Image analysis – Applications – Mail processing
Patent
1996-08-20
1998-04-07
Johns, Andrew W.
Image analysis
Applications
Mail processing
382164, 209584, G06K 900
Patent
active
057374384
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to computerized mail sorting and, more particularly, to an image processing method and apparatus for identifying and locating labels on digitized images of parcels.
BACKGROUND ART
With the ever increasing volume of parcel mail, automating parcel sorting is becoming of vital importance to post offices around the world and to the transportation industry in general.
Generally, in order to automate parcel sorting, it is necessary to capture a digital image of the parcel and extract from the image routing information, such as the destination address. This routing information may then be used by appropriate apparatus to sort the parcel appropriately or to generate e.g. a bar code to be printed on the parcel for subsequent use in the sorting process.
However, the label may be located anywhere on the parcel and thus anywhere in the digital image of the parcel. Generally optical character reader (OCR) technology will be used to extract the routing information from a reasonably high resolution image of the label. In order to efficiently make use of this technology and avoid the processing of the whole of the image of the parcel, it is necessary to locate the label on the image of the parcel. Once this has been achieved it is only necessary to process the portion of the image corresponding to the label.
DISCLOSURE OF THE INVENTION
The object of the invention is the provision of an image processing apparatus for locating an address label in an image of a parcel.
Two kinds of problems must be solved to perform such label detection. First, achieving the required speed is very difficult. The image processing must be performed in real time with currently available technology. Second, the image data is not ideal: the label may be contaminated by noise, the label may be somewhat transparent and therefore corrupted by the parcel background, and text may appear both on the label and on the parcel itself. Moreover, the label may appear anywhere on the parcel.
To solve the above problems the invention enables image processing apparatus to be provided comprising: means to generate and store in digital form an image of the parcel comprising pixels arranged in rows and columns; classification logic for classifying each pixel as either a label pixel, a background pixel or neither, based on the pixel color; segmentation logic for reclassifying each pixel as either label or background based on its original classification and the classification of pixels in its neighborhood; and identification logic for identifying the boundaries of regions in which all pixels are classified as label pixels.
The invention is based upon the observations made by the inventors that almost all parcels have white labels with black text and that no parcels are as white as their labels. Therefore, color information may be used to separate the label from the background.
The pixels are initially classified as either being in the label, the background or neither. Typically the pixels classified as neither background nor label pixels will correspond to text on the label or the body of the parcel or be due to noise. A segmentation technique is then used to re-classify the pixels as either label or background pixels on the basis of their context. The segmentation technique can, for example, employ known features of the text, for example the fact that pixels corresponding to text will not form long runs either horizontally or vertically in the image. In addition the segmentation logic can make use of the fact that label pixels can be expected to occur in relatively long runs and that the occurrence of background pixels in the label is quite rare.
In one embodiment, the classification logic is arranged to classify white pixels as label pixels, black pixels as neither label pixels nor background pixels and all other pixels as background pixels. However there are other possibilities. For example schemes could be devised which employ labels of a particular predefined color. In this case, the apparatus would be adapted to ide
REFERENCES:
patent: 4475234 (1984-10-01), Nishijima et al.
patent: 5025475 (1991-06-01), Okabe
patent: 5311999 (1994-05-01), Malow et al.
Downton et al., "Pre-Processing of Envelope Images for Optical Character Recognition," 9th Int. Conf. on Pattern Recognition, IEEE, 1989, pp. 27-31 .
Sommer Ziva
Zlotnick Aviad
Clay A. Bruce
International Business Machine Corp.
Johns Andrew W.
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