13. An image based method generating fine-grain fingerprints for identifying patterns in a rendered image, the method comprising: supplying a rendered document page; scanning the rendered document page one scanline at a time; examining, for each scanline, image pixels of the document; determining at each current pixel location if the current pixel is a member of a new or previously existing blob; using a small neighborhood of pixels around the current pixel to iteratively build up the blob structure and keypoints for the document page; storing, in advance, all possible blob processing actions in an action look-up table; gathering the pixel neighborhood for each current pixel and assembling an address to the action look-up table that defines the action that is to be applied at the current pixel location, based on the configuration of the neighboring pixel values and the previous blob assignments; fetching the appropriate action out of the action look-up table based on the assembled address; executing the fetched action, resulting in the current pixel content being at least one of, (i) added to an existing blob, (ii) having a new blob allocated to the current pixel, or (iii) merging existing blobs together at the pixel location; updating the blob status to reflect the state of the current pixel; determining if the current pixel location is a candidate keypoint; moving to a next pixel location in a scanline under review and repeating the previous steps, and continue moving and repeating the processing until the end of the scanline under review is reached; launching a closed blob process when the end of a scanline is reached to determine if any of the currently open blobs can be closed, wherein a blob can be closed if no new pixels have been added to the blob during the current scanline operation; processing all blobs that can be closed to compute their attributes at the end of a scanline operation; outputting the resulting data and keypoints corresponding to the processed closed blobs at the end of the scanline operation; moving to a next scanline when a final pixel on a preceding scanline has been processed and repeating the above processing steps; and forming distinct visual 2-D fine-grain fingerprints by combining locations of the keypoints identified with the processed closed blobs.
13. An image based method generating fine-grain fingerprints for identifying patterns in a rendered image, the method comprising: supplying a rendered document page; scanning the rendered document page one scanline at a time; examining, for each scanline, image pixels of the document; determining at each current pixel location if the current pixel is a member of a new or previously existing blob; using a small neighborhood of pixels around the current pixel to iteratively build up the blob structure and keypoints for the document page; storing, in advance, all possible blob processing actions in an action look-up table; gathering the pixel neighborhood for each current pixel and assembling an address to the action look-up table that defines the action that is to be applied at the current pixel location, based on the configuration of the neighboring pixel values and the previous blob assignments; fetching the appropriate action out of the action look-up table based on the assembled address; executing the fetched action, resulting in the current pixel content being at least one of, (i) added to an existing blob, (ii) having a new blob allocated to the current pixel, or (iii) merging existing blobs together at the pixel location; updating the blob status to reflect the state of the current pixel; determining if the current pixel location is a candidate keypoint; moving to a next pixel location in a scanline under review and repeating the previous steps, and continue moving and repeating the processing until the end of the scanline under review is reached; launching a closed blob process when the end of a scanline is reached to determine if any of the currently open blobs can be closed, wherein a blob can be closed if no new pixels have been added to the blob during the current scanline operation; processing all blobs that can be closed to compute their attributes at the end of a scanline operation; outputting the resulting data and keypoints corresponding to the processed closed blobs at the end of the scanline operation; moving to a next scanline when a final pixel on a preceding scanline has been processed and repeating the above processing steps; and forming distinct visual 2-D fine-grain fingerprints by combining locations of the keypoints identified with the processed closed blobs. 16. The method according to claim 13 wherein the candidate keypoint locations tend to congregate one candidate keypoint each in the upper-left and bottom-right corners of each character shape, making the resulting candidate useful for estimating various parameters, including average character width and height, baseline position, and text attributes including ascenders and descenders, skew of the page, grouping of characters to form words by measuring the intra-character spacing distance.