Abstract: This paper presents a study done on the use digital image processing techniques to detect, quantify and classify plant diseases from digital images. Although disease symptoms can manifest in any part of the plant, only methods that explore visible symptoms in leaves are considered. This was done for two main reasons: to limit the length of the project and because methods dealing with stems, roots, seeds and fruits have some peculiarities that would warrant a specific survey. The selected proposals throw light into three classes according to their objective: detection, severity quantification, and classification. Each of those classes, in turn, varies according to the main technical solution used in the algorithm. This paper is expected to provide a comprehensive and accessible overview of this important field of research.

Keywords: Digital Image Processing, Image Acquisition, Image Pre-processing, Image Segmentation, Feature Extraction, Classification, Disease Diagnosis.