The paper deals with selected problems of image transmission through extremely narrow communication channels using very high compression rates. Such condition is very frequent in the security technology field. The same problem relates to the image retrieval systems when a limited storage capacity is available. As an example of tpical security picture a seven-segment display was chosen and such a test was compressed for various compression rates. The subjective identification threshold was consequently evaluated. Four recent compression techniques were involved JPEG (DCT), LuraWave (WT), JPEG2000 (WT) and fractals. Relevant compression rates were evaluated for the identification threshold and standard test image LENA was processed under identical conditions. Finally the results are discussed.

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