Abstract: A fingerprint image is divided into blocks of pixels. The blocks are determined to be within the foreground or background of the image. Each of the foreground blocks are assigned a block direction. If an image consists of the complete impression of the fingerprint, there should exist at least one path (ridge), composes of foreground blocks, which lies on both half planes of a coordinate system with an origin at the centroid of the foreground and that comes sufficiently close to the x axis once the path crosses to the second half plane of the coordinate system.

Abstract: A fingerprint image is divided into blocks of pixels. The blocks are also determined to be within the foreground or background of the image. A dryness process determines a mean intensity of pixels within each foreground block, a second mean intensity of pixels for those pixels whose intensities are smaller than the mean intensity, a standard deviation of intensities of all pixels within the respective foreground block, and a contrast measure being a function of a first ratio of the second mean intensity to the standard deviation. A comparator that determines that the foreground block is a dry block if the contrast measure is larger than a dryness threshold and that the image is a dry image if a second ratio of the number of dry blocks to total number of foreground blocks is larger than a third dryness threshold.

Abstract: A fingerprint image is divided into blocks of pixels. The blocks are marked as directional or non-directional. The blocks are also determined to be within the foreground or background of the image. Contiguous regions of blocks that are in the foreground and are directional are selected. The quality measure is the ratio of the area of all these selected contiguous regions to the total area of the fingerprint image (i.e., the foreground.) The contribution of each of the blocks of the regions to the quality measure can be given by a distance from a block containing a reference point (a block of reference) within the foreground. Further, the block of reference can be located at the centroid of the foreground. Images are judged to be of poor quality if the quality measure is below a quality threshold and are judged to be of good quality if the quality measure is above the quality threshold. Optionally, poor quality images are examined further to determine if they are smudged or come from a dry finger.

Abstract: A fingerprint image is divided into blocks of pixels. The blocks are determined to be within the foreground or background of the image. Poor quality images are examined to determine if the imaging process is corrupted, e.g. by a wet finger, by determining if a smudginess measure is above a smudginess threshold. For each foreground block, a mean intensity (.mu.) of pixels is computed for those pixels whose intensities are smaller than the mean intensity of all pixels within the respective foreground block. Further the standard deviation (.cuberoot.) of intensities of all pixels within the respective foreground block is computed. For a foreground block with good contrast, .mu. is small and .cuberoot. is large. But for a block with low contrast due to smudginess, .mu. is small and .cuberoot. is small. Subsequently, to measure the contrast (a contrast measure) within a block, a function of the product (C.sub.S) of corresponding .mu. and corresponding .cuberoot. is determined.