Add is_rgb_merged method to check if image is RGB

src/imagej/_java.py

@@ -166,6 +166,10 @@ def ImgView(self):
     def ImgLabeling(self):
         return "net.imglib2.roi.labeling.ImgLabeling"
 
+    @JavaClasses.java_import
+    def IntegerType(self):
+        return "net.imglib2.type.numeric.IntegerType"
+
     @JavaClasses.java_import
     def Named(self):
         return "org.scijava.Named"

src/imagej/metadata/__init__.py

@@ -17,6 +17,34 @@ def _python_metadata_to_imgplus_metadata(py_metadata: dict):
     return sj.to_java(py_metadata['imagej'])
 
 
+def is_rgb_merged(img: "jc.ImgPlus") -> bool:
+    """
+    Check if the ImgPlus is RGB merged.
+
+    :param img: An input net.imagej.ImgPlus
+    :return: bool
+    """
+    e = img.firstElement()
+    # check if signed
+    if e.getMinValue() < 0:
+        return False
+    # check if integer type
+    if not isinstance(e, jc.IntegerType):
+        return False
+    # check if bits per pixel is 8
+    if e.getBitsPerPixel() != 8:
+        return False
+    # check for channel dimension (returns -1 if missing)
+    ch_index = img.dimensionIndex(jc.Axes.CHANNEL)
+    if ch_index < 0:
+        return False
+    # check if channel dimension is size 3 (RGB)
+    if img.dimension(ch_index) != 3:
+        return False
+
+    return True
+
+
 def create_xarray_metadata(img: "jc.ImgPlus") -> dict:
     """
     Create the ImageJ xarray.DataArray metadata.