Objective Quality Estimation for Digital Images in Multimedia Environments

In the context of multimedia and hypermedia systems, the aspects of image quality measurement and guarantee are gaining increasingly in importance. To achieve this goal, two tasks have to be fulfilled: First, the definition and implementation of methods for complete media quality control is necessary. Secondly, suitable quality levels for visual presentations in the context of task specific requirements, compression and bandwidth limitation have to be achieved. At the beginning we will provide a definition and discussion of the term quality with respect to the use of visual information in multimedia applications. This leads to the development of a classification scheme for image quality aspects, which shows the relationships between task-oriented presentations and quality aspects, quality parameters and quality control. After this, a short introduction into state-of the-art image quality measurement is given and the advantages and limitations of the individual techniques are discussed. Considering the analysis of the objective measurement methods MTFA and SQRI, we present two enhancements that allow the application of these two measurements to digital systems. Our modifications and enhancements treat the aspects of frequency amplification and attenuation and the consideration of the human perception threshold. As an application of our classification scheme and the enhancements of MTFA and SQRI, we present approaches to estimate the quality of the colour reproduction of images in multimedia systems. Furthermore, we present a framework to integrate several measurements into a general quality measurement environment (GQME). Finally, questions concerning the achieved results and future work are raised.