Htykuut

I am looking for an automated way to measure leaf area from a picture taken by a general camera. I would like to use my phone camera since it would make the job easier. I can use ImageJ but I believe there could be a faster way to do it.

So far I know the following features:

• pixel resolution ( 3042 x 4032 )


• focal length of the camera ( 26 mm equivalent )


• camera sensor ( 7.01 mm x 5.79 mm )


• height of camera ( 25 cm )

I'm asking for R because I have been working on it for a while and I wouldn't change software.
I tried some packages such as EBIimage and magick but I didn't go that far. I can load a picture but I cannot work out any calculation from number of pixel.

Anyone ever tried to do something similar in R?

Please comments and answers would be very appreciated.

Thank you.

Use calibrators.

1. Take three (or more) sheets of paper with different area.


2. Then take pictures of the sheets at the same distance (25 cm)*.


3. Calculate the pixel area of each sheet.


4. Divide metric area by pixel area of each sheet. Let's call this number k.


5. Calculate the average k.


6. Calculate the metric area of the leaf by using this formula: metric_area = k * pixel_area.

*You can also use calibrators for different distances from the leaf. That's a bit more complicated, but probably more precise than calculating.

Be aware that lens with focal length of 26mm will have some distortion on the edges of the image. You would be better off if you used 50 mm or more lens. Otherwise, always center the leaf on the image and leave some space around the leaf.

That's how I would do it. I would use Python and scikit-image instead of R, I find it easier and better documented for image analysis.