Measurement of food volume based on single 2-D image without conventional camera calibration

Food portion size measurement combined with a database of calories and nutrients is important in the study of metabolic disorders such as obesity and diabetes. In this work, we present a convenient and accurate approach to the calculation of food volume by measuring several dimensions using a single 2-D image as the input. This approach does not require the conventional checkerboard based camera calibration since it is burdensome in practice. The only prior requirements of our approach are: 1) a circular container with a known size, such as a plate, a bowl or a cup, is present in the image, and 2) the picture is taken under a reasonable assumption that the camera is always held level with respect to its left and right sides and its lens is tilted down towards foods on the dining table. We show that, under these conditions, our approach provides a closed form solution to camera calibration, allowing convenient measurement of food portion size using digital pictures.