when i use imagemagic montage by im4java,the -tile row x clos option throws a file unable to open exception - im4java

Question

./magick -version
Version: ImageMagick 7.0.8-46 Q16 x86_64 2019-05-19
https://imagemagick.org
Copyright: © 1999-2019 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI
Delegates (built-in): bzlib freetype jng jpeg png tiff xml zlib
im4java-1.4.0.jar
when i run the command,it throws a exception
org.im4java.core.CommandException: org.im4java.core.CommandException: magick: unable to open image ' 9x4': No such file or directory # error/blob.c/OpenBlob/3497.
at org.im4java.core.ImageCommand.run(ImageCommand.java:219)
at dsl.Tools.ImageDealTool.ex(ImageDealTool.java:246)
at dsl.Tools.ImageDealTool.montage(ImageDealTool.java:122)
at dsl.Tools.ImageDealService.imageLayout(ImageDealService.java:106)
at dsl.controller.ImageDealController$2.run(ImageDealController.java:133)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.im4java.core.CommandException: magick: unable to open image ' 9x4': No such file or directory # error/blob.c/OpenBlob/3497.
at org.im4java.core.ImageCommand.finished(ImageCommand.java:253)
at org.im4java.process.ProcessStarter.run(ProcessStarter.java:314)
at org.im4java.core.ImageCommand.run(ImageCommand.java:215)
... 7 more
files.stream().forEach(s->{
if (!s.equals("transparency")) {
op.addImage(PIC_MODEL_PATH+s+".png");
}else {
op.addImage(MODEL_PATH+s+".png");
}
});
op.geometry(+0,+0);
op.addRawArgs("-geometry","+0+0");
op.addRawArgs("-background","none");
op.addRawArgs("-tile",cols+"x"+rows);
op.addImage(ARRAY_RESULT_PATH+result+".png");
ImageCommand cmd = new MontageCmd(false);
cmd.run(op);
why the -tile 9x4 option not work?