Drop-on-demand (DoD) inkjet printing is used in precise-dosage deposition applications where consistent drop volume is important. Existing drop volume regulation in DoD inkjet printing are mainly open-loop approaches that are not effective in compensating for uncertainties during high volume printing applications. In this paper, a real-time image-based feedback system is proposed for regulating drop volume. A rotational symmetric model estimates drop volume from real-time images. Estimation accuracy is analyzed and validated. A simple feedback controller is developed to regulate drop volume. Experimental results validate the effectiveness of the proposed approach.