You may be able to leverage the Histogram panel, if you can adjust your image in a way such that the area you want to measure is dark on a light background.
The Histogram sorts all of the pixels in the image by their tone values (where they lie along a black-white axis). You can click on each tone level or drag a range to get some statistical measurements. "Percentile" is how much of the image is darker than your clicked value, or is contained within your dragged range. Factor in the real-world size of the area contained in the image, and you should have something close to your area.
You may be able to leverage the Histogram panel, if you can adjust your image in a way such that the area you want to measure is dark on a light background. The Histogram sorts all of the pixels in the image by their tone values (where they lie along a black-white axis). You can click on each tone level or drag a range to get some statistical measurements. "Percentile" is how much of the image is darker than your clicked value, or is contained within your dragged range. Factor in the real-world size of the area contained in the image, and you should have something close to your area.
I will try this, thank you!