Verfahren und Vorrichtung zur Kodierung von digitalen Bilddaten

摘要

In the coding of image data corresponding to a raster of pixel values a generalized run length coding is used in respect of the difference between the pixel values in the raster line to be coded and the pixel values in the same position in the preceding raster line. In multi-value pixels (grey values), the generalized run length coding comprises an approximation of the course of the differences as a function of the position in the raster line with a linear function. The code then contains the number of pixels and a characterisation of the approximating function (90). In binary pixels (on/off) the length is simply determined of the series of pixel values each equal to the pixel value in the same position in the preceding raster line. In a particularly effective embodiment, this generalized runlength coding with respect to the preceding line is combined with generalized run length coding of the pixel values within a line. In this case both these methods are each time performed in parallel, and the method delivering the most effective code (that is the longest series of pixels, compensated for the length of the code itself) is selected for the actual encoding. <IMAGE>