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Báo cáo hóa học: " Quality Evaluation and Nonuniform Compression of Geometrically Distorted Images Using the Quadtree Distortion Map"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Quality Evaluation and Nonuniform Compression of Geometrically Distorted Images Using the Quadtree Distortion Map | EURASIP Journal on Applied Signal Processing 2004 12 1899-1911 2004 Hindawi Publishing Corporation Quality Evaluation and Nonuniform Compression of Geometrically Distorted Images Using the Quadtree Distortion Map Cristina Costa Department of Information and Communication Technology DIT University of Trento Via Sommarive 14 38050 Trento Italy Email costac@ing.unitn.it Francesco G. B. De Natale Department of Information and Communication Technology DIT University of Trento Via Sommarive 14 38050 Trento Italy Email denatale@ing.unitn.it Fabrizio Granelli Department of Information and Communication Technology DIT University of Trento Via Sommarive 14 38050 Trento Italy Email granelli@ing.unitn.it Received 1 September 2003 Revised 7 January 2004 The paper presents an analysis of the effects of lossy compression algorithms applied to images affected by geometrical distortion. It will be shown that the encoding-decoding process results in a nonhomogeneous image degradation in the geometrically corrected image due to the different amount of information associated to each pixel. A distortion measure named quadtree distortion map QDM able to quantify this aspect is proposed. Furthermore QDM is exploited to achieve adaptive compression of geometrically distorted pictures in order to ensure a uniform quality on the final image. Tests are performed using JPEG and JPEG2000 coding standards in order to quantitatively and qualitatively assess the performance of the proposed method. Keywords and phrases geometrical distortion picture coding quality evaluation. 1. INTRODUCTION Images acquired by optical sensors usually present some kind of geometrical distortion due to the characteristics of lenses and sensors adopted in the acquisition system or to the physical structure of the object under inspection such as in the case of textures projected onto nonplanar surfaces 1 . In specific applications such effects may also become more significant due to the specific nature of the .