Hi,
Refer to the workflow proposed by the MathWorks Support Team to store an image or figure into a database from MATLAB using the Database Toolbox in this MATLAB Answers post - https://www.mathworks.com/matlabcentral/answers/97768-how-do-i-insert-an-image-or-figure-into-a-database-using-the-database-toolbox-in-matlab.
This workflow can be used on “PNG” formatted images as well as the function “imread” can take “PNG” images as input. Refer to the following link for more information about the function “imread” - https://www.mathworks.com/help/matlab/ref/imread.html#btnczv9-1_sep_mw_88d166d0-41d5-499a-ac3c-ef35689b87eb:~:text=Example%3A%20%22C%3A%5CmyFolder%5CmyImage.png%22.
Hope that helps!