1. A method for locating blobs in an image, the method comprising: forming a blob reference mask from the image, the blob reference mask including a portion indicating a portion of the image containing a first blob, if any; forming a reference image from the image, the reference image corresponding to the image; forming a modified image from the image by replacing the portion of the image containing the first blob, if any, with a portion of the reference image corresponding to the portion of the image; and locating a second blob in the image in response to the modified image.