Fig. 2

Assignment of foreground pixels using Z-score thresholding a. Kernel density plots were made of Z-scores for pixels obtained from 21 images of malaria thick film specimens. Z-scores were calculated from the distribution of pixel brightness values from the combined 21 images (average brightness = 0.5640; SD = 0.0849). Foreground objects were assigned by manual inspection of the images and were delimited by drawing circles around them. All pixels within the boundaries of these objects were assigned as foreground pixels, and all others outside were assigned as background. The Z-score threshold of −1 (indicated by the dashed line) was incorporated into the algorithm for automatic assignment of foreground pixels for EDoF composite image construction. b Representative specimen showing foreground pixel assignment using different Z-score thresholds. The original image captured from the Giemsa-stained specimen is shown on the far right. The adjacent panels show the background masked areas in white and the foreground in black using Z-score thresholds of −0.5, −1, −1.5, and −2