes the latest FreeType 2.9.1, a newer version than the one found on most systems. �� Wait another year and see what changes are made to FreeType,if any, when the ClearType patents expire. This option, though, doesn��t solve the problem that users of Ubuntu and other Debian-based distributions have now. The problem originates in decisions made by the developers of FreeType, Debian, Fedora, and OpenJDK concerning the Microsoft ClearType patents [1]. �� In 2007, FreeType 2.3.0 added a compiler configuration macroto the file ftoption.h named FT_CONFIG_OPTION_SUBPIXEL_RENDERING. If defined, the FreeType library includes patented ClearType techniques in its subpixel rendering. But there��s a catch. When the ClearType methods are enabled,the subpixel rendering is not filtered, which results in severe color fringes. Clients of the FreeType library must make an explicit call to the function FT_Library_SetLcdFilter to apply color filtering. The filter was disabled by default, explained one of its authors, ��toavoid major surprises to existing clients, including libXft and Cairo which already perform some wacky color filtering on top of FreeType.�� In 2009, Debian created a patch to FreeType 2.3.9, named enable-subpixel-rendering.patch, that defines the macro and enables ClearType-style rendering. The change log states, ��This is considered no more or less evil than the bytecode interpreter which we also enable.�� Ubuntu, based on Debian, applies the patch as well. Fedora created the same patch in 2007, named freetype-2.3.0-enable-spr.patch, but does not apply the patch by default. �� In 2017, FreeType 2.8.1 included a new subpixel rendering technique, called Harmony, that is nearly identical in output to the ClearType technique but uses a different algorithm, avoiding the patents. FreeType now uses Harmony subpixel rendering when the ClearType methods are disabled, with no need for clients to set the LCD filter. (This would have been a good time for Debian to remove its subpixel rendering patch.) The latest Fedora Workstation 28 runs FreeType 2.8.0, which does not include Harmony. �� In 2019, the Microsoft ClearType patents expire. So now we have two variants of the FreeType library: one that requires a function call to set the LCD filter in Ubuntu and other distributions based on Debian, and another that doesn��t require the function call in Red Hat Enterprise Linux, Oracle Linux, and other distributions based on Fedora. To demonstrate the problem, I built four versions of the JDK from the latest OpenJDK sources. I built a version that uses the system FreeType library and another that uses the bundled FreeType library. Then I changed the OpenJDK code to set the default LCD filter and built the two versions again. The four builds were named: jdk-12-system-lcdnone jdk-12-system-lcddefault jdk-12-bundled-lcdnone jdk-12-bundled-lcddefault The system library is FreeType 2.8.1 in Ubuntu 18.04.1 LTS, which has the Debian patch applied (ClearType methods enabled), while the bundled library is FreeType 2.9.1 in OpenJDK 12, which uses the library default (ClearType methods disabled). I wrote a simple Java Swing application called FontDemo [2] that displays two text areas with the Adobe Source Code Pro font [3] in TTF and OTF formats (the latest non-variable download). The results are shown in the two images below: fontdemo.png https://raw.githubusercontent.com/jgneff/openjdk-freetype/master/files/fontdemo.png fontdemo-detail.png https://raw.githubusercontent.com/jgneff/openjdk-freetype/master/files/fontdemo-detail.png When using the Ubuntu system FreeType library, setting the LCD filter is critical. The screenshots show the ClearType-style rendering without setting the LCD filter, and after adding the change to set the filter. The ClearType configuration macro is defined in the Ubuntu build of FreeType, so the function to set the filter returns success (0) when called and applies color filtering. When using the OpenJDK bundled FreeType library, setting the LCD filter does nothing. The screenshot shows the FreeType Harmony subpixel rendering, which is the same whether or not the LCD filter is set. The ClearType configuration macro is not defined in the OpenJDK build of FreeType, so the function to set the filter returns FT_Err_Unimplemented_Feature (7) when called and does nothing. The test system I used is a QEMU/KVM guest virtual machine running Ubuntu 18.04.1 LTS (Bionic Beaver) with the details shown below. The display is a 27-inch Dell UltraSharp U2717D monitor with a resolution of 2560 �� 1440 pixels at 109 pixels per inch. ubuntu@bionic:~$ uname -a Linux bionic 4.15.0-36-generic #39-Ubuntu SMP Mon Sep 24 16:19:09 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux ubuntu@bionic:~$ ldd --version ldd (Ubuntu GLIBC 2.27-3ubuntu1) 2.27 ubuntu@bionic:~$ getconf GNU_LIBPTHREAD_VERSION NPTL 2.27 ubuntu@bionic:~$ $HOME/opt/jdk-12-system-lcdnone/bin/java -version openjdk version "12-internal" 2019-03-19 OpenJDK Runtime Environment (build 12-internal+0-adhoc.ubuntu.jdk) OpenJDK 64-Bit Server VM (build 12-internal+0-adhoc.ubuntu.jdk, mixed mode) Below are the full test results using five versions of FreeType built first with the ClearType methods disabled (the default) and then again with them enabled. I ran all 10 libraries under OpenJDK 12, first with no LCD filter and then again after adding the code to set the default LCD filter. No LCD Filter 2008 FreeType 2.3.5 (libfreetype.so.6.3.16) in Ubuntu 8.04 LTS ClearType Off: Grayscale, ClearType On: Mild fringes 2014 FreeType 2.5.2 (libfreetype.so.6.11.1) in Ubuntu 14.04 LTS ClearType Off: Grayscale, ClearType On: Severe fringes 2016 FreeType 2.6.1 (libfreetype.so.6.12.1) in Ubuntu 16.04 LTS ClearType Off: Grayscale, ClearType On: Severe fringes 2018 FreeType 2.8.1 (libfreetype.so.6.15.0) in Ubuntu 18.04 LTS ClearType Off: Harmony, ClearType On: Severe fringes 2019 FreeType 2.9.1 (libfreetype.so.6.16.1) in OpenJDK 12 ClearType Off: Harmony, ClearType On: Severe fringes The OpenJDK does not set the FreeType LCD filter, so there are severe color fringes when using a FreeType library built with the ClearType methods enabled. The only reason the older FreeType 2.3.5 shows mild color fringes is because it uses full hinting, so the glyphs are simply too skinny to see their colors. Default LCD Filter 2008 FreeType 2.3.5 (libfreetype.so.6.3.16) in Ubuntu 8.04 LTS ClearType Off: Grayscale, ClearType On: ClearType filtered 2014 FreeType 2.5.2 (libfreetype.so.6.11.1) in Ubuntu 14.04 LTS ClearType Off: Grayscale, ClearType On: ClearType filtered 2016 FreeType 2.6.1 (libfreetype.so.6.12.1) in Ubuntu 16.04 LTS ClearType Off: Grayscale, ClearType On: ClearType filtered 2018 FreeType 2.8.1 (libfreetype.so.6.15.0) in Ubuntu 18.04 LTS ClearType Off: Harmony, ClearType On: ClearType filtered 2019 FreeType 2.9.1 (libfreetype.so.6.16.1) in OpenJDK 12 ClearType Off: Harmony, ClearType On: ClearType filtered After changing the OpenJDK to set the default LCD filter, there is no version of the FreeType library that shows the severe color fringes. Note that Fedora Workstation 28 includes FreeType 2.8.0 with the ClearType methods disabled, so it displays grayscale anti-aliasing for the OpenJDK whether it sets the LCD filter or not. (FreeType 2.8.0 does not include Harmony.) For background information on LCD filters see Section 2.2.1 [4] of The Raster Tragedy at Low-Resolution, which has an interactive demonstration of the filters used in ClearType (Microsoft), CoolType (Adobe), FreeType (open source), and Quartz 2D (Apple). Hover your mouse over each of the samples in the illustration to remove the filter. Below is the relevant section of the file ftoption.h in FreeType 2.9.1 bundled with OpenJDK 12, edited for formatting: java.desktop/share/native/libfreetype/include/freetype/config/ftoption.h /* Uncomment the line below if you want to activate LCD rendering technology similar to ClearType in this build of the library. This technology triples the resolution in the direction color subpixels. To mitigate color fringes inherent to this technology, you also need to explicitly set up LCD filtering. Note that this feature is covered by several Microsoft patents and should not be activated in any default build of the library. When this macro is not defined, FreeType offers alternative LCD rendering technology that produces excellent output without LCD filtering. / / #define FT_CONFIG_OPTION_SUBPIXEL_RENDERING */ Links [1] http://david.freetype.org/cleartype-patents.html [2] https://github.com/jgneff/openjdk-freetype/blob/master/src/org/status6/FontDemo.java [3] https://github.com/adobe-fonts/source-code-pro [4] http://rastertragedy.com/RTRCh2.htm#Sec21 Patch diff -r 1aa9beac610e src/java.desktop/share/native/libfontmanager/freetypeScaler.c --- a/src/java.desktop/share/native/libfontmanager/freetypeScaler.c Thu Oct 04 16:39:07 2018 +0200 +++ b/src/java.desktop/share/native/libfontmanager/freetypeScaler.c Thu Oct 11 08:30:00 2018 -0700 @@ -38,6 +38,7 @@ #include FT_SIZES_H #include FT_OUTLINE_H #include FT_SYNTHESIS_H +#include FT_LCD_FILTER_H #include "fontscaler.h" @@ -397,6 +398,8 @@ if (errCode == 0) { errCode = FT_Activate_Size(scalerInfo->face->size); } + + FT_Library_SetLcdFilter(scalerInfo->library, FT_LCD_FILTER_DEFAULT); } return errCode;
11-10-2018
Proposed fix : diff -r 1aa9beac610e src/java.desktop/share/native/libfontmanager/freetypeScaler.c --- a/src/java.desktop/share/native/libfontmanager/freetypeScaler.c Thu Oct 04 16:39:07 2018 +0200 +++ b/src/java.desktop/share/native/libfontmanager/freetypeScaler.c Thu Oct 11 08:30:00 2018 -0700 @@ -38,6 +38,7 @@ #include FT_SIZES_H #include FT_OUTLINE_H #include FT_SYNTHESIS_H +#include FT_LCD_FILTER_H #include "fontscaler.h" @@ -397,6 +398,8 @@ if (errCode == 0) { errCode = FT_Activate_Size(scalerInfo->face->size); } + + FT_Library_SetLcdFilter(scalerInfo->library, FT_LCD_FILTER_DEFAULT); } return errCode;
11-10-2018