ImagePlus conversion leads to multiple compatible inputs being listed

[imagejan]

Consider this Groovy script (run after opening e.g. the Blobs sample image):

#@ ObjectService os
#@ ConvertService cs

import ij.ImagePlus
import net.imagej.Dataset
import net.imagej.ImgPlus
import net.imagej.display.ImageDisplay
import ij.WindowManager

imp = WindowManager.getActiveImage()

def printAvailableObjects(type) {
    println "       $type direct:"
    os.getObjects(type).each {
        println "           --- ${it.class} $it"
    }

    println "       $type converted:"
    cs.getCompatibleInputs(type).each {
        println "           --- ${it.class} $it"
    }
}

println "***** Before conversion:"
printAvailableObjects(ImagePlus.class)

img = cs.convert(imp, Dataset.class)

println "***** After conversion:"
printAvailableObjects(ImagePlus.class)

null

which will output:

***** Before conversion:
        class ij.ImagePlus direct:
        class ij.ImagePlus converted:
            --- class net.imagej.legacy.convert.ImageTitleToImagePlusConverter$ImageTitle blobs.gif
***** After conversion:
        class ij.ImagePlus direct:
        class ij.ImagePlus converted:
            --- class net.imagej.legacy.convert.ImageTitleToImagePlusConverter$ImageTitle blobs.gif
            --- class net.imagej.DefaultDataset blobs.gif
            --- class net.imagej.display.DefaultImageDisplay [net.imagej.display.DefaultDatasetView@50305626]

Consistently, when using a script like this one:

#@ ImagePlus imp1
#@ ImagePlus imp2

... three options will be shown for each parameter, despite a single image being open (because the AbstractInputHarvester uses the same mechanism to retrieve compatible inputs).

[imagejan]

With a different variation of these scripts, it can happen that a reference to a Dataset and its DefaultImageDisplay remains present even if all image windows have been closed.

To reproduce:

1. Run this Groovy script:

   
   #@ ObjectService os
   #@ ConvertService cs
   #@ OpService ops
   #@ DatasetService ds
   #@ UIService ui

import ij.ImagePlus import net.imagej.Dataset import net.imagej.ImgPlus import net.imagej.display.ImageDisplay import ij.WindowManager

img = ops.create().img([32, 64] as int[])

def printAvailableObjects(type) { println " $type direct:" os.getObjects(type).each { println " --- ${it.class} $it" }

println "       $type converted:"
cs.getCompatibleInputs(type).each {
    println "           --- ${it.class} $it"
}

}

println "***** Before showing:" printAvailableObjects(ImagePlus.class)

ui.show(img)

println "***** After showing:" printAvailableObjects(ImagePlus.class)

null

<details>
<summary>Output (as expected)</summary>

Before showing: class ij.ImagePlus direct: class ij.ImagePlus converted: After showing: class ij.ImagePlus direct: class ij.ImagePlus converted: --- class net.imagej.legacy.convert.ImageTitleToImagePlusConverter$ImageTitle --- class net.imagej.DefaultDataset --- class net.imagej.display.DefaultImageDisplay [net.imagej.display.DefaultDatasetView@670929a6]

</details>

2. Run this second script, make some choice for the inputs, and click OK:

```groovy
#@ ImagePlus imp1
#@ ImagePlus imp2

3. Close the image window

4. Run the script from step 1.) again, and observe this output:

***** Before showing:
        class ij.ImagePlus direct:
        class ij.ImagePlus converted:
            --- class net.imagej.DefaultDataset <unnamed data>
            --- class net.imagej.display.DefaultImageDisplay [net.imagej.display.DefaultDatasetView@6968dbc3]
***** After showing:
        class ij.ImagePlus direct:
        class ij.ImagePlus converted:
            --- class net.imagej.legacy.convert.ImageTitleToImagePlusConverter$ImageTitle 
            --- class net.imagej.DefaultDataset <unnamed data>
            --- class net.imagej.DefaultDataset <unnamed data>
            --- class net.imagej.display.DefaultImageDisplay [net.imagej.display.DefaultDatasetView@6968dbc3]
            --- class net.imagej.display.DefaultImageDisplay [net.imagej.display.DefaultDatasetView@3863b7a8]