1 / Capture
Load a UV image
Place the petri dish inside the guide. Avoid direct glare from the UV source.
For comparable results, use a dark box, fixed distance, fixed camera settings, and a consistent sample layer.
2 / Region of interest
Position the sample
The ROI is the circular sample area used for all descriptors. Adjust the sliders so the circle stays inside the biochar and excludes the dish rim.
4 / Results
Quantitative descriptors
How these values are calculated
Mean and median intensity use grayscale pixels inside the circular ROI. Bright-area fraction uses the selected threshold. Hotspots are connected bright components after small-noise filtering. Heterogeneity is the coefficient of variation. Entropy uses the grayscale histogram. Radial uniformity compares average intensity across concentric rings.
Capture guidance
Use a fixed 365 nm UV source and keep the camera distance and angle consistent.
Use a dark enclosure and prevent the phone from seeing the UV lamp directly.
Do not treat these descriptors as a chemical identification without independent validation.