Adaptive quantization in overlapped transform coding of medical x-ray images
Richard R. Heusdens, Marcel M. Breeuwer, Rene Klein Gunnewiek · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1995
In previous papers, we presented an overlapped transform-coding method for efficient data compression of medical x-ray image series. In this paper, we address two improvements of this method. Firstly, we applied the method to so-called enhanced x-ray images, i.e. to images of which the middle and high frequencies had been emphasized. In this paper, we explain how to code raw instead of enhanced images under the constraint that enhancement of the coded raw images does not lead to a clear visibility of coding artefacts. Secondly, the coding artefacts introduced at high compression ratios by the previously published method are more clearly visible in the dark than in the bright areas of an image. In this paper, we explain what provisions can be added to our data-compression system to achieve a better balance between the perceptual image quality in dark and bright areas.