| 摘要 |
A method of detecting staining on a media item is described. The method comprises: receiving an image of the media item (step 418), where the image comprises a plurality of pixels having different intensity values within a range of intensity values. Central weighting is applied to the received image to expand a central portion of the range of intensity values (step 422). A threshold is applied to each pixel in the centrally-weighted image (502) to transform each pixel to a binary value thereby creating an evaluation image (504) comprising a plurality of pixels, each having one of two possible values (step 424). A difference image (510) is created by comparing a pixel in the evaluation image (504) with a pixel in a binary reference image (206) at a corresponding spatial location (step 430), so that the difference image (510) includes (i) a stain pixel at each spatial location in which a pixel in the evaluation image (504) has a low intensity pixel and the corresponding pixel in the binary reference image (206) has a high intensity pixel, and (ii) a non-stain pixel at all other spatial locations. The media item is identified as stained (step 434) in the event that the difference image meets a staining criterion (step 432). |
