Digital image colorimetry on smartphone for chemical analysis: A review

Digital image colorimetry (DIC) on smartphone is regarded as a powerful, fast and low-cost analysis method to measure target analyte with color changes of digital image obtained by the built-in camera. We summarized the basic procedure of DIC, the color spaces (RGB, CMYK, HSB/HSL, CIE XYZ, L*a*b*, and YUV), the principal architectures (tools for capturing image, lighting conditions, and color quantification APPs and DIC APPs), and current status of DIC on smartphone in analysis of metals/heavy metals, herbicides, pesticides, antibiotics, biological and medical indicators, natural compounds, and bacteria/viruses. The advantages and disadvantages of DIC are also revealed. Nowadays, DIC on smartphone must be further refined with controlled geometry and standard lighting sources to become robust and reliable analytical procedures. And it will be improved in the near future with the continuous development of smartphones owing to the rapid development of smartphone’s camera technology and the continuous optimization of related software.