The aim of this article is to present a new online image analysis based method for monitoring the Crystal Size Distribution (CSD) during batch solution crystallization processes. An in-situ imaging probe allows real time acquisition of 2D images of particles during the batch process. From these images, restoration and segmentation algorithms are performed in order to identify the particles. Thereafter, mathematical morphology enables to get geometrical and morphological particle measurements. Therefore, the CSD can be deduced all along the time of the crystallization process (until moderate solid concentration).