Current OpenJDK can load src/etc/testcases/taskdefs/optional/image/src/badimage.jpg the test image because it is treated as a CMYK image (with four bands). As a result, the scaling operation fails at a later point:

[junit] but: was "Created dir: /builddir/build/BUILD/apache-ant-1.10.9/build/testcases/tmp/testoutput_1805_mainProcessing File: /builddir/build/BUILD/apache-ant-1.10.9/src/etc/testcases/taskdefs/optional/image/src/badimage.jpg Scaling to 44.510384% x 44.510384%java.lang.IllegalArgumentException: Unknown image type 0
[junit] at org.apache.tools.ant.taskdefs.optional.image.ImageIOTask.processFile(ImageIOTask.java:320)
[junit] at org.apache.tools.ant.taskdefs.optional.image.ImageIOTask.processDir(ImageIOTask.java:241)
[junit] at org.apache.tools.ant.taskdefs.optional.image.ImageIOTask.execute(ImageIOTask.java:345)
[junit] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
[junit] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
[junit] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)