Automatic quality analysis of a virtual slide (parameter used: blur). A represents the thumbnail of a whole slide image (H&E staining) whose upper third part is in focus and lower two thirds part is totally out of focus. Each thumbnail B to F shows sharp tiles in green and blurry tiles going from white (a little blurry) to red (the most blurry). Out of 43 tiles at 1.25× (B), 83% were detected as non-blank, and 36% were detected as sharp. For C, D, E and F, the respective values were (146 tiles, 2.5×, 86% non-blank, 34% sharp), (493 tiles, 5.0×, 83% non-blank, 33% sharp), (1751 tiles, 10.0×, 77% non-blank, 31% sharp), (6589 tiles, 20.0×, 76% non-blank, 25% sharp). The WSI is thus considered as of insufficient quality in terms of blurriness, for all its magnification levels being under their respective blur assessment thresholds.