Fig. 1

Gradient based algorithm. a The original micrograph with two rosettes, one single pRBC and multiple healthy RBC. b The Prewitt filter is applied and the threshold of the resulting gradient map displayed. c The edges from b are dilated like shown in Fig. 2. d Capsuled parts of the cells are filled. e The diamond shaped erosion filter shrinks the outline of the marked areas to a size comparable to the before detected outermost edges. f The edges are taken as outlines and plotted onto the original image for better visualization