Int. J. Computational Vision and Robotics, Vol. 11, No. 5, 2021 461 Copyright © 2021 Inderscience Enterprises Ltd. A review on content-based image retrieval system: present trends and future challenges Narendra Kumar Rout and Mithilesh Atulkar Department of Computer Application, NIT, Raipur, 492010, C.G., India Email: narendrarout@gmail.com Email: matulkar.mca@nitrr.ac.in Mitul Kumar Ahirwal* Department of Computer Science and Engineering, MANIT, Bhopal, 462003, M.P., India Email: ahirwalmitul@gmail.com *Corresponding author Abstract: The issues of getting similar images with better accuracy is now a challenge in content-based image retrieval (CBIR) system due to exponential rising volume of image databases. In CBIR, first of all image features are extracted. Importance of each low level feature is graded by their repute based on citations in various comparable studies. With this, different weight assignment methods for features like individual weightage, equal assignment of weights and other assignment methods employed in the CBIR systems have been reported. However, the weight assignment to the features of the image is calibrated manually based on its importance in doing accurate searches on particular databases. This paper presents a review on CBIR systems and frequently used features with different weight assignment methods. The future challenge identified from this study is, to make the CBIR system automated for assigning weights to image features. Solutions for reported challenge are also suggested. Keywords: content-based image retrieval; CBIR; low level features; feature extraction methods; weight assignment method; image database. Reference to this paper should be made as follows: Rout, N.K., Atulkar, M. and Ahirwal, M.K. (2021) ‘A review on content-based image retrieval system: present trends and future challenges’, Int. J. Computational Vision and Robotics, Vol. 11, No. 5, pp.461–485. Biographical notes: Narendra Kumar Rout is currently pursuing his PhD degree in the Department of Computer Application from National Institute of Technology, Raipur (C.G.), India. He has more than ten years of teaching experience under Biju Patnaik University of Technology, Odisha, India. His research interests include optimisation and image processing, machine learning, and computational intelligence. He has attended various workshop, seminars and conferences.