Current noninvasive breathing measurement approaches contain electrical impedance tomography, respiratory inductance plethysmography, capnography, tracheal sound measurement, spirometers, respiratory belt transducer, and electrocardiography-derived method.10–12 Nonetheless, the above devices carry out breathing rate estimation in a contact way, which leads to discomfort, stress, and even to soreness of a subject.12 Increasing daily and clinical demands for contactless and unobtrusive yet accurate breathing measurement alternatives in uncontrolled environments have spurred considerable interest among researchers on the application of innovative tools for breathing observation solutions. Doppler radar was used in the noncontact and through-clothing breathing evaluation via the measurement of chest wall motion.13 This method is yet limited by the potential radiation and high sensitivity to motion artifacts. A laser Doppler vibrometer determined the breathing rate by the assessment of the chest wall displacements;14 however, its result will not be accurate when, for example, improper measurement points are selected on the thoracic surface. Min et al. developed an ultrasonic proximity sensing approach to measure breathing signatures by means of calculating time intervals between the transmitted and received sound waves during the abdominal wall fluctuation.15 The subjects under this test are required to remain still and refrain any other movements. In addition, owing to the mature image processing techniques, visible imaging sensors have attracted much attention for breathing evaluations.16,17 Shao et al. determined the breathing patterns using the cameras in the visible region to track the small shoulder movements associating with breathing.18 Although the random body movements can be corrected by the motion-tracking algorithm, breathing rate estimation based on visible imaging is by nature sensitive to the slight movements, thus not being appropriate for the long-term monitoring.