How to increase the GUI font size?

Dear all,
I’m using Fiji on Linux (Slackware64, KDE). My problem is that the font size in the GUI looks so tiny that it is very difficult to read the menus.
Is there a way to change the interface’s font size? or maybe an option to scale the complete GUI?

My screen is configured at 3200x1800 and 276ppi

Thank you in advance,

See this ImageJ mailing list thread from October.

In short: there is no easy way now (though you could peruse this article, or use OS X or Windows 10 instead). But it looks like HiDPI will work out of the box with Java 9, which is great news.

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Thank you for your reply. I customized KDE for HiDPI and it works fine for almost all applications but Fiji. I think, by now I only have to wait for Java 9, I hope it will solve the problem. Meanwhile, I can work in another machine.

Thanks again!

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Hey there!

I had the same problems with ImageJ on my 14" WQHD display, read Curtis’ comment here, downloaded the early access JRE9 from here: Java 9 early access and indeed, it fixed the scaling issue. My system is running on Win 10 64-bit.

I hope this will help many others here.
Thanks a lot Curtis!

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Just a quick note for those of you using Linux and interested in Java 9 as a possible solution: as of this writing, it does not work yet, at least on my Ubuntu 16.04 system. From a recent ImageJ mailing list thread:

Is anybody successfully using Fiji with Java9 on linux?

I gave it a shot yesterday as well, and encountered similar problems. The ImageJ Launcher passes a couple of flags to Java which are no longer supported by Java 9. It is possible to prune out those flags:

$(./ImageJ-linux64 --dry-run | sed 's/-Xincgc //' | sed 's/-XX:PermSize=128m //')

However, this is not enough: when ImageJ2 spins up, it tries to use a library called Javassist to patch/enhance the ImageJ1 code, and this process fails spectacularly (over 4000 lines of errors) under Java 9. So unfortunately, ImageJ2 is not usable with Java 9 yet.

Let’s try vanilla ImageJ1!

java -jar /path/to/

But on my system, that doesn’t work either; I get:

# A fatal error has been detected by the Java Runtime Environment:
#  SIGSEGV (0xb) at pc=0x00007f020abed009, pid=3702, tid=3703
# JRE version: OpenJDK Runtime Environment (9.0) (build 9-internal+0-2016-04-14-195246.buildd.src)
# Java VM: OpenJDK 64-Bit Server VM (9-internal+0-2016-04-14-195246.buildd.src, mixed mode, tiered, compressed oops, serial gc, linux-amd64)
# Problematic frame:
# C  []  JNU_GetEnv+0x19

So it seems Java 9 still needs to bake for a bit longer.

Edit: Actually, I tested with a too-old version of Java 9. With a recent version, you can start ImageJ1, and it does scale on HiDPI. So this is good news! I will work on fixing ImageJ2 to work with Java 9 as time allows.