Storm Technology

Storm Software, Inc.

Adrianus Ligtenberg

William John Gulland

Adolf Gerard Starreveld

A method of processing an input image for storage includes decomposing the input image into a number of images at various resolutions, subdividing at least some of these images into tiles (rectangular arrays) and storing a block (referred to as the 'tile block') representing each of the tiles, along with an index that specifies the respective locations of the tile blocks. In specific embodiments, the tiles are 64.times.64 pixels or 128.times.128 pixels. The representations of the tiles are typically compressed versions of the tiles. In a specific embodiment, JPEG compression is used. In a specific embodiment, an operand image is recursively decomposed to produce a reduced image and a set of additional (or complementary) pixel data. At the first stage, the operand image is normally the input image, and, for each subsequent stage, the operand image is the reduced image from the previous stage. At each stage, the reduced image is at a characteristic resolution that is lower than the resolution of the operand image. The processing is typically carried out until the resulting reduced image is of a desired small size.

Method and format for storing and selectively retrieving image data

An enhancement to a standard lossy image compression technique wherein a single set of side information is provided to allow decompression of the compressed file. Certain portions of the image are selected (either by the user or automatically) for more compression than other portions of the image. A particular embodiment is implemented for use with the JPEG image compression technique. JPEG calls for subdividing the image into blocks, transforming the array of pixel values in each block according to a discrete cosine transform (DCT) so as to generate a plurality of coefficients, quantizing the coefficients for each block, and entropy encoding the quantized coefficients for each block. Techniques for increasing the compression ratio include subjecting each selected block to a low pass filtering operation prior to the transform, subjecting the coefficients for each selected block to a thresholding operation before the quantizing step, subjecting the coefficients for each selected block to a downward weighting operation before encoding them, or, where the entropy encoding uses Huffman codes, mapping coefficients to adjacent shorter codes.

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Palo Alto, CA, United States of America

Adrianus Ligtenberg