An improved image processing chain for mobile terminals

Abstract

Based on the proposal in the report by Tryggve Mikkelsen [Mikkelsen, 2001] this thesis investigates and discusses the implementation of a simplified image processing chain for modern mobile terminals. Previous work on image processing in this field of application has shown that the demosaicing operation, color space conversion and downsampling are resource demanding pre-processing operations. The simplification potential of the signal chain lies within the pictured scenario of using Bayer RGB from the image sensor directly as input to the compression scheme. By omitting these pre-processing operations, unnecessary use of limited resources of a mobile terminal is prevented, making it capable of reducing the computational costs. The work has shown that the simplified image processing chain can be implemented two different ways. Either by using Bayer RGB as it appears from the image sensor as input to the compression scheme or by using composite Bayer RGB where the colors red, green and blue are distinguished into three arrays. Both implementations reveal overall better results for SNR compared to classical JPEG when lossless compression is applied. Furthermore, both implementations are capable of better color reproduction than JPEG. Comparing the two implementations, however, Bayer RGB appears to be capable of the best overall performance. In fact, taken into account the expected computational savings of the simplified image processing chain, conventional JPEG falls short on most evaluation criteria in this work compared to Bayer RGB.