Browse Prior Art Database

Selective Area Image Compression

IP.com Disclosure Number: IPCOM000039269D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Van Blerkom, R: AUTHOR

Abstract

X-ray radiographic images can be digitized by dividing the image area into pixels arranged in horizontal rows and vertical columns. In order to obtain a useful resolution for the digitized representation of the radiographic image, a typical X-ray picture must be divided into 1,024 pixels in the horizontal direction and 1,024 pixels in the vertical direction. If each pixel is given a gray scale range of 256 different values, then an eight-bit byte of information is required for each pixel. Thus, a typical X-ray picture will require a megabyte of storage for adequate resolution. In order to reduce the storage requirements for digitized X-ray pictures, various techniques have been tried in the past to compact the image.

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Selective Area Image Compression

X-ray radiographic images can be digitized by dividing the image area into pixels arranged in horizontal rows and vertical columns. In order to obtain a useful resolution for the digitized representation of the radiographic image, a typical X-ray picture must be divided into 1,024 pixels in the horizontal direction and 1,024 pixels in the vertical direction. If each pixel is given a gray scale range of 256 different values, then an eight-bit byte of information is required for each pixel. Thus, a typical X-ray picture will require a megabyte of storage for adequate resolution. In order to reduce the storage requirements for digitized X- ray pictures, various techniques have been tried in the past to compact the image. Non-destructive techniques, such as run-length encoding, have been employed, but a greater degree of compaction can be obtained by "destructive" compaction techniques, such as the Mitchell algorithm, where a portion of the information in the image is discarded in the process of compaction. Upon reconstruction of the image from a destructively compacted form, a certain amount of resolution is lost due to the discarded information in the compaction operation. The invention disclosed herein provides for the higher degree of compaction with destructive image compaction techniques and yet enables the production of a high resolution reconstruction of areas of interest in the X-ray picture. Referring to the figure, an X-ray picture is shown which is divided into 1,024 pixels in the horizontal direction and 1,024 pixels in the vertical direction. The principal image depicted in the X-ray picture, in this example, is a bone image which contains a fracture. Normally, the image compaction operation is applied to the entire X-ray picture. However, in accordance with the invention disclosed herein, o...