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(RSS) Point-of-Sale Printers -- Image capture with dynamic range balancing and enhanced compression. Disclosure Number: IPCOM000018618D
Original Publication Date: 2003-Jul-28
Included in the Prior Art Database: 2003-Jul-28
Document File: 1 page(s) / 40K

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Point-of-sale printers are expected to perform with little of no customer maintenance. Some of the printers are equipped with optical read/imaging systems. Given the physical nature of the hardware components and a bit harsh environment, namely optical components and paper dust etc., the images are likely to become darker and drift into regions where they are not visually acceptable. The disclosed technique defines the process of combatting the problem and ensuring a good delivered image.

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  (RSS) Point-of-Sale Printers -- Image capture with dynamic range balancing and enhanced compression.

      A freshly calibrated image capture device is likely to produce an image spreading over the entire possible digital values. The resulting video has a healthy dynamic range of nearly 255 with a median of 128. The images have adequate brightness and are considered of high quality and acceptable.

    As the image video begins to drift, regardless of the reason, two things happen. The dynamic range reduces and the video median deviates from the center 128. Both of these result in degradation of image visual quality.

    Disclosed is methodology that produces near perfect images with optimal image compression, using the following image processing steps:
a) Analyze the video of the captured image for minimum and maximum video and calculate the video median.
b) Translate the video median to be near 128 DN, thus linearly moving the image window.
c) Apply dynamic range correction to expand the range to full video levels. Limited amount of video clipping on both extremes and low pass filtering can also be applied.
d) Compress the image using JPEG.
e) When a user views the image by decompressing it normally, a vivid image appears.

Following the above steps, the delivered image has all the desirable properties.

Disclosed by International Business Machines Corporation