Low-cost device for the acquisition of digital images: Application in wine analysis

Chemical analyses based on digital images have been widely investigated due to their non-invasive character and simplicity on the measurement. Based on a bibliographic survey, it is possible to notice the importance of controlling instrumental and structural parameters for image acquisition, which can compromise the repeatability and reproducibility of the analyses. However, despite the remarkable progress in literature, the role of many of these parameters has not yet been thoroughly unraveled. Another, more practical, limitation concerning image acquisition is related to the high cost involved in accessing more robust instruments. To circumvent these limitations, a low-cost prototype was built to evaluate conditions that directly influence the quality of the digital images. Thus, an image acquisition system based on a Raspberry Pi (R) 4 4 GB (a single board computer) coupled with electronic components (luminosity and temperature sensor) and a Pi Camera (R) 5MP was designed. To control, integrate and automate the process of acquisition and analysis of digital images, an algorithm in Python programming language was developed. To analyze the images obtained, multivariate tools were used for exploratory analyses. And the results were validated (repeatability, reproducibility and robustness) by evaluating the similarities of the colors (Euclidean distance of the predominant intensity between the colorgrams and the comparison of the cosines between the histograms) and compared to those obtained by spectrophotometry in the visible region.