Abstract: Blobs are detected in an image using closed curves having a predetermined shape such as a circle. Positions in the image are analysed. The size is determined at which there is a maximum in the differential of the average intensity around a closed curve with respect to the size of the closed curve. Detection scores are derived, representing the proportion of rays, out of a plurality of rays crossing a closed curve of the determined size, along which the intensity differential across the closed curve exceeds a contrast threshold. Detection of blobs is performed on the basis of the detection scores exceeding a threshold. Pixels of a detected blob are segmented for calculation of a centroid using a blob-separation threshold which is the average intensity around the closed curve of the determined size. The technique allows accurate and rapid detection of blobs of the predetermined shape.

Abstract: Blobs are detected in an image using closed curves having a predetermined shape such as a circle. Positions in the image are analysed. The size is determined at which there is a maximum in the differential of the average intensity around a closed curve with respect to the size of the closed curve. Detection scores are derived, representing the proportion of rays, out of a plurality of rays crossing a closed curve of the determined size, along which the intensity differential across the closed curve exceeds a contrast threshold. Detection of blobs is performed on the basis of the detection scores exceeding a threshold. Pixels of a detected blob are segmented for calculation of a centroid using a blob-separation threshold which is the average intensity around the closed curve of the determined size. The technique allows accurate and rapid detection of blobs of the predetermined shape.