Using PyimageJ to collect width by height for individual objects.

Hello! I have been playing around with `pyimagej` by completing the tutorial notebooks but I have ran into a few errors. I am reaching out for help and to see if anyone has done similar work and maybe have used different programs or code.

A little background of what I am trying to do: I am currently trying to obtain the width and height of a singular object on an image, with the end goal of creating a batch system that allows me to insert the image into my code and obtain the dimensions automatically.

I have had luck using `ImageJ` by using the `analyzing particles` feature.

This is my process for Image J:

Convert cropped images to a stack:
- process>binary>make binary
- process>binary>watershed to separate overlapping leaves (confirm visually that this does not change major/minor axis lengths for each image)
- analyze particles:
size: 10-infinity
circularity 0.5-1.00
show: outlines
CHECK: display results, summarize, include holes. do NOT select "in situ show" Check outline drawings and adjust analyze particles settings as necessary. Use width and height measurements for leaf max width and height

Per the tutorial I first ran:
```python
# HACK: # HACK: Work around ImagePlus#show() failure if no ImagePlus objects are already registered.
if ij.WindowManager.getIDList() is None:
ij.py.run_macro('newImage("dummy", "8-bit", 1, 1, 1);')
```
which returns:
```
---------------------------------------------------------------------------
ImportError Traceback (most recent call last)
Cell In[13], line 2
1 # HACK: # HACK: Work around ImagePlus#show() failure if no ImagePlus objects are already registered.
----> 2 if ij.WindowManager.getIDList() is None:
3 ij.py.run_macro('newImage("dummy", "8-bit", 1, 1, 1);')

File ~/anaconda3/envs/pyimagej/lib/python3.10/site-packages/imagej/__init__.py:801, in GatewayAddons.WindowManager(self)
795 @property
796 def WindowManager(self):
797 """Get the original ImageJ `WindowManager` class.
798
799 :return: The `ij.WindowManager` class.
800 """
--> 801 return self._access_legacy_class("ij.WindowManager")

File ~/anaconda3/envs/pyimagej/lib/python3.10/site-packages/imagej/__init__.py:804, in GatewayAddons._access_legacy_class(self, fqcn)
803 def _access_legacy_class(self, fqcn: str):
--> 804 self._check_legacy_active(f"The {fqcn} class is not available.")
805 class_name = fqcn[fqcn.rindex(".") + 1 :]
806 property_name = f"_{class_name}"

File ~/anaconda3/envs/pyimagej/lib/python3.10/site-packages/imagej/__init__.py:819, in GatewayAddons._check_legacy_active(self, usage_context)
817 def _check_legacy_active(self, usage_context=""):
818 if not self.legacy or not self.legacy.isActive():
--> 819 raise ImportError(
820 "The original ImageJ is not available in this environment. "
821 f"{usage_context} See: "
822 "https://github.com/imagej/pyimagej/blob/main/doc/Initialization.md"
823 )

ImportError: The original ImageJ is not available in this environment. The ij.WindowManager class is not available. See: https://github.com/imagej/pyimagej/blob/main/doc/Initialization.md
```
As per the next tutorial:
```
# open test image and convert from Dataset to ImagePlus
dataset = ij.io().open('/Users/brandonulin/Downloads/Hognut/test_scan/test3.jpeg')
imp = ij.py.to_imageplus(dataset)

# show the image
ij.py.show(imp)
```
which returns:
```
[java.lang.Enum.toString] [INFO] Populating metadata
[java.lang.Enum.toString] [INFO] Populating metadata
[java.lang.Enum.toString] [INFO] Populating metadata
[java.lang.Enum.toString] [INFO] Populating metadata
[java.lang.Enum.toString] [INFO] Populating metadata
[java.lang.Enum.toString] [INFO] Populating metadata
---------------------------------------------------------------------------
ImportError Traceback (most recent call last)
Cell In[14], line 3
1 # open test image and convert from Dataset to ImagePlus
2 dataset = ij.io().open('/Users/brandonulin/Downloads/Hognut/test_scan/test3.jpeg')
----> 3 imp = ij.py.to_imageplus(dataset)
5 # show the image
6 ij.py.show(imp)

File ~/anaconda3/envs/pyimagej/lib/python3.10/site-packages/imagej/__init__.py:485, in ImageJPython.to_imageplus(self, data)
476 def to_imageplus(self, data):
477 """Convert the data into an ImageJ ImagePlus.
478
479 Converts a Python image (e.g. xarray or numpy array) or Java image (e.g.
(...)
483 :return: An ij.ImagePlus.
484 """
--> 485 self._ij._check_legacy_active("Conversion to ImagePlus is not supported.")
486 return self._ij.convert().convert(self.to_dataset(data), jc.ImagePlus)

File ~/anaconda3/envs/pyimagej/lib/python3.10/site-packages/imagej/__init__.py:819, in GatewayAddons._check_legacy_active(self, usage_context)
817 def _check_legacy_active(self, usage_context=""):
818 if not self.legacy or not self.legacy.isActive():
--> 819 raise ImportError(
820 "The original ImageJ is not available in this environment. "
821 f"{usage_context} See: "
822 "https://github.com/imagej/pyimagej/blob/main/doc/Initialization.md"
823 )

ImportError: The original ImageJ is not available in this environment. Conversion to ImagePlus is not supported. See: https://github.com/imagej/pyimagej/blob/main/doc/Initialization.md
```
The last tutorial I tried before reaching out had to do with analyzing particles like on `ImageJ` but it also did not work. Here is the code:
```
imp = ij.openImage("/Users/brandonulin/Downloads/Hognut/test_scan/test3.jpeg")
imp2 = Duplicator().run(imp, 3, 3, 1, 1, 14, 14)
IJ.run(imp, "Enhance Contrast", "saturated=0.35")
IJ.setAutoThreshold(imp, "Moments dark")
IJ.run(imp, "Analyze Particles...", " show=Overlay display clear")
```
Which returns:
```
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
Cell In[24], line 1
----> 1 imp = ij.openImage("/Users/brandonulin/Downloads/Hognut/test_scan/test3.jpeg")
2 imp2 = Duplicator().run(imp, 3, 3, 1, 1, 14, 14)
3 IJ.run(imp, "Enhance Contrast", "saturated=0.35")

AttributeError: 'net.imagej.ImageJ' object has no attribute 'openImage'

Simple
```

Like I started off with, if anyone has experience with collecting width and heights of objects within an image using either `pyimagej` or other programs please let me know. Any and all help would be greatly appreciated as I am excited to use this package for my summer research project. I have also included the image of what I am trying to gather the dimensions of.


Start with the pyimagej Initialization documentation referenced in the traceback and the tutorial notebooks that use WindowManager, to_imageplus, and particle analysis. Reproduce the reported ImportError and AttributeError with the shown examples, then establish whether the documented initialization and object-measurement workflow works end to end.

Written by the indexing model from the issue text.