Reversible Medical Image Watermarking for Tamper Detection and Recovery with Run Length Encoding Compression

Digital watermarking in medical images can ensure the authenticity and integrity of the image. This design paper reviews some existing watermarking schemes and proposes a reversible tamper detection and recovery watermarking scheme. Watermark data from ROI (Region Of Interest) are stored in RONI (Region Of Non Interest). The embedded watermark allows tampering detection and tampered image recovery. The watermark is also reversible and data compression technique was used to allow higher embedding capacity

Tamper Localization and Lossless Recovery Watermarking Scheme with ROI Segmentation and Multilevel Authentication

Tamper localization and recovery watermarking scheme can be used to detect manipulation and recover tampered images. In this paper, a tamper localization and lossless recovery scheme that used region of interest (ROI) segmentation and multilevel authentication was proposed. The watermarked images had a high average peak signal-to-noise ratio of 48.7 dB and the results showed that tampering was successfully localized and tampered area was exactly recovered. The usage of ROI segmentation and multilevel authentication had significantly reduced the time taken by approximately 50 % for the tamper localization and recovery processing

Landsat-5 Thematic Mapper Cold Focal Plane Characterization

The gain response of the detectors in the cold focal plane of the Landsat 4 ad 5 Thematic Mapper (TM) is known to fluctuate temporally. This is believed to be caused by an interference effect due to a film build-up on the cold focal plane dewar window. This paper analyzes the effect using a thin-film interference model. This model relates detector gain to film thickness through indices of refraction of the materials involved The dewar window material is Zinc Selenide (ZnSe) a known index of refraction, thus the index of refraction of the film in TM Band 5 and Band 7 can be determined by fitting the model to - the gain data from each detector The film is found to be absorptive in Band 7, but this is not apparent in Band 5. Film thickness has been determined to be as much as 1400nm from the data sample used. This model is also used to remove gain variation for gain characterization over instrument lifetime. An accurate model of this effect can improve the calibration of Landsat 4 and 5 by three to four percent in Bad 5 and Band 7. It is also applicable to the Landsat 7 Enhanced Thematic Plus (ETM+) if this thin film build-up is present