From high-quality analogue images that are properly digitized, many dimensional and shape-related measurements can be extracted using image processing techniques. These measurements play a crucial role across various domains, including the verification of dimensional tolerances in mechanical components, quality control in industrial manufacturing, support for civil engineering applications, and processes such as product design and reverse engineering. Additional applications extend to medical diagnostics, physical and materials analysis, precision agriculture, the development of digital twins, and the documentation and study of artworks. This chapter presents the foundational principles of performing 2D measurements through image-based methods. It addresses critical elements such as appropriate lighting strategies, core image processing algorithms for edge detection, and procedures for computing distances between points along edges to determine object dimensions. Furthermore, it explores techniques for detecting and analyzing key points, often referred to as blobs, examining their features, characteristic “signatures,” shapes, and classical geometric descriptors.