From 7489d27823f8f873655839583807ddea177cb137 Mon Sep 17 00:00:00 2001
From: Cameron Lloyd <lloyd@med.unideb.hu>
Date: Sat, 14 Jun 2025 23:48:01 +0100
Subject: [PATCH] fix: avoid saving empty .zip archive

---
 cellpose/io.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cellpose/io.py b/cellpose/io.py
index 48184e65..edaa7280 100644
--- a/cellpose/io.py
+++ b/cellpose/io.py
@@ -648,6 +648,10 @@ def save_rois(masks, file_name, multiprocessing=None):
     Returns:
         None
     """
+    if masks.max() == 0:
+        io_logger.warning("no masks found, will not save ImageJ ROIs to .zip archive")
+        return
+
     outlines = utils.outlines_list(masks, multiprocessing=multiprocessing)
     nonempty_outlines = [outline for outline in outlines if len(outline)!=0]
     if len(outlines)!=len(nonempty_outlines):