1. Drop Shape Analysis Quick Start Guide with ImageJ
Chris Roske, 8/19/2018

2. Requirements
ImageJ version 1.46 with Java. (Newer versions have issues with the plug-in.)
For the 64-bit version used to produce this instruction set:
setup2.exe
Download the drop_analysis.zip, available here:
Extract the folder (drop_analysis) from drop_analysis.zip into the “plugins” folder of ImageJ. In my case, the plugin folder is located at: C:\Program Files (x86)\ImageJ\plugins
Start ImageJ
Verify the presence of “drop_analysis” in the Plugins

3. Fixing sizing issue with Windows 10
On Windows 10, this version of ImageJ has issues with how the operating system handles graphics related to the GUI scailing.
Locate the ImageJ.exe binary, for me located here: C:\Program Files (x86)\ImageJ
Right click on ImageJ.exe, pick Properties from the drop-down menu. Choose the Compatibility tab. Check “Override high DPI scaling behavior” and select “Scaling performed by System”. Click apply and viola for next execution.
Abnormally small size
Normal size

4. Steps for using Drop Snake
Freshly start ImageJ (plug-in is finicky, therefore you may need to close and start a new instance of ImageJ for best results on each image or attempt you wish to analyze).
Drag-and-drop image onto ImageJ.
Within ImageJ, select the “Plugins” from the menu, then select “drop_snake”, and “Drop Analysis – Dropsnake”.
The menu within ImageJ will update with icons from the plugin. Use the blue cursor to add points for the curve trace. Start at the left-interface between the reflection and the droplet. Left-click along the droplet’s boundary going clockwise in a monotonic fashion. More points help the curve fit, but use 7 as a minimum.
Once your addition of points reaches the right-hand interface, double click with left mouse button to indicate completion of manual trace. An initial projection of the reflection will appear.
Click the “Snake the Curve” button to initiate curve fitting.
Move your mouse over to the image to force the screen update necessary to see the red fit results.
Ideally, you accept the curve by click the green arrow head “Accept red snake”. A dialog popup appears, press “Select” for accepting the red curve.
Now you can see the water contact angle, in blue, on the top left of the image or in the dialog menu behind the image.

5. Animation illustrating steps

6. Trouble with your specific image?
Make sure you convert the image to 8-bit grayscale. To do so, once you drag-and-drop the image into ImageJ, select “Image”, then pick “Type”, and finally select “8-bit”.